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combination of metalled logging roads, extraction tracks and loading areas with "high lead"
logging destroyed 7% of top soil in well stoeked forest. A higher figure of 22% was for
e$raction by small crawler tractors in similar forest. Overall, for forest yielding l0 to 50
m-lha of logs, l0% to 15% topsoil damage can be anticipated. Tfp damage will generally be
most noticeable near scces{r roads and also on either side of creek crossings. On steeper
ground there are generally more scattered extraclion tracks. Measurernents showed that
crewler tractor tracks mostly were less than 5 m wide, and that compaction and removal of
topsoil was always severe efter two or more turns of logs were extracted. On flat ground
little topsoil compaction or removal occurred when only one or two logs were removed,
provided Lhe tractor did not have to bulldoze a path through trees. Once vegetation, usually
in bhe form of'climber, covers Lhe compacted ground, there is a slow buildup of vegetable
detritus and later colonization by trees. After 25 to 40 years the trecks can still be seen,
but quite large trees can have established m the compacted soil wiLh their roots spreading
on either side to rnore favourable areas.
Assessrnents of canopy damage have been carried out in e number of localities in the
Solomons within the 181000 ha of logged forest that have been line planted. These show that
even with heavy logging taking out small trees wiJh diameters down to about 45 cm diameter
above buttress, 25% to l0% of the original canopy is relatively untouched, largely on the
steeper hillsides and in valleys. About 15c/o of the original canopy is completely destroyed and
the rest zuffers severe damage in some form or another.
Natural forest reqeneration
Relatively few studies of natural regeneration following logging in tropical rain forests
have been carried out in the Pacific Islands. The patterns of natural forest development on
Kolombangara in the Solomons were studied in detail between 1964 and 1971, with some areas
studied for a longer period. ln 1967 Cyclone Annie struck part of the island, so that.
subsequent assessnents gave an indication of natural regeneration patterns [hat followed the
cyclone. Provided the forest is in the mature phase, and only a relatively small proportion
has been destroyed by a c/clone, increment more or less balances losses. Species like
Endospermum, Campnosperma and Elaeocarpus are capable of 2-5 centimetres diameter
increment per year when in the upper canopy; while more dense species like Schizomeria,
Dillenia and Pometig grow more slowly and with greeter variability according t6 tFE; ila;e
ttre canop@p-bvlfuq however has remarkable uniform increments of about I cm per
year regardless of size.
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A numben of studies were carried out in the Solomons starting about 20 years ago ln
logged forest. Natural regeneration in Kauri forests was studied separately. The first
hardwood forests logged were predominantly of Pometia and Calophyllum and the most
prolificearlyregenerationwasfromthesespecieslT-teraseiiilofassessmenBsiteoon
became obvious that there was an extremely rapid loss of seedlings due to weeds, lack of
light and competition. After a short while it became appsrent tha! qerat,ions to successfully
enhance the development of slower growing more valuable species would be very tricky.
At about this time Iogging operations transferred to forest of markedly different types
in which Campnosperma and Dillenia were dominant,, excepl in swamps which carried
Terminalia brassii stands.
Four quotations from Solomon Islands Forestny Division Research Reports on the silvics
of species have been adapted to illustrate the likely pattern of natural regeneration:
"The traditional idea of growing shade lolerant species by rnanipulation of
the upPer canopy has serious drawbacks. Netural regeneration of Kauri is
scattered' partieularly in areas nearer to the cosst where the original stocking
was low. On Vanikolo' areas that had been logged 20 years or so before, were
trealed by poisoning and weeding designed to release saplings and poles over 2
metres height from within a matrix of older and taller weed species. After.
Lreetment mly )0% to 45% of 0.0I hectare sample units were slocked with Kauri
of all sizes of which only l0% of Lhe sample units conbained Kauri poles over I0
centimetres diemeLer which were suff ieiently vigorous to stand a chance of
developing to maturity. In areas Lhat were logged more recently, poisoning was
more drasLic, especially where the Kauri regeneration was small and there was
more thorough weeding. It is likely that the original stocking of Kauri