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Foregt zonetion
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In broad termg there are two types of islend in the Pacific region. Lo,v lying coral
atolls hsve vegetetion that has generally been wholly rmdified by local populations, and now
cqrsistg largely of trees with locel uaes, of which coconut and Pandanus are the most
obvioug Ttese low lying coral islande have no forertry potentiiTFinhabitants are
generally short of building timbers and fruit trees, and these can be planted in and around
villages and food gardens. The larger islands nearly ell heve a rpgged volcanic core fringed
by coral reefs which may have been uplifted on more then one occaeion. The volcanic core
may range from relatively low altitudes to the snow cepped mountains of West lrian and
Papua New Guinea. The larger islands east of Papua New Guinea seldom exceed 2,000 m in
altitude. On the geologically youngest and active volcanic islands like Tinakula in the Santa
Cruz group there rnay be no fringing reef. On older islands on the tectonic interface between
the Australia and Pacific plates, land building is still continuing and zuccessive corel and
limestone platforrns have been r+lifted to altitudes in excess of ]00 m above sea level. Such
formetions can be neen on Malaita, Guadalcanal and elsewhere, with the oldest of these
platforms being now considerably eroded, and dissected. Forest composition is influenced by
increasing altitude, by increasing distance from the sea, and by the underlying soil. Figure 2
gives a simplified vegetation zonation common in the Solomon Islands.
Mountain
(Mist)
orest
Protection
Water Supply
FIGURE 2 : DIAGRAMATIC VEGETATION ZOI,IATION
Typical of the Solomon Islands
Forested
F oothills
Alluvial
Riverine
Subsistence Farming
Production Coconuts
Forestry Cocoa
Cattle Cattle
Mangrove Littoral
F
Protection Villages
F ishing Coeonu ts
Firewood
Mangrove swamps are limited to sheltered water, oflen protected by reefs. Despite
timited risl and fall of the tides, gecies vegetational zonation is precise. Large areas of
mangroves mly occur in West lrian and Papua New Guinea. Elsewhere they are generally of
limited extent and are loo valuable as sources of Iocal building material, fruits and seafood
to be allocated to commercial exploitation.
In rnost of the coastal zones the natural littoral vegetation on beaches' with its ability
to provide coast protection, has largely been removed [o make way for coconut plantations
and villages. Reintroduction of the protective screen of native Iittoral species would retain a
measure of protection from erosion by the sea.
The vegetation developed on the low-lying raised platforms is generally lime-tolerant in
nature, with Pometia pinnata a prominent timber and fruit species. The species mixture found
on the tow lffigrerraces is generally very similar to that found on successively higher
terraces with soils of varying depth developed over limestone, which by the standards of
tropical soils contain modest reserves of nulrient. These sites have often been heavily used in
the past by strifting cultivetors, and more recently are those to which Agricultural Officers
direct their extension programmes.