Year of The Tree
1. PLANTS, TREES AND THE ENVIRONMENT
Acknowledgements:
Compiled by the Rhodesian Forestry Commission for the Natural Resources Board with acknowledgements to:-
The Department of Conservation and Extension, Ministry of Agriculture.
The National Herbarium and Botanic Gardens.
The Timber Promotion Council of Rhodesia.
The University of Rhodesia
.
PLANTS, TREES AND THE ENVIRONMENT
Green plants
All life on this planet is
ultimately dependent upon green plants whether it is the whale in the sea, the
lion on the veld, the swallow in the air or the microbes in the soil.
It is only green plants
which can photosynthesis that is, convert carbon dioxide and water from the
air into carbohydrates (the building blocks of life), using the energy of
sunlight. Other plants without this capability such as the fungi obtain their
food from substances already made by green plants or animals. All animals,
including man, either eat plants or other animals.
When plants and animals
die their constituents are eventually recycled to the soil, the atmosphere, or
the sea, mostly through many intermediate plant and animal forms. The soil is
involved in the biochemical re-cycling of many nutrients. There are a whole
series of delicately balanced interdependent biological and physical cycles
involved in this complex web of life, and it is the green plants which provide
the basic raw materials. We can have an Earth, populated entirely by green
plants, which is probably what we did have at an early stage of the Earth's
evolution, but we cannot have an Earth with animals and no plants.
Genetic gold
Various movements for the
conservation of nature and natural resources have devoted much time to exhorting
countries to conserve examples of typical or specialized vegetation whether
forest, grasslands or wetlands as part of our scientific, cultural and aesthetic
heritage. Apart from these reasons, excellent though they are, there is an
overriding practical reason for seeking out and protecting examples of natural
vegetation all over the world. This has to do with providing the food and plant
materials we require from renewable resources in both the immediate and the
distant future.
Plant breeding has
achieved very great successes in increased productivity of crops, especially
cereals. Relatively few natural species were used to breed these high yielding
varieties, which have made possible what has been called the "green revolution".
However, plant breeders wage a continual war with disease and repeatedly have to
develop disease resistant varieties to keep ahead. To do this they need to be
able to draw upon the widest range of varieties of the species of crop plant
which they are improving.
In the future we are
likely to turn more and more to plants as the source, of renewable materials, as
finite sources of "mined" materials such as oil and coal diminish. We shall then
want to develop and extend plant breeding to all kinds of plants which may be
used for food, fibre, wood and very likely raw materials for the chemical
industry. To do this we shall need a very wide range of plants as a genetic
natural resource or. gene pool. No one can say at this stage just what material
will be needed. It is certain however that if we lose the genetic gold
represented by any single species through allowing it to become extinct, we have
lost it forever.
In recent years there has
been much concern at the rate of destruction of natural vegetation occurring on
a world wide scale at the same time that rapidly increasing amounts of oil and
coal are being burnt every year. The argument is
that less plant life moans loss oxygen released to the atmosphere
and that the greater volumes of oil and
coal being burnt are at the same time
contributing more and more carbon dioxide. Thus it has been said
that animals and man will have less and less
oxygen to breathe and that increased
carbon dioxide in the atmosphere could load to increases in the
average temperature of the Earth sufficient to cause the polar ice
cans to melt with disastrous results for hundreds of large coastal
cities.
There is evidence that
carbon dioxide levels in the atmosphere are increasing but the entire global
picture including all the factors at work is far from being as completely
understood as some environmental writers would have us believe. Nevertheless
global monitoring of atmospheric constituents is very necessary and is now
underway. In the meantime it is valuable to recognize this further function of
living plants as a major contributor of oxygen to our air supply.
Trees are the largest
members of the plant kingdom and far and away the longest lived of any living
thing. The oldest Baobabs are in the region of 2000 years old and the oldest
Bristle Cone pines, natives of the United States, are more than twice that age,
which means they were seedlings at the same time the
first ancient Egyptian dynasty began, three hundred
years before the great Pyramids were built. The most massive living thing on
Earth is the biggest known California big tree
(Sequoiadendron giganteum)
which is 83 metres tall (nearly twice the height of Nelson's Column in Trafalgar
Square). Its weight is over 2 000 tonnes. It is not difficult to understand why
trees are regarded with affection and respect, almost awe, by many peoples.
Trees, and other plants
as well, play an important part in relation to water supplies and in preventing
or controlling erosion. In water catchments all vegetation, natural or exotic,
uses water as well as levelling out storm flows and reducing silt loads in
streams and rivers. Large scale removal of vegetation in mountain catchments
leads to catastrophic flood damage as is happening now in the Indian
sub-continent. This region always has had floods due to the melting of the
Himalayan snows but with steadily increasing population and poor agricultural
practices in the mountain catchments these floods are now reaching levels where
the lives of millions of people are at risk.
Management of vegetation
in catchment areas is therefore a highly important science where the most usual
compromise is to use a proportion of the water where it falls for the production
of crops, as well as discharging into streams the maximum amount of water that
can be controlled and used elsewhere. Trees are often the most suitable
vegetation for catchment areas, providing a valuable crop which also protects
the land and soils in the catchment from erosion.
In farm lands trees have
many uses besides the obvious one of producing poles and timber for consumption
on the farm. Windbreaks of trees, usually two or three rows deep, protect soils
from drying out and subsequent wind erosion. They are effective over a distance
equal to thirty times the height of the trees to leeward and two or three times
to windward. Under South African conditions on flat terrain the Forest Authority
advise that about five per cent, of the total area of the farm should be under
windbreaks. Certain species however, especially those that sucker, should not be
planted next to field crops because of the effect on the yield of the crop next
to the trees.
Individual trees or
groups of trees are often used for shelter and shade for stock. In times of
drought a few shade trees in the vicinity of
watering places will reduce the amount of water
needed by livestock. If possible, fodder trees should be used and there are
several indigenous and exotic species in Southern Africa which are useful from
this point of view.
Forests and plantations of
trees can and have been used to dispose of treated sewage effluent. The effluent
whilst biochemically safe still contains high concentrations of nitrates and
phosphates in solution. If these effluents are discharged to rivers and lakes in
large quantities the growth of algae is excessively stimulated and the lake
environment becomes degraded with death of fish and other unpleasant side
effects. Excess nitrates in drinking water can also cause a particularly
dangerous condition in young babies. It is usually prohibitively expensive to
remove dissolved nitrates and phosphate by any chemical process but tree
plantations are able to take up and use these nutrients so that the water
remaining has greatly reduced concentrations of these substances.
It is more and more
recognized that trees and forests are most valuable for the physical and
spiritual well being of humans especially those who normally work and live in
cities. Trees^ in cities moderate local temperature variations and provide a
restful antidote to acres of steel, concrete and glass. The hundreds of
different kinds of ornamental trees are a constant delight to all who are
captivated by colour and form. Forests, both natural and exotic, often in areas
of splendid mountain scenery, provide a haven in which man can refresh his
spirit.
Booklets in this series are:
1 PLANTS. TREES AND THE ENVIRONMENT
2 WOOD. THE RENEWABLE RESOURCE
3. TIMBER TREES OF RHODESIA
4. RHODESIAN TREES FOR GARDENS AND PARKS
5. KRAAL WOODLOTS
6. INDIGENOUS WOODLAND ON THE FARM
7. FIRE. TREES AND FORESTRY
8 THE FOREST AND TIMBER INDUSTRY OF RHODESIA
9 FORESTRY AND THE RHODESIA FORESTRY COMMISSION
WOOD, THE RENEWABLE RESOURCE
Acknowledgements:
Compiled by the Rhodesian Forestry Commission for the Natural Resources Board with acknowledgements to: -
The Department of Conservation and Extension, Ministry of Agriculture
The National Herbarium and Botanic Gardens.
The Timber Promotion Council of Rhodesia.
The University of Rhodesia.
End of Pg
2. WOOD, THE RENEWABLE RESOURCE
At a time when there is a
world-wide concern over the rate of depletion of non-renewable resources such as
oil, coal and many metals, wood begins to assume a new and greater importance
because apart from food crops, it is the major raw material which is renewable.
Wood was one of the
earliest materials used by man for tools and for transport in the form of the
dug-out canoe, and when he began to use mechanical principles he turned to
wooden disk wheels made from round tree trunks and round logs to roll the
enormous stone blocks of the Pyramids into position.
Although wood has always
held its own up to the present day, and a moment's thought will show that man is
surrounded by wood every day of his life, the industrial revolution began the
present age in which metals and plastics are used to enormous extent in modern
society. Oil and coal (from. which plastics are made) and metals are mined from
the ground however, and the Earth only possesses fixed amounts of these
materials which are non-renewable. These materials will in many cases still last
for a long time into the future and some used material may be "re-cycled" and
used again, but they will become scarcer and will cost more to win from the
ground or to re-cycle so that they will become steadily much more expensive.
Wood, therefore, because
it is a renewable resource and because it is a very versatile material is
perhaps beginning a new era of importance in man's history.
The versatility of wood
All wood can be wrought
and shaped mechanically, it can be nailed, screwed, mortised and glued. It can
be used for the walls and roofs of houses, for furniture, for decoration and for
the most delicate sculpture. Wood can also be mechanically broken down and then
reconstituted into new materials such as particle board, hardboard and newsprint
which have new properties not possessed by the original material. Just as
important or more important, wood can be chemically modified and altered either
to make pulp from which all kinds of paper and cardboard containers can be made,
cellulose from which rayon fibre for clothing is produced, and even alcohols and
sugars which can serve as raw materials for a variety of chemical industries.
Wood used as wood
Wood used as wood has
tremendous variability depending upon the species of tree from which it comes.
Balsa-wood weighs 100 kg per cubic metre, can be dented with a finger and was
used to build the Kon Tiki raft.
Lignum vitae,
or the "wood of lite", weighs 1 200 kg per cubic metre, is three or four times
as hard as English Oak and is used for ships' propeller bushes and bearings.
Wood is used in the round
for power transmission poles, telephone poles and fence posts for which
expensive steel would otherwise have to be used. The gum and wattle wood used
will not withstand termite attack or rot but has the property of being permeable
to preservatives such as creosote which is forced into the wood under pressure
to give long life in contact with the ground. Slabbed roundwood is used as "mat
packs" in the mines to support the roofs of galleries. A useful property here is
that these wood supports creak and groan before they give way—a warning not
given by steel or concrete.
Sawn wood as boards, beams and battens is used
in all sorts of construction work from roof trusses to tile battens
and ceiling board. The smaller sizes are used to make wooden cases
for packing agricultural produce such as tobacco and fruit. Here a
high strength/weight ratio and workability are the important
properties. Not many people realisealso that wood beams are often
safer than steel beams in cases of fire. The wood, especially
if treated with a fire retardant, chars but keeps its position and
much of its strength but steel expands and buckles and can push the
building apart. High quality hardwoods are sawn to produce
decorative furniture, panelling and flooring. The heavier woods are
not generally used for furniture because the individual chairs and
tables would be too cumbersome to move, They may be used for
flooring, provided they are capable of resisting wear and abrasion.
Timber specialists didn't foresee the very high loads
concentrated in the steel stiletto heel however, and many fine
timber floors have been ruined by this fashion in women's
shoes.
Resilience is another valuable property of wood, possessed to a
greater extent by some timbers than others. Australian tallow wood
is highly prized for dance floors because of this property.
Toughness is a particular quality of some woods such as ash and
hickory. When it is combined with flexibility and the ability to be
permanently bent using steam, as in ash, the timber is especially
suitable for sports goods such as tennis racquets and for bentwood
furniture. The willow used for cricket bats, which is actually
called cricket bat willow, is 40 per cent, lighter than ash but only
about 15 per cent, less tough; combined properties which make it
ideally suited for its use.
A property of the logs of some species of tree is that they peel
readily to produce a continuous thin veneer. These veneers are cut
into sheets and glued together under heat and pressure to form
plywood. The grain of each sheet is at right angles to the next and
the result is a thin, strong board which is equally stiff in both
directions. Plywood is widely used in the furniture industry where
the face veneer is usually a particularly decorative wood like
Mukwa. It is also used to make containers such as tea chests which
are light and strong, and can be manufactured so as to be
particularly resistant to weathering and water so that "marine ply"
is much used in small boat construction.
Thick plywood, or more commonly coreboard, a composite made up of
sawn components with veneer faces, is used and re-used as shuttering
for concrete work. Wooden matches are cut from veneer having the
same thickness as the matchstick. Poplar wood is used which peels
well and gives strong match splints which easily soak up the wax
used to make the splints burn more evenly.
Altered wood
Paper packaging has two
important advantages over plastic packaging. The first is that it is much easier
to re-use or re-cycle and the second is that it rots down instead of remaining
unaltered for years as unsightly and sometimes dangerous litter as is the case
with plastics.
Cellulose from wood is
also dissolved, reconstituted and spun as rayon fibre or made into cellulose
acetate fibre. Wood cellulose is also used to make photographic film and as
nitrocellulose in explosives. Rayon yarn forms 15 per cent, of the total world
textile production. Cotton, wool and rayon are the fibre materials from
renewable, resources as opposed to nylon and terylene produced from
non-renewable oil and coal.
3. TIMBER TREES OF RHODESIA
Unfortunately the
indigenous woodland or natural bush of Rhodesia contains very few
tree species which can be exploited commercially on any scale. This
is not only because the quality of the timber is unsuitable and the
logs often small and crooked but because the more valuable species
are sometimes so widely scattered that it does not pay to harvest
them.
It must not be forgotten
however, that this natural woodland plays a highly important part in the lives
of thousands of African families who draw upon it for timber for houses, cattle
kraals, household effects, fuel-wood, fruits and medicines. The rapid rate at
which this woodland is disappearing outside those areas under the charge of the
Forestry Commission and in private lands is therefore of grave concern.
The indigenous hardwood
woodland is thus rich in species but poor in terms of timber productivity. The
rate of growth of indigenous trees is, on the whole, extremely slow. They are
often subjected to f£re and generally have a poor form. Much of their timber is
unsuitable for the major part of industrial requirements. Even the timbers of
the commercially important hardwood species have limited uses.
To supplement the
inadequate indigenous timber resources and to provide more versatile types of
wood, man-made forests, or plantations of exotic trees i.e. trees from outside
the country, have been established.
Hardwoods and softwoods
All timbers fall into two
main groups, the hardwoods (from broad-leaved trees) and softwoods (from
coniferous trees). These are unfortunate and rather confusing terms, because
although most broadleaved trees have harder and denser wood than most coniferous
trees, this is not always so. The true differences lie in the actual cell
structure of the two types of wood. The conifers (pines, cypresses, firs) were
the first trees to evolve on the earth and were followed later by the
broad leaved species.
The indigenous hardwoods
Only three indigenous tree
species are harvested on any scale in Rhodesia, although there is currently
interest being shown in the utilization of msasa timber which is common and
widely distributed.
The commercial operations
are carried out over some 800 000 hectares of Kalahari Sands woodlands in
northwest Matabeleland which are protected and managed as demarcated forest by
the Rhodesia Forestry Commission, and in certain other woodland areas in this
region which are in due course destined for agriculture. The demarcated forests
are worked on a sustained yield basis such that only as much timber is taken out
as is being replaced by the growth of younger trees.
The rainfall in these
areas is generally less than 600 mm per annum and therefore this is the zone of
the lowest rainfall in Rhodesia. All three species are much slower growing than
the exotic trees taking 100 to 150 years or more to reach maturity and generally
only reaching heights of about 15 to 20 metres, although the diameter of the
trunk may go up to 0,6 to 0,9 metres. The timbers are much heavier and harder
than most of the exotic trees.
Pterocarpus angolensis
(Mukwa, kiaat, bloodwood)
This tree is very widely
distributed, growing in South Africa (where it is known as kiaat, Angola,
Mozambique, Malawi, Tanzania and Zambia as well as
occurring in Rhodesia in the Kalahari Saudi and in the soils of
the mid and high veld areas.
Mukwa is a very handsome furniture wood with a world reputation. One
of its most important features, apart from its appearance and fine finish, is
the stability towards changes in the moisture content of the atmosphere, a most
important attributable for a cabinet wood. It is of course used for furniture,
panelling and high class joinery and the lohgs are peeled to produce a veneer
which is used to face plywood or block board. With such a valuable timber that
takes ao long to grow veneer is the most economical way to use the wood. In
contrast to the two other indigenous hardwoods Mukwa is of medium weight (abut
600 kg per cubic metre) which also makes it more suitable for furniture than the
other two heavier woods.
Baikiaea plurijuga
(Rhodesian teak,
mukusi)
Baikiaea
is not related to
the true teak of India and Burma which is a much lighter, more versatile wood.
It grows extensively on the other side of the Zambezi in Zambia and also in
Angola and Botswana as well as in Rhodesia.
The wood is heavy
and hard with a density of 850 to 950 kg per cubic metre. It is thus some 50 per
cent, heavier than mukwa and about twice as heavy as pne or poplar. It is a
handsome reddish-brown wood which makes a highly decorative floor, either in
strip or parquet form, with a high resistance to wear. It is very durable and
resistant to termite attack which makes it particularly useful for railway
sleepers, and it is sometimes used for furniture.
Again, the name Rhodesian mahogany is a misnomer as this tree is not a true
mahogany. The name probably refers to the red colour of the wood. This species
has almost the same distribution as
Baikiaea
and the timbers are very similar, with similar densities and very much the same
uses.
Other species
Interest has
lately been shown in the utilization of Msasa timber. The tree,
(Brachystegia spiciformis)
is common and widespread in this country, reaching its largest size in the
Kalahari sand areas. The timber is suitable, with appropriate preservative
treatment, as railway sleepers and has also been successfully peeled for
plywood.
Small quantities
of timber of the following savannah woodland trees have also been exploited
commercially, from time to time:
Pod mahogany (Afzelia
quanzensis)
a reddish-brown durable attractive wood used for veneer, furniture and flooring
blocks.
African blackwood
(Dalbergia melanoxylon),
a very hard,
heavy,
dark purple to black wood similar to
ebony used for carvings and woodwind musical instruments. The density is 1 200
kg per cubic metre.
Umgongo
(Ricinodendroti rautanenii) very much in contrast
to African
blackwood, is
an
extremely light,
pale
coloured wood
(density
only 245 kg
per cubic metre about half that of exotic
pines) used
tor making
curios
and
toys.
Muwanga (Pericopsis
angolensis), is
yellow to
greenish-brown,
hard
and close
textured and is
probably the best carving wood available in
Rhodesia
Plantation trees (Exotics)
The exotic species on
which plantation forestry is founded in this country are relatively few in
number. There are three main pine species, a few eucalypts, black wattle and
very small areas of poplar.
Exotics were introduced in
the 1890s and a visiting forest officer from South Africa remarked in 1903 that
Saligna gum growing near Salisbury was "the best planted tree I saw in Rhodesia"
with heights of 75 feet attained in 10 years.
Up to 1923 the main
plantation effort was the work of private enterprise, nearly 1 200 hectares
having been established, almost all eucalypts planted on farms for fuel and
poles, the plantations serving a dual purpose as windbreaks.
In 1923, the Forest
Division of the Department of Agriculture, itself only three years old,
commenced planting eucalypts at Mtao Forest near Umvuma. Large scale planting of
pines was pioneered by the Forest Division, later to become the Rhodesia
Forestry Commission, at Staple-ford Forest in the Eastern Highlands in 1926.
Most of the exotics
established in plantations are, however, intolerant of the arid conditions which
characterise large areas of the country. Some 65 per cent, oi the total area of
the country suffers such conditions and is thus unsuitable for exotic
plantations, except perhaps under irrigation. Only about 4 per cent, of the
country is suitable for afforestation with exotic conifers and eucalypts on a
large scale, while some 9 per cent, is suitable for small scale afforestation.
The remaining 22 per cent, of the country is considered marginal for exotic
plantations, especially where soil depth is limited. The confines commercial
plantations of exotics in Rhodesia to areas with rainfall of over 700 mm per
annum.
Exotic softwoods
In Rhodesia there are now
about 58 000 hectares of plantations of exotic softwoods in the high rainfall
areas of the Eastern districts {over 1 000 mm of rain per annum). The
plantations start to produce logs which can be used to make pulp at about 8
years of age and logs which can be sawn into boards at about 13 years old. The
large yields of sawn timber, however, come from a final clear felling at around
30 years.
Although there are
differences in the timber of the three main pines described here the timber
industry generally does not separate them. Small logs are completely ground up
by a mechanical process to produce "mechanical" pulp used for newspaper. Logs
are also peeled to make the centre or core ply layer in plywood. The major use,
however, is for sawing into building timber which is used for roof trusses, pine
ceilings, doors, door frames, etc. Pine timber has, in general, high strength
for its weight (density 400 to 500 kg/cubic metre) and is easily planed, cut,
nailed, etc. On good sites all three pines grow to about 30 m in height in 30
years.
Pinus patula
(Mexican, or spreading
leaved pine)
This pine comes from
central Mexico but has been very widely planted in South Africa and in Malawi as
well as in Rhodesia. It forms about 70 per cent, of the total area under pines
in this country.
Pinus elliottii
(Slash pine)
Slash pine comes from the
south eastern United States and is more suited to lower altitudes, and more
shallow and poorly drained sites than Pinus patula will tolerate. The timber
tends to be more resinous and heavier than that of patula.
Pinus taeda
(Loblolly pine)
This tree grows naturally
over a wide area in the south east United States and is the principal commercial
timber species in the south of its range. It is likely to be planted on a much
larger scale in Rhodesia in the future, and is (suitable for areas similar to
those in which Slash pine is grown.
Other species
A pine which has good
potential for commercial planting in the better softwood areas of medium
altitude (1 100 m to 1 500 m) and low to medium rainfall (600 mm to 900 mm) is
Pinus keysia
from south-east Asia and the Philippines.
Altogether, some 46
species, varieties and hybrids of exotic pines have been planted as
introductions into Rhodesia of which only about six show potential as commercial
forest trees, other than those mentioned above.
Exotic hardwoods
Eucalypts have been far
more widely planted in Rhodesia than any other exotic hardwood introduction,
indeed even more so than the conifer introductions, being generally more
adaptable to site and climatic conditions. About one hundred species of eucalypt
have been introduced on a trial basis but only some twelve have shown commercial
possibilities. Of these Saligna gum is the most important and the only eucalypt
it is possible to cover in the short compass of this article.
Eucalyptus grandis
(Saligna gum or "saligna")
Eucalyptus grandis
has suffered some confusion over its name since it was first introduced to
Southern Africa about eighty years ago. It was for a long time called
Eucalyptus saligna
(hence its most usual popular name, saligna gum) and more recently
"Saligna/grandis" since it was thought to be a hybrid between two species. The
botanists now tell us that the tree known as "saligna" in Rhodesia should more
correctly be called
Eucalyptus grandis.
E. grandis is
not only the fastest growing tree in Rhodesia but Rhodesian trees hold the world
record for the shortest time taken to reach 100 feet. Trees at the John Meikle
Forest Research Station have reached 100 feet (30,48 metres) in only 5 years
from planting.
E. grandis
at Inodzi Farm, Penhalonga
are amongst the tallest trees in the world with top heights of 85 metres and
diameters of 1,25 metres at 60 years of age. At Inodzi 1 707 cubic metres of
round wood (over 1 000 tonnes) stands on just under 0,5 hectares. These are
enough logs, when sawn, to produce the timber needed for 110 average
three-bedroomed houses.
These are very exceptional
trees on very exceptional sites but they indicate the enormous potential of this
tree, which is probably capable on good average sites in the Eastern Highlands
of approaching double the volume production of the fastest growing pines. The
tree will still show good though much slower growth in areas down to 600 mm
annual rainfall.
The tree is mainly used in
pole form for power transmission and telephone poles and for fence posts when it
is treated with creosote preservative against attacks by termites and rot. It is
also used for mining timber to hold up the roofs of underground galleries and
the sawn wood is used for boxes, crates and pallets and to a small extent for
furniture. This does not exhaust its versatility as it also plays an important
role as a raw material for the chemical
pulp industry. The timber is heavier than pine (density 550 to 600 kg per cubic
metre) and is light red in colour. The main disadvantage is the splitting which
occurs during sawing and seasoning.
Saligna gum is the main
species of tree being planted in the tribal trust lands for local pole and fuel
supplies. Like nearly all eucalypts it coppices strongly, that is when cut down
it produces vigorous new shoots from the stump, unlike the conifers for instance
which die if cut down. The ability to coppice is most important for a tree used
for pole and fuel supplies. The removal of large areas of natural woodland for
agriculture and to meet increasing demands for poles and fuel have led to a
situation where there are severe shortages of wood in many tribal trust land
areas. The Year of the Tree—1975 campaign marks the start of a fresh effort to
remedy this situation by creating small plantations of gum, which can produce
about 20 times the amount of wood per hectare than indigenous woodland.
Acacia meamsii
(Black wattle, tan bark wattle)
This tree is also a native
of Australia which has been planted extensively in South Africa and Rhodesia for
its bark, an extract of which is used in tanning leather. It requires a high
rainfall and mist belt conditions for satisfactory growth, that is, areas in the
Eastern Highlands which have a substantial amount of mist and light rain during
the winter months.
Extensive planting of
black wattle commenced in the late 1940's and by 1960 28 000 hectares had been
planted. Since that time however, there has been a decline in the area of wattle
plantations some which have been converted to softwood plantations or to
agriculture. This has been due to a slump in the price of the tan bark extract.
When grown for bark the
tree is harvested after about ten years. It shows very rapid growth during this
period reaching heights of over 18 metres and diameters of 0,15 to 0,18 metres.
Although originally grown
for its bark the timber of wattle has found increasing applications. The wood is
hard and tough compared with the pines and has a surprisingly high density of
700 kg per cubic metre. After preservative treatment the poles are used for
fencing and the timber for parquet flooring and mining timber. In South Africa
it is used extensively for parquet and pulp.
Populus deltoides
(Carolina Poplar, Southern Cottonwood)
Although the common name
of this exotic tree is Carolina poplar it grows naturally over a much wider
range than its name would indicate, from southern Canada right down to Louisiana
in the United States.
Carolina poplar is very
exacting in its requirements and needs a -rich, deep, well watered and well
drained soil. From this it will be seen that the finest poplar soils are often,
the best agricultural soils. The tree shows very fast early growth (up to 1,5
metres per year) and grows to over 30 metres in height. When grown commercially,
however, it is usually grown for 15 to 20 years before felling, reaching heights
of about 20 to 25 metres, and diameters of 0,3 to 0,4 metres.
The wood is white,
straight grained and of even texture and is about the same density as the pines,
that is about 450 kg per cubic metre. Its main use is for match splints which
are cut from a thick veneer peeled from the log by rotating it against a long
knife blade. The wood peels and cuts into splints which are tough and can absorb
wax to help them burn easily. This combination of properties is not easily found
and the timber therefore commands a good price.
4. RHODESIAN TREES FOR GARDENS AND PARKS
Too often exotic trees such as Jacaranda or Nandi Flame are chosen to ornament parks and gardens. No one would wish to decry the beauty of these favourites, but why not pay more attention to our own Rhodesian trees many of which have very handsome flowers or foliage? No doubt one reason has been that the exotics satisfy the impatient because they tend to grow faster and another is that seedlings of Rhodesian trees are not always readily available. Many of the trees described below, however, under garden conditions, will reach a size of 3 to 4 metres in 5 years from seed. A number of them will in fact reach maturity as soon as exotics. Indigenous Rhodesian trees are now more readily available from nurserymen, or those interested can often collect their own seed and grow their own trees.
Growing your own tree
If you cannot obtain seedlings or seed, you can collect your own seed. In some cases the trees are most easily raised from sections of branch (normally called truncheons) planting them as if they were outsize cuttings.
If you collect your own seed you may need someone else's help to make sure that you have identified the tree properly. You'll be disappointed if your carefully nurtured plant turns out to be quite a different tree to the one you intended to grow. If you can't solve your identification problem the National Herbarium are willing to help whenever their staff have the time.
It is essential to obtain seed that is fresh and fully ripe, and not diseased or damaged by insects. A hard pod will fall from the tree when ripe. Others are mature when the pod is on the point of splitting. Soft fruit must be soft and have reached its ultimate colour when ripe.
Seed must be planted when it is fresh. If possible the seeds should be sown as soon as they are collected, although those which are collected in the autumn can be stored and planted in the spring. If it is necessary to store seeds make sure they are clean and dry and keep them in a container, such as a glass jar, in a cool place. The container must not be completely airtight, and the seed should be lightly dusted with fungicide.
Use individual containers. Either polythene tubes or waxed paper African beer containers can be used. Tins are sometimes difficult to remove when planting out the tree.
Good drainage is important, and with containers other than the open ended polythene tubes, several holes must be made in the bottom and a handful of small stones placed inside. Add half sieved topsoil and half sieved compost well mixed, or if the top soil is heavy clay, mix in some river sand.
As a rule seeds should be planted at a depth equal to their diameter, covered with sieved top soil and watered. Place 2 or 3 seeds, not too close together, in the same container. When they have germinated remove all but the most vigorous one. The soil should never be allowed to dry out or become waterlogged. Place the containers on level ground and shield from the midday sun. You will have to be patient as germination times may vary from one week to six weeks. If you are experimenting however, it is futile to expect any success after 18 months, by which time the most difficult indigenous species will have germinated.
When your tree is well established in the container about 10 to 30 cm high, or when the roots begin to seek a way through the bottom — it can be transplanted to the open ground. It is advisable do this at the beginning of the rains.
Choose the place where the tree is to be planted with care, take into account account its eventual size, remember that you intend it to stand for a long time. The hole you dig should be 1 m x 1 m by 60 cm deep. Take out the first half (about 30 cm) of top soil, mix this with a generous quantity of compost and set it aside. The second half of the soil should be well dug and the top soil/compost mixture replaced at the top half of the hole Water, and allow the soil to settle for 24 hours before you plant, Most trees dislike having their roots disturbed, so remove the container from around the seedling with great care. Be sure you plant it at the correct depth; the soil level in the container, and the level of the surrounding soil must be the same. Tamp the earth around the plant firmly and make a small earth dam at the edge of the hole to contain the water. Water it well.
Truncheons
Some species of tree can be grown from truncheons and Erythrina abyssinica and Sclerocarya caffra are examples from the list of trees given below.
Take a branch of the parent tree — up to 2 m long and plant h in a hole deep enough to seat it firmly, with a layer of sand at the bottom to ensure good drainage. Keep it moist until the rains have settled.
If the tree is evergreen, truncheons should be taken during the rainy season, while those which are deciduous should be taken in the spring when the sap is rising and the first leaf buds make their appearance.
List of suitable trees
The following list of indigenous trees contains only a few of the many species which can be grown. They are all easily grown from seed. "Fast growing" trees should reach a size of 3 or 4 metres in 5 years and "medium growth rate" in 10 years. Common names are given in English (E), Shona (S) and Ndebele (N) but local African names for trees can vary and it is easy to be misled.
ACACIA GALPINII
(E) Monkey thorn
(S) Muchinanga
(N) Umkhaya
A fine deciduous tree 18 to 30 m tall having an erect cylindrical bole, massive spreading limbs, and a luxuriant rather grey/green crown. It is armed with strongly hooked thorns. The sweet smelling spikes of fluffy yellow flowers about 8 cms long appear in September/October and the dark brown flat woody pods some 18 cms long ripen in February/March.
Monkey thorn is common on alluvium in lowveld areas and grows on anthills in medium and high altitudes. It reaches its best development on deep, well drained loamy soils, is moderately drought and frost resistant, and makes an attractive fast growing shade tree.
ALBIZIA GUMMIFERA
S) Mupambangoma
A stately semi-evergreen tree with dark green foliage 20 to 30 m in height, with a flat wide spreading crown. The white flowers appear from August to November and the flattened bean like fruits, about 2 cms. long with hard flat seeds, arc green when young and brown when they ripen in the following dry season.
The tree grows in evergreen forest and is most commonly found on the margins of this type of forest in the eastern highlands. It requires deep good soil and plenty of water and under these conditions is fast growing.
BOLUSANTHUS SPECIOSUS
(E) Rhodesian wistaria
(S) Mupaka
(N) Impaca
One of Rhodesia's most beautiful indigenous trees, small (about 5 to 6 m tall) semi-evergreen, with a fairly erect, but much divided stem, bearing masses of showy violet blue Wistaria-like flowers in long hanging sprays at the ends of largely leafless branches. After flowering in September/October the tree produces clusters of flat brownish pods 6 to 8 cms long. The pods ripen from March to May when they split and scatter seed.
Bolusanthus is widespread in Savannah woodland and requires an open sunny situation in gardens, withstanding drought but relatively little frost, and showing medium growth rate.
CALODENDRUM CAPENSE
(E) Cape Chestnut
(N) Umbaba
A medium sized semi-deciduous tree reaching 20 m in height and having a heavily branched rounded head. Some would maintain that of all the indigenous trees its sweetly scented flowers are the most beautiful. The flowers are large, pale pink and white, measuring 5 to 8 cm across and borne profusely in sprays at the ends of branches. Flowering time is October to January and the fruits, which are a woody 5 angled capsule resembling a horse chestnut, appear in June or later and contain 4 or 5 large angular black seeds.
Cape Chestnut is widespread but not common at high and medium altitudes in high rainfall areas and is suitable for gardens in these areas where it is fast growing.
CASSIA SINGUEANA
(E) Cassia
(S) Munzungu
(N) Isihaqa esincinyana
A small, deciduous tree about 6 m in height which bears a profusion of bright yellow flowers either in April/June or August/September. The fruit pods are 8 cm long, flat, bean like, yellowish in colour and ripen either in November/December or January/March
Cassia is widespread throughout savannah woodland and a very suitable garden subject for medium rainfall areas where it shows medium growth rate. A similar tree of the lowveld is Cassia abbreviata which is more suited to drier areas and also shows medium growth although flowering when quite young.
DOMBEYA ROTUNDBFOLIA
(E) Wild Pear
(S) Chitowe
(N) Umwane
An attractive small deciduous tree 5 to 6 m tall, often forking near the ground and producing a rounded moderately spreading dark green crown. The flowers appear before the new leaves unfold in July or August when the tree is covered with a mass of white or pinkish fragrant flowers which sometimes persist as long as until October eventually turning a brownish colour. The leaves are distinctive, simple, and almost round, about 8 cm by 8 cm. The fruit is a hairy capsule which ripens in November and December.
Wild pear is widespread and common at medium to high altitudes. It is fast growing and suited to most areas.
ERYTHRINA ABYSSINICA
(E) Lucky Bean Tree
(S) Mutiti/mutete
(N) Umqogqogqo
An exceedingly showy medium sized tree about 10 m tall with a short stout trunk and an open rounded, moderately spreading crown. The [clusters of brilliant red flowers are borne at the tips of the branches from July to November before the tree comes into leaf. The fruit is a long round bean-like pod, appearing from October, constricted between the seeds which are bright red with a black spot — the well known lucky bean.
Erythrina is widespread in savannah woodland and vlei areas, grows easily from truncheons as well as from seed, is suitable for all areas and is fast growing.
KHAYA NYASICA
(E) Red mahogany
(S) Mubawa/Mururu
A stately evergreen tree with an erect, straight, clean bole and a luxuriant massively branched oval to rounded head, some 30 to 40 m tall. The "Big Tree" of Chirinda Forest is a Khaya, and shows exceptional growth, at 65 m being the tallest indigenous tree in Rhodesia, about one and a half times the height of Nelson's Column in London's Trafalgar Square.
The flowers which are small and white and appear in the Spring are not conspicuous. The fruits are round, grey, and up to 5 to 6 cm in diameter splitting into 4 segments on ripening. Old split fruits are conspicuous under the trees for many months after they fall.
Khaya grows in evergreen forests in the eastern districts and as a riverain tree elsewhere. It makes a superb shade tree for parks and large gardens and is fast growing on good soils with plenty of water.
KIGELIA AFRICANA
(E) Sausage Tree
(S) Mumyee
(N) Umvebe
End of Pg
An arresting, medium-sized, semi-evergreen tree with a short, stout trunk and a spreading crown reaching a height of about 15 m. Large, showy, reddish-purple, tubular flowers about 10 cm across are produced in hanging sprays in early summer. The unmistakable "sausage" greenish-grey fruits appear in autumn or winter and ripen in the rains. These enormous fruits are 25 to 60 cm long, up to 10 cm in diameter, and hang at the end of cord-like stalks up to 1 metre in length. The numerous hard seeds are imbedded in the central portion and may be easily obtained from well rotted fruit.
The tree is normally found along rivers in the lowveld. It shows medium growth rate and while very resistant to drought is sensitive to frost, and is best planted at the lower altitudes.
LONCHOCARPUS CAPASSA
(E) Rain tree, Lilac tree
(S) Mupandapanda
(N) ipanda
A medium-sized deciduous tree 10 to 15 m tall with grey-green foliage and a heavily rounded crown. Fragrant, lilac purple flowers are produced in showy sprays from September to November. The fruit is flat and creamy coloured, usually contains one seed, and ripens the following June to August after flowering.
It is called the rain tree because drops of water often, in quite large amounts, fall from the tree just before the rains commence. This is caused by an insect called the froghopper (Ptyelus grossus) which feeds on the sap of the tree.
It is common in Savannah woodlands at low to medium altitudes and is fast growing.
PELTOPHORUM AFRICANUM
(E) Rhodesian Wattle
(S) Muzeze
(N) Umsehla
A shapely, medium-sized tree about 10 m tall, very striking when in flower. The lemon-yellow flowers are borne in erect sprays 7 to 15 cm long from September to January, and the broad, flat pods appear from February to May and persist on the tree through the winter.
Peltophorum grows in the low to medium rainfall areas and is medium to fast growing, hardy to drought, but will not stand a great deal of frost.
SCHOTIA BRACHYPETALA
(E) Rhodesian Walnut, Fuchsia Tree
(S) Mutondochuru
An exceedingly handsome, semi-deciduous, medium-sized tree about 10 m tall forming a dense rounded, spreading head and bearing attractive showy crimson flowers about 2 cms in length. The flowers, which appear in September or October, are so well supplied with nectar that it sometimes drips from them attracting sunbirds, bees and other birds and insects.
The fruit is a broad, flat, woody pod, light green when young, becoming dark brown with age and ripening about April/May. The pods contain hard yellowish-brown seeds.
The Fuchsia tree is widely distributed and often found in savannah woodland on termite mounds. It is a most desirable tree for ornament and shade. Showy, medium growth but flowering well only in hot, dry, sunny situations where frost is not severe.
If difficulty is experienced in germinating the seeds they can be treated with near boiling water and left to soak before sowing. The tree can also be grown from truncheons.
SCLEROCARYA CAFFRA
(E) Marula
(S) Mapfura
(N) Umganu
A handsome, medium-sized deciduous tree 12 to 15 m tall, generally with a fairly straight, clean trunk and a rounded, dark bluish-green crown. The flowers are small, borne in spikes 4 to 9 cm long and dark red in colour appearing from September to November.
The tree is best known for its oval, plum-sized fruits, pale yellow when ripe which have a tough skin and juicy white flesh, enveloping a large, hard stone. Each stone contains two or three seeds, and the fruits appear in November and ripen the following April/June.
Both the foliage and fruits of the tree are relished by game and stock. Marula is widely distributed in the lowveld. It shows a medium growth rate and is drought resistant but a little tender to frost when young. Trees may also be easily raised from truncheons.
TRICH1LIA EMETICA
(E) Natal Mahogany
(S) Muchichiri
(N) Mutsikini
A luxuriant large evergreen tree 15 m and more tall, having a short erect bole and a wide-spreading, rounded, exceedingly dark green crown which casts a particularly deep shade.
Small, creamy white scented flowers are produced from August to October. The fruit, which ripens about March, is a capsule 2 to 4 cm long splitting open to reveal three to six highly attractive black seeds each of which is largely enveloped in a shiny scarlet aril.
Trichilia prefers the deep fertile soil along our lowveld rivers and shows medium to fast growth in well watered areas but it can stand little frost or drought. The seed must be sown when fresh. An exceptionally fine shade tree.
5. KRAAL WOODLOTS
The interesting shortage of wood for all
purposes in many of the
Tribal Trust Lands has been a serious
matter for a number of years. The position is very variable, ranging
from the few areas which can still obtain their entire requirements
from natural woodland to those where it has become commonplace to
burn dung as fuel in the absence of any sufficiently cheap
alternative. In many areas the most practicable solution is to plant
trees specifically to provide for fuel and pole needs. These can be
in large blocks established by Councils or smaller communal
plantations established by a family unit or a kraal unit. The
latter, are almost certainly the most important means of providing
for wood needs in the future and are here termed "kraal woodlots".
History and Attitudes
In much
of Africa, and indeed over most of the world at one time or another, natural
woodland has been the age old source of building materials, firewood, tools and
simple furniture. Almost as important perhaps, it provided a wide variety of
plant medicines and food supplies, particularly important in times of crop
failure, such as fruits, edible roots and honey.
The cutting down of trees
and the late firing of woodland were however, inevitable processes in making
available crop land and grazing land. In earlier times with far fewer people the
practice of shifting cultivation was reasonably sound agriculture in Savannah woodland regions. The trees were felled and crops planted and harvested for two
or three years, and then the clearing abandoned. When there were very few people
it was not necessary to use this piece of land again for crops until perhaps
thirty or forty years had passed, by which time the woodland had grown up again
and the soils had fully recovered their fertility. As population and food needs
grew, this very long "bush fallow" period was not possible. The practice
continued, however, so that the woodland never had time to recover before it was
again cut back for crops.
This stage marked the
beginning of the progressive and often heedless destruction of natural woodland.
As in the earliest days of industry in Europe, where whole forests were cut to
provide charcoal for smelting iron, the pioneering mining industry in Rhodesia
also consumed large areas of woodland. Much of this clearing was an essential
part of the increasing agricultural and industrial requirements of a growing
country. Nevertheless, it was carried out with little thought for setting aside
and protecting areas for future needs. It was the familiar story of the resource
thought to be so vast that it was inexhaustible. The woodland had been part of
the scenery for centuries and no one could quite believe it could disappear and
with it the firewood, poles and other useful things which I had always been
free.
It was true too, that the
woodland was an enemy as well as a friend since it harboured wild animals
dangerous to man and damaging to his crops and cattle. By the same token, fire
had always been a friend in hunting, helping to destroy woodland and in
frightening off marauding animals. Large fires (which burnt a great deal of
wood, of course) were an important part of cheerful social gatherings.
Unfortunately, the
destruction of natural woodland has progressed so far in many of the Tribal
Trust Lands that it is only in relatively few areas that there are still
possibilities for setting aside and protecting woodland for local
supplies. Properly managed, such areas could supply limited quantities of wood
products forever. In these Tribal Trust Lands the rainfall and land productivity
is generally low.
In other areas natural
woodland has already disappeared or is so scarce that it can provide only a part
of the fuel and pole requirements. These areas tend to have a higher rainfall
and are more productive areas with higher populations. Even if it were
practicable to recreate natural woodland here, the need for higher productivity
per hectare for ail crops to supply local needs dictates the establishment of
much more 4 productive plantations of exotic trees if wood needs are also to be
met locally. The only alternative to growing local crops of trees is to import |
wood or substitutes for wood into these areas from outside.
Although in many areas it
is difficult to find any natural woodland, attitudes entrenched in past
generations die hard as they do in many lands. Wood should be available to be
gathered free as a gift from nature and should not have to be planted, weeded
and protected like a food crop. And who wants to forego the traditional cheer of
a pile of logs and branches burning merrily, if some wood can still be found?
Consumption and Requirements
When there is extensive
woodland close by, wood fires for cooking, heating or social gatherings can be
large and huts rebuilt frequently; Quite a lot of wood can be wasted. When
someone has to walk a kilometre to bring back a few sticks, fires are too small
for comfort or proper cooking and huts merely get repaired when they ought to be
rebuilt. It is difficult to assess the volume of wood involved in different
levels of consumption and even more difficult to arrive at a volume which
represents a reasonable requirement for a family.
Wood requirements depend
also upon whether the house is a permanent structure, and if the family can
afford alternative fuels such as paraffin or coal.
Although calculations of
total needs in the Tribal Trust Lands and the areas needed to supply them are
subject to many errors, in the absence of a census type sampling exercise, some
indication of wood needs is useful. One reasonable estimate takes the volume of
wood needed by a family as 7,2 cubic metres of solid wood each year. This level
of consumption would mean setting aside 44 per cent, oi the total Tribal Trust
Land area under natural woodland, or 3,2 per cent, under gum plantations.
Forty-four per cent, is
obviously an impracticable proportion of all land to use for wood production,
except in extremely thinly populated areas. The total Tribal Trust Land
population in 1924 would have only required 9 per cent, of the total Tribal
Trust Land area in natural woodland which might perhaps have been considered at
that time a practicable proportion. On these figures the population in most
areas has now far outstripped the practicability of using natural woodland for
all fuel and pole needs. It just is not productive enough and too great an area
would be needed.
Gum plantations on the
other hand, produce fourteen to twenty times the volume of wood per annum, and
can be considered as part of an intensive farm economy. If all the wood needs of
a family on the above scale were met from a gum plantation rather less than one
hectare per family would be required, and this would be reduced to about half a
hectare in high rainfall areas.
Countries and people
change although the process is often slow. It has been assumed above that total
wood needs would relate to the building of traditional pole and dagga huts, not
permanent houses, and that all wood needs would have to be provided within the
area and not imported from outside. Where the local economy permits, however,
permanent houses which do not require frequent replacement of wood poles are
constructed and paraffin or coal are used to a limited extent for cooking and
heating. These changes, reducing the demand for local wood, will become more
widespread and become part of an accepted way of life as development progresses.
So far they affect only a proportion of the people however and although they
help the wood shortage position they are not taking place nearly fast enough to
solve the problem before very real hardship sets in.
Kraal Woodlots
Reservation of natural
indigenous woodland can only provide the answer in a few areas and bringing wood
or wood substitutes from outside means expense which very many families cannot
meet. While these aspects should not be overlooked, and there are possibilities
such as charcoal or perhaps fuel briquettes from sawdust, by far the most
important method of solving or alleviating the problem is to plant trees.
Even if only part of a
kraal or family unit's needs are provided for in this way, the worst shortages
will be avoided and present or future local expenditure on fuel or poles
reduced. Kraal woodlots can also serve a very useful purpose as windbreaks for
kraals or crops, as shade, and often as a source of honey. These additional
features are by no means unimportant particularly in areas now devoid of almost
any natural vegetation.
Farming in the Tribal
Trust Lands will always have a place for farm or kraal woodlots, not necessarily
supplying the whole of local needs but a substantial part of them. Awkward
corners unsuitable for arable cropping can be utilized for trees, and
individuals with a bent for growing trees may well grow for sale to their
neighbours. Woodlots must therefore be considered in agricultural training and
practice as much a part of the farming pattern as maize, tobacco or grazing.
Despite efforts over a
long period of years the numbers of council plantations or kraal woodlots in the
Tribal Trust Lands are woefully small and provide no more than a very small
fraction of the overall needs, even though they are locally most important where
they exist. The reasons are many; the attitude that wood is traditionally
gathered free, reluctance to embark on the hard work and sometimes expense
involved in growing wood that is to be harvested in six or eight years' time
when some natural woodland is still available, difficulties in setting aside
land suitable for trees when it is often also suitable for arable crops, lack of
experience and consequent failure to get trees established.
The Young Farmers Clubs
(Youth for Conservation Movement) started a campaign in 1974 to alleviate the
shortage by encouraging all its members to become involved in tree planting
throughout the Tribal Trust Lands. Over
3 000 primary
schools nave been approached and supplied with seed of various eucalypts (gum
trees). Ten per cent, of the trees raised are to be planted at the schools and
the remainder taken home in their containers by pupils to be used in the
establishment of kraal wood-lots. The decision to adopt 1975 as the YEAR OF THE
TREE arose from this campaign and the initiative of the Y.F.C. Movement. It is
stressed that this is only the start of a series of annual campaigns which will
continue for several years beyond 1975.
There is
insufficient space to include here technical details of sites tree
species and nursery work related to the planting and management of
kraal woodlots. This information is available in other publications
from the Rhodesia Forestry Commission and the Young Farmers Clubs.
6. INDIGENOUS WOODLAND ON THE FARM
Most Rhodesians' farms
have areas of indigenous woodland. If any do not, then somebody has spent a lot
of money and energy in digging the trees out in order, as it is claimed "to
improve the grazing". Unfortunately if the job is not done thoroughly, the
opposite result is achieved. If you want more grass on your farm, then
undeniably the trees must come out. But not all of them. It is possible, by
proper practices, to achieve a balance between woodlands and grassland on your
farm, to the benefit of both communities.
Some farmers, having
planned their farm, or had it planned for them, stump the arable land, fence the
paddocks and leave the bush or woodland areas to look after themselves,
regarding them as areas where cattle may get some browse and grazing, at best.
Such treatment, or rather lack of treatment will only result in deterioration of
these areas.
A prudent farmer will
follow the advice of President Coolidge, who said "... our farmers, all our
citizens, must learn to treat our forests as a crop, to be used but also to be
renewed. We must learn to tend our woodlands as carefully as we tend our farms."
In other words, do not let your indigenous woodlands go to waste as a no-man's
land. Take a good look at your woodland, separate the "trees" from the "bush"
select an area, and set it aside for management, with the aim to produce wood
for your farm requirements and possibly for sale to your less fortunate
neighbours.
A farmer might well ask
why he should need to grow wood. One answer would be the current cost of
firewood, delivered. His bill for buying firewood for compound fuel, for tobacco
curing, for boilers, kitchens and dairies would be enormous. In addition he
requires poles for compound houses, for roofs of sheds and barns, for
scaffolding, for cattle kraals and dips, for poultry runs and for every kind of
temporary shelter.
Having selected an area,
or areas, of woodland the first thing to do is to mark out the boundaries. Put a
fence around the area, if you can afford to, or a clean scoffled trace at least
five metres wide. This boundary lets your labour know just where your managed
woodland is, so that they have no excuse for indiscriminate cutting. It also
serves as a firebreak, if not to stop fire, it will be a base from which to bum
back in the case of a fire.
Make it a special job for
one of your labourers to look after your area of woodland, give him authority to
keep people out and make him report weekly on the work that you Want carried out
in that woodland, or on the occurrence -of poachers, fires—anything that will
give him a feeling of personal responsibility for that area of woodland.
Now, it takes the
indigenous bush, on the average, about forty years to produce trees worth
felling from the seedling stage. Therefore, to manage your woodland on what is
called a "sustained yield" basis you must divide the area up into 40
approximately equal blocks. Cut in each section for one year only, so that by
the time you have worked right through the whole woodland, the first section is
ready for cutting again.
If you want only firewood
from your woodland, the routine is easy. Fell everything, even the big trees.
Fell the trees at ground level and trim the stumps. All branch wood and slash
that is too small for firewood should be dragged into heaps or lines and burnt
off carefully. A few months after felling the stumps will throw up new shoots,
or coppice. In addition many species will
send up shoots from underground roots, especially if the ground between the
stumps is heavily disturbed. The new shoots will be your future timber crop.
It is possible to improve
the second crop of timber by carefully selecting one or two poles per stump
which are straight and vigorous, when they are big enough for you to make a
choice. Cut off the remaining shoots — you may have to do this for several
years, as the coppicing power of some indigenous species is phenomenal. To
assist the growth of new coppice or root suckers, keep the grass in your
woodland down. This can be done by controlled grazing. A certain amount of
damage will be done to the tree shoots by browsing, but the cattle will do more
good by grazing and trampling down the grass. If your woodland is thorn-bush,
then heavy grazing positively encourages bush growth and will eliminate most
grass.
Grass can also be
controlled by early burning in the woodland area. Before the grass gets really
dry, between April and early June, patches of grass are deliberately burnt off
throughout the area. The heat from this patch burning is not severe enough to
damage the young trees. The numerous burnt patches arrest any grass fires that
may get into the area later in the dry season. It may take several years before
the effect of early burning shows in the increase in the number of young tree
shoots in the area. Do not annually late burn the area or eventually the reverse
effect will be achieved and the woody vegetation may disappear and be replaced
by grass.
Managing your woodland
area to produce poles is somewhat more difficult than managing it for firewood
only. It means that the labour has to be disciplined to refrain from cutting
useful species and to learn that the cutting of straight, healthy young saplings
which will make a reasonable pole in a few years' time is "taboo". The man in
charge of the woodland will have to be shown how to mark for an "improvement
felling" which means leaving all the good, young trees to grow up to the best
sizes. Reduction of coppice resulting from the felling must be carried out to
keep the woodland in an improved condition. Branch wood and slash must be burnt
or removed and early burning carried out to improve growth and regeneration, as
in the case for firewood areas.
A third management
objective is the improvement of both tree and grass cover in the woodland area.
This involves a careful selection of healthy, preferably useful trees at a
spacing so that there is no touching or overlapping of their canopies. It is
virtually impossile to lay down how many trees per hectare should be retained.
That depends on the species and sizes of trees and the existing grass cover,
type Of soil, etc. The number may vary from four or five to as many as forty. A
range of ages should be included, from seedling to mature trees. The unselected
trees should be removed by stumping or by ring barking and felling when dead.
The latter method is cheaper and. is effective if done properly, but of course,
the effect may not be achieved for several years, whereas stumping produces a
virtually immediate effect. The shrub layer in the woodland should be reduced to
a few browse species if not completely eliminated. It may be advantageous to put
a burn through the area in the dormant season, after it has been opened up to
your satisfaction, to remove accumulated dead grass and herbaceous weeds and
give the fresh grass a good start under the reduced cover of the tree canopy.
The result to aim at in this type of management is what may be called a
park-like effect, a scattering of fairly evenly spaced trees with a well
distributed age class gradation, below which is relatively good grass cover
which can be grazed by cattle, which at the same time are afforded shade by the
trees. It is possible to exploit the improved woodland, if it is sufficiently
dense, removing the occasional straight, young trees for poles and the older
trees, as they become moribund, for firewood. If the area is not grazed, an
occasional controlled, light burn will benefit the grass without too much damage
to the trees.
Indigenous woodland can be
brought into the farm plan as windbreaks between arable lands or pasture. To
compensate to some extent for the relatively low height of indigenous woodland,
the windbreaks should be at least 30 metres in width. Indigenous windbreaks have
less edge effect than gums on crops and they give definition to paddocks. They
should be protected and managed for poles, firewood, etc., as described above.
Apart from management for
the production of timber, poles and firewood or for windbreaks, indigenous
woodland on your farm should be preserved for its aesthetic value; its
conservation value, i.e. control of surface water run-off during rains and
general stability of the soil; for the browse and fodder it may contain; and
last, but not least, for its value as a sanctuary for animal and bird life,
which in itself is a valuable asset to your farm.
When selecting trees for
retention for one or other of the purposes outlined above, a knowledge of the
useful qualities of the various indigenous species is important. A short list of
the more common indigenous trees likely to be found on your farm with their
uses, is given on the next page.
7 FIRE, TREES AND FORESTRY
Man and Fire
Before man appeared on the world scene fires only
occurred through infrequent and widely scattered natural events such as volcanic
eruptions or most commonly lightning. It seems most likely that man started to
use fire about 50 000 years ago.
Man, probably didn't get sufficiently numerous, however,
for his fires to seriously affect forests and woodland until less than ten
thousand years ago. By then he was using fire in hunting to drive game, and soon
began to use fire to destroy woodland and replace it by grazing or primitive
agriculture. Fire was used to drive away dangerous animals and for cooking and
warmth.
If it were not for man most of the land surface of the
earth, except for the polar regions, tundra and some deserts, would still be
covered with forests, as true natural grasslands only occur to a limited extent.
That means that most of the grasslands of to-day used to carry forest, and the
main agent which originally caused the change from forest to grassland and still
maintains the grassland to-day is—FIRE.
Africa was no exception and the journals of early
explorers, missionaries and hunters abound with references to fire. The log
books of Bartholomew Diaz and Vasco de Gama reported fires along the Cape coast
in the 15th century. Much later, in 1866 Livingstone described the burning of
trees and grass in Nyasaland in preparation for the growing of crops, and the
burning off every year of the tall grasses on the flood plains of the lower
Zambezi. Selous described June and July annual burning in Mashonaland in 1883.
Where the original forests were composed of trees very
susceptible to fire like the mahoganies and other trees of Chirinda Forest near
Chipinga die entire forest was quickly and completely destroyed by fire. Today
we only have a few tiny relics of these rare evergreen forests which have only
survived because they were especially wet areas or protected in kloofs. Even so
they are very much in danger from fire >and cutting.
Over vast areas of tropical Africa, north and south of
the Equator, the result of centuries of firing has not been the complete
destruction of all trees however. In most areas the original closed types of
forest with litde or no grass have been replaced by an open type of woodland
with grass between the trees. This is usually called savannah woodland, and it
is the usual type of woodland seen in Rhodesia. Many trees in the savannah
woodland have a substantial resistance to fire and so persist where the
evergreen forest trees would quickly be killed outright.
The development gf man, however, is also the history of
disturbance and change in natural vegetation. Farming crops or livestock must
mean changing and managing the vegetation, and even forestry management of
indigenous woodland certainly does not mean just keeping things as they are.
Unfortunately, especially in Southern Africa, there has
been a conflict in the use of fire between the forester and the grazier. Fire
can be used as a tool either to promote grass for grazing and kill trees and
shrubs, or as a tool to assist in preserving and managing woodland, as will be
described below. What was unfortunate is that the grazier and forester sometimes
tried to apply their different fire methods to the same areas of land and so
often came into bitter dispute. This wouldn't have been necessary if it had been
possible to agree which pieces of land ought
to have been grazing land and which forest or woodland.
Trees and Fire
Some trees, such as Mukwa
(Pterocarpus angolensis) the valuable savannah
woodland timber tree, are very resistant to fire and are adapted to an
environment in which quite regular and often fierce fires occur. When it is a
very young seedling Mukwa concentrates, not upon growth of leaves and shoots,
but upon developing a large carrot-like tap root which is a food reserve. The
above ground leaves may be regularly burnt off year after year but the tap root
gets bigger and bigger until the tree has enough reserves to rapidly put up a
shoot which gets above the main grass fire level. The older tree has a thick
bark which often blackens and slightly chars but which insulates and protects
the living wood inside the tree. The lucky bean tree (Erythrina)
and cabbage tree
('Cussonia) likewise have thick oark which protects
the older trees from fire to a substantial extent.
Other trees, in particular the trees of evergreen forest,
have bark which is thin, burns easily or does not give the required insulation
against fire i.e. Red Mahogany
(Khaya) or Black Bark
(Diospyros abyssinica). Most of the exotic plantation
species also have little or no resistance to fire, although resistance varies.
The major pine species, in plantations
Pinus patula, is thin barked and very susceptible but
Slash pine ([Pinus
elliottii) has a thick bark and considerable capacity
for recovery after light fires.
Although some trees, have a remarkable resistance to
fire, even they are often damaged. Fire causes scars which heal over but leave
defects in the timber, or the leading shoots are burnt so that the shape of the
tree is changed and straight logs are more difficult to find. Except for the
most resistant kinds of tree like Mukwa fire easily kills seedlings especially
after they have started to flush.
FIRE AND SAVANNAH WOODLAND
The optimum way to manage most indigenous savannah
woodland therefore is to exclude fire. This is an expensive undertaking, and
more often such wcodland is managed by a technique known as "controlled early
burning" by which' is meant burning off the grass as early as possible in the
dry season so that a light fire results at a time when tree seedlings and
suckers are not flushing. The object is to prevent dry grass accumulating and
burning late in the dry season to give a fierce not fire taking place at the
time when flushing has begun, thus killing tree seedlings.
The operation of early burning sounds easier than it is
in practice. The grasses dry out at different times in different areas due to
species differences or ground moisture. If the operation is done well only
fairly small areas burn at one time which means arduous walking over large areas
to burn remaining areas. Heavy frosts can crisp and dry all the grass in an area
almost overnight so that it is difficult to avoid an extensive burn.
Often the woodland is mostly burnt round the perimeter
and along paths or tracks and un-burnt grass remains in the interior (patch
burning).
The danger with complete protection however, unless one
has fire spotting and fire fighting staff and good access, is that the area may
well be successfully protected for 3 or 4 years and then be accidentally burnt
in a late fire. These fires have 3 or 4 yeas
accumulation of
dry grass to feed upon, so they are much
fiercer than an annual late burn and are much more difficult to stop. Older
trees are damaged and seedlings and small trees destroyed.
Complete protection
of savannah woodland coupled
with wet season grazing offers an interesting method
of annually removing the grass
over at least a proportion
of the woodland area and thus
very much reducing the risk of fires in the dry. A limitation is placed on this
system by the amount of dry season grazing available to sustain the cattle
population. This method, which gives a beef yield as well as a timber yield, is
successfully employed by the Forestry Commission in the Rhodesian Teak forests
of Matabeleland.
Grass and fire
Since we have talked about the different way in which
fire is used by the grazier as opposed to the forester, a very brief note is
given here in explanation of the use of fire to improve and maintain grazing
land.
In fact it is fairly easy to see what is wanted on land
already carrying trees or shrub growth which is required for grazing. This is to
kill off and discourage woody growth and encourage greater grass growth in its
place. Thus fierce late burns every three or four years are generally used. The
best results are obtained from fires as late as possible in the dormant season
for the grasses but before they begin to grow, so that a good fire can be
obtained without damage to the living parts of the grass plants.
Such burns have other purposes such as the removal of
unpalatable dead grass left over from previous .seasons, and the destruction of
parasites such as ticks which carry and transmit stock diseases. In open
grassland where there is no longer much tendency for woody plants to encroach,
the main reason for burning will be to remove accumulated inedible growth rather
than the suppression of trees and bush.
FIRE AND TIMBER PLANTATIONS
As we have seen the trees used for plantations in
Rhodesia (and in South and Central Africa generally) and the trees in natural
evergreen forest are mostly very susceptible to fire and fierce fires will kill
trees of almost any age. Plantations and evergreen forest MUST therefore be
completely protected from fire. Fire however is very often used as a tool to
burn off and remove inflammable vegetation from firebreaks or fireguards which
help to halt the spread of fires and provide lines from which fires can be
fought.
Fire hazard
Hazard is a term which refers to the quantity and
inflammability of any fuel. In young plantations the hazard is the grass which
persists under the trees until they close up and shade it out This grass
obviously becomes inflammable in the dry season and varies in quantity. In pine
crops the pruning of the lower branches, which are then left on the ground and
dry out, provides a different sort of hazard with more fuel involved. Thinnings
and fellings of plantations in which only the stems of the felled trees are
extracted provides an even larger volume of fuel on the ground from branch wood
and the tops of trees.
The inflammability of these materials will vary depending
upon how dry they are and this in turn will depend upon air temperature and
humidity
and upon wind strengths.
Pruning's and branch-wood do rot away
but this may take some years.
The degree of fire hazard will determine how easily a
fire can start and how fierce it will be, but every fire has to have a cause.
This may be natural, such as lightning, but is far more usually due to people
throwing down lighted matches or cigarettes, not making absolutely sure that
camp fires are extinguished or perhaps children hunting mice. Unfortunately
another main cause of fires is losing control of the fire when burning off
fireguards.
Fire prevention
Fire prevention measures are concerned with stopping
fires starting or with limiting the spread of fires once they have started.
Since the main causes of fire are people, education and propaganda is directed
at those who use the plantations for recreation. Attention must also be paid to
improving the training and methods of those whose job it is to burn off
fireguards. If the hazard is very high the public may have to be excluded from
plantation areas, and legal provisions exist to do this for Government forests
and protected private forests.
Fireguards or firebreaks are strips of land kept clear of
inflammable material during the dry season. The making of fireguards to stop all
fires is impracticable. They will however, stop some fires and slow down others
so that they are easier to fight. Fireguards are first needed on the boundaries
of the plantation or the common boundary with adjoining property. The minimum
legal width of fireguards on common property boundaries is 18 metres or 9 metres
on either side. In many cases this is not sufficient and the Forestry Commission
for instance have a minimum boundary fireguard width of 50 metres for pine
plantation areas.
It is necessary also to have a number of internal breaks
if the plantation area is large. The Forestry Commission use 50 metre wide
breaks to divide pine plantations up into blocks of a maximum size of 800
hectares. Other internal breaks are formed by roads and scoffled lines depending
upon the hazard in the area.
Fireguards are often sited on ridges or along un-plantable
vleis and as far as possible are placed at right angles to the prevailing wind
direction during the dry season. They are most usually cleared by burning off
the vegetation between ploughed or hoed lines on either side of the break.
Fire Fighting
ANY FIRE CAN 'BE PUT OUT BY ONE MAN IF HE GETS THERE SOON
ENOUGH. This should be the number one maxim for all those concerned with
complete protection of any vegetation from fire! The emphasis therefore is
placed upon getting fire fighting teams to the fire as quickly as possible.
This means that the reporting of the fire must be fast
and accurate, that access through the area-is good and suitable for fast travel,
and that men, vehicles and equipment are ready to leave for the fire as soon as
it is reported.
In plantations and also in the Rhodesian Teak forests
fires are spotted from fire-towers or high lookout points and the information
telephoned or radioed direct from the tower to a central control point.
Plantation areas are generally well roaded to allow reasonably fast vehicle
access to points at or near possible fires.
Men with beaters (usually made from old conveyor belting
securely attached to a 1,5 m stick) are the first line of fire fighters. They
must have reasonable clothing and footwear if they are to tackle fires. Hoes and
rakes are also used.
Water is sprayed on to burning vegetation from knapsack
sprayers carried by labourers and replenished from tractor towed water bowsers.
Pumps delivering a fog or mist of water are also used. Small dams or underground
tanks serve to store water at convenient points inside the plantations.
Actual fire fighting operations and techniques cannot be
discussed in detail here. One important method is to "back burn" from a
fireguard or a prepared line so as to remove the fuel in the path of the fire.
This method can easily cause a worse fire in inexperienced hands however.
Training of staff at all levels is very important.
FIRE IS A GOOD SERVANT BUT A BAD MASTER
This saying applies equally to all uses of fire in
relation to the management of land whether it is early burning to favour
Savannah woodland, complete protection for plantations or evergreen forest or
late burning every three or four years to improve and maintain good grazing.
It means that trouble comes when the user does not
understand exactly what he is trying to achieve by burning, or when he under-esti-mates
how easily a fire can get out of control
In 1969 the Natural Resources Board estimated that the
area burnt by uncontrolled fires in some seasons is over two and a half million
hectares. The immense size of this area can be grasped by picturing a burnt out
belt 65 kilometres wide extending from Bulawayo to Salisbury.
Indiscriminate casual burning coupled with over-grazing
has produced large areas of bush encroachment in Rhodesia. The fires responsible
were neither controlled early burns to favour woodland nor controlled late burns
to favour grass. Thus these desolate areas have neither much useful wood nor
grass but are in a degraded state consisting of scrub-growth often with bare
soil in between.
The Law
The Forest Act (1949), taken together with the Forest
Amendment Act of 1965, contains far reaching provisions concerning fireguards,
notification of the intention to burn, and the lighting and extinguishing of
fires. The most important provisions of the Act are briefly given below, but
reference should be made to the complete legislation for the full details.
Owners or occupiers who want to protect their land from
outside fires can call upon their neighbours to assist in the making of
fireguards on their common boundary. These fireguards may not be less than 9
wide on each, side of the boundary.
No one may burn standing or growing vegetation without
giving proper notice to his neighbours, unless he has made a prior agreement in
writing with them. In either case he must inform the nearest police station of
his intention to burn.
Any person oh someone else's land shall carefully
extinguish any fire lit or used by him before he leaves the area.
Any person acting in good faith may enter upon any land
for the purpose of extinguishing a fire that may become dangerous to life or
property. Any such person or any owner may call upon anyone else present to
provide reasonable help in putting out such a fire.
The maximum penalties provided under the Forest Act show
quite clearly the determination of the Government lo halt indiscriminate and
careless burning. The major penalties are shown below.
For intentionally starting a fire on State or private
forest—$4 000 fine or 10 years imprisonment or both.
For leaving unattended a fire on open land—$800 fine, or
2 years imprisonment or both. (This is irrespective of whether it causes a veld
fire or not).
For starting a fire in other cases—$400 fine, or 1 year's
imprisonment or both. For refusing to obey a reasonable request to help
extinguish a fire, $40 fine or 3 months' imprisonment.
For smoking, striking matches or throwing down burning
material where smoking is prohibited by notice $100 fine or 6 months'
imprisonment or both.
Any land owner or occupier of land who fails to
extinguish a dangerous fire—$40 fine or 3 months' imprisonment
8. THE FOREST AND TIMBER INDUSTRY OF RHODESIA
To most Rhodesians, forestry conjures up thoughts of the
crisp tang of the pine forests through which they walked or drove on their last
holiday visit to the Eastern Districts. Timber is epitomised in the new knotty
pine ceiling or the Mukwa dining room suite, bought with the last bonus.
What is not always appreciated, however, is that the
forestry and timber industry in Rhodesia is one of the country's industrial
giants, worth in the region of $50 million. It employs approximately seven
thousand workers throughout the country, although the majority of these are
located in the Eastern Districts. In the form of salaries and wages, the
industry contributes more than $6 million per annum to the economy of Umtali
alone, and on a countrywide basis, this probably exceeds S10 million per annum.
The timber industry really began in 1908 with the
exploitation of Rhodesia's indigenous hardwood forests in Western Matabeleland.
Today 100000 tonnes of Rhodesian teak, mahogany and Mukwa logs are extracted
annually from these woodlands to make railway sleepers, parquet flooring and
furniture. It was early realized, however, that the slow growing indigenous
trees, taking one hundred and fifty years or more to reach maturity, were not
adequate to supply all the timber needs of a growing Rhodesia, and the
introduction of fast-growing exotic (foreign) species begun in the early 1900's,
resulted in sizeable areas of eucalypts being planted on farms for poles and
fuel. By 1923 about 1 200 hectares had been planted by farmers. In that year the
Forest Division of the Department of Agriculture, itself only three years old,
commenced commercial plantings of eucalypts at Mtao Forest near Umvuma. Large
scale plantings of pines was pioneered by the Forestry Division (later to become
the Rhodesia Forestry Commission) at Stapleford Forest in the Eastern Highlands
in 1926. In the 1930's and 1940's plantings continued on a variable scale, and
black wattle was introduced in the Eastern districts.
By 1950, the total area of plantations was about 25 000
hectares most of which, however, was in plantings of eucalypts of very varying
productivity. More significant for the future of the industry was the 4 000
hectares of softwood plantations already established by the Forestry Commission
by this date, and the fact that private enterprise had already commenced large
scale plantings both of pines and wattle.
The decade 1950 to 1960 was the period of major expansion
for Rhodesia's plantations which totalled some 83 000 hectares by the end of the
decade (37 000 hectares of pines, 28 000 hectares of wattle and 18 000 hectares
of eucalypts)—more than four times the area in 1950.
In the last 14 years the softwood area has increased by
57 per cent, to some 58 000 hectares. The area under eucalypts has also
increased substantially, but the area under wattle, originally planted for its
bark (used in tanning leather), decreased owing to a slump in the price for this
product, and wattle plantations have been converted to softwood plantations or
to agriculture. Approximately two thirds of the softwood plantation area is
owned by private enterprise and the remaining one third owned by the State
through the Forestry Commission.
The main softwood plantation species are
Pinus patula whose home is in Mexico, and
Pinus elliotti (slash pine) and
Pinue taeda (loblolly
pine) both of which are indigenous to the southern
United States. The wood is used for building construction, box and case
manufacture, particle board and for mechanical pulp. By far the largest area
under plantations is Patula pine which is highly productive over a wide range of
soil conditions. Rhodesia now produces over 90 per cent, of its own softwood
requirements.
Although about one hundred species of eucalypt have been
introduced into Rhodesia on a trial basis probably only about twelve have shown
commercial possibilities. Of these "Saligna" gum shows great versatility in its
uses as well as being the species most tolerant of a variety of soils and
climates in Rhodesia. Saligna is used in the round for power transmission poles,
fencing posts and mining timber, and as sawn timber for boxes, crates, pallets
and to a small extent furniture. It also plays an important role as the raw
material for the chemical pulp industry. "Saligna" gum is the name commonly used
for Eucalyptus grandis
which is now the more correct name according to the botanists.
Wattle, as previously explained, was originally planted
for its bark which yields an extract used for tanning leather. After removal of
bark, however, the timber is used for creosoted fence posts, and can provide
attractive parquet.
Small areas of poplar (Populus
deltoides) have been planted for the match industry.
This tree grows rapidly when planted on the right sites, which, however, are of
limited occurence. The logs are peeled and cut into match splints, a specialized
use which requires particular properties from the timber.
The Timber Industry
The present day size of the timber industry is shown in
the following table, which gives the intake of logs in thousands of metric
tonnes which would be needed by various sectors of the industry if all their
wood raw material was in this form. The table excludes roundwood used for poles
and wood fuel.
Sawmilling............803 000 tonnes
Mechanical pulp..........44 000 tonnes
Chemical pulp..........260 000 tonnes
Particle Board..........34 000 tonnes
TOTAL: 1 141 000 tonnes
By the year 2 000, it is estimated that the country will need the following tonnages of logs:—
Sawmilling............853 000 tonnes
Mechanical pulp . 475 000 tonnes
Chemical pulp..........1 680 000 tonnes
Particle board 144 000 tonnes
TOTAL: 3 152 000 tonnes
This total is nearly three times the 1974 log intake. The
industry, already large, has therefore a tremendous future but it will take
skilled long-tetn planning and co-ordination if it is to achieve its full
potential.
In order to form a clear picture of the industry it is
necessary to follow the movement of round logs from the grower through to the
end products.
Firstly a considerable amount of wood is directly used in
its round form as power transmission poles, telephone poles and fence posts. The
wood used is usually gum and wattle treated under pressure with preservatives of
which the most common is creosote. Indigenous and gum roundwood is also used in
the mining industry for roof supports in underground workings.
The largest primary converter* of roundwood are the
sawmills who consume mainly the larger sawlogs. Pine logs are sawn into boards
of suitable sizes for direct use in the building industry, or smaller sized
boards may be built up in to larger, more useful sizes, by jointing and glueing
techniques to produce what is known as finger jointed and laminated timber.
Small size logs of pine and gum are sawn into small boards which are used to
make cases. Such containers, made both from sawn wood and plywood are used by
the tobacco, tea, beverage and citrus industries.
Indigenous logs are sawn into boards for the furniture
industry, parquet flooring and railway sleepers.
A proportion of indigenous, eucalypt and pine logs are
peeled to produce thin veneers which are made up into plywood used for doors,
furniture and boxes. The best quality indigenous logs are peeled to produce
attractive face veneers for plywood" used in the furniture industry.
Some wood, both indigenous and exotic, is chipped or
macerated and reconstituted under pressure with suitable glues to make chip
boards or partide boards which are also used extensively in the building and
furniture trades.
Finally, small pine logs are completely ground up by a
mechanical process to produce "mechanical" pulp for the paper used in newspaper
which is called newsprint. Hardwood logs, mainly eucalypts, are chipped and
cooked with chemicals to produce chemical pulp used mainly to produce cardboard
containers and paper packaging.
Tree Breeding
The work of the Research Division of the Forestry
Commission is of particular value to the timber industry especially the major
part of the Division's work which is concerned with tree improvement. This work
is similar to the plant breeding research in agricultural crops which has led to
such startling increases in crop yields in recent years. As may be imagined,
however, tree breeding takes a good deal longer than breeding work with an
agricultural crop which produces seed in one year instead of five or ten.
Tree breeding work commenced some 14 years ago and the
seed orchards of today are now producing sufficient improved seed of the three
main pine species to satisfy the existing needs of all growers in Rhodesia.
Improved seed of Pinus
patula, the main pine species, now available is
already giving a conservative 25 per cent, increase in productivity from
enhanced growth rates plus improved stem form and branch habit compared with
commercial seed supplies or seed from selected trees in local plantations.
One way of looking at this is that the same yield of
usable wood can be produced from 80 hectares of land instead of the 100 hectares
of comparable land formerly required to give this yield. This is of great
economic importance for the industry by any standards but tree breeding still
has a long way to travel so that further increased yields can certainly be
expected. These will probably be much greater for some of the other plantation
species than for Pinus
paiula. Tree breeding is not static — it is a
continuing step-wise process adjusting also to the changing timber needs of the
industry.
Organization
The Government, through the Rhodesia Forestry Commission
and the Consultative Committee for the Forest Industry, keeps in close touch
with the industry which itself is well organized in the form of associations who
represent the various branches and who serve as their mouthpiece. So we have the
Timber Growers' Association, the Lumber Millers' and Timber Processors'
Association and the Timber Trades' Association, all very active bodies.
These associations, with the Rhodesia Forestry
Commission, and major timber companies joined together in the formation of the
Timber Promotion Council of Rhodesia early in 1974. The objects of the Council
are—
(a) to encourage and promote the use of timber and timber
products.
(b) to develop and expand both internal and external
markets for Rhodesian timber and timber products.
In order to achieve these objects, the Council has
engaged the services of a full-time manager and secretary, with offices in
Salisbury. These offices also act as a Timber Information Centre where members
of the public can direct their inquiries and problems concerning timber.
The address of the Council is as follows:
Room 402, Shell House, Jameson Avenue, Salisbury.
(Telephone Salisbury 702401).
This, in a nutshell, is the forest and timber industry —
an industry of great diversity — spanning the growing of long term crops,
applied research of some complexity and a wide variety of manufacturing
processes and end uses. On the planning and growing side it needs practical
managers who are not deterred by the uncertainties of the long term future and
on the manufacturing side alertness and ingenuity in making the most profitable
use of a very versatile but demanding raw material. Research staff need to be
thoroughly competent in a number of diverse fields and at all times responsive
to the needs of the industry.
9. FORESTRY AND THE RHODESIA FORESTRY COMMISSION
The Forest Service prior to the Forestry Commission
In 1903, D. E. Hutchins of the Cape Forest Service, later
Sir David Hutchins, visited Rhodesia and prepared a report for the Rhodes
Trustees on forest policy and on trees suitable for planting in Southern
Rhodesia.
Even at this very early date Hutchins mentions "some
remarkable results in tree planting at Inyanga and Umtali on rich soils with
good rainfall." He also mentioned Saligna gum planted at Arlington near
Salisbury in 1893, ten years old and already 75 feet tall "the best planted tree
I saw in Rhodesia".
Much more important however, Hutchins made sound
proposals as to Rhodesia's future forest policy. He recommended the demarcation
and legal protection of forest reserves which were to become the future National
Forests. These Forests were to supply at home "the timber that will otherwise
have to be imported at great cost from abroad". He emphasized the need for fire
protection in indigenous forests, and plantation crops of trees, especially
trials of softwoods.
The exploitation of the Rhodesian teak forests in
north-western Matabeleland began in 1908 and in 1910 the British South Africa
Company, facing demands for timber concessions along line of rail invited James
Sim, another Cape Forest Officer, to advise. Sim expanded upon his predecessor's
proposals and recommended the establishment of a forest authority and the
appointment of a forest officer.
Unfortunately most of Hutchins and Sims excellent advice
was to go unheeded not only by the authorities of the day but for decades
afterwards, even though the country's first forest officer was appointed in
1920. He was J.. S. Henkel, previously Conservator of Forests in Natal, who
headed a new Division of Forestry which was part of the Department of
Agriculture. Despite Hutchins and Sims advice and Henkel's proposals the new
Division was not given the teeth, in the form of adequate legislation and
support, to make it work as it should have done. The lack of legislation
establishing a national forest estate and providing adequate powers over the
cutting of indigenous timber was to cause the very small Forestry Division grave
difficulties for many years. The position was not in fact resolved until 1949
when the Forest Act was passed.
Meanwhile the introduction of a large number of exotic
tree species was being actively encouraged through the establishment in 1903 of
the Government Forest Nursery at its present Highlands site in Salisbury. This
nursery supplied increasing numbers of tree seedlings of a wide range of
species. Farmers established tree plantations for poles and fuel and as
windbreaks. By 1923 private enterprise had established 1 500 hectares of
plantations — nearly all eucalypts.
Despite the deficiencies imposed upon it the Forestry
Division made remarkable progress in the interwar years. Mtao Forest near Umvuma
was acquired in 1922 and became a very valuable eucalypt plantation area and in
1929 the planting of pines began at Stapleford Forest. Much valuable work on
natural vegetation types and assessment of timber resources was carried out and
fire protection measures introduced in the Kalahari Sands woodlands. During most
of this period and indeed up until the early 1950s the Forest Service also
administered National Parks and Game Reserves including Wankie and Victoria
Falls, and were responsible for other matters relating to name find fi%| so the
small staff was more than fully stretched.
Probably the most important pro-war development was the
pioneering of pine planting at Stapleford, and the early discovery that pine
seedlings in the nursery needed to be inoculated with soil from under older pine
crops if good nursery and subsequent growth was to be assured. This was
due to the lack of certain fungi called
mycorrhiza in many of the soils. These fungi form a
permanent beneficial association with the roots of many pine trees and assist
the tree taking up nutrients from the soil.
The existence of 4 000 hectares of well established pine
up 20 years old by 1950 paved the way for the rapid post-war expansion A
softwoods plantations both by Government and private enterprise are thus now 58
000 hectares of softwood plantations of which approximately two thirds are owned
by private enterprise and one third by the Rhodesia Forestry Commission. This
excludes a substantial
area of private wattle plantations, and a steadily
increasing area of eucalypt plantations, again mostly privately owned.
In 1949 the long awaited Forest Act, which had
a gestation period of several
years, finally became law. It was now unlawful to withdraw any land from a State
Forest "except with the approval by
resolution of Parliament".
From the earliest days one factor thoroughly inimical to
sound forestry practice had been that indigenous woodland had been largely
reserved for the use of the mining industry. The new Act recognized indigenous
timber as part of the land on which it was growing and the rights to such timber
under mining law were curtailed and made subject to permits issued by a special
board. Further provisions of the Act regulated trade in timber and forest
producc, provided for the hammer marking of logs and timber so that it could be
identified, and made rules concerning the control of fire and the burning of
vegetation.
The Rhodesia Forestry Commission
The formation of a commission had been under discussion
since 1943, but it was not until April, 1954, that the Forestry Division of the
Department of Agriculture became the Rhodesia Forestry Commission under the
provisions of the Forest (Amendment) Act of 1953.
The Commission is charged with the following duties—
(a) the consideration of all questions and matters
arising out of or relating to general forest policy and the making of reports
and recommendations thereon to the Minister;
(b) the control, management and exploitation of State
forests, nature reserves, plantations and forest nurseries belonging to the
Government and such other land as may be acquired by the Government for forestry
purposes;
(c) the establishment, maintenance, improvement, renewal
and exploitation of plantations and forest nurseries;
(d) the survey of the forest resources of Rhodesia;
(e) advice and propaganda on all forestry matters;
(f) conducting research and investigation into all
matters pertaining to forestry and forest products.
and with such other duties as the Minister may from time
to time direct
The Commission has powers to borrow funds either from
Treasury or from other sources with the permission of Treasury, and to carry out
afforestation and sawmilling operations, All land managed by the
Commission remains land owned by the State however, and in carrying out its
duties it row ill lift responsible to the Minister for Lands and Natural
Resources, Under the broad charges laid on the Commission above, a distinction
is made between activities carried out as a service to the public on behalf of
Government, and trading activities, which have as their object afforestation and
the exploitation of forest produce.
In the initialing Act of 1933 the Commission consisted of
the Chief Commissioner, who was also a Forest Officer with a degree in forestry
plus the necessary experience, and two suitable private persons appointed ai
Commissioners by the Head of State. This was subsequently altered in a further
amendment to the Act to the appointment of not less than three and not more than
five private individuals as Commissioners, one of which is appointed by the Head
of State as Chief Commissioner.
The Commission is today responsible for 929 000 hectares
of demarcated forest, of which 847 000 hectares are indigenous forests in
Matabeleland containing Rhodesian teak, Rhodesian mahogany, and Mukwa. In order
to ensure that these forests do not deteriorate by being over-exploited, they
are managed on the principle of sustained yield. Thus the volume of timber
removed annually is regulated so that it does not exceed the volume put on by
the annual growth of the trees.
Multiple land use is practised in these forests where
game, cattle and forestry are integrated into an overall plan in which each
complements the other. Game viewing and limited game hunting safaris are
permitted in the forest areas as. part of the multiple land use policy.
The Commission own some 19000 hectares of pine and
eucalypt plantations, almost all in the Eastern Districts, where it operates
three sawmills with a central timber depot and finger-jointing and laminating
plant in Umtali. A pressure plant for treating poles and posts with creosote
preservative operates at the Commission's main eucalypt plantation area at Mtao
near Umvuma.
Although the Ministry of Internal Affairs is responsible
for administering matters relating to" forestry in Tribal Trust Land the
Commission is directly involved through its advisory service, in providing
forestry training to agricultural extension staff of the Ministry of Internal
Affairs, and in providing supporting services to tree planting campaigns such as
the one initiated by the Youth for Conservation Movement which was responsible
for the adoption of 1975 as the Year of the Tree. The Commission also
administers five Forest Areas in Tribal Trust Land set aside for forestry, and
supervises the exploitation of timber in large areas of forest in Tribal Trust
Land which are being felled to clear the land for African agriculture and
settlement. The exploitation of the timber from these areas and its utilization
is carried out by private enterprise, but the revenue obtained is paid to the
Ministry of Internal Affairs.
The Commission's advisory services are available to the
public on all aspects of forestry. The planting of trees on farms is encouraged
by the Commission which makes tree seedlings available to bona fide farmers at
reasonable prices, complemented by on-the-spot advice on the planting of the
trees, if this is required.
Research work has been carried out since the early days
of State forestry. In 1948 a Research Branch was formed, controlling and
coordinating all forest research. Its headquarters is in Salisbury. In 1960 the
John Meikle Forest Research Station was opened on Stapleford forest Reserve in
the Eastern Districts. The Melsetter Research Station was opened in 1962.
The Research Division serves the needs of the whole
industry both Government and private. This industry is now estimated to be worth
$50 million and to employ approximately 7 000 workers throughout the country
with a wages bill of some $10 million" a year. The Division tackles a variety of
research projects but the tree breeding programme is currently the most
important. This is already making available improved seed of the main pine
species (capable of increasing wood yields by 25 per cent.) in sufficient
quantities for the whole of the industry's present needs.
INDIGENOUS TIMBERS
by G. Shepherd
Principal of Mlezu Rural Technical Institute, Que Que
It is perhaps unfortunate that knowledge of the Rhodesian
timbers has declined since the arrival of Europeans in the country. In the short
span of 85 years we have moved from the ox-wagon to jet propulsion and in the
process have left the veld timbers far behind us.
The pioneers were forced by necessity to use our local
hardwoods for everyday repairs and simple construction work.
The African is also losing his knowledge of veld trees,
knowledge which at one time was common to every tribesman. Today the young men
go to school instead of herding cattle, and the old familiarity with the bush
has gone, perhaps forever. Only the elderly men have the names of the trees at
their fingertips, but even information from this source is not always useful.
The African assessment of a timber is always in relation to its usefulness
around the kraal. A number of our beautiful woods suitable for cabinet work are
rated poorly by the tribesman. Mukwa for instance was of relatively little value
to the village.
Recently, however, there has been renewed interest in our
wood products other than the well-known hardwoods from the Kalahari Sands.
Economic pressures may compel us to use such lowly rated but plentiful trees as
the Msasa, Mnondo and Mfuti.
With this little booklet we hope to arouse interest in
the use of our indigenous trees, some of which produce very attractive wood.
Because many of these are found widely scattered on the veld they may never
become an economic proposition but if made available they would certainly
interest the craftsman. The farmer, also, should be aware of what he has on his
land.
Generally speaking Rhodesian woods are hard and difficult
to work. In the tougher drier areas of the country the timber usually matches
the conditions. It is fairly true to say that the slower the growth the harder
the wood. This applies to trees of the same species grown under different
conditions.
The woods described and shown here are fairly typical of
the central area of the country but obviously only a small number can be dealt
with.
These timbers have all been used successfully for making
small and sometimes large items of furniture or joinery.
1. MUKWA,
Pterocarpus Angolensis
This timber is so well known that it hardly needs
describing. Indeed we take it so much for granted that some of its special
qualities are over-looked. In one authoritative British book on timber Mukwa is
described as having the lowest shrinkage rate of all hardwoods tested at an
English timber research station.
It is of course common knowledge that all woods shrink
when drying out but what is less well known is that all woods shrink more around
the log than across it. This results in the familiar appearance of a cracked log
which has dried out in the open. The diagram shows what is meant.
In the case of Mukwa the percentages of shrinkage given
by Scott, Department of Forestry. R.S.A. are:
Tangential (around the log) 2.1% and
Radially (across the log) 1.5%
Compare this with average Saligna Gum figures of 9 per
cent, and 4,5 per cent and one can see how stable Mukwa, called Kiaat in South
Africa, is.
Mukwa is so stable in fact that boards cut from a wet log
can be left leaning against a wall until dry with little or no distortion.
The tree has a yellow or dirty straw-coloured sapwood
which is not durable and a golden-brown to reddish heart which gives the
familiar "Kiaat" look.
t would appear that well-grown Mukwa from the better
forest areas is softer and
easier to work than isolated trees found growing
under harsher conditions.
Old wounds and disease give a reddish streaky appearance
to the heartwood and it is not uncommon to find an old axe cut deep inside the
trunk, complete with the red colouring around the scar.
A phone call to the nearest timber stockist will convince
you of the value of all
brown
(i.e.
heartwood) Mukwa. It could almost be held as a security against inflation.
The wood itself is of medium weight, fairly easy to work
and some people like to use the contrasting yellow sapwood with the brown
heart-wood. Insects can, however, attack the yellow sapwood, but more of this
later.
When machining dry Mukwa the dust can be a severe
irritant to the nose and throat.
This important hardwood will become scarce in the near
future and trees take a long time, perhaps more than 150 years, to mature.
The
tree itself is not scarce but like so many species appear to germinate only in
certain years. For instance, there are hundreds within the ? 1 000 hectares of
Mlezu Rural Technical Institute but only a few are over 200 mm in diameter.
2. MSUSU,
Terminalia sericea
In sandy areas where this tree grows every farmer knows
and uses Msusu or Mangwe although mostly as poles for fencing and cattle pens.
It is unfortunate that this most useful all-purpose tree is of fairly small size
with a rather short bole. The occasional large specimen occurs, however, up to
about 400 mm in diameter and between 3 and 4 metres long. Most of the larger
trees have rotten or completely hollow hearts.
The wood, known as Yellowwood in some districts, but no
relative to the South African Yellowwood, has indeed a yellow colour with a
slightly darker heart which oxidizes to a light brown. Both sapwood and
heartwood are durable but when green the sapwood can be infested with borer.
Peeling the bark just after felling appears to lessen the
risk of insect attack.
The timber is heavy and finishes well. In appearance it
is fine grained but is rather plain looking. The wood is stable, easily sawn
when green, and can be used in almost any situation where a good quality
hardwood is needed. Being rich in tannin, like oak in this respect, it stains
very badly when in contact with iron hardware. In fact the whole tree, wood and
bark, is so rich in tannin that it can all be used for tanning animal hides.
Msusu or Mangwe is very common, is a bush encroachment
species in some areas, and is unlikely ever to be scarce. Large specimens will,
however, become more difficult to find.
3. KNOB THORN,
Acacia goetzei
The true Knob Thorn is
Acacia nigrescens, but
A. goetzei, which is common around Que Que, is
described here. It grows to a great size and trees measuring over a metre in
diameter have been cut. The true Knob Thorn which has very similar timber was
formerly cut for railway sleepers and mining work.
The timber is extremely hard, heavy and difficult to
work. It is dark brown, oxidizing to reddish-brown after exposure to the air.
The narrow band of dirty yellow sapwood has no value. Because of ripples in the
grain of most of these acacias the wood is very difficult to finish by hand
methods and a sanding machine makes the work much easier. The ripple finish is
very attractive and well worth the effort.
The timber, which is very stable and free of movement,
can be used for heavy structural work, heavy joinery work and large solid type
articles of furniture. Experiments have shown that it would make excellent
parquet flooring.
Although not scarce this tree is slow growing and good
specimens should be looked after. Its extreme hardness and good germinating
abilities will ensure its survival.
4. MTSVIRI,
Combretum imberbe
If knob thorn is hard to work then Mtsviri is all but
impossible to fashion into useful woodware.
Combretum imberbe is common in the drier parts of
Rhodesia and forms the greater part of the excellent, timber fencing erected by
ranchers in the south-east of the country.
Perhaps the common name Leadwood comes from the weathered
appearance of the ends of the cut poles. They certainly have a grey leaden look.
The Afrikaans name hardekol refers to the excellent firewood obtained from this
Combretum.
The narrow yellow sapwood is readily eaten by borers but
nothing will touch the dark brown to black heartwood. The small wooden crosses
at the Tuli Fort Pioneer Cemetery appear to be made from leadwood. These were
still sound in the late sixties after over seventy years in the sun and rain.
The wood can be used for small ornaments and tables but
is really too heavy for normal furniture. Being so dense, Mtsviri takes a really
superb polish if care is taken to finish the wood properly.
Farmers cut this tree extensively for fence posts but the
really big ones are safe for the time being unless they have to be cleared for
development.
5. MUBVUMIRA,
Kirkia acuminata
Considering the availability of this tree and the beauty
of the wood it would at first seem surprising that it has not been used
commercially. The trees grow to great size under favourable conditions and are
perhaps more widespread than Mukwa. In addition, it nearly always has a well
shaped cylindrical hole.
The heartwood is one of the most attractive of all our
timbers; warm brown, well marked and not unlike walnut in some respects. The
sapwood is strong and tough but with a dull grey straw-like colour which make it
rather uninteresting.
The snags, however, are several. Perhaps the most serious
drawback is that the wood, quite soft in texture, is very hard on the cutting
edge of hand and machine tools. This is evidently caused by some mineral
deposits in the timber itself, although it has been said that trees from some
areas 4o not suffer from this fault.
Another fault is that the heartwood from medium sized
trees forms a rather small proportion of the total wood. In other words the ring
of sapwood is wide. The timber takes a very long time to dry out under normal
air drying conditions and a certain amount of end splitting occurs in the
process.
Despite the drawbacks, Mubvumira must rate as a very good
choice cabinet wood. It is of medium weight and takes a very fine polish.
6. MSESETU,
Faurea saligna
African Beech, known as Boekenhout to the old South
Africans, has been used over a long period in South Africa. Resembling European
beech to the early settlers, this timber is easy to work, quite attractive in
appearance with a larger fleck than its European namesake. The sapwood is paler
in colour, very soft in texture and quite useless.
The timber is very stable and can be used for all types
of furniture. It is not strong, in fact it is fairly brittle, and is therefore
unsuitable for structural work. A good finish can be obtained but the bright
biscuit colour oxidizes to a dark brown eventually.
The tree itself is fairly common but most of them are
small in diameter, large sawable logs being rather scarce.
Because long straight lengths are available, the timber
has possibilities for all sorts of work. Though it is moderately difficult to
work the wood takes a good finish.
Some boards develop long splints when drying and
seasoning has to be done carefully to avoid loss through this fault.
7. MARULA. Sclerocarya cafjra
Being a fruit tree the Marula would only be cut when it has to be removed for development, clearing of lands, etc. In some countries this tree is protected species
The wood is fairly light in weight and plain looking, varying from slightly pink to grey in colour. It is susceptible to staining if left lying wet
As it is fairly soft Marula is one of the few hardwoods that can be nailed The timber is very unstable, changing shape with almost every shower of rain or change in humidity.
It can be used for rough farm work and being a non splitter is used by the Africans for carving plates and other utensils.
Unless treated it is very prone to borer attack.
8 MPAK.A. Bolusanthus speciosus (Tree Wisteria)
This beautiful flowering tree is familiar to most farmers as a very durable fence pole. In the Que Que district there are fence poles in good condition still standing after forty years in the ground.
Trees of the Wisteria are nearly always of poor shape. They are often multi-stemmed and specimens large enough for cutting into boards are rare. The timber of Mpaka is exquisite, light in colour with well marked rings of darker brown.
The stems are usually of small diameter but practically the whole tree is heartwood. with only a very narrow ring of yellow sapwood of about 6 mm surrounding the heart.
Moderately heavy, the timber is stable and takes a high polish.
The Wisteria will only be cut as a rarity and can have no commercial value. The craftsman who obtains a few boards of this wood is fortunate.
9. MUZEZE, Peltophorum africanum
This showy tree which sends out its multitude of yellow flowers before Christmas is well known to most Rhodesians by sight if not by name. Stems of this tree, which is sometimes called African Wattle, are usually of small size.
The wood of the Muzeze is a useful non splitter; biscuit in colour and sometimes with dark streaks on the heart wood. It is soft but with a fine texture and finishes well. It is, however, very susceptible to blue sap stain if allowed to stand wet
Useful for small articles of furniture and ornaments the wood is sometimes used by Africans for making mortars for stamping grain.
10. MUWORA. Albizia amara
A large common tree which is rated, as the name suggests, very lowly by the Africans. Evidently the wood is not at all durable in the ground and rots very quickly when not protected.
The timber, however, is quite useful for furniture or internal work. The heartwood is reddish-brown with darker streaks, rather mixed up in appearance but attractive to some people.
The timber finishes well, but because of the interlocking grain, machine sanding is recommended. It is also fairly stable.
11. MUNYUNA. Monotes glaber (Yellow wood)
The English name is a misnomer but perhaps refers to the leaves which at certain times have a yellow appearance.
The wood of this very common tree is certainly not yellow but has an astonishing variety of colours and shades; everything from pale pink through biscuit colour to dark brown with all kinds of markings and no uniformity.
Cutting every tree into boards brings a fresh surprise.
When sawn green it has a sour, unpleasant smell and the local Africans have no real use for the wood. The timber is heavy and close grained and although it finishes well it is very hard on the cutting edges of tools. Being rather brittle it is not very suitable for structural work but makes excellent small articles of furniture.
In the Que Que district the tree is often of poor shape, sometimes leaning badly, but around the Hartley-Selous area fine specimens can be seen from the main Salisbury road.
Difficulty in working this timber could rule out this tree as a commercial proposition, but it would qualify in terms of appearance.
12. MUUNZE, Brachystegia glaucescens (Mountain Acacia)
The Mountain Acacia is very well known even to city dwellers, and is largely responsible for our beautiful hilly landscapes from Balla Balla to the Eastern Districts.
The tree itself is in no danger, occupying as it does places unsuitable for cultivation or large scale development. It does not even suffer from competition, and where it has been cut reasserts itself as the dominant species in a fairly short time.
The timber is fairly hard, the heartwood being a well marked brown. The sapwood. however, is very susceptible to borer attack and appears to be a really choice nourishment for these pests. Sapwood should be cut out of sawn timber.
13. MUTOHWE. Azanza garckeana (Snotapel)
7. MARULA. Sclerocarya cafjra
Being a fruit tree the Marula would only be cut when it has to be removed for development, clearing of lands, etc. In some countries this tree is protected species
The wood is fairly light in weight and plain looking, varying from slightly pink to grey in colour. It is susceptible to staining if left lying wet
As it is fairly soft Marula is one of the few hardwoods that can be nailed The timber is very unstable, changing shape with almost every shower of rain or change in humidity.
It can be used for rough farm work and being a non splitter is used by the Africans for carving plates and other utensils.
Unless treated it is very prone to borer attack.
8 MPAK.A. Bolusanthus speciosus (Tree Wisteria)
This beautiful flowering tree is familiar to most farmers as a very durable fence pole. In the Que Que district there are fence poles in good condition still standing after forty years in the ground.
Trees of the Wisteria are nearly always of poor shape. They are often multi-stemmed and specimens large enough for cutting into boards are rare. The timber of Mpaka is exquisite, light in colour with well marked rings of darker brown.
The stems are usually of small diameter but practically the whole tree is heartwood. with only a very narrow ring of yellow sapwood of about 6 mm surrounding the heart.
Moderately heavy, the timber is stable and takes a high polish.
The Wisteria will only be cut as a rarity and can have no commercial value. The craftsman who obtains a few boards of this wood is fortunate.
9. MUZEZE, Peltophorum africanum
This showy tree which sends out its multitude of yellow flowers before Christmas is well known to most Rhodesians by sight if not by name. Stems of this tree, which is sometimes called African Wattle, are usually of small size.
The wood of the Muzeze is a useful non splitter; biscuit in colour and sometimes with dark streaks on the heart wood. It is soft but with a fine texture and finishes well. It is, however, very susceptible to blue sap stain if allowed to stand wet
Useful for small articles of furniture and ornaments the wood is sometimes used by Africans for making mortars for stamping grain.
10. MUWORA. Albizia amara
A large common tree which is rated, as the name suggests, very lowly by the Africans. Evidently the wood is not at all durable in the ground and rots very quickly when not protected.
The timber, however, is quite useful for furniture or internal work. The heartwood is reddish-brown with darker streaks, rather mixed up in appearance but attractive to some people.
The timber finishes well, but because of the interlocking grain, machine sanding is recommended. It is also fairly stable.
11. MUNYUNA. Monotes glaber (Yellow wood)
The English name is a misnomer but perhaps refers to the leaves which at certain times have a yellow appearance.
The wood of this very common tree is certainly not yellow but has an astonishing variety of colours and shades; everything from pale pink through biscuit colour to dark brown with all kinds of markings and no uniformity.
Cutting every tree into boards brings a fresh surprise.
When sawn green it has a sour, unpleasant smell and the local Africans have no real use for the wood. The timber is heavy and close grained and although it finishes well it is very hard on the cutting edges of tools. Being rather brittle it is not very suitable for structural work but makes excellent small articles of furniture.
In the Que Que district the tree is often of poor shape, sometimes leaning badly, but around the Hartley-Selous area fine specimens can be seen from the main Salisbury road.
Difficulty in working this timber could rule out this tree as a commercial proposition, but it would qualify in terms of appearance.
12. MUUNZE, Brachystegia glaucescens (Mountain Acacia)
The Mountain Acacia is very well known even to city dwellers, and is largely responsible for our beautiful hilly landscapes from Balla Balla to the Eastern Districts.
The tree itself is in no danger, occupying as it does places unsuitable for cultivation or large scale development. It does not even suffer from competition, and where it has been cut reasserts itself as the dominant species in a fairly short time.
The timber is fairly hard, the heartwood being a well marked brown. The sapwood. however, is very susceptible to borer attack and appears to be a really choice nourishment for these pests. Sapwood should be cut out of sawn timber.
13. MUTOHWE. Azanza garckeana (Snotapel)
This fruit tree grows to a large size if allowed to do
so. Mutohwe grows very readily from seed and in disturbed or cultivated areas
small saplings of this species are common.
The mature tree is usually of poor shape perhaps partly
due to abuse by fruit pickers who climb all over the tree breaking off branches
in the process.
The wood of the tree is almost unknown and yet has very
superior qualities. The heartwood is brown in colour, not unlike the true teak
of south-east Asia, fine in texture, easily worked and completely stable.
The poor shape and relative scarcity of sawable logs are
the only snags in using this timber.
The wood is excellent for cabinet work and makes superior
saw and tool handles.
One peculiarity of the wood is that it contains some
retardant which slows the drying of some modern wood varnishes and polishes.
Wiping the surface of the timber with turpentine or other spirits appears to
remove or deactivate this retardant. Without this pre-treatment some varnishes
will take weeks to dry out.
Timber cutting
A few hints on the cutting and handling of timber might
be useful but it is impossible in a publication of this nature to give details
of sawmilling and manufacturing techniques.
The old fashioned pit-saw was commonly used in the past
in Rhodesia. In parts of Africa it is still used for converting logs into
boards. Good work can be done with this tool and a pamphlet on pit-sawing,
originally issued by the Ministry of Agriculture and Lands is reprinted in the
back of this booklet.
The work is very arduous, frequent sharpening being the
rule, and considerable skill is required to produce boards which are even in
thickness, flat and straight.
At one time teams of two or
three sawyers could be found, complete with saws. These teams would usually work
on a contract basis. Perhaps some of these are still around..
Machine cutting is usually done with a circular saw. With
our hardwoods the only suitable type is the inserted tooth saw blade. This saw
blade, which is initially expensive, has special removable teeth that are fitted
in sockets on the rim of the blade. The teeth can be sharpened with a
carborundum grindstone, some even with a file.
Another type of saw blade which is gaining popularity,
especially for re-cutting heavy sections of timber into smaller boards, is the
tungsten carbide tipped blade. This very expensive blade gives long service
between sharpening but requires expert service for reconditioning and
sharpening.
Though not practised by the big producers, saws can be
kept sharp, longer, by debarking the log immediately before conversion. The bark
obviously has collected sand, dust and ant heap over the years and this is very
hard on tool edges.
One rule for all timbers is that conversion into boards
should take place as soon as possible after felling the tree. The wet sap in the
wood makes cutting easier and cracks and shakes have no time to develop in the
log. Logs lying on the ground are also prone to insect attack.
The time of year for felling timber is not really
important. Cutting in the wet season means greater risk of insect attack, and
cutting in the dry season can mean too rapid drying resulting in degrade of the
timber.
Immediately after converting to boards the following
points help towards producing good material.
Timber susceptible to borer attack, and most sapwoods
have this characteristic, can be given a wash or dip in insecticide. Proprietary
compounds are available but the insecticide powders used on crops are perfectly
satisfactory. Of course this is only a surface treatment, effective usually for
the seasoning period only. When subsequently cut for work on the farm, the fresh
timber will be once more exposed to attack by pests. Dry timber however, is less
susceptible than green.
Msusu, for instance, is almost immune from insect attack
when dry but Marula is always likely to suffer, even when dry.
The ends of the cut boards can be given a coat of
bituminous paint as a sealer; in fact any old gloss paint is better than
nothing. This helps to prevent the rapid drying of the ends of timber which
causes the familiar splits, resulting in a waste of wood.
End of Pg
Some form of stacking of sawn wood in the shade is
essential. The diagram shows what is meant. This air seasoning takes a long
time. The old rule was a year per inch (25 mm) of thickness of the plank.
With our difficult hardwoods rapid drying out is
disastrous, splits, shakes and distortion being the result. The stack of wood
therefore should not be exposed to drying winds and stickers should be fairly
thin, about 12 mm.
Special kiln drying is practised by the experts but
putting your wet wood through the grain dryer will certainly not work!
Wood finishing
For rough farm work timber can be used in the half dry
state.
There are many suitable wood preservatives on the market
for rendering the timber ant and rot proof. Some of the woods mentioned,
especially the hearts of the trees, need no treatment and most of our local
timbers take preservatives badly; being so hard and dense, penetration is poor
and only the surface gets the treatment.
For finer work, and furniture
particularly, the wood must be well seasoned and rendered as stable as possible.
If it can be done, avoid * sapwood unless you want the contrast of colour often
found in our timbers.
The following method of finishing works well with the
woods described earlier:
(a) Sand down the surface to a perfect finish using fine
glass paper in the final stages. Every single blemish must be removed and our
woods are difficult to machine finish without tearing the grain.
Faults in the wood surface will be exaggerated, not
concealed by the polish.
Remove all dust in preparation for applying the finish.
(b) Mix one part turpentine (petropine) to one part of a
clear polyurethane varnish and apply with a clean brush.
Work indoors in a dust free atmosphere. Work with the
grain and not across it.
Work quickly without going back over areas previously
covered.
(c) When completely dry and hard, rub down with fine
steel wool, until all bright shine has disappeared.
This rubbing down is one of the secrets of getting a good
finish. The work must be done thoroughly. Work with the grain. Remove all dust.
(d) Repeat (b) and (c) at least three times.
A layer of fine smooth polish will gradually be built up
if the work is done properly.
(e) If
a superior natural polish is aimed at, the final coat of turpen-tine/polyurethane
should also be rubbed down carefully.
fc Most people fight shy of rubbing down the last coat.
Finally a coat of ordinary furniture cream or wax polish
will complete the work.
Other timbers:
Only a small percentage of our woods have been dealt with
and some well known commercial timbers have been left out, for example,
Rhodesian Teak and Pod Mahogany.
MSASA
Brachystegia spiciformis produces a rather poor wood,
unstable and very prone to borer attack. The heartwood is not unattractive but
it has never been considered as a useful timber except, of course, as a
firewood.
Msasa along with Mnondo and Mfuti
may have to be considered for plywood and other
manufactured boards when existing supplies of better woods run out.
MNONDO
Julbernardia globiflora is quite a tough timber but
it seasons badly, with marked distortion and cracking. The hearts of large trees
are often completely rotten but the wood could be used for rough farm jobs.
Fence droppers have been made from sawn Mnondo.
MFUTI
Brachystegia boehmii also seasons badly. It is quite
a tough plain -looking wood, cream or straw in colour. Mfuti is very fibrous in
nature.
When completely dry this wood is impossible to saw and
plane by machine without a respirator being worn. Nose and throat irritation
caused by the dust is very severe.
MOPANI
Colophospermum mopane. The qualities of Mopani as a
fence pole are known to many farmers and ranchers. The wood is finely textured.
Very heavy and takes a very fine finish. In appearance the timber is not unlike
Rhodesian Teak. Mopani when sawn bends badly and severe splitting also takes
place. It could be used for small ornamental work and makes excellent wooden
bearings for machinery.
PIT-SAWING
At the present time when squared timbers are both costly
and difficult to obtain the ancient but extremely serviceable method of ripping
wood with the pit-saw is well worth consideration.
In the hands of expert sawyers the pit-saw can achieve
work of great accuracy, so that in most cases no re-sawing is required to obtain
squared timber of the required dimensions, but to those who are in possession of
mechanically driven circular saws of low power the pit-saw is very useful in the
preliminary breaking down of large logs.
The following article does not pretend to give an
exhaustive account of pit-sawing. Expert pit-sawyers have various labour-saving
devices and gadgets, but the article gives the main essentials which will enable
even the novice to train two intelligent labourers to carry out what is really a
very simple and cheap operation. If trained pit-saw boys are available they
should be engaged on the best terms possible, as they are worth it. If none are
available all that is required is a few days' patience to give the necessary
training. Training should start on a poor quality log, and not on the special
log which has been held until a suitable opportunity presented itself to saw it
for a special piece of furniture.
In brief, pit-sawing requires two operators — guide and
sawyer — a specially designed rip saw, a pit (or platform) of sufficient depth
to allow the sawyer to stand comfortably upright, two or three transverse
movable logs of equal dimensions to carry the log to be sawn and wedges or
clamps to bold the log in position.
THE SAW
Fig. I shows two pit-saws with 1,8 m blades. The broader
top portion of the blade carries the handle used by the guide. The lower tapered
portion is provided with a double grip with a slit to envelop part of the blade,
to which it is attached either by means of a wooden wedge or by a pair of bolts.
The grip is readily detachable to allow the saw to be taken out of the saw cut.
At the present time a 1,8 m rip saw costs about $15, and
apart from the small cost of a saw set and files, and, of course, the labour
employed ,R digging the pit and operating the saw, this is the sole
outlay.
 |
| Thirty millimetre boards stacked for seasoning. Note foundation log. Foundations should be about 0,6 m apart. |
It is highly important that the saw should be correctly set and sharpened before use, and that setting should take place before sharpen-m8- The saw teeth should be "spring set", i.e., the teeth are bent right and left alternately exactly the same amount on both sides. The amount of set to be given must be
determined by practice and will largely
depend on
the type of wood to be sawn — the wider the set the more exertion required and
the greater the "kerf" and waste of wood. If the
teeth
are set exactly equal on both sides the saw may be worked with less set than if
the teeth are irregular4. Generally the set should start from about
ooe-third of the way down the tooth and should never start at the root of the
tooth.
In sharpening the saw,
avoid files with sharp corners; hold the file level and at right angles to the
blade so that the tooth is filed square across the face.
THE PIT
An average pit
(Fig.
2) would be about 3 m x 1 m wide and 1,7 m
in
depth,
due allowance being made for the fact that the log to be sawn will be higher
than the top of the pit by the amount of the diameter
of the transverse bearers
MARKING THE LOG
The log to be sawn is first barked, crosscut at both ends
and then placed on the transverse bearers in such a position as to obtain from
it a square or rectangular baulk of greatest dimensions if squared timbers are
required, or. if planks of a certain thickness are wanted, in such a position
that the greatest number as wide as possible can be obtained.
The log shown in Fig. 5 was intended to produce 76 mm x
50 mm material.
A nursery or mason's line is now soaked in a mixture of
ground charcoal and water and is drawn taut along the length of the log so as to
give one of the lines shown on the log in Fig. 4. The tautened line is then
pulled up in the middle and released to leave the black mark shown. The same
line (or a shorter) with a plumb-bob attached is then used at both ends to give
corresponding marks across the cross-cut faces. From these lines the required
width of the baulk is set off at right angles at both ends, making due allowance
for the kerf of the saw. The plumb is then placed so as to fall through the
marks so obtained, and the vertical lines are struck as before. The two ends are
then joined by the charcoal line, which is tautened and released to give the
second mark
.
The whole log is then turned over through 180 degrees and
corresponding marks made along the original underside of the log by joining up
through the vertical lines previously obtained.
Instead of a plumb-bob a builder's level can be used for
the vertical lines, and in the case of a log which is to be sawn to produce
planks of a given thickness but any width, all the marks are made beforehand.
SAWING
 |
| Types of pit-saws. |
 |
| Pit with transverse bearers. |
 |
| Marking vertical line by use of plumb-bob. |
The log is now set firmly on two transverse bearers and
is kept in position (after ensuring that the vertical marks are truly plumb) by
means of wedges, as shown in Fig. 3, or longitudinally placed poles (Fig. 5), or
by a series of spikes. The spikes may be made by bending over at right angles a
bar of iron 1 metre in length at about 25 cm from each end and pointing the
ends. One end of the clamping spike is driven into the transverse bearer and the
other into the log. Spikes are particularly useful with logs of small diameters
or sawn material of small dimensions.
The operators then take up their positions as shown in and the first cut is made by a series of short strokes until
there
is a sufficient depth of cut to ensure that the saw is
working in the correct plane. The functions of the top operator — the guide —
are to raise the saw from the downward stroke, to see that the saw works in one
plane and to ensure that it holds to the line. He does not saw nor push down the
saw. That is the function of the sawyer below who performs the actual ripping
stroke. This is a steady out-down-in pull somewhat reminiscent of the action of
a man sculling a boat standing and facing the direction of the boat's progress.
The action of the two operators is not a continuous up-and-down motion. The
guide pulls the saw and there is a pause, the sawyer sweeps the saw down, at the
same time following his line on the under-side of the log, and there is another
pause, followed by the upward and backward pull of the guide. The latter often
provides himself with a horse-tail switch with which he brushes aside the
saw-dust which tends to collect and obscure the marked line. This he performs
with a neat flick in the momentary pause which follows the downward stroke.
The cut on the first line proceeds for about a metre,
e.g., to the guide's right foot in Fig. 5. The saw is then withdrawn and a fresh
cut started on the next line until it reaches the same distance as the first
cut. This operation is repeated until all the cuts have reached this length,
when the first cut is continued another stage, and so on until all the cuts are
near the end of the log, when the flitches or planks should be sawn completely
through. It is a mistake to endeavour to turn the log end-for-end, start at the
other end and to try to make the cuts meet in the middle. From time to time the
front transverse bearer is moved backwards or forwards to ensure that the saw
has full play and that the log is being supported to the best advantage.
The log shown in Figs. 3 and 4 was squared on two sides
and then turned with one square face down as shown in Fig. 5. The log was then
marked with the charcoal line to give 50 mm widths and sawing proceeded as with
the original log.
In sawing logs which are destined to give, say, 25 mm
thick material for furniture, or eucalypt logs which are inclined to warp, it
will be found best to saw to required depth only in the first instance and not
to edge the planks until they have seasoned. Where the completed article is
required to have exact dimensions allowance should be made for shrinkage and
final planning.
SEASONING
 |
| Marking the longitudinal lines. |
 |
| Baulk being finally squared. Note switch in guide's band and method of gripping handle. |
 |
| Temporary platform to show position of sawyer. |
 |
| Temporary platform to show positions of guide and sawyer. |
It is well in all cases to stack the sawn material for
seasoning. The pile may be in an open shed or under outside shade well exposed
to the air.
The
pile should be raised on suitable foundations at least 0,3 m above ground level.
"Stickers" of squared material 19 mm x 38 mm should he placed at regular
intervals of about 0,45 m,
vide Fig. 8. Heavy logs or stones should be placed on
top of the stack to give weight, and the top should be covered with any material
which will keep off the rain and sun.
Material such as 76 mm x 50 mm, 115 mm x 38 mm etc., is
best cross-piled,
i.e., one layer is placed on the foundations with the planks 0,45 m apart, and
the next layer placed on top at right angles with the same 0,45 m intervals, and
so on. No "stickers" are used.
The above article has been metricated and reprinted,
1976, from: "Pit-sawing", by E. I. Kelly Edwards, M.A. Dip. For. (Oxon.),
Conservator of Forests, Bulletin 1381 (reprinted from Rhodesia Agricultural
Journal", Vol. XLIV No. 1, January, 1947, pages 6-8).
Printed by the Government Printer. Salisbury.
End of Publication.
Source. Documentation received from Hylton Garriock. Thanks Hylton
Comments are always welcome, please mail them to Eddy Norris at orafs11@gmail.com
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