Which tree species, for what purpose?

How should I choose which trees to plant?

Making sensible decisions depends on taking several things into account, including:

1. The particular conditions and type of planting site (D 20–29);
2. How well different species have thrived locally;
3. How long various species have been grown in the region (D 31);
4. Their usefulness, for protection (D 1, D 23) as well as for products (D 33–40);
5. The need to mix different species together to maintain and improve the soil (D 32, D 53);
6. Reducing risks by “not putting all your eggs into one basket”. A single species might fail, and the need for products may change.

For most kinds of use there are several, or many, suitable tree species to choose from.

Are there tree species to avoid?

Yes, there are a few, including:

1. in general, those that might turn into troublesome weeds, such as Acacia nilotica in western Queensland and Melaleuca quinquenervia in Florida. Marabú (Dichrostachys glommerata), is a persistent species (which produces suckers - see A 3 in Manual 1) and spreads in human-induced grasslands (D 25) in Cuba;
2. in agroforestry, those which cast too heavy a shade for the crops, or whose roots would compete too strongly (D 3, D 21, D 51). Similarly, when domesticated animals are being raised (D 34), avoid trees with poisonous leaves or fruits.

Isn't it safer to stick to what has always been grown?

It depends on the circumstances. For instance:

1. on most of the area to be planted, it is generally sensible to use mixtures of locally known species (D 31, D 53). You could choose the best provenances, and include selected and tested clones or varieties, if they are available (Manuals 1 and 2);
2. on a smaller scale, you might try out new species, and untested selections of familiar ones;
3. on more stressful sites, concentrate on species that grow there naturally;
4. on degraded land, abandoned pastures and unthrifty plantations, planting soil-improving trees or shrubs (D 32) in pure stands (D 53) may be needed to regain reasonable soil fertility before introducing other trees and crops.

Are there some guidelines?

1. Avoid planting most of the land with a single new species;
2. Don't resist all change, but try to combine caution with innovation;
3. Exchange ideas, information and plants with other growers.

Why should I use mixtures?

Planting one species over large areas (monoculture) has been widely practised in the mid-20th century, but can lead to serious problems, for example with:

1. increased soil erosion, particularly if the trees are leafless for part of the year (D 23);
2. decreased soil fertility, with only one type of litter and root system (D 13);
3. a greater risk of pests, diseases and sometimes fire (D 66);
4. changes in demand, markets and price;
5. loss of genetic diversity (Manuals 1 and 2).

Smaller blocks (D 54), with a mixture of species (D 53), generally fit in better with existing land use, avoiding the many problems (D 4) caused when people are displaced.

Are there some disadvantages of mixtures?

1. It can be simpler to plant and manage a single species;
2. A large processing factory might not be supplied so readily from mixed stands;
3. Gathering information on several species and their interactions may be more difficult.

Certain tree species may compete too strongly with each other, or with crops, to be suited to mixtures.

What are their special advantages?

1. Soil fertility is more likely to be maintained or improved under mixtures, mainly through more efficient capture and recycling of nutrients (D 13);
2. Various kinds of products can be harvested, often at different times;
3. Diseases and pests may not spread so easily;
4. Fire risks may be reduced, because less dry leaf litter of one type accumulates at a single time of year. For example, teak plantations can constitute a serious fire risk (D 66) to neighbouring trees and crops;
5. Adapting to changing needs is easier.

How should different species be mixed?

There are many different possibilities (D 53–54), including examples where:

1. two or more species are mixed together intimately;
2. groups of about 5 to 10 plants of one species are planted amongst one or more other species;
3. small pure plots (0.05 to 0.5 ha) of several species are planted next to each other.
4. one species is underplanted beneath moderate shade of larger trees of a second species, creating a two-storey arrangement (D 52).

Three-tier arrangements, more closely resembling the structure of a natural forest, can also be grown.

Isn't this all very confusing?

No, it needn't be. Here are some guidelines for effective tree planting:

1. Look on your activities as modifications to natural ecosystems (D 2, D 10, D 50).
2. If possible, base your main planting upon local methods that have stood the test of time. For instance, local farming systems often involve mixtures of several different fruit and timber trees, useful shrubs, etc, intercropped with short-lived food crops (D 3, D 21).
3. Try out newer species or varieties by doing an informal or formal trial (D 6) on a small scale.
4. Watch out for demonstration plantings to go and see (D 29), and local publications to read, for instance about sustainable production methods.

Which local species might I plant?

You could choose a mixture of trees and shrubs (D 30), and include some:

1. that have been cultivated for a long time;
2. whose products have traditionally been collected from the wild, but could become scarce;
3. that could give additional products for sale or local use;
4. that would rapidly provide extra soil protection (D 32);
5. where superior clones (Manual 1) or selected seed sources (Manual 2) of existing species are available.

Useful guidelines include:

1. not to concentrate too much on any one species, variety or clone;
2. not to abandon completely the older varieties in favour of new;
3. remember the advice to combine innovation with caution (D 30).

Mountain farm-garden.

What about kinds that have been grown for years?

Advantages of locally known trees are that:

1. they often form the most secure part of the planting;
2. seeds may be easily available, and propagating them may be easy;
3. suitable growing systems may have been worked out for them (D 50–54);
4. the products are usually well-known, and markets well-established;
5. other useful information may have been published (D 70–72).

Disadvantages could include problems with:

1. reductions in soil fertility, if cover over the soil (D 51) is insufficient for part or all of the year;
2. loss of diversity, if grown in large blocks;
3. lack of market, as with some extensive pine plantations.

Even with species such as cocoa, which yield for many years, think about the need to make regular, small, plantings to replace and diversify the older stands.

How about trees with products collected from the wild?

They are particularly important to include, because:

1. they supply many vital everyday needs;
2. the number of wild tropical trees is decreasing rapidly; and so
3. these products may become hard to find or be lost altogether (D 4).

Such trees need to be planted now, to allow time for them to grow large enough to yield.

Where can I get information about growing them?

This is often a problem, because:

1. published information is usually lacking or difficult to obtain;
2. in the past, there may have been enough naturally regenerated trees (D 2), so that there is little or no local experience of planting them;
3. it is not always easy to get good seeds and seedlings;
4. occasionally, diseases or pests may kill or severely damage planted trees, as with Milicia (Chlorophora) and some mahoganies (Meliaceae).

Can these Manuals help?

The main purpose of this series of Manuals is to provide the general background, suitable for the majority of tropical trees, on:

• rooting cuttings (Manual 1);
• raising seedlings (Manual 2);
• planning nurseries and growing good plants (Manual 3);
• preparation for planting (This Manual);
• planting and successful establishment (Manual 5).

What about tree species with new uses?

The best approach is to try them out on a small scale (D 6), to find out:

1. whether the trees thrive;
2. how soon they might yield;
3. what products they give, and how they could be marketed;
4. how well they protect the soil; and
5. whether they are much affected by diseases or pests.

Remember not to reject a potentially useful species too quickly. It could have performed poorly because the seeds were of an unsuitable provenance, or were taken from only a very few parent trees (Manual 2).

Local advice on particular species can sometimes be available from growers, government departments, universities and colleges, international projects, etc.

Dune stabilisation by planting shrubs.

What kind of soil protection can local species provide?

Being well adapted to local conditions, they are often the safest choice. They can be particularly valuable on difficult sites; for example as:

1. shelterbelts to reduce erosion by wind (D 41);
2. ground-cover on steep slopes (D 23);
3. restocking of over-exploited mangrove woodland (D 26).

How about using improved varieties?

These can often give higher yields than unimproved sources. They could either be rooted cuttings of a mixture of selected clones (Manual 1), or seedlings from sources that have done well in trials (Manual 2).

However, try them out first on a limited scale.

What sorts of introduced species might I plant?

You could consider those that:

1. help reclaim sites with degraded soil (D 22, D 32);
2. produce items that supplement supplies from local trees;
3. give promise of higher and/or quicker yields.

While considering an introduced species, also think whether there are any local species that might serve the same purpose. Then try out the two together.

What specific advantages might exotics bring?

Here are some examples:

1. Some trees and shrubs are particularly suitable for casting light shade (D 3, D 21, D 41) over crop plants in 2- or 3-storey systems (D 52), for example Erythrina, Gliricidia and Grevillea.
2. Species such as Casuarina and Leucaena are particularly good at restoring degraded land, so that other trees or crop plants may be planted later (D 32);
3. Some may be resistant to browsing (D 34), or to pests or diseases;
4. Some shade trees and ornamentals are particularly useful for village or town planting and for parks (D 28, D 41).

Will I get a better performance from exotics?

Expectations of higher yields and quicker cropping may or may not be fulfilled, which is why it is sensible to plant first in relatively small numbers, and to continue to compare them with local species (D 6).

Are there some disadvantages?

Yes. These could include:

1. the trees might be unable to withstand a rare event, such as a particularly severe drought (D 11);
2. there may be no market for the intended product or it might not be of acceptable quality;
3. the species could possibly become a serious weed, as has happened to those mentioned in sheet D 30, and might occur with Acacia auriculiformis, Albizia falcataria and Spathodea in S.E. Asia.

But exotics are very often planted!

The trouble is that they have sometimes been over-used. However, they have an important place in tree planting, and may also:

1. have published information on growing them (see D 71–72); and
2. be available commonly as planting stock, making them somewhat easier to establish.

However, one does not really want to get into the position where the choice of species is being made by default.

Replanting important local tree species is also needed.

What are soil-improvers?

Species of evergreen trees, shrubs, cover crops or grasses that are especially good at protecting and restoring the soil (D 1, D 60), making conditions more favourable for tree or crop growth (D 50).

How do they do that?

By helping to maintain and improve soil stability, structure, function and fertility (D 12–13). Soil-improvers are particularly important in farmland, on degraded sites and on steep slopes (D 21–23).

Restoring degraded land with a pure stand of a soil-improving tree, Acacia mangium.

How do they protect soil stability?

1. Their foliage and the litter they drop on to the ground surface prevent raindrops from hitting the topsoil with great force, and their root systems also help to hold the soil together (D 23). Therefore:
   1. fine soil particles are not washed away nearly so quickly; and
   2. erosion gullies and mud-slides are much less likely to form.
2. Similarly, with a cover of soil-improvers, fine soil particles will be less liable to be blown away by the wind as dust, and in sand-storms.

How do soil-improvers maintain soil structure?

As well as helping to retain the important fine particles within the topsoil, their presence means that:

1. the soil is less likely to become hard and compacted, and is aerated by roots penetrating it (D 12); and
2. organic matter is continually being added to the soil as leaves, roots and twigs die and decay (D 13).

What effect do soil-improvers have on water supplies?

Although the shade from the trees reduces direct drying out of the topsoil, they themselves may lose quite a lot of water from their foliage, and this is replaced from the soil. So, during long dry periods, some tree species could deplete water, at shallower or deeper levels.

A — bare soil in degraded farmland.

What does “improving soil functioning” mean?

The soil is not an inert mass of earth, but a place where large numbers of different organisms live. Many of these are important or essential in making the soil a suitable environment for good root growth (D 50).

B — soil restored 18 months after direct sowing of Leucaena.

How are the soil organisms affected?

They can thrive because the topsoil does not become so hot (D 11) when there is a cover of trees. For example:

1. earthworms and other decomposers actively break down the rich litter from the soil-improvers to release nutrients;
2. conditions are more suitable for mycorrhizas and root nodules to form.

How do soil-improvers improve the fertility of the ground?

By combining effectively these effects on soil stability, structure and functioning, they allow its fertility to increase without the need to apply expensive fertilisers (D 13):

1. Current nutrients are captured and recycled, rather than being easily washed away in run-off, or leached to deep levels, out of reach of the roots (D 13). For example:
   1. potassium is conserved by the bamboo Dendrocalamus hamiltonii;

   2. calcium is efficiently captured by Gmelina arborea.

2. Extra nutrients can be made available in the soil:
   1. nitrogen from the atmosphere is changed into plant nutrient within the root systems of some soil improvers;
   2. phosphate in the soil that is otherwise unavailable to plants can be tapped by other soil-improvers.

What kinds of plants fix nitrogen?

1. Some leguminous plants, but not all of them. Nitrogen-fixers include:
   1. Shrubs and small to medium sized trees, such as Acacia auriculiformis, A. mangium, A. senegal, Gliricidia sepium, Inga edulis, Leucaena leucocephala, Prosopis juliflora and Sesbania grandiflora.
   2. Larger trees, for example Andira inermis and Dimorphandra davisii.
   3. Cover crops, including Pueraria and Centrosema pubescens;
   4. Crop plants such as beans and groundnuts.
2. A few trees in other families, including Alnus, Casuarina and Parasponia;
3. Some bacteria can also fix nitrogen, as can a few small mosses, liverworts and green algae that grow on the surface of leaves of trees.

How do they fix nitrogen from the air?

The roots have nodules on them, containing micro-organisms that are able to change inert nitrogen gas into nitrogen salts that the tree can use (Manual 3):

1. For leguminous plants and Parasponia, these are bacteria called Rhizobium;
2. For Alnus and Casuarina, they are a group related to fungi, called Frankia.

What kinds of plants have mycorrhizas?

It is now thought that nearly all tropical tree species may have mycorrhizas, though only a few have yet been studied. There are two different types (see Manual 3):

1. Ectomycorrhizas - many fine roots in the topsoil end in short, forked branches, with the fungus covering the outside. Most of these fungi form fruiting bodies (mushrooms) that come above ground and shed many tiny spores. Many Caesalpineaceae (Afzelia, Brachystegia) and Dipterocarpaceae (Shorea, Dipterocarpus and Monotes) form ectomycorrhizas, and they have also been found in Uapaca.
2. Endomycorrhizas - these are much more common, but harder to identify, as the fungus is inside the root system. Examples that have been studied so far include species of Albizia, Hopea, Khaya, Parkia, Terminalia and Triplochiton. Spores tend be present in the soil unless it has been greatly disturbed.

Both types of mycorrhiza can be formed by Intsia and some Australian species of Acacia and Eucalyptus.

Can one tree have both nodules and mycorrhizas?

Yes. Examples include some species of Acacia and Casuarina. The latter may also have dense masses of proteoid roots.

Through associations with micro-organisms, trees may perhaps also obtain trace elements (D 13) that are in short supply.

How do soil-improvers re-cycle nutrients?

1. By shedding nutrient-rich leaves that are easily broken down;
2. By having large, efficient root systems, with a mat of fine roots taking up nutrients from the topsoil, and direct from the litter. Other roots may tap extra minerals from deeper layers;
3. In mycorrhizal trees, the fungal strands attached to the roots penetrate the soil very thoroughly, and can often release unavailable nutrients.

When cut back, many soil-improvers quickly re-sprout and cover the soil again. The cut shoots can be used for fodder (D 34) or mulch (Manual 5) and the nutrients released once more.

When should I use soil-improvers?

1. When restoring degraded land (D 22) so that crops and other trees can be grown again;
2. Amongst crops to improve the yields (D 21), without the need for applying so much fertiliser;
3. Mixed with other kinds of trees (D 30, D 53), to encourage them to grow better;
4. As useful trees for marking boundaries (D 54).

How should they be planted?

This depends on:

1. the type of planting site (D 20–28);
2. how many existing trees there are (D 2); and
3. the growing system chosen (D 50–54).

Here are some examples:

1. seeds of cover crops sown densely amongst trees planted on bare ground;
2. shelter-belts of trees and grasses for soil cover in savanna areas (D 25, D 41);
3. lines of shrubs planted on the contour when terracing (D 65) a steep slope (D 23);
4. trees planted in groups or at wide spacing (D 54) in farming (D 21) or logged forest (D 24, D 62).

Which species do I choose?

Try out several, taking into account the points raised in sheets D 30–31, and that:

1. evergreen or leaf-exchanging trees will cover the soil better than deciduous species (Manual 3);
2. you might visit any demonstration plantings (D 29), or do some informal trials yourself (D 6);
3. there is some published information on soil-improvers (D 71).

Is there anything else that soil-improvers do?

Yes, they can sometimes:

1. colonise open ground and achieve woodland conditions more rapidly than most other tree species; and
2. keep down strong growth of unwanted, choking weeds, such as the shrubs Eupatorium (Chromolaena) odoratum and Lantana camara, or the grass Imperata cylindrica.
3. act as multipurpose species (D 40).

When are soil-improvers not needed?

1. on very fertile soil, such as alluvial or volcanic soils (D 12);
2. if there are already plenty of established trees on the site that can do the job (D 2);
3. when restoring mangrove woodland (D 26), where planting mangroves themselves is the best approach.

Isn't food the most important product of tropical land?

It is certainly one of them. However, fuel to cook the food (D 35) and fodder for animals (D 34) are also vital products, while trees provide timber (D 36–37) and many other items that people need in their daily lives (D 38–40).

But surely you clear away the trees in order to farm!

Dense forest or savanna woodland will need some opening up (D 51) to grow crop plants (D 21), or to provide forage for domesticated animals (D 34). But:

1. some trees should generally be left to protect the soil (D 2–3, D 60). These may be scattered across the area, or in groups or lines nearby; or surrounding the farm plot (D 54);
2. a fallow period under trees may be needed (D 3), if the soil is not to become degraded (D 22); and
3. planting trees can build up soil fertility on degraded pastures, croplands and slopes (D 23, D 32), and provide valuable shelter or shade (D 41) for crop plants and animals, so that food production can continue.

Are there other foods that trees ‘produce’ indirectly?

Yes, trees do this by providing suitable conditions for:

1. bush meat, including regular supplies of leaves and fruits, and breeding and resting sites for wild herbivores and carnivores (D 15) to survive and reproduce;
2. fish, which in mangrove areas and flooded forests depend on the trees for their populations to thrive (D 5, D 26);
3. honey, through year-round nectar supplies, and hollow trees for bees' nests;
4. insects, some of which are edible;
5. snails, which are prized as a delicacy in some regions;
6. fungi, fruiting bodies of species that are associated with trees.

Note: Some kinds are poisonous!

Are any of these important for people's diet?

Yes, many are. For example, bushmeat, fish and edible insects can be substantial sources of proteins that are vital in human nutrition. Many indirectly-produced foods also provide minerals and vitamins that are important for health, especially for growing children.

What foodstuffs do trees produce directly?

Fruits, seeds (including nuts), flowers, leaves, and other parts, such as root tubers. Some foods also have medicinal properties.

What tropical species yield edible fruits?

Many hundreds of species, producing millions of tonnes of food each month. Some are widely cultivated, such as bananas and citrus fruits, and are substantial items in international trade. But most fruits are sold in local markets or at the roadside, or are collected and eaten directly by individuals and families.

A regular supply of fruits that are eaten by wild animals can be indirectly important, by keeping up the supply of bush meat.

Are these fruits nutritious?

Many of them provide vitamins and minerals that are essential for health, as well as sugars that give energy. Some, such as bananas, are substantial sources of other carbohydrates.

Pejibaye fruits, produced by the palm Gulielma gasipaes, contain many of the ingredients of a balanced diet.

How about seeds?

A considerable number of trees produce edible and often nutritious seeds, including for instance Anacardium, Avicennia, Blighia, Brosimum, Cola, Garcinia, Pentadesma and palms such as Borassus, Elaeis and Nipa.

Cooking oils or fats are extracted from some seeds, for example Butyrospermum parkii, Ceiba pentandra, Cocus nucifera, Elaeis guineensis and Pentadesma butyracea.

Certain nuts are chewed, such as some species of Cola, and betel nut (Areca catechu) with betel pepper (Piper betle).

Do people eat tree flowers?

Yes, there are some that are a useful food supplement, such as Azadirachta, Gliricidia, papaya (male flowers), Sesbania and Tamarindus.

Are male and female flowers different, then?

Tropical tree species can have:

1. female parts (stigma and ovules) and male parts (pollen) in the same flower;
2. female and male parts in different flowers on the same tree;
3. separate female and male trees. These usually cannot be told apart before flowering starts. (See Manual 2.)

How long is it before young trees start to yield fruits?

First the tree has to grow large enough to reproduce, and then its crown must receive sufficient light for flowers to be formed. The female parts usually need to be pollinated before fruits can be set, grow in size and ripen.

Some tree species can start to flower as early as 2 – 3 years after sowing, whereas others may not do so until they are 20–30 years old, or more.

But that is too long to wait!

It will only be necessary to wait if the older trees have all been felled without being replaced naturally or by new plantings.

Tree planting may sometimes be done for the benefit of one's children or grand-children.

Can fruiting be speeded up?

1. In a few tree species, there are techniques which can be used to stimulate heavy flowering earlier in the life of the tree (Manual 2).
2. Within most tree species, some individuals start to flower earlier than others. Selections can be concentrated on these if flowering is a desirable character. However, where wood, forage or latex is to be produced, flowering might reduce the yields. In teak, early and repeated flowering tends to result in frequent forking and crooked stems.

Isn't it old-fashioned to eat leaves?

Not at all. Freshly collected green leaves of suitable species will provide a balanced source of the proteins that are an essential part of our diet.

How about medicines?

Some foods, including the leaves of certain tree species, are eaten because they appear to protect against diseases or to have general healing properties. In addition, special preparations are often made using tree parts as treatment for a particular disease or condition.

Are these traditional medicines of any use?

It is likely that quite a lot of traditional medicines do have positive effects, and indeed they are the only remedies available to many tropical people.

Relatively few of them have been rigorously tested, but in preliminary trials in Mexico for instance, half of the 250 plants studied showed activity against organisms causing diseases. Quinine from Cinchona officinalis and reserpine from Rauvolfia serpentenina are two examples of long-used medicines which are extracted commercially from tropical trees.

Can some foods protect against disease?

It is quite hard to separate out any effects that one component of the diet might be having. However, certain trees are retained or planted because they are held to prevent disease.

Minerals essential to human health appear to be present in above-average quantities in the leaves of Alchornea cordifolia, Mallotus oppositifolius, papaya and Phyllanthus reticulatus.

What kinds of foods have healing properties?

In West Africa, for example, the Asian tree Azadirachta indica is often planted right in the family compound because of its many products with healing properties.

How many ‘non-food’ medicines are obtained from trees?

All over the world, plants have been valued for their medicinal properties. Three out of many thousands of tropical examples are Ricinodendron heudelottii which is sometimes used for dysentery and fevers, Alstonia scholaris for beri-beri and to stop bleeding, and Ficus capensis for dysentery and rickets.

Which parts of trees are usually used?

1. Stem or root bark, generally ground and applied to the skin.
2. Leaves, stems, roots or seeds, often boiled, cooled and the liquid drunk. Thick and succulent leaves may, for example, be laid on the skin to treat boils.

Parts of trees are also used as antidotes for poisons or snakebites, in the treatment of mental illness, and sometimes for and against spirits, charms, spells, etc.

Can trees produce any drinks?

Yes, both indirectly, because woodland:

1. slows down the passage of rainwater (D 23);
2. filters impurities out of it;

And also directly, through woody plants that provide:

1. watery sap that can be collected and drunk, for instance the water liane Uvaria scabrida, and the water vines Beilschmedia anay and Vitis tilifolia;
2. cold drinks, such as coconut milk, Annona, Citrus, Cola, etc.;
3. hot drinks, like tea, coffee, cocoa and yerba maté (Ilex paraguensis);
4. alcoholic drinks, for example those made by fermenting sugars from Elaeis, Lannea, Nipa, etc.

NOTE: methyl alcohol (methanol) may be formed as well as ethyl alcohol (ethanol) when fermentation takes place. Methyl alcohol is very poisonous.

Do trees provide anything else that is edible?

Yes, several spices, herbs and flavourings that are added to food while it is cooking, for example from Blighia, Cinnamomum, Fagara, Monodora, Piper and Xylopia. In addition:

1. Cooking salt is sometimes obtained from Acantorhiza, Avicennia, Calamus, Pandanus, Raphia, Sabal and Voacanga;
2. Powerful sweeteners that do not make people fat are produced by Thaumatococcus daniellii, Synsepalum dulicificum and Duoscorcophyllum commisii.

How can I choose between all these different trees?

They are examples of the great diversity available. Here are some suggestions:

1. Concentrate on some whose products are in short supply, and try to foresee others which soon may be;
2. Try rooting cuttings of selected trees (Manual 1) as well as growing plants from seed (Manual 2);
3. Plant out mixtures of food-producing and medicinal trees as small trials (D 6, D 29), to see how they thrive;
4. If possible also keep some areas of woodland where useful trees can regenerate naturally (D 2).

What is forage?

Food of any kind for domesticated animals. It can be divided into:

1. fodder: food that is carried to them;
2. browse: woody shoots that animals eat for themselves;
3. pasture: grassy areas where they can graze; and
4. pannage: roots and organisms living in the soil under trees which animals dig out and eat.

How important is it?

It is vital. In most parts of the humid and dry tropics, forage means that meat, which is rich in essential proteins, can be included in people's diet.

Bushmeat also provides proteins, but if a lack of trees means that the wild animals are competing strongly with the domesticated ones for enough plant foods to eat:

1. both sources of meat will decrease; and
2. the herbivores (D 10, D 15) may turn to eating the crops.

Agroforestry (D 3) offers an opportunity of keeping trees, livestock and crops in balance.

What kinds of fodder can be cut?

1. Leaves and young shoots from trees and shrubs of many local species (D 31), especially evergreens, as well as introduced species like Artocarpus, Erythrina, Gliricidia or Leucaena;
2. Grasses and other herbaceous leaves and young twigs;
3. Crop wastes from the farm, or weeds from a young plot of trees;
4. Waste vegetable matter from the house;
5. A supplement of richer foods, to encourage healthy growth.

Do all these make suitable animal foods?

Many of them do, but they should:

1. be clean, and not mouldy, so that the animals do not become ill. If fodder is to be stored for later use, spread it out to dry thoroughly, soon after cutting;
2. be as fresh and nutritious as is possible. A varied diet, with a supplement from time to time, is more likely to include all the amino-acids that are needed to form the animal's proteins, and the important minerals and trace elements for healthy growth;
3. preferably be readily digestible. A sudden change to a different fodder plant may make an animal sick, so add small quantities at first;
4. not contain shoots, fruits, seeds or roots that are harmful or poisonous;
5. not encourage the spread of troublesome weed seeds in the animals droppings.

Will fodder form all of an animal's food?

Yes, for some animals like rabbits;
No, for many others, such as cattle, goats, pigs, sheep, horses, camels and elephants, which will usually forage for themselves as well.

Some kinds of leaves, such as Leucaena, are slightly toxic, and should therefore form less than one-third of an animal's diet.

What trees should not be used for fodder?

1. Very toxic parts, including tomato and potato leaves, the fruits of some trees and the seeds of others.
2. Very spiny or prickly shoots, except for goats.
3. Trees needed for other purposes, especially when they are young, since removing shoots will restrict their growth.

Note that (1) and (2) can sometimes be used up in biogas generators (D 35), or as mulch (Manual 5).

What sort of richer foods?

1. fresh, young shoots of leguminous plants, which can be especially rich in amino-acids. These include various soil-improvers (D 32) as well as cover crops, beans, groundnuts, etc.
2. grains such as maize, millet and sorghum (not rice);
3. special ‘cakes’ made out of the residues when oil has been pressed out of seeds such as coconuts or groundnuts.

Some of these richer foods can be added from time to time, especially for female animals during the month before and after the date when the young are born.

How about browse?

A much wider range of woody plants can be eaten directly by several kinds of domesticated animals, particularly by goats.

However, browsing needs controlling to reduce the damage to trees to a sustainable level!

What sort of damage might animals do?

1. killing young planted trees and natural regeneration by repeatedly browsing or breaking them, or by stripping off the bark;
2. removing a lot of the foliage so that growth is reduced;
3. making young trees bushy or crooked by taking out the leading shoot;
4. damaging food crops;
5. taking fruits and seeds that have already been harvested;
6. disturbing experimental plots (D 55), including labels.

Is it similar with pastures?

Yes, any young trees there are particularly likely to be damaged. Work out how to avoid overgrazing, especially on steep land (D 23). If there are too many grazing animals, they may:

1. eat more than the plants can replace;
2. break into the soil, damage the plant cover, and encourage rapid erosion and loss of soil fertility;
3. compact the soil, especially near water.

Wouldn't it be better just to have grasses?

No, this would usually be a mistake. Remember that in the:

1. humid tropics - trees, not grasses, are the dominant species of the natural vegetation (D 11);
2. semi-arid tropics - savanna, where grasses are dominant, still contains trees scattered through it, and along water-courses (D 25).

Pastures consisting entirely of grasses may not provide enough cover for the soil, so that the site may become too degraded (D 22) to allow continued grazing.

What can I do about such damage?

1. Avoid having too many animals for the particular site;
2. Tether or watch animals;
3. Move them on to a new area before much damage has been done, and allow fallow periods when no animal food is taken;
4. Use fodder for part or all the animal feed;
5. Try pollarding (cutting fodder trees at 2 – 4 m above ground) to discourage over-browsing;
6. Grow hedges or make fences around tree-planting areas, crops and houses;
7. Plant and protect trees that help retain the soil and improve the site (D 21, 32), and will re-grow from coppice shoots (Manual 1);

Won't pannage damage the soil and trees?

Yes, if there is too much disturbance, particularly on steep slopes (D 23);
No, if there are plenty of established trees. Patches where pigs have disturbed the soil and ground vegetation sometimes form good seed beds for natural regeneration of trees (D 2), or sites for underplanting in groups (D 54).

Can browsing and grazing help trees at all?

Yes, if they are not done excessively. For instance:

1. the animal manure puts nutrients and organic matter back into the soil (D 3, D 13, D 21);
2. tree seeds may be distributed to places where they may germinate;
3. weeds may be kept down.

Are there tree species that are especially good for forage?

1. For fodder: Avicennia and Rhizophora are nutritious and also provide essential salts;
2. For browse: Avicennia marina is extensively browsed by camels in Pakistan;
3. For planting in pastures: Acacia, Eucalyptus, Grevillea and Sesbania are examples.

A number of multipurpose (D 40) and shade (D 41) trees are useful for forage.

Do trees provide any medicines for animals?

Yes, some species are used for veterinary purposes, such as Azadirachta indica oil or the seeds and bark of Anogeissus leiocarpus to rid animals of tape-worms in the gut.

What kinds of fuel come from trees?

1. Firewood and charcoal;
2. Twigs and other materials for lighting fires;
3. Alcohol obtained from wood as a raw material, and biogas from decaying foliage, etc (D 37).

Surely oil, coal and nuclear power are far more important!

It depends on how you view energy resources. Sunlight harnessed by trees to form organic matter (D 10–11) is the reason that most people in the tropics have fuel to cook their food. This makes firewood by far the most important tropical energy source.

It also means that water can also be boiled to make hot and cold drinks (D 33) that are safe because harmful micro-organisms have been killed.

Is firewood really that important?

Yes, it is vital for three out of every four people in the tropics, and any shortage seriously affects them.

But what about transport and industry?

1. Oil and natural gas: lorries, cars, ships and aeroplanes certainly depend on oil products, and these are also used for tarmac for roads and airports, and for making plastics. But this is actually a reason for saving oil and gas reserves for transport, rather than using them up in industry, for they are non-renewable energy resources that will run out.
2. Coal: the carboniferous rocks that can include coal seams are not common in the tropics; and coal is also non-renewable.
3. Nuclear energy: in many countries nuclear power stations are being phased out, because of the risks to human health from radiation. Small quantities of many different radioisotopes are released from nuclear reactors, and much more is left behind as waste (D 16). Some of these substances remain in the environment, slightly increasing the amount of low-level, background radiation for years, centuries, or even longer. It is not yet clear just how harmful this is, but the dangers are obvious if a reactor should fail, spreading large quantities of radioactive substances over a whole region.

How can people get energy and electricity, then?

By moving the emphasis to renewable energy sources such as sustainably-grown trees; and also:

1. solar energy, including small solar electric systems that can give lighting, and power small tools and appliances;
2. biogas converters, which use waste vegetable and animal matter;
3. hydro-electric generators, especially larger numbers of smaller scale units, to avoid the problems of very large dams.

Oil products will clearly remain very important for specific purposes, such as diesel and petrol for transport, and paraffin for lighting.

Will any kind of tree do as firewood?

It is possible to burn practically any species. However, some are not very suitable because the wood:

1. is too hard to cut or split;
2. gives out little heat;
3. burns poorly, making a lot of smoke;
4. would give off poisonous fumes (D 66);
5. ‘spits’ a lot, producing sparks that could be dangerous;
6. is so valuable that it would be better to use it for example in furniture (D 39) or to make small ornaments.

Are there tree species that are specially good for burning?

Yes there are several (D 72). Here are some examples:

1. Casuarina is said to produce the best firewood in the world. In addition, some species are multipurpose trees (D 40) that can be used to reclaim degraded sites (D 22), and can thrive close to the sea.
2. Faidherbia (Acacia) albida is another multipurpose species, producing fodder and tannins as well as firewood. It grows in semi-arid sites, and gives shade during the dry season when most other tree species are leafless.
3. Rhizophora is widely used in mangrove areas for smoking fish, and Avicennia is sometimes utilised for drying salt.

Local as well as introduced species might be chosen for fuelwood planting (D 31).

What about charcoal?

The wood of many kinds of trees can be converted into charcoal, providing a smoke-free fuel that gives out a lot of heat. Examples that are particularly suited include Butyrospermum parkii, Casuarina and Coula edulis.

Coconut shells can also be made into charcoal, and indeed provide a lot of heat when burnt direct.

How is wood alcohol made?

The wood is fermented, and then heated within special containers, so that the alcohol can be distilled off.

What other things can be burnt?

1. Various dried grasses, bark and twigs are used for lighting fires;
2. Dung from domesticated animals is used in some tropical areas where firewood and charcoal are in short supply, and expensive to buy.

Note: this can seriously reduce the return of nutrients and organic matter to the soil (D 13), so that crops and trees may grow poorly.

Well, what else can people do?

It is certainly very difficult if there are few trees left. Some suggestions are:

1. Plan and carry out community tree-planting schemes for firewood (D 5, D 27);
2. Plant soil-improving (D 32) and multipurpose (D 40) trees in farms (D 21) and villages (D 28), and on degraded sites (D 22), all of which can provide some fuel;
3. Encourage the use of simple but improved cooking stoves that give out more heat from less firewood, and produce less smoke and fumes;
4. As soon as possible, use the unburnt dung to fertilise the ground for crops (D 3) or forage trees (D 34);
5. Also work the ash from the fires into the soil amongst the new plantings.

Doesn't wood smoke cause pollution?

There can be problems, especially for large towns in windless weather. These can be reduced by using improved stoves, and by:

1. drying the wood thoroughly, so that it burns more completely;
2. burning charcoal;
3. growing and using species that are more suitable for firewood.

Can fuelwood production be sustainable?

Yes, it is one of the easier tree systems to manage. Important points include:

1. using species that coppice freely (A 21 in Manual 1);
2. choosing several suitable species, rather than just one (D 30, D 53);
3. including soil-improvers (D 32), and using other methods to replace the nutrients and organic matter that are removed each time the fuel is cut;
4. finding out from surveys and trials (D 6) how long the cutting cycle should be (D 14), to get the highest average yearly yields of fuelwood of a convenient diameter;
5. discussing carefully how people are to be involved in community schemes (D 27), and agreeing what each family may cut (D 5);
6. planting plots for each year of the cutting cycle. These should be enough to provide for more than the expected demand.

How does biogas work?

Organic waste, such as sawdust, food that has gone rotten, leaves and waste products from humans and livestock, is put into a special ‘digester’. With little oxygen present, it is broken down by micro-organisms to form inflammable gases that can be burnt to provide lighting.

Cleaning a blocked pipe in a biogas digester.

Isn't timber the most important thing tropical trees produce?

That depends on one's point of view. The answer could be:
Yes, when thinking only of the very large amounts of timber used locally and entering world trade; but it might be:
No, if one looks for example:

1. as a smallholder, realising that trees which maintain soil fertility are vital if yields are to continue (D 21);
2. at local markets, in which foods, medicines, forage and fuel may be the most important tree products (D 33–35); and
3. at degraded land, where soil-improving trees could restore its capacity to produce (D 22, D 32).

And even as a forester, watching timber supplies dwindling because stands of trees have been exploited rather than managed, one might have doubts about the future of tropical timber.

But timber brings in vital foreign exchange!

Yes, it has done this, but often by destroying the resource it came from.

Wasn't that a necessary part of development?

No, because living resources such as trees, fish or herds of wild animals can be managed so that they go on yielding in perpetuity. To use them all up without replacement deprives present and future generations of ongoing supplies.

Why haven't they been managed sustainably?

For instance because:

1. timber, particularly for export, has in the past been the driving force behind logging;
2. most of the full value of the timber was realised abroad;
3. the many other products and the protective functions of trees, have generally been undervalued and sometimes completely ignored.

What is needed?

It would be much better to:

1. regenerate stands by cutting selected trees on a felling cycle (D 14, D 24, D 26), rather than by exploitation or clearfelling;
2. retain soil stability by careful directional felling and minimal damage from vehicles (D 60, D 62);
3. replant open sites with sufficient trees to renew soil protection and regain yields of diverse useful products (D 1, D 22–23);
4. receive a fair share of the full value of sustainably produced timber and other products within the region where the trees grow.

Do timber trees grow fast?

Rates of height and diameter growth vary a lot according to:

1. the species chosen (D 30–42), and the provenances, varieties and clones selected (Manuals 1 and 2);
2. the quality of the planting stock (Manual 3);
3. the site, including its altitude, soil fertility and previous use (D 10–16); and
4. how well the trees are planted, and the extent of competition with other plants and damage from animals (Manual 5).

How long do timber trees take to mature?

Some species take:

1. a remarkably short time - for example, Gmelina arborea, Ochroma lagopus and some appropriately chosen eucalypts could begin to be felled in 10–20 years;
2. a moderate period - a number of species, such as Terminalia or Triplochiton might take 40–50 years to mature; or
3. a relatively long time - some of the heavier constructional timbers (D 38) may take as long as 100–125 years to reach maturity.

But I can't wait that long!

You won't have to, if the trees have been managed sustainably, with new trees continually being planted and/or coming up naturally as the older ones are harvested.
You will have to, if the natural resource has been over-exploited. Where there are no larger timber trees left, it may be your children or grandchildren who benefit from the tree you plant now.

However you can still get some timber, wood for raw materials (D 37) or poles (D 38–39) when the stand needs thinning to favour the best trees. The maturing trees may also produce fruits, seeds or other useful items.

In what different ways are timber trees used?

1. Cutting them up, by:
   1. sawing the trunk up into boards;
   2. peeling or slicing large sections of the bole into thin veneers for finishing furniture or for making plywood;
   3. carving pieces to make household and agricultural implements (D 39), or hollowing-out the trunks to make canoes (D 38);
2. Chipping the wood into small pieces for use as a raw material in making particle boards, paper and cardboard, or in the manufacture of chemicals (D 37); or
3. Using them more or less intact, to construct many kinds of buildings, bridges, fences, etc. (D 38–39).

How many different uses are there for sawnwood?

Very many; for an even larger number of tree species. A few examples are:

1. in constructing houses and other buildings (D 38);
2. for making furniture (D 39);
3. for flooring: Calophyllum, Doona, Dryobalanops, Hymenaea, Peltogyne and Vitex;
4. for bridges, railway sleepers, ship-building and harbour piles (D 38);
5. for boxes: Campnosperma zeylanica, Simaruba amara and Triplochiton scleroxylon.

Sawnwood is sometimes glued together to make laminated wood or blockboard.

Which kinds of trees can be used for plywood?

For plywood and veneers the wood needs to:

1. be able to be peeled or sliced after soaking in hot water;
2. be available in straight pieces, with few knots;
3. be strong when cut thin, not splitting much on cutting or drying;
4. have a finished surface that is smooth and strong, and if possible attractive.

Here are some examples from:
South America: Dalbergia nigra, Laurelia serrata, Swietenia, Virola, Vochysia.
South and South-east Asia: Chukrasia tabularis, Dalbergia latifolia, Pterocarpus, Shorea.
West Africa: Alstonia boonei, Antiaris africana, Mitragyna ciliata, Pycnanthus angolensis, Tieghemella heckelii, Triplochiton scleroxylon.

How should I plant timber trees?

The best way is usually in a mixture with other trees (D 30, D 53), and under some shade (D 41, D 50, D 60). This fits in with the longer rotation that many of them need, since other products can be harvested from the site while the timber trees are maturing.

Are there some guide-lines?

1. plant timber trees at a wide enough spacing to suit their final crown and root spread, though allowing for failures and for thinning;
2. keep them far enough away from buildings and roads (D 61, D 66);
3. avoid swampy ground or very steep slopes, if possible, where there could be felling problems.

Isn't wood always used as a raw material?

In a way, yes. However, when it is:

1. used directly, more or less as it is, for building, fencing, etc (D 38–39), it is hardly a raw material;
2. sawn into planks, or made into veneer and plywood (D 36), the timber still retains its structure and characteristics;
3. burnt for fuel or made into charcoal (D 35), it is being used to provide energy.

But when wood is chipped in a machine into produce small pieces a few millimeters in diameter, and these are used in bulk, then it really is a raw material.

How is wood chipped?

The bark is removed, either beforehand or during the process, and the wood is cut down to smaller lengths as necessary. These are fed into the machine, which has many rotating knives that cut off small pieces from the ends.

Large stock of wood chips.

How are the chips used?

1. Made back into boards by mixing them with glues, etc;
2. Chemically digested, and then made into paper and cardboard;
3. Completely broken down to produce various chemicals.

Why make wood into chips and then back into wood again?

At first sight this does seem a strange thing to do. However:

1. some species have unsuitable properties when sawn directly. For example, the boards may twist or split when dried, or lack strength;
2. crooked stems, forks, large branches, and waste wood from a sawmill can be used up.

In addition:

3. wider boards can be produced;
4. special types of board can be manufactured for different purposes, and of more uniform quality than sawn wood;
5. lightweight planks can be produced that are still quite strong;
6. chemicals can be included for lasting protection against insect damage.

How are the chips made back into boards?

1. Particle boards and chip boards. The chips are sieved to separate them into different sizes. Then chips of a uniform size are mixed with glue and rolled out into layers of the appropriate thickness. Next they are hot-pressed, sanded smooth and the edges trimmed, and finally allowed to set.

2. Fibre-boards. Larger-sized chips are cooked in a digester to soften and break up the tissues. The fibres are then separated in a defibrator, and pressed strongly together while they are still hot to create the fibre-board.

What are these boards useful for?

They can be used in many types of construction, especially for ceilings and walls, and for shelves, boxes and parts of furniture, etc.
Some have specialised uses, for instance as insulation board.

What tree species can be used?

Most kinds of trees could be utilised as raw materials. However, those which are easy to chip, and have reasonably uniform wood are preferred. Very hard timbers and trees with many knots are usually avoided because they quickly blunt the cutting edges of the machines.

Mixtures of woods may be used to combine the qualities of different tree species, provided that they still give a uniform product.

How is paper made?

The wood is turned into chips in a similar way, and then steeped in chemicals which break down the lignin and separate the individual cells of the wood. The pulp is washed, sometimes bleached, further chemicals added, and it is then rolled out into thin sheets and dried.

Are there different sorts of paper?

Yes, there are many kinds, including:

1. high quality papers, used in books and for writing, typing and photocopying paper, are made out of the best grades of pulp, with longer cells that can be bleached and rolled out very thin;
2. newsprint, for newspapers and some magazines, is also bleached and rolled thin, but is of lower quality;
3. cardboard, used for boxes and packing, consists of thicker sheets made from coarser, unbleached pulp.

Can any tree be used?

Nowadays, it is possible to make paper out of almost any kind of tree, which could either be:

1. a disadvantage, if this encourages complete clearing of trees; or
2. an advantage, if it stimulates less wasteful, sustained-yield management of wooded areas.

In general, softer, knot-free wood is preferred for paper making. In some species, trees that have grown fast may have lower density wood and this can make good pulp.

The wood of conifers such as Pinus is often preferred for high quality paper.

What chemicals can be made out of wood?

The substances of which wood is made need to be broken down, either by:

1. heating the wood;
2. digesting it with chemicals; or by
3. using micro-organisms, such as various fungi and bacteria, that are able to split up complex organic chemicals, making them available to:
   1. provide an energy source for the micro-organisms to grow on;
   2. convert carbohydrates into wood alcohol, for example (D 35);
   3. produce chemicals that are hard to make in the factory.

Other useful substances that are by-products of wood can be extracted from industrial wood wastes or from chimneys.

Is much wood wasted?

In some countries a great deal; while wood of any kind is in very short supply in others. Since trees are disappearing much faster than they are being replaced (D 1), reducing wastage makes obvious sense throughout the tropics.

Can waste wood be used as a raw material?

1. Sawdust can be used:
   1. for burning to produce useful heat, either directly in special stoves or furnaces at a sawmill, or in any fire after being compressed into briquettes;
      WARNING - mixtures of sawdust and air can sometimes explode!
   2. to build up low-lying, waterlogged areas;
   3. as packing for transporting materials and storing food;
   4. in biogas digesters (D 35) to provide gas lighting;

   5. when weathered, as a component of the rooting medium into which cuttings form their new roots (A 35 in Manual 1).

2. Sawmill waste, such as the sawn-off edges of logs, cores from peeled veneers, the cut ends of planks, etc, instead of being left to rot, or burnt to waste, can often be used for:
   1. firewood or for making charcoal (D 35);
   2. cutting into smaller planks (D 36);

   3. carving suitable pieces into implements and ornaments (D 39).

3. Branch wood and tops can be taken away for firewood, burnt or left to rot down within the stand. The nutrients released will encourage new trees to grow well (D 63), and the decaying wood provides habitats for insects and wildlife, some of which may be beneficial (D 15).

Do trees produce other raw materials besides wood?

Yes, several products are important internationally or locally, such as:

1. latex, tapped from the bark to make rubber, especially obtained from Hevea brasiliensis, but also from Castilloa elastica, Ficus elastica, Funtumia elastica, Landolphia comorensis, etc;
2. gums, resins and waxes, including Acacia senegal which produces gum arabic from the bark, and certain species of Shorea in which the fruits yield a valuable wax;
3. soap- and candle-making substances, for example from Butyrospermum parkii;
4. non-edible oils, for instance from Salvadora persica;
5. alcohol for use as a motor fuel, and vinegar for preserving food. Both can be obtained from the sugary sap of Nipa palms, for example;
6. poisons used in hunting and fishing;
7. insecticides against pests (D 39); and
8. dyes, stains, inks, colour-fixing agents and many other substances.

Using a portable saw-mill and adopting a suitable cutting cycle can allow sustainable production of raw materials.

What building materials come from trees and palms?

Very many different kinds. The wood is often used intact or shaped on the spot, rather than being processed into sawn timber or plywood (D 36), or forming a raw material for manufacturing particle boards, paper, etc (D 37). Such building components include:

1. materials used for making houses;
2. poles and other items used in farming;
3. construction materials for bridges and harbours;
4. wood used for making ships and boats.

Are these particularly important?

Yes, they are. Forests and savanna woodlands provide essential materials for building most people's homes, for farming and fishing, and to permit travel.

What is generally used for the walls of houses?

This varies greatly from region to region, but traditionally for example:

1. Corner posts and doorways are often made of sizeable unsawn poles, often using a species with a heartwood which is strong, durable and preferably resistant to termite attack. Examples include Haematoxylum, Irvingia gabonensis, Mitragyna ciliata, Tectona grandis and Vitex pinnata.
2. Other wall supports may be made from thicker poles or bamboo. Any species can be used that gives straight, strong poles.
3. The wall itself, whether or not it is made of bricks or clay, may be supported by thinner poles. Woven wood and palm fronds are also used as complete wallpanels.

The substantial long-houses in parts of Borneo are built largely of bamboo on supports of the very durable Eusideroxylon.

And for the roof?

1. The supporting beams are often strong poles of species such as Artocarpus nobilis, Aspidoderma, Doona, Sapindus or Achras sapota. Bamboo or the midribs of palm fronds such as Raphia are also used.
2. Covering materials include the leaves of Cola gigantea, Mitragyna, palm fronds (Borassus, Raphia, etc), strongly growing grasses, split bamboo (alternating up and down), woven leaves of cocoa and Marantaceae, bark (Bombax buonopozense), shingles (Terminalia ivorensis), etc.

How are the materials for houses fixed in place?

1. Using scaffolding, often made of planks on supports of bamboo or other poles, rather than metal;
2. Making holes in the ground to locate the basal ends of supports;
3. Weaving materials together as they are built, often using fibrous woody climbers to tie split or intact poles and foliage together;
4. By allowing wet clay or bricks to set in the sun.

What about modern houses?

Sawnwood is needed in large amounts, particularly for the roof and as shuttering for concrete.

Which kinds of building materials are used for farming?

1. Sheds and shelters: for example, storage barns for grain; temporary shelters from the rain; hutches for domesticated rabbits, etc. These are often constructed like a house, although less durable wood can be used.
2. Fencing is widely used to keep domestic animals in, but also to keep wild animals out, and to demarcate boundaries.
   Many fences, gates and pens are built with whatever poles can be easily cut nearby, or with bamboo, sawn timber (D 36), palm fronds, etc. They may be interwoven, or tied with lianes.
   As an alternative, hedges of living plants are often used, such as species of Baphia, Ficus, and Spondias that root easily from leafless cuttings (A 4 in Manual 1).

What sort of wood is needed for heavy construction?

The heartwood must be strong and very durable, and for:

1. bridges, the trunks used for main structural supports also need to be resistant to termites, and the working surface to abrasion. Some examples are Fagraea fragrans, Milicia (Chlorophora) excelsa, Ocotea rodiaei and Lophira alata.
   When lianes are plaited and used to suspend a smaller bridge, they need to have considerable tensile strength and be slow to rot.
2. harbour piling, the wood needs to be resistant to shipworms (Teredo), as well as to salt and wave action. Examples include: Afzelia, Eusideroxylon, Koompassia malaccensis, Lophira, Ocotea and Xylia.
3. railway sleepers, for example Aspidosperma, Intsia, Mesua and many of the timbers used for bridges.

Which trees are used for ships and boats?

1. For ships: species such as Calophyllum inophyllum, Milicia (Chlorophora) excelsa, Mora excelsa, Nauclea diderrichii, Ocotea rodiaei and Tectona grandis.
   Bearings for the propeller shaft are sometimes made of lignum vitae (Guaiacum officinale).
2. For boats that are made from a hollowed-out trunk, the wood needs to be relatively light and not too hard, as for example Triplochiton scleroxylon or Terminalia ivorensis.
   A lack of such suitable large trees could lead indirectly to less protein in human diets, if fishing was thereby reduced. This would be particularly serious in regions with no tradition of boat-building from planks.

What other things can be made with materials from woodland?

1. Transmission poles for electric cables and telephone wires are important sources of cash for many farmers. Examples of suitable species include some eucalypts and Strombosia pustulata.
2. Shade (temporary or more permanent) for growing trees can be put up: in the nursery, for stockplants (A 24, Manual 1), for the first months after planting in difficult sites and for many other purposes.

Do many things used in the house come from trees?

Besides food and medicines (D 33), and house-building materials (D 38), a large number of household items come from trees and woodlands. They can be grouped into:

1. furniture;
2. tools and implements;
3. containers of various kinds;
4. other objects and materials.

What can furniture be made from?

1. Sawnwood, plywood and veneers, where hundreds of different species can be used (D 36). Some of them are preferred because of their colour, grain patterns or capacity to take a smooth finish. A few examples include Aspidosperma and Paratecoma (peroba), Entandrophragma (sapele), Shorea and Parashorea (seraya).
2. Carved wood, where similar properties are needed. In Ghana, for example, Ashanti stools are often made out of Holarrhena floribunda, Alstonia boonei or Triplochiton scleroxylon;
3. Bamboo, which is widely used ‘ready-made’ or split into lengths, with little need for finishing, and is usually strong and durable;
4. Woven canes, for example Calamus, Elaeis, Raphia, and many rattans (climbing palms), of which there are more than 500 species in S.E. Asia, for example.

How about household tools?

Many different tools and other implements are made by carving, or by turning on a lathe, sometimes with parts fastened or glued together. They include:

1. pestles and mortars for pounding cooked food as well as de-shelling grains. The pestle needs to form a rounded end that withstands long use, and in West Africa, for instance, might be made from Celtis or Azadirachta indica. The mortar should be able to withstand wetting, drying and pounding, and not contain any poisonous substances. It could be carved, for example, from Nauclea diderrichii or Milicia (Chlorophora) excelsa;
2. plates and bowls are made from a suitable wood such as Rauvolfia;
3. Stirrers and spoons which may be made out of Napoleonaea or Alstonia boonei;
4. brushes and brooms which might be taken from Borassus, Cocos, Elaeis, Pandanus, etc.

What kinds of containers come from trees?

1. bags are made, for instance, out of Acacia, Borassus, Hyphaene, etc, and the handles out of the tough inner bark of various tree species;
2. baskets are woven from rattans, Elaeis, Phoenix, Raphia, etc, from some climbers such as Monstera, or from small twigs of Azadirachta indica;
3. water and food containers are sometimes made from gourds (calabashes), the hard coats of the fruits of Crescentia cujete as well as Lagenaria. Food may be wrapped in leaves such as Maranta;
4. pots for growing plants in can be made out of sections of bamboo.

And what else do trees produce that is used in the home?

Many other useful objects and materials, for example:

1. mats for various purposes, often woven from Raphia, rattans or certain grasses;
2. pillows and mattresses, that might be stuffed with kapok from the fruits of Ceiba pentandra and the leaves from Annona senegalensis;
3. chewsticks, made from split pieces of wood, frequent items on sale in local and city markets. Many different species are used, but Garcinia kola and G. epunctata are thought to contain a disinfectant, emphasising how significant the continuing availability of a single item like this can be for dental health in the tropics.
4. sponges for washing and for kitchen use, often taken from lianes or tree roots, and beaten to break up the fibres;
5. ornaments and toys, including items carved from the spines on the trunks of Ceiba and Fagara;
6. many other items, such as tying materials, clothing, tapers and musical instruments; and
7. numerous other substances such as dyes, soaps and waxes.

How about trees and agriculture?

Important items produced under woodland conditions include:

1. fodder for domesticated animals to eat (D 34);
2. wood for farm buildings and animal pens (D 38);
3. handles for tools and implements, for example Baphia nitida, Calycophyllum candidissimum, Celtis, Pterocarpus soyauxii;
4. gates, fencing materials (D 38) and protection for small trees.

Living trees are often used as hedges to restrict animal movement, and as supports for climbing crop plants like yams and pepper.

Are there other materials used in agriculture?

Yes, these include:

1. tying materials and ropes, including many lianes, palms and the fibrous inner bark of species such as Pileostigma, Sesbania and Tiliacora;
2. woven materials for shelter and as mats for drying crops and seeds;
3. shading materials, such as palm leaves, used for example in tree nurseries and for farm stock;
4. soil components for nurseries and for planting trees, such as forest top soil, materials for composting and rooting media for cuttings (see Manual 1);
5. pharmaceuticals used for veterinary purposes for farm stock, and against pests.

What about fishing and hunting?

Plants in woodland areas are used for such items as:

1. fish traps from woven canes, etc;
2. fishing rods from trees such as Ocotea rodiaei;
3. fishing lines, bowstrings and ropes, for example from Triumfetta cordifolia;
4. bows and arrows and other hunting equipment,
5. poisons used in fishing and on arrow tips.

Live trees are also used to act as a spring for traps.

But no-one could possibly plant all these kinds of tree!

Most of them grow naturally in undisturbed forest or savanna (D 24–25), and in sites that have been only moderately opened up (D 51). One of the reasons for retaining existing trees (D 2) is to continue to have free supplies of many useful products, for everyone loses out if they are no longer available.

You could choose which tree species are a priority to re-plant, bearing in mind:

1. kinds that have been over-exploited;
2. those that provide products in short supply;
3. soil-improvers (D 21–23, D 32); and
4. multi-purpose species (D 40).

What is meant by a multipurpose tree?

A tree species that is useful in more than one kind of way.

But isn't that true of most tropical trees?

Yes, it is. “In general, multipurpose trees include all woody perennials which are able to meet many household needs of small-scale farmers.” This is a definition by Anoja Wickramasinghe (see Gunasena, 1991 in D 71).

The term is often applied to tree species that yield several different useful products, usually protecting or improving the site as well.

What species are good multipurpose trees?

Many kinds of trees and shrubs, including species of Acacia, Albizia, Artocarpus, Azadirachta, Brosimum, Calliandra, Erythrina, and Sesbania. Numerous palms and bamboos are also multipurpose species.

Which is the best multipurpose tree to use?

This depends on many factors, including the:

1. climate (D 11);
2. general terrain and soil type (D 12);
3. kind of site (D 20–29), and how it has been used previously (D 16);
4. amount of vegetation on it, and whether the soil is degraded (D 22);
5. intended use of the land (D 5); and the
6. products that are needed (D 33–39), for sale and for direct use.

You could look out for local trees in your area that might be planted, perhaps in mixture with introduced species (D 31).

Would mixing different kinds be best?

There are usually several advantages in using mixtures of tree species (D 30, D 53). Certain trees might go particularly well together, such as Azadirachta indica and Prosopis cineraria.

How many different things can one tree produce?

Here are some examples:

1. Adansonia digitata has edible seeds, fruit pulp and young leaves, and can also provide fodder. This long-lived and hardy tree is also a source of medicines, the inner bark of the trunk yields a strong fibre, and the wood ash is useful as a fertiliser that is rich in potassium (D 13).
2. Cocos nucifera, the coconut palm, is one of the best known multipurpose trees, sometimes called the Tree of Life. It produces more than 100 products, including food, a valuable germ-free drink, oil for cooking or making into soap or candles, a nutritious fodder (copra) to supplement animal diets, ladles and bowls from the shells, and coir for matting, brushes and a substitute for peat in potting composts (A 53 in Manual 1). The large fronds are also useful for shade, thatching, house building (D 38) and windbreaks (D 41).
3. Faidherbia (Acacia) albida produces forage (D 34), tannins and firewood (D 35) in semi-arid regions. It holds its leaves during the dry season while losing them during the cloudier rainy period, which makes it an unusual shade tree (D 41).

Which species has the largest number of uses?

Probably coconut and the Central American Brosimum alicastrum. Besides giving soil cover, the latter produces large annual crops of nutritious seeds (edible by humans as well animals), valuable forage, medicines, fuel, gums, drinks and an easily-worked timber.

What should I do before planting them?

1. Consider how best to space the multipurpose trees out across the area (D 54);
2. Think about whether to plant every few years, to provide a succession of trees of different sizes, or whether to plant once and have them all the same size (D 52); and
3. Make a plan of work (D 4).

What are the key thoughts about multipurpose trees?

They allow you to:

1. combine getting several useful products with soil improvement;
2. have items for sale as well as for using yourself;
3. avoid the extra risks of producing only one type of yield.

Aren't shade trees less important than other kinds of tree?

Not necessarily, because they can:

1. provide a more productive environment for some crops (D 3, D 21, D 52);
2. be planted as soil-improvers (D 32) to restore degraded land (D 22);
3. prevent farm animals from becoming over-heated;
4. themselves produce foods and medicines (D 33), forage (D 34), fuel (D 35), timber (D 36) or other useful materials (D 37–40).

At the same time, they may:

5. allow other tree species to become established underneath them (D 50–54);
6. provide humans with cooler places for working, meeting and relaxing, and filter out some of the dust, soot and other pollution in urban areas (D 16, D 28);
7. encourage birds to nest and breed, including those which eat insect pests (D 15).

What are the features of a good shade tree?

1. a moderate-sized trunk that divides into a spreading crown;
2. little or no tendency to drop large dead branches;
3. foliage that casts the required depth of shade;
4. an evergreen or leaf-exchanging habit, so that the tree gives some shade throughout the year, or at least during the season it is most needed;
5. a root system that does not compete too strongly with other plants;
6. a tolerance of exposure to strong sunlight, animal browsing and human activities.

It is also helpful if the shade tree species are easy to propagate, or if any problems over producing plants can be solved (Manuals 1–3).

How heavy should the shade be?

1. As an overstorey for planting trees: moderate shade is desirable for establishing most tree species, to provide a more favourable environment for this (D 50), and to protect the soil (D 60);
2. When regenerating shade-bearing forest trees: an even, moderately dense shade can be left, that can be reduced later by thinning or poisoning, or at the next harvest in the cutting cycle (D 14, D 24);
3. Over crops in farmland: small leaves or leaflets that cast an even, moderately light shade are desirable (D 3, D 21), or a somewhat denser shade that can be periodically reduced by lopping, pollarding or coppicing;
4. For grazing animals: moderate levels may be best, with reliable patches of deeper shade (D 25);
5. In towns and parks: moderate shade is needed along the edges of roads and paths, with irregular denser patches in parks (D 28).

Which species make good shade trees?

Several leguminous trees, including species of Acacia, Albizia, Cassia, Caesalpinia, Delonix, Faidherbia and Pterocarpus.
Amongst many other examples are Artocarpus, Azadirachta indica, Eugenia grandis, Grevillea robusta, Khaya senegalensis, Swietenia macrophylla and various species of Eucalyptus and Terminalia.

What are the features of a good shelter tree?

1. Being tolerant of the local conditions, including unusual climatic events (D 11);
2. Being windfirm, with a strong and extensive root system;
3. Having a stout stem and wiry branches that are not easily broken;
4. Retaining foliage on the lower crown;
5. Preferably having an evergreen or leaf-exchanging habit.

Dune stabilisation by planting shrubs.

Which tree species provide good shelter?

1. Along coast-lines: examples include Terminalia catappa and Casuarina equisetifolia, which is also a soil-improver (D 32) that yields a high quality firewood (D 35);
2. Providing wind-breaks against desertification: some species of Acacia, Faidherbia and Prosopis.
3. Around tree nurseries: hedges of close-growing trees such as Cupressus lusitanica and other cypresses, except where they are liable to be killed by insect pests.

Are shelter belts difficult to establish?

They can be, especially if the wind is blowing the soil away. Sometimes extra help is needed to get the trees established (Manual 5).

What tree products can be used for shelter?

Coconut palm fronds, for example, may be woven into strong panels for use as a windbreak.

What about ornamentals?

Planting ornamental trees and shrubs can transform the appearance of an individual home, street or village, and can help to make a town or city an attractive place to live, work or visit (D 28).

Where should they be planted to do this?

Ornamental shrubs and small trees can be put:

1. Amongst buildings - especially where these are tall or crowded together, though not too close to houses, walls, etc (D 28);
2. Along roads - set back from the edges (D 61), and with suitable low-growing shrubs in the middle of dual carriageways;
3. In parks - where there is more scope for using a range of different kinds of trees to produce attractive landscapes (D 28).

Won't they be dangerous?

Not if they are well chosen and maintained. Avoid trees and shrubs that:

1. may grow too large;
2. could drop branches or large leaves on roads, paths or buildings;
3. have poisonous fruits, leaves or bark;
4. might harbour ants' nests, snakes, etc (D 28).

Good maintenance includes:

1. checking for damaged specimens while clearing up dead leaves and twigs;
2. noticing where some pruning is needed;
3. planning replacement planting in good time.

What makes a good ornamental?

1. A size at maturity that is appropriate for the planting site;
2. An attractive growth habit that does not require much pruning;
3. Eye-catching foliage or bark; and
4. Beautiful flowers that are produced over several weeks or months, or continuously, starting even when the plants are still relatively small; Ornamentals also need to be tolerant of urban environments (D 28) and reasonably easy to propagate (Manuals 1–3).

Are there a lot of ornamental species?

There are many that have been grown successfully. A few examples are Araucaria cunninghamii, Caesalpinia ferrea, Cassia fistula, Delonix regia, Lagerstroemia flos-reginae and Milletia atropurpurea.

In addition, you could look into local species (D 31) that have potential.

Can I be sure that they will grow as I want?

One can never be completely sure of success, as so many different factors may be involved.

However, you could increase the chances by:

1. going to look at successful plantings elsewhere;
2. including some of the same species and clones (A 11 in Manual 1) that have been successful before;
3. trying new kinds out in small trials first (D 6);
4. using a succession of large tubs of ornamentals that can be brought back to a nursery, perhaps to recover before being used again.

What tree species are best planted in parks?

A combination of shade, shelter, ornamental and unusual trees, that will:

1. provide a pleasant place to wander in and relax;
2. educate the public about trees and their great importance;
3. allow the study of particular groups of trees; and
4. conserve rare species and genetic diversity (Manuals 1 and 2).

How can parks help in conservation?

Parks, as well as Nature Reserves (D 28), can help maintain in existence those tree species in danger of becoming extinct (D 16). This could be done for instance by:

1. planting them in several small groups (D 54);
2. careful protection and maintenance (Manual 5);
3. storage of seeds or pollen (Manual 2);
4. experiments on rooting them as cuttings (A 45 in Manual 1).

Preparing a place to plant rare trees.

A sacred grove that is the only place where trees still grow.

Aren't most people too busy for culture and religion?

Whether by choice or necessity, this may often be true. Yet for many people who live in cities, towns or villages, trees and woodland represent something valuable and timeless.

The old Cotton-tree (Ceiba pentandra) in Freetown, Sierra Leone, under which slaves were freed.

How are trees seen as culturally important?

In many different ways. For instance:

1. Ceiba pentandra was regarded as a sacred tree by the Mayans, and is the national symbol of Guatamala.
2. Ficus benghalensis (banyan) and F. religiosa have long been regarded as special trees in south Asia.
3. Adansonia digitata, Blighia sapida and Elaeophorbia drupifera are quite often retained for cultural or religious reasons in Ghana, and a ban was imposed on exporting Milicia (Chlorophora) excelsa. In some districts it is considered a mistake for people even to look at Okouabaca aubrevillea.

Are these trees prized because of their products?

Although such species may have one or more uses, their products are generally not the main reasons for keeping them.

Sometimes each clan in a region may have a different tree species that is symbolic, and is not cut or otherwise used by them. This may have the effect of preserving some tree cover, and a greater diversity of species in a region.

Would such trees be planted too?

Yes. Sometimes this is done for special reasons, such as:

1. to record the birth of a child, and often to follow its subsequent development;
2. for religious reasons - for instance Aegle marmelos is planted in temples in Sri Lanka, while in Ghana Alstonia boonei is regarded as God's tree, and is planted at the entrance of the home;
3. as a shade tree (D 41) in the centre of the village, for example Azadirachta indica or species of Ficus.
4. to mark a semi-permanent boundary to a piece of land (D 21), perhaps using very hardy trees such as Dracaena arborea, which forms suckers from the roots (A 4 in Manual 1).

In what ways do people find woodland important?

In several different ways. For example as:

1. a source of protection for water supplies, particularly on slopes (D 23), along rivers and around lakes and storage ponds;
2. a burial ground not far from where they live;
3. the abode of gods and the spirits of ancestors;
4. an environment for meditation and spiritual insight;
5. an area for childhood games;
6. the location of an adolescent romance;
7. a spot where one can escape social pressures; or
8. a reminder of when they were a place to hide in time of war.

Does all this matter today?

In many regions tropical trees are disappearing very rapidly (D 1). If the last trees were eliminated from an area:

1. much wisdom, accumulated over many generations, would be lost too;
2. the erosion of soil (D 23) and the degradation of sites (D 22) would proceed even faster, threatening the lives of many more people (D 5);
3. many vital products would no longer be available (D 33–40);
4. the living environment for humans would be severely altered (D 41).

But are groves of sacred trees relevant, though?

Yes, sometimes they can help to cement communities together with a common set of aims. Even small areas still under woodland may also contribute, directly or indirectly, towards maintaining:

1. a greater number of plant and animal species;
2. more genetic diversity within individual tree species;
3. locally adapted sources of crop seeds for planting, even through times of famine. In some Kenyan villages, for instance, a secret garden amongst trees (often with a religious significance) is kept by one particular woman for seed conservation reasons.

Is woodland important for education?

Yes, this is another critical reason for keeping some parts of the land under trees. Each new generation needs to experience the ‘feel’ and the diversity of the forest, to learn about how their ancestors valued it, and to play their part in studying, conserving and replanting trees.