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Preparing the ground

D 60

- introduction: minimising soil damage

What should I do before preparing the ground?

Before starting:

  1. decide on the growing system to use (D 50–55);
  2. make sure you have an adequate supply of good planting stock of the chosen species (Manuals 1–3), that will be of an appropriate size at planting time; and
  3. plan the best planting date (Manual 5).

Remember to protect the trees before planting, so that they remain in good condition. Trees will also be especially vulnerable to damage during the first week after planting (Manual 5).

What is the basic aim of preparing the ground?

Trying to do two things:

  1. Maintain protection of the soil against rapid erosion and nutrient loss by rain, sun and wind. This needs cover and the presence of many roots (D 1, D 11–13, D 23); and
  2. Insert a group of young trees into what may be a closed community of plants. This usually involves some opening of the canopy and of the rooting space, to allow them to become established and grow well (D 10, D 50).

Wholesale soil erosion from a field of upland rice on an unprotected slope.

But how can I do two opposite things at once!

By striking a balance between too much soil exposure and too much shade and root competition (D 51), for example by:

  1. remembering that plants may help each other as well as competing (D 14);
  2. using a growing system with more than one storey (D 52);
  3. choosing a planting pattern where trees are planted in small groups or lines (D 54);
  4. avoiding unnecessary tearing up and compaction of the soil and damage to other trees when felling, logging and making roads (D 62);
  5. minimising damage to existing trees if the area is burnt (D 63);
  6. avoiding waterlogging caused by blockage of streams and drains (D 65), or unnecessary tilling of the soil (D 64);
  7. considering terracing (D 65).

Why might the soil get damaged?

If soil is exposed to various kinds of degradation (D 12–13, D 22–23), it may:

  1. be completely washed, or blown, away;
  2. lose many of its fine particles;
  3. become compacted and have a poor structure;
  4. overheat and/or dry out in the surface layers, causing:
    1. unfavourable physical and chemical changes in its structure;
    2. death of many of the fine roots and mycorrhizas (D 32);
    3. loss of useful decomposers; and so
  5. fail to recycle nutrients efficiently.

How can I stop this damage to the soil?

The most important steps are to retain some trees on the area (D 2), and to plant a variety of other trees and shrubs (D 30, D 53).

What is meant by a good soil structure?

Having good aeration and drainage, and physical, chemical and biological components that are suitable for the growth of roots.

Ways of encouraging a good soil structure include:

  1. maintaining or restoring favourable woodland or grassland conditions by not completely clearing land (D 50–51);
  2. avoiding soil compaction by heavy vehicles (D 12, D 62);
  3. cutting drains or creating terraces where needed (D 65);
  4. adding some organic matter when planting, especially if there is not much in the soil (Manual 5).

What else can I do to protect the soil?

  1. Consider using animal power such as bullocks, elephants or horses for extracting logs, instead of heavy vehicles;
  2. Alternatively, saw logs up into boards on the spot, perhaps using a portable sawmill (D 62);
  3. In open sites, use some quick-growing colonisers to cover the soil as quickly as possible (D 22, D 25, D 32);
  4. Plant soon after clearing, to reduce the period that soil is exposed;
  5. Use mulch on bare ground, especially around young trees (Manual 5).

Do soil conditions vary a lot in the tropics?

Yes, a great deal. There are many contrasting kinds of tropical soil (D 12, D 70), and sites often show a lot of soil variation over quite short distances.

Does this matter?

Yes, it is important to recognise the ‘patchiness’ of the site, because this can provide some guidelines on:

  1. deciding which individual trees to leave and which to take out;
  2. planning just where the new trees should be planted; and
  3. recognising how to use site variation to develop sustainable methods of land-use.

Past civilisations that have avoided destroying most trees (and therefore been able to continue living in a region) often had a detailed understanding of the ‘patchwork’ of different soil types and the various trees and other plants growing on them.

Is past history of any use today?

Yes, especially if it is combined with modern understanding of ecosystems (D 10–15). All available sources of knowledge need to be tapped if human societies are to support themselves without destroying their environments (D 16).

Soil variation over short distances. Patches of wilting groundnuts in the sun show up soil variability, perhaps indicating the position of previous termite mounds.

How has this soil variability come about?

It may have been caused for instance by:

  1. differing terrain, parent rock or local site differences (D 12);
  2. damage by climatic or other natural disturbances (D 11);
  3. effects of plants or animals (D 14–15); and/or
  4. changes caused by previous human activity (D 16).

What kind of differences in soil or terrain?

Contrasting conditions such as:

  1. shallow, stony soils or rocky ridges (D 12), on which only hardy tree species might be suitable;
  2. steep slopes (D 23), where trees whose roots retain soil well could be planted, and terracing (D 65) considered;
  3. small depressions with poor drainage, which might be left under the existing vegetation (D 2) unless an appropriate tree or crop species was available;
  4. areas liable to occasional or regular flooding, where tree species tolerant to this would be required;
  5. waterlogged soils on coasts and estuaries, where different mangrove species might be appropriate according to slight variations in elevation, saltiness and the depositing or washing away of mud (D 26).

How would plants and animals make a difference?

The position of existing trees can ‘set the pattern’ for planting, especially when liberation thinning is done (D 36, D 51).

Plants also make the site irregular by:

  1. survival being poor among choking weeds, clumps of bamboo or big tussocks of tall grass;
  2. young trees growing much better next to a log or a large, dead stump (D 63);
  3. inhibition of growth near to certain tree species (D 14).

Animals may also influence tree growth in an irregular way, for example by:

  1. browsing some kinds of plants more heavily;
  2. changing the local soil conditions, as happens in termite mounds; and perhaps
  3. protection of trees containing ant's nests from insect pests.

Supposing the site is not covered with plants?

The presence of an open community usually means that:

  1. trees have been removed by human activities (D 16);
  2. there has recently been a natural disturbance (D 11); or
  3. the rainfall is only enough for semi-desert vegetation (D 25).

Here, all or most of the existing plants can usefully be retained as soil cover (D 2, D 22), apart from encroaching weeds.

What other guidelines are there?

  1. Natural vegetation is generally very efficient at recycling limited supplies of nutrients, keeping soil erosion rates low and maintaining soil structure. Such ecosystems provide a bench-mark for developing sustainably-managed systems that maintain protection while yielding multiple products.
  2. Converting the site to extensive pure plantations or grazing land by removing all the trees is often both costly and risky. It may prove unsustainable, by not providing sufficient soil cover or effective nutrient recycling.


D 61

- access to the planting site

How important is access?

Good access to the planting site helps by making it easier to:

  1. look at the area, and decide which patches to plant;
  2. take out any timber, poles, etc from felled trees;
  3. bring in workers and planting tools;
  4. transport plants quickly; and
  5. protect them afterwards.

However, good access can have undesirable effects as well, such as:

  1. extra soil erosion (D 23) at the sides of roads;
  2. clearing of trees by incoming farmers for crops or grazing, on land intended for managed forest (D 24) or savanna (D 25); or
  3. a greater chance of illicit tree cutting (D 66).

Checking erosion along a main road on a slope, by tree planting and various types of drain.

How can I prevent extra erosion from roadsides?

In several ways, including:

  1. careful siting of roads to avoid the steepest land;
  2. avoiding unnecessary damage by bulldozers and graders;
  3. using cart-tracks and pack animals in place of heavy mechanised vehicles;
  4. having good drainage channels (D 65), with frequent run-off points;
  5. leaving existing trees along the road edges, and/or planting suitable quick-growing tree species there.

Surely farmers need to have new land!

Yes, they often may, particularly when human populations are rising and the fertility of other sites is declining. However:

  1. people also need many other products from the land (D 33–40);
  2. incoming farmers may not understand local conditions;
  3. extensive fires (D 63), over-grazing (D 34) or too much browsing can undermine tree-planting efforts.

Unsustainable farming will just produce a lot of degraded ground (D 22), and make the shortage of land for agriculture more serious.

What about the stealing of timber?

In some regions this is a very difficult problem (D 66). You could try:

  1. involving everyone in decisions (D 5);
  2. employing local people as watchmen;
  3. giving workers a stake in keeping the trees there;
  4. finding a way of marking and recording standing trees;
  5. increasing the effectiveness of legal controls.

Do access roads need to be kept up after planting?

At first, it is useful to be able to reach the trees easily, for weeding and any replanting that may be needed (Manual 5).
After that, it may be possible to reduce road maintenance, although access in case of fire (D 66) and to check progress may still be required.

Losing easy access might be an advantage if logs were being stolen.
Keeping good access would be important where yields are produced annually, or at intervals of a few years.

What if the terrain is too difficult for roads?

  1. Access by boat may be an alternative;
  2. If fairly small numbers of trees are to be planted, it might be possible to use pack animals or carry them by hand;
  3. A temporary ‘flying’ nursery may be established close to the planting site (Manual 3), perhaps with ‘wildings’ collected nearby, or direct sowing tried (Manual 2).

Detailed photographs or maps are sometimes available, obtained by radar or satellite photography, which can give an accurate picture of what is there.

How about getting to all parts of the planting site?

Problems can include:

  1. steep slopes or rocky cliffs (D 12);
  2. swamps or rivers;
  3. dense shrubs, weeds or clumps of bamboo (D 14);
  4. unpleasant plants or dangerous animals (D 66).

What else is important?

Avoiding stress to plants in transit (Manual 5), for instance from:

  1. overheating and drying;
  2. shaking them about, which can damage fine roots and spill soil from the pots;
  3. non-vertical positions, that can cause bent leading shoots in actively-growing trees.

Patch of naturally regenerating seedlings that could thrive after careful felling and logging.


D 62

- felling and logging

What do I need to do before felling trees?

  1. Visit the area, and make an inventory (D 24) and a sketch-map of what is there;
  2. Choose which planting pattern will be appropriate (D 54);
  3. Decide how much to open the canopy (D 51);
  4. Select individual trees for felling which:
    1. have reached a large enough size;
    2. will fit in with (2) and (3); and
    3. will allow good immature trees, saplings and seedlings to put on extra growth (D 2, D 24);
  5. Plan the best felling direction, in relation to the terrain and to access tracks, roads or rivers (D 61);
  6. Think about safety (D 66), and the best time to fell (D 60).

How do I make an inventory?

If the area is relatively small and open, a sketch-map could be made by pacing the distances between the larger trees. It should show:

  1. the position, species and diameter at 1.3 m height of individual trees above a certain size, perhaps with an identity number;
  2. patches of saplings or seedlings that could thrive; and
  3. where there are steep slopes, rocky or swampy areas, streams, etc.

This will allow a complete inventory of the area to be prepared, giving:

  1. the frequency of each species present;
  2. the number of trees per hectare;
  3. their basal area (the cross-sectional area of each tree at 1.3 m height, added together).

But what if the area is a large block of forest?

If this is so, or it is difficult to walk about and see the trees clearly, make an estimate of what is there by doing a sample inventory.
Cut a straight path on a compass bearing, and record the diameter and species of all trees within 10 metres on either side.

If such transects are done every 200 metres on the same compass bearing, the sampled portion will be 10 percent of the total area.

What about mapping?

Making sketch-maps can be more difficult for larger blocks, unless there is a recent air photograph or satellite map available, which can give:

  1. a clear picture of the ‘patchiness’ of the area (D 60);
  2. an accurate estimate of the total area; and perhaps
  3. a chance to see whether the sample transects look reasonably representative of the whole block.

Why don't I just take out all the most valuable trees?

For a lot of important reasons (D 24, D 26, D 36). In particular:

  1. fewer seed trees would be left of the valuable species (D 33);
  2. because the best individuals were taken, this could involve negative selection. Only the genetically poorer trees might remain to provide plants for the future (Manuals 1 and 2);
  3. the life-cycles of beneficial animal species such as pollinators might be upset (D 15);
  4. parts of the canopy might be opened up too much (D 10, D 50–51).

What should I do, then?

Use the money from the logs to increase the value of the stand in the future, by:

  1. carrying out liberation thinnings to let immature trees grow more rapidly (D 51), to be cut after about 15–30 years;
  2. keeping some larger trees of each important species to provide seeds, before being cut at the next time of felling;
  3. removing or poisoning poorer trees to allow groups of natural saplings or seedlings, and planted trees, to grow well and supply logs in the future.

Will this make the stand sustainable?

The aim is to replace:

  1. selective logging - mere exploitation (‘creaming off’ or ‘high-grading’) of the best trees; by
  2. sustainable forest management - periodic cutting of trees in a way that maintains or improves the yields and protective value of the stand in perpetuity. For more details, see sheets D 24, D 26 and D 70.

Depending on the present condition of the stand, and on the way it is logged, progress towards full sustainable management may be quicker or slower. It can be more rapid when planting is used to supplement natural regeneration of trees (D 2).

Liberation thinning, directional felling and group planting.

Why is directional felling important?

  1. When the logs are pointing in a similar direction, the soil is less churned up or compacted by heavy vehicles as they are dragged out;
  2. The remaining trees, saplings and seedlings are less damaged;
  3. There is usually less breaking of stems when the crown of a tree hits the ground, rather than falling across the trunk of another felled tree.

However, if the first log has been cut up with a portable sawmill, a second tree might be felled across the same gap.

How can trees be felled?

  1. by chainsaw;
  2. with hand tools;
  3. by bulldozers;
  4. with other machinery.

Aren't chainsaws the best?

They are very commonly used today, and are quick and efficient if frequently sharpened and the engine properly maintained. However, they are dangerous if used without proper training and precautions (D 66), and may not be feasible for very large trees or species with very hard wood.

An indirect disadvantage is that they make the illicit cutting of timber much quicker (D 61).

What sort of hand tools?

Axes, saws or machetes may be well suited for smaller trees, for example in short rotation fuelwood plots (D 35), and they are also used for clearing undergrowth, climbers, etc (D 63). Replaceable blades and teeth with hardened steel tips have made bow saws a practical way of felling and sawing trees up to about 15–20 cm diameter.

Isn't a bulldozer the quickest way of felling trees?

It is certainly fast, once it is on the site, and it can push over most trees. But there are several disadvantages, including the:

  1. high cost of buying, running and maintaining them;
  2. ripping out and compaction of soil that occurs (D 12, D 60);
  3. relatively poor control over the direction of felling;
  4. extra damage to valuable immature trees, also caused when backing and turning;
  5. crushing of many saplings and seedlings; and the
  6. lack of coppice shoots when trees are uprooted, which could otherwise quickly protect the soil.

What other equipment can be used to fell trees?

Some machines, for example, grip a small or medium sized tree, 10 metres or more above the ground, and shear the trunk off at the base. Felling damage can be greatly reduced, but they can only operate on relatively flat, smooth terrain. They are more suited to plantations with trees of similar size, with fairly soft wood.

At what height above ground should the trees be cut?

This varies according to the species, the terrain and the circumstances.

Advantages of cutting 1 metre or more above ground level include:

  1. one avoids working down amongst weeds and dead branches;
  2. there is less risk of a chainsaw hitting stones;
  3. coppice shoots can more effectively provide some protection for the soil, and shade for young trees;
  4. it is easier when the tree has heavy buttresses.

Advantages of cutting at 0.5 m or below include:

  1. less timber is wasted;
  2. planting, weeding and carrying out checks will be easier.

How can logging damage be reduced?

One of the most important ways is by directional felling. Others are:

  1. Sawing logs up in the forest, for example with a portable saw-mill;
  2. Using animals rather than heavy machinery to drag out the timber, or carrying sawn planks out by hand;
  3. Avoiding blocking streams and drains;
  4. Not working in very wet weather.

Portable sawmill.


D 63

- clearing or burning?

Isn't it best to burn a site before planting?

There are some advantages of burning, but these need to be weighed up against the adverse effects.

What are the advantages?

  1. Releasing nutrients into the soil for the growth of new trees, crop plants, etc;
  2. Removing branches, undergrowth, tall grass, thorny plants, etc, without having to cut all of them, and making it easy to work on the planting site;
  3. Encouraging fire-hardy shrubs, small trees and perennial grasses to make a new flush of succulent growth that farm animals can eat (D 34);
  4. Reducing the growth of fire-sensitive weeds;
  5. Driving away snakes, scorpions, ants and some crop and tree pests;
  6. Decreasing the risk of fire occurring later on (D 66).

How about the disadvantages of burning?

  1. The organic matter in the litter (D 13) is lost by burning, and the soil is left completely bare for some time (D 1, D 23, D 60);
  2. Most of the nutrients released are very easily washed or blown away (D 23), and some are lost as gases;
  1. Run-off may be increased if the topsoil becomes less permeable to rainfall, as can occur, for example, in burnt pine plantations;
  2. The fine roots of trees, nodule-forming bacteria, mycorrhizal fungi (D 32) and many decomposers (D 13) could be killed;
  3. Existing trees (D 2) of any size may be damaged or destroyed, and sometimes need to be felled simply to provide enough fuel for the fire to burn successfully;
  4. Fires could spread and threaten nearby woodland, crops or houses (D 66);
  5. Fire-hardy, choking weeds often regrow and quickly colonise burnt land;
  6. The nests and young of useful wild animals (D 15) may be destroyed.

What's needed to burn an area?

Some ecosystems, such as savanna (D 25) and dry forests, undergo natural fires regularly or occasionally (D 11). These can usually be burnt relatively easily in dry weather.

Moist forests burn naturally only in exceptional droughts (D 11), unless they have been opened up. Some felling is usually needed, plus a period for the material to dry, for a fire to burn well here.

When might burning be a good idea?

  1. In savanna areas, existing trees and grasses may well be tolerant of fire, and re-grow rapidly;
  2. In forest land, burning might be chosen if:
    1. there is too much material on the ground to plant through;
    2. the fires can be controlled easily;
    3. fire protection lines need to be kept clean (D 66);
    4. quick-growing trees are to be planted; or
    5. fire-hardy coppice will quickly resprout.

Is burning sometimes impossible?

Yes it can be:

  1. if there is little combustible material on the ground;
  2. when prolonged rain has made the vegetation thoroughly wet; or
  3. where the ground is flooded or swampy.

Where should burning be avoided?

  1. On forest land, where repeated burning is especially liable to damage the soil (D 60);
  2. Near young trees.

What alternatives to burning are there?

  1. Clearing with hand tools and chainsaws;
  2. Clearing by bulldozer;
  3. No clearing.

Isn't clearing by hand too difficult?

Sometimes it may mean a lot of hard work, but not for instance when small groups or lines of trees are to be planted under tree cover (D 52, D 54). Advantages of manual clearing include:

  1. the nutrient recycling systems in the soil (D 13) are less affected;
  2. not so much damage is done to existing trees D 62), useful animals, etc;
  3. combining natural regeneration with planting (D 2) is easier;
  4. just the specific planting area can be cleared.

What are the advantages of using a bulldozer?

  1. Trees that have been uprooted, branches and some smaller trees may be pushed into rows for easier, safer burning;
  2. Access tracks (D 61) can readily be prepared;
  3. Large areas for planting can be prepared in a relatively short time.

Are there a lot of disadvantages?

Yes, there are several important problems (D 62), for instance concerning:

  1. compaction of the soil (D 12);
  2. damage to existing trees (D 2);
  3. high costs of maintainance.

In addition, bulldozers cannot be used in steep or swampy terrain.

When would neither clearing nor burning make sense?

  1. if there is little undergrowth;
  2. on abandoned farmland and degraded sites (D 22);
  3. in open parts of savanna or derived grassland (D 25);
  4. for shade-bearing trees in small natural gaps in forest, or where only 1 – 3 trees have been cut (D 24, D 54).

NOTE: If planting can be done among logs, branches and twigs, these may act as a mulch, and continue to release nutrients slowly after planting. Growth of planted trees can be very rapid in such favourable micro-environments (D 50).


D 64

- soil cultivation

Don't farmers generally till the soil?

Yes they do in some regions, but not in others. Soil cultivation has some advantages, but it can also cause problems.

What are the advantages of cultivating the soil?

The main reason is to discourage the growth of weeds that would compete with, or choke, crop plants.
Where the soil is compacted or contains a high proportion of clay and silt (D 12), cultivation could also help by aerating the soil.

How does tilling the soil cause problems?

The chief disadvantages are that it:

  1. makes the soil much more liable to be washed or blown away;
  2. decreases the stock of nutrients and organic matter in the topsoil; and
  3. by leaving the surface bare, can damage the fine roots of trees, the litter layer and the decomposers (D 13).

Are there any alternatives?

  1. Keeping enough overhead shade to reduce weed growth (D 2, D 50–51);
  2. Cutting the weeds above the soil level;
  3. Mulching (Manual 5);
  4. Growing a cover crop.

‘Zero-tillage’ methods have been worked out at some agricultural stations.

When might tilling be especially liable to damage the soil?

  1. On steep, unterraced slopes (D 23, D 65);
  2. If the soil has already been degraded (D 22);
  3. Where there are few trees left on the site;
  4. During the dry season, when the amount of wind erosion may be increased by cultivation;
  5. In very wet weather, when cultivation can increase erosion by water, especially if all trees and shrubs are leafless.

Are there times when cultivation would be a good idea?

Yes, there are several situations when it might be appropriate, for example:

  1. when the risk of very rapid soil erosion is low, for example on flat ground (D 12);
  2. where there are terraces or ‘ridges and hollows’ (D 65);
  3. if the soil is going to be covered with mulch immediately;
  4. when a rapidly growing cover crop is to be established at once; and
  5. if there are troublesome, fire-tolerant weeds in the area.

Can I alter the degree of cultivation?

Yes easily. You could reduce it for instance by:

  1. cultivating only those parts having strong grasses or woody weeds;
  2. hoeing only a little way into the soil;
  3. ploughing less deeply; or
  4. tilling less often.

D 65

- draining and terracing

Why is draining needed?

  1. To carry away excess water:
    1. when the usual water level is too near the topsoil for the species to thrive;
    2. if seasonal flooding might harm the root systems (D 11);
    3. in order to carry away floodwater from exceptional storms;
    4. along roadsides (D 61) and around buildings;
    5. to protect tree nurseries (Manual 3).

  2. To regulate water movement:
    1. to maintain waterlogged soil for crops like swamp rice;
    2. to retain water during the rainy season which can then be used during the dry season;
    3. to channel water in a particular direction.

Isn't drainage just used for farm crops?

No, cutting drainage ditches may also be needed if the chosen tree species are to thrive on sites that are, or may be, waterlogged.

What should I do first?

  1. Familiarise yourself with the terrain, making a rough sketch-map;
  2. Survey the area, including measurements of levels and gradients;
  3. Draw a more accurate map, and plan where drains should run;
  4. Peg out the drain lines on the ground, adjusting plans as necessary.

Should drains go straight downhill?

Yes, on gentle slopes; but
No, on moderate and steep slopes, where drains need to be slanting or in zigzags, sometimes nearly horizontal, in order to check the flow of water, which might:

  1. carry away a lot of valuable soil (D 12, D 23);
  2. cut erosion channels into the slope; and
  3. deposit excessive loads of silt, mud and stones on lower ground.

How should they be made?

  1. Sometimes by repeated soil cultivation (D 64). A system of low parallel ridges and shallow hollows running down a moderately gentle slope can be formed in a decade or two by repeatedly ploughing or digging over the soil in the same direction.
  2. Usually by digging out ditches. Often these are 25 – 75 cm wide and of variable depth. Leaving small ‘dams’ at intervals along the drain is sometimes done, in order to slow down the movement of water, restrict erosion and allow more soil particles to be deposited.

Is it best to start at the top or bottom?

Digging the drain from the bottom of the slope upwards often reduces the amount of water at the point where digging is going on.

When should drains be dug?

In the drier part of the year, unless the soil is then too hard. It is generally best to do the drainage well before the holes are dug for tree planting (Manual 5), especially if the soil has to dry out.

What is terracing?

Altering a slope so that the surface descends in a series of ‘steps’.

Terraces made by system A.

What is the point of it?

The main aim of terracing is to reduce the amount of soil erosion when food crops are being grown, especially if the soil is being tilled (D 64). It can also help to:

  1. retain more moisture into the dry season; and
  2. restrict the amount of silt deposited on lower ground.

Planting appropriate trees on a terraced hillside can also help stabilise soils for farm crops, and maintain soil fertility.

How is terracing done?

System A - building a series of walls along the contour, behind which soil accumulates, and digging appropriate drains; or

System B - planting double rows of trees or shrubs (such as Leucaena) along the contour, so that soil eroded from above the rows accumulates within them.

How is it planned?

In a similar way to that described for a drainage system, using a levelling instrument to mark out lines along the contours.

What sort of levelling instrument?

Pegging out the contour lines can be done easily and effectively with an A-frame, without the need for expensive surveying equipment. This simple device has a carpenter's spirit level or plumb bob which shows when the two legs are standing at the same level. Moving one leg at a time, a series of pegs is put in along the contour. The process is then repeated a measured height (such as 1.4 m) further downhill.

Is it worth all that effort?

In some parts of the tropics, steep slopes were terraced hundreds of years ago, using system A, which suggests that:

  1. well-made terraces can last a long time;
  2. their effects on soil stability and fertility had been recognised;
  3. the hard work was thought worthwhile, and sometimes also cleared the land of stones.

The newer system B involves much less digging and no building of walls.

How do the trees help?

With system A, suitable tree species planted just behind the walls can help to prevent the soil near the front edges from being washed away.
In system B, the trees actually produce the terraces, because they slow down water movement and trap soil particles.

In both systems, additional widely spaced trees can be used to stabilise the soil further and increase its fertility (D 32).

How quickly does system B work?

A ‘stepped’ slope can begin to be seen after only a few years.

Won't the trees get too big?

The species that are generally used do not grow to a large size, and in any case are often cut back regularly.
The cut branches can be allowed to drop their leaves as mulch on the crop land, and then put under the cut trees on the front edge of the terrace, to help trap more soil.

What kinds of trees are suitable on terraces?

Those which hold the soil well, cast a moderately light shade and do not compete unduly with the food crops. Examples that have been used include Leucaena glauca, and Gliricidia sepium. Various multipurpose trees (D 40, D 72) might be suitable, and other species that can be repeatedly pruned, pollarded or coppiced.

Are there some kinds to avoid?

It is best not to plant tree species that:

  1. have very ‘aggressive’ root systems that might break down the walls;
  2. cast too heavy a shade; or
  3. grow to an inconveniently large size.

Doesn't all this mean too much digging?

Drainage and terracing by system A both involve quite a lot of hard work. However, if well planned, the benefits can be considerable, and last for a long time.

What other kinds of digging could be needed?

Several, including:

  1. hole-digging before planting (Manual 5);
  2. access paths and roads (D 61);
  3. low earth walls (bunds) to maintain high water levels in swamp rice fields to reduce weed growth;
  4. similar earthworks to restrict the spread of salty water into an area at high tide (D 26).

D 66

- safety measures

What sort of safety measures are needed?

It is a good idea to think about the safety aspects of any job. You could consider the risks to:

  1. the people involved in the work;
  2. other people and their property;
  3. existing or planted trees;
  4. domesticated animals;
  5. vehicles and equipment.

What kind of risks?

  1. Falling trees and branches;
  2. Sharp implements;
  3. Accidents with vehicles;
  4. Unpleasant plants;
  5. Dangerous animals;
  6. Vandalism and theft;
  7. Fire and lightning;
  8. Flooding (D 11, D 65).

Men wearing protective clothing to saw a log up into boards in the forest.

But can anything be done about these things?

Yes, both beforehand, by:

  1. holding a ‘brainstorming’ session to spot potential risks;
  2. working out ways of minimising them;
  3. training people in applying safety procedures;
  4. putting up easily seen warning notices.

And at the time, by;

  1. using well-trained people to do potentially dangerous jobs;
  2. checking frequently to see that safety precautions are being observed.

What else can be done about falling trees and branches?

For tree-felling teams, by:

  1. having thorough training courses;
  2. wearing suitable protective clothing, particularly helmets and boots;
  3. paying special attention to the risks from neighbouring trees, which might be linked by woody climbers to the one being felled;
  4. avoiding payment by piece-work (which tends to make people hurry) in favour of bonuses for accurate directional felling (D 62), minimising damage to boles and standing trees, and adherence to safety precautions;
  5. sounding an alarm before felling or lopping.

And generally, by:

  1. siting new buildings carefully;
  2. checking regularly for dying branches or whole trees, especially around forest nurseries (Manual 3), in parks and on roadsides (D 28, D 41), and dealing with them promptly;
  3. considering temporary fencing to exclude the public.

Isn't there still bound to be a risk from overhead?

Yes, but it can be greatly reduced. Other points to watch include:

  1. avoid sheltering under risky trees during storms;
  2. remember that heavy fruits can also be dangerous; and perhaps
  3. choose species that are less likely to cause problems.

How about sharp tools?

  1. Chainsaws are particularly dangerous, both to the operator and to other people. Besides proper training, good maintenance is vital so that the blade cuts the wood cleanly;
  2. Other saws and axes - use them in such a way that if anything goes wrong the blade is unlikely to strike yourself or anyone else;
  3. Machetes, etc - cut away from your other hand, and from your legs, and be aware of others nearby;
  4. Digging tools - wear strong boots and don't swing pick-axes wildly.

NOTE: Care is needed with sharp tools not only during use, but also when:

  1. carrying or transporting them; and
  2. sharpening or maintaining them.

Are there any useful general rules?

  1. Keep machines maintained, and moving parts lubricated;
  2. Watch out for springy branches, vines, weeds, etc, that could cause tools to twist;
  3. Make sure handles are well fixed; and
  4. Follow any manufacturer's instructions carefully.

Can vehicle accidents be minimised?

Yes, for instance by:

  1. training courses for drivers;
  2. regular, competent servicing;
  3. avoiding driving for too long;
  4. not overloading vehicles.

Do unpleasant plants really matter?

Sometimes they do, because in most tropical forests and savannas there are plants with:

  1. spines or thorns on the trunk, branches, twigs or leaves. A few, such as Scleria barteri, can cause painful cuts that may become infected;
  2. poisonous sap in the bark, leaves and/or fruits, which means that:
    1. many of them are toxic (or even fatal) if eaten by humans (D 33) or domesticated animals (D 34);
    2. even sheltering from the rain under certain rengas trees in Borneo (e.g. Melanorrhoea beccarii) can cause severe blisters that fail to heal quickly;
    3. many other members of the mango family (Anacardiaceae) contain toxic substances. In West Malaysia, for instance, it is unwise even to breathe in the vapour from freshly bruised tissues, or smoke from burning leaves of Mangifera caesia and M. lagenifera.

Is there anything I can do about these problems?

Yes, you could for instance:

  1. spread knowledge about poisonous species;
  2. avoid planting or encouraging them;
  3. use fencing to protect farm stock;
  4. wear appropriate clothing, including gloves where necessary;
  5. carry a simple first aid kit, including antiseptics and plasters.

What can be done about dangerous animals?

  1. Snakes and scorpions:
    1. be observant, especially near buildings, rivers and caves;
    2. wear long trousers, and boots (but look inside them first);
    3. use a tool or a stick rather than your hands;
    4. if possible have access to antidotes.

  1. Large carnivores:
    1. learn about their habits, and avoid places they frequent;
    2. avoid disturbing females when they are with young;
    3. if necessary, consider carrying weapons.

  2. Insects carrying diseases:
    1. clear away objects that might hold rainwater where mosquitoes could breed;
    2. cover nursery rainwater containers tightly, or add a few drops of paraffin (kerosene) to the top;
    3. if necessary, spray places where insects breed and hide, and consider draining swampy land (D 65);
    4. if possible, try and arrange work times to reduce the risk of infection.

Can anything be done about theft and vandalism?

This is one of the most difficult of safety problems (D 61), in some cases even involving the unauthorised cutting of large timber trees by armed gangs.
You could try:

  1. holding discussions with communities nearby, and if possible involving them in some positive way in the tree planting (D 5);
  2. putting up clear, explanatory notices;
  3. locking away tools and vehicles;
  4. employing watchmen;
  5. planting thorny hedges;
  6. if necessary, putting up high fences and gates.

What about fires?

During exceptional droughts (D 11), fires have destroyed millions of hectares of tropical trees. They are also one of the commonest kinds of damage to young trees, equipment and buildings. Ways of minimising the risk of fires caused by humans include:

  1. clearing fire-lines regularly, or planting fire-breaks with species that tend to stop fires spreading;
  2. avoiding tree species like teak and pines that help fires to spread rapidly, or mixing them with other kinds and noting the extra risks;
  3. training staff and workers to avoid carelessness with matches, and to know what to do in an emergency;
  4. putting up warning signs when the fire risk is high, and having fire brooms and/or water handy so that small fires can be quickly put out;
  5. having adequate supervision, and enough people nearby, when areas are being intentionally burnt (D 63).

But you can't do anything about lightning!

Not to prevent it, but you could note that:

  1. lightning can light fires naturally, when the vegetation is dry enough; and
  2. tall buildings and towers can be protected by a lightning conductor. Run a thick piece of wire from just above the top, right into the ground.

When is special care needed over safety?

Particularly when:

  1. felling large trees;
  2. burning vegetation;
  3. using vehicles in woodland;
  4. working on steep slopes or near cliffs; or
  5. walking in swampy places.

How about damage to trees from goats, pests and diseases?

This can be very important, and is covered on sheet D 34 and in Manual 5.


D 67

- experimental areas

What is different about preparing an experimental area?

It is worth putting more into it, because the results of experiments:

  1. could make a big difference to the survival, growth, yields and protective functions of many trees planted later on; but
  2. might be misleading if the work was not done carefully.

Which things need thinking about?

You could for instance:

  1. put extra effort into choosing a suitable site (D 29), with adequate access (D 61);
  2. do any opening of the canopy as evenly as possible (D 51);
  3. make special efforts to reduce damage to the soil (D 60);
  4. choose uniform planting stock (Manuals 1–3);
  5. plant and look after all the trees in the experiment as one unit (Manual 5).

How can I make the site more even?

Tropical soils and vegetation are often quite variable (D 12, D 14, D 60), but you could consider:

  1. measuring the distances apart and crown sizes of trees on the site, before felling some of them;
  2. leaving cut branches and foliage evenly scattered over the ground, or clearing them away altogether;
  3. removing stumps, small boulders or stones;
  4. tilling the soil, where appropriate (D 64);
  5. making any drainage or terracing very regular (D 65);
  6. planting a quick-growing shade tree (D 41) that casts an even shade;
  7. putting a similar kind and quantity of mulch (Manual 5) around each tree on the same day.

How should the work be done?

  1. There needs to be adequate supervision;
  2. It is best to use people who are experienced in the various jobs;
  3. Where possible, allow sufficient time to try out the methods on a spare area nearby, before starting on the experiment itself;
  4. Complete any operation on the whole experimental area at one time, or do the work Block by Block (D 55).

What if the trial is on farmland?

  1. Think carefully about how the trees should be positioned (D 21);
  2. Avoid any harvesting of crop or tree produce that goes unrecorded; and
  3. Use fencing to protect the experiment from grazing or browsing animals (D 15, D 34).

Supposing the experiment is within a closed stand of trees?

  1. In primary or secondary forest (D 24), or savanna woodland (D 25):
    1. consider which types of growing system (D 50–54) are most relevant;
    2. when small groups are to be planted, prepare more of them than are needed, and then choose the most similar ones for the experiment;
    3. if line planting is to be done, take accurate compass bearings and measurements, and take special care to make the canopy opening as even as possible, whether by directional felling, frill-girdling or poisoning.
  2. Within plantations: conditions are likely to be more uniform here, but you would need to:
    1. check that all parts of the experimental area are well stocked; and
    2. remember that the stand may need to be thinned later on.
  3. In mangrove woodland (D 26):
    1. pay particular attention to variation in tidal action and salinity;
    2. consider how to account for natural as well as planted trees.

The edge of a small gap in the forest.

Is it different if the land is bare?

  1. For grassy parts of savanna (D 25): the conditions may be more uniform than under trees, but there could be problems with large clumps of perennial grasses or termite mounds.
  2. On degraded land (D 22): Here there may be few obstacles to avoid. Soil-improvers (D 32) may be the only trees likely to thrive on very poor patches of soil.
  3. In towns or parks (D 28): Temporary fencing will probably be needed, and the layout (D 55) might be constrained by the sites available and the planting patterns normally used.

Soil variation over short distances. Patches of wilting groundnuts in the sun show up soil variability, perhaps indicating the position of previous termite mounds.

Are there some general hints?

You might avoid:

  1. using bulldozers or other heavy vehicles (D 62);
  2. cutting up the soil surface by working in very wet or very dry weather;
  3. burning the vegetation (D 63). Alternatively, you could make sure it is done evenly, spreading the ash about before it rains; and
  4. choosing areas with a high risk of fire spreading into them (D 66).

On the other hand, you could:

  1. explain the need for extra care to workers, and the purpose of the experiment to people living locally (D 5); and
  2. make a more detailed sketch map of the experimental area (D 55), perhaps drawn to scale, with an easily recognised object as a base point.

What needs doing after the experiment is set up?

Manual 5 will deal with:

  1. assessing the results of field trials; and
  2. protecting them from damage.
Tropical Trees: Propagation and Planting Manuals. Volume 5

Food Chains

Note: All living organisms release carbon dioxide to the air as they break down organic matter to release energy.

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