Vegetation of Southeast Asia Studies of Forest Types 1963-1965

there are usually three stories, of tall trees to shrubs, in addition
to a ground cover of grasses, herbaceous plants, cycads and ferns.
In the Dry Dipte,rocarp forest of Southeast Asia, on the other hand,
the trees are of uniform height, widely apetced, have little or no
undergrovth, so that stratification is not veil demarcated.
In addition to the stature and general, habit of the trees, additional
characters, considered as life-forms and often present in
tropical forests, include; type of branching; plank buttresses;
presence of stilt roots, pneumatophores or 'breathing roots', viiicb
may be erect or knee-shaped; thorns on trunks and/or branches; characteristics
(color, thickness, scaliness) of the bark; exudations,
if present; and succulent stems or leaves. Other special life-forms
that may be present are: woody vines or lianes, palms, cycads, rattans,
pandans and epiphytes.
Other salient features of a life-form are: whether a tree is
Evergreen or Deciduous; and the thickness and especially the size of
the leaf. The latter factor is indicative of habitat, and can be
determined by assigning it to one of Raunkiaer's 'life-size classes'
(see Bibliography).
Ploristics; The floristic composition of a plant community is
b«vsed on assembling and identifying as many as possible of the plant
species present. It involves the accumulation of precise information
on the species present in a community, and some quantitative estimate
of basal area, cover and density. Generally, it is possible to evaluate
the physiognomy of a forest type from its floristic composition, whereas
the contrary is usually not possible.
Climate: Despite existing deficiencies in accurate and consistent
classification of the major forest associations on a regional or
world-wide basis, there is an unmistakable relationship between climate
and vegetation. That climate has a decided influence on the type and
distribution of vegetation has attracted the attention of ecologists
and plant geographers for more than 50 years.
The distribution of natural vegetation types in the tropics is influenced
in large measure by rainfall, its amount, distribution, •timing
and intensity. Schimper (1903) maintained that a broad clinatiovegetative
community can be segregated, on the basis of precipitation,
into & series of progressively drier formations in conformity with increasing
latitude.
In general, precipitation, and particularly the rainfall pattern,
are functions of latitude. The inner tropics are usually very wet,
with little or no seasonal changes. The middle latitudes have less
rainfall.> usually in alternating wet and dry seasons which may occur
twice annually. The outer tropics are still drier, most frequently
with a single wet and dry-season each year. The rainless period increases
steadily in length and severity until forests finally give
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