- MANAGING THEWOODLOT
Eucalypts are extremely sensitive to weed competition and must be clean cultivated and free from weeds. Early planting is vital for eucalypts. Planting can commence when the soil is thoroughly moist down to 30cms which is often the case in late November or early December. Site and nursery stock should, therefore, be ready by late November. The site needs fencing before planting commences. This avoids any damage which may be caused by livestock trampling and browsing. The seedlings must be thoroughly watered in their containers before planting. Once planting has started, it can continue irrespective of the weather, overcast conditions are not necessary for the actual planting operation but, should more than one week elapse without rain, planting operations should stop.
Figure 1: lines of harvested trees
Early planting is vitally important for eucalypts and the operation should be completed by mid- January. When planting the pocket or sleeve must be removed or it will cause restriction of the root system and cause the death of the plants, even several years after planting. Plant so that the soil level in the container is at the same level as the soil on site and firm the soil around the plant.
Clean cultivation is even more important on low rainfall sites. Two or three or even four cultivations or weeding’s may well be necessary in the first year after planting. A last weeding should take place in late March or early April towards the close of the main rains.
The effect of clean cultivation coupled with good plants and early planting should be such that the trees close canopy during their second rainy season, after one or two further cultivations at the beginning of the second rains, even in low rainfall sites. If this does not happen it might be well worthwhile seeking advice on using fertilizers. Except in years of less than average rainfall, thorough attention to the foregoing points should secure a plantation which has 90% or better of stocking with no need for any blanking operations either in the year of planting or secondyear.
The farmer will want to know what yields of utilisable poles or amounts of firewood can be expected in how many years from his projected gum plantation. The answer will depend upon the following:
- Productivity of the particular site for the specieschosen;
- Number of trees growing perhectare;
- Type of produce requiredand;
- Standard ofmanagement.
The following general rules will be useful:
If it is assumed that, for farm use the main requirement is either poles in the 11 – 16cm butt diameter range (with say, a useful pole length of 4 – 10m), or firewood of convenient size (i.e. logs of a diameter not more than 20 to 25cm) or for both types of produce together. It must be noted that all the details refer to plantations established at the recommended spacing of 2,5m by 2,5m, giving a theoretical stocking of 1 600 trees perhectare.
Allowing for minor losses on planting, one can take this to mean an effective stocking of 1 500 trees to the hectare.
This species is recommended for planting only in areas having more than 900mm rainfall, and should produce 60% to 70% stems at 11-16cm diameter in 6 to 8 years. That is, 900 to 1 000 poles of this size per hectare with about half of the remaining 500 to 600 poles below 11cm and half above 16cm. An average 850 – 1 000mm site will probably produce this result in 6 years but at the lowest end of the rainfall range (700mm), 8 years will be needed.
Tereticornis and E. Camaldulensis:
Knowledge of yields of these two species over the range of sites available (500 – 700mm rainfall), is far less complete than for E. Grandis. The growing of a tree crop would not be considered viable with a rainfall of less than 700mm. Nevertheless if a farm is short of wood the costs associated with slower growth smaller yield and greater uncertainty have to be balanced against the cost and security of importing the requirements for poles and fuelwood.
At the appropriate rotation age, the first planted area is clear felled and the produce removed. This operation is preferably carried out in early spring when the sap is rising. It is then easier to strip bark from the poles and the coppice re-growth is at its most vigorous. The sporadic felling of stems as and when required is, for very many reasons, very unsatisfactory.
The trees must be cut low down (10cm or less from the ground and saws are preferable to axes). If the cut is higher, timber in the butt is lost, the trees do not coppice well and the coppice shoots can break off easily in a wind. A sloping cut is made so that rain water is thrown off the cut surface and does not lie on it causing rot and death of the stump or‘stool’.
A coppice is a different crop from the first rotation derived from planted seedlings. Each time an area is coppiced some
stools will die, depending on a number of factors including poor timing or poor techniques when coppicing, soil impoverishment on poor sites and finally, increasing age. In order to control the total yield of wood attention must be paid to the number of coppice shoots to be left to grow on each hectare for the next rotation. It is necessary to keep only the most vigorous and straightest of the coppice shoots. This means that the decision of which to choose is left for 2 years after felling (1 year if the site and rainfall are very favorable). There will possibly be 4,5 or more coppice shoots per stool.Theseshouldbereducedtonotmorethan2after18monthsto2yearswhenthetallest
shoots are 3.5 – 4.5 metres high. The material removed can be used as tobacco sticks, small material for hut building or for firewood.
As long as the number of shoots is equal to, or more than, the original seedling stock (1 500 per hectare), it can be said that the total yield of solid wood will be approximately equal to that of the seedling rotation. This is acceptable for a firewood yield but if poles are required of the previous size of 11 – 16cm diameter and the stocking of coppice shoots is now much in excess of 1 500 per ha, more poles of a smaller diameter will be produced in the same rotation period.
If the farm has a need for small poles or tobacco sticks, the total coppice reduction can take place at 18 months to 2 years. When the coppice reduction is done the most vigorous and straightest shoots are left. Where 2 are left per stool they should be opposite, or as far apart as possible and not close together on the same side of the stool. The better shoot should be on the windward side if possible.
With each coppice rotation more stools die however good the management. After a number of rotations the yield drops to the point where it is uneconomic to carry on and the areas have to be replanted with seedlings. The remaining live stools should be killed beforehand by axing down the bark to below ground level, piling trash on top of the stool and burning, or by the use of chemical agents.
Three or four coppice rotations should be possible before replanting becomes necessary
Farmers will be fully aware of the dangers of fire; a ground fire within a gum plantation can certainly kill the trees or damage them very severely. Therefore there should be little or no grass in the plantations to carry a fire if good management practices are followed, but trash left after felling, or after coppicing can certainly carry a fierce fire. A 4 metre fireguard is recommended around the plantation. This will not stop a fire from entering a plantation but will stop small external fires and provide a line from which serious fires can be fought to prevent them from entering.
Unfortunately, in Southern Africa there has been a conflict in the use of fire between the forester and the grazier. Fire can be used as a tool either to promote grass for grazing or kill trees and shrubs or to assist in preserving or managing woodland. Some trees such as mukwa, the valuable savannah woodland timber tree, is very resistant to fire and is adapted to an environment in which quite regular and often fierce fires occur. Although some trees do have a remarkable resistance to fire, even though they are often damaged. Fire causes scars which heal over but leave defects in the timber, or the leading shoots are burnt so that the shape of the tree is changed and straight logs are more difficult tofind.
The best way to manage most indigenous savannah woodland is to exclude fire. This is an expensive undertaking and often such woodland is managed by a technique known as ‘controlled early burning’, which means burning off the grass as early as possible in the dry season so that a light fire results at a time when tree seedling and suckers are not flushing.
The operation of early burning sounds easier than it is in practice. The grasses dry out at different times in different areas owing to species differences and ground moisture. If the operation is properly done only fairly small areas are burned at one time which saves a great deal of walking over large areas. Heavy frosts can crisp and dry all the grass in an area almost overnight so that it is sometimes difficult to avoid an extensive burn.
The degree of fire hazard will determine how easily a fire can start and how fierce it will be but every fire has to have a cause. This may be natural such as lightning, but is far more often due to people throwing down lighted matches or cigarettes and not making sure that camp fires are extinguished. Unfortunately, another main cause of fires is losing control of the fire when burningfireguards.
Any fire can be put out by man if he gets there soon enough. This should be the number one maxim for all concerned with complete protection of any vegetation from fire. The emphasis therefore is placed upon getting a fire-fighting team to the fire as quickly as possible. This means that the reporting of the fire must be fast and accurate and that access through the area must begood.
Figure 2: A fire going through a plantation
It is best to cut your gums in early Spring to late October. At this time the new coppice grows well and it will be easy to strip the bark from the poles. The tree must be cut low down (10cm or less from the ground) and, if possible, with bow saws and not axes. Care must be taken to leave the surface as smooth as possible to avoid the danger of rot entering thestump.
Figure 3: Stool sawn low down and left with a sloping surface
After the crop is cut, each stool will throw up perhaps 4 or 5 more shoots. If these are all left to grow the poles will be small and thin when cut after a further 6 to 8 years, so it is necessary to reduce the number of coppice shoots on each stool.
2 shoots or stems are left on each stool but before these 2 are selected some time must pass to see which are going to be the strongest and straightest stems. The most suitable time to reduce the coppice to 2 stems per stool is again in the growing season. Thus the reduction of coppice will take place 18 months to 2 years after felling. 2 large strong, straight stems should be chosen, well spaced round the stool, preferably not close together. The coppice reduction operation gives a very useful yield of small poles.
Remember again, the 5 basic rules for growing gum plantations:
- Plant the right tree on the rightsite;
- Plant strong, healthy seedlings of the right size;
- Plant early, as soon as the soil is moist down to30cm;
- Keep plantations free of weed until the tree canopy closesand;
- Keep fire and livestock out ofplantations.
Figure 4: Regrowth of coppice shoots