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When the objective is Lo create industrial plantations, the following criteria should be
ueed when selecLing species:
- Lcal seeding at a relatively early age, say before 15 years; or seed easily obtainable
in bulk from a nearby territory.
- Seed easy to collect and handle in the nuftlery.
- Height growth of at least 4 m in lhe first three years after planting.
- Development of a potential log, free of major forks or faults, of a leasl 6 m length
by the fifth year after planting.
- A mean crop diameter at breast heiqht of I0 cm over bark; a mean crop height of l0
m 5 years after planting.
- A main crop with a stocking of 100 logs of 8 to I0 m length with top-diamelers of J0
cm under bsrk, or J5 cm over bark, in 25 years for furniture and construction
species, or in less than 20 years for utility species.
- For utility species development of logs with small end diameter of at least 15 em and
log lengths of over 6 m m at least 100 stems per ha by l0 years after planting.
- Yields of about 140 - 150 rl/n" of sawlogs.
In ternperate elimates, mixtures are seldom successful and tree form is usually enhanced
by close pacing. In New Zealand the form of final crop trees is often improved by pruning. A
number of tropical species, including Campnosperma, Swietenia, Tectona, Pometiet
Calophvllum, end Cedrela grow unbranched in the first few years provided there is overhead
nghE-Others like TCrminalia, Eucelyptus, and Gmelina arborea need both overhead and lateral
illumination, and relative freedorn from competition before full vigour is developed. In the
former group the intenrow matrix can be manipulafed to give s narrow corridor within which
full vigour and adequate unbranched gtems lengths are developed. Later a heavy etown should
develop above the interrow matrix. Where land pressures ate low the interrow matrix in line
planting can be the former understorey, or regeneration of weed trees Iike Trema and
Macaranga
Where competition for land is higher on the smaller islands, silvicultural techniques
need to be modified. The scele of qerations cen generally be smaller since the plantations
mainly eupply the local population with sawlogs. Examples of proposed epecies selections in
parts of the Solomons, P4ua New Guinea, Fiji and Western Ssmoa are given in Table 4.
Optimum land use
On most of tJre smatler islande, population growth will increase so rapidly thatr within
the next generation or two, relatively little forest will remain unmodified. Already there are
cleer examples that the pressures of indigenous agriculture ere leading not only to
degradation of vegetation complexity, but also to severe reduction of the productive
po[entiel of hill soils. Thie can easily be eeen in western and centrel Viti Levu in Fiji'
Malaite in the Solomon Islends and Upolo, Western Samoa. Within two rnore decades the
poeition could be critical unless traditional agricultural techniques are rnodified to give more
intensive production from the better sites by mulching and crop rotations. Already in Tonga
and Weatern Samoe linee of Securineqa trees are planted between houses and along paths to
provide buitding materials. Thge trende are likely to increase and be introduced to other
island tFor.ps.
Lerge areEs of land have been allocated to cocoa, oil palm and cattle on many small
ielande, and this ia likely to be questioned in the longer term. On Malaitar large eteas are
degrading because of the bush fellow cycles being rcdueed in plecee to legs than a year. On
noittr Cuiaalcanal, where there io a 'rrein shadow", increasing ptessure of use is resultinq in a
rapid epread of Themeda dorninated grassland with increasing soil eroeion and goil
degradation. Theoe trendg must be checked and if possibb revereed.