Vegetation of Southeast Asia Studies of Forest Types 1963-1965

Under natural conditions the boundaries between tropical forests
and savannas depend, generally speaking, upon the humidity factor.
An exact determination, however, of the amount of rain necessary for
the existence of forests is very difficult. General considerations
which lead to the establishment of rain factors, aridity coefficients,
and climatic types of formulae do not include the important physio-
Ipgical factors of plant transpiration or the existence of subterranean
water reserves which may be stored at great depths in tropical
soils.
The data on water requirements of forests from classical plant
ecology are based upon the assumption that the present distribution
of tropical forests and savannas corresponds to the ecological conditions
of their environment. 'It is known, especially from researches
in central equatorial Africa, that great areas of savannas,
now occupying deteriorated soils, were forested in former times.
More reliable data are obtained from the direct determination
of transpiration values, which are scarce because of difficulty to
obtain, or from a computation based on the knowledge of the total
precipitation and of drainage water of an entire river basin covered
by equatorial forest.
The practical importance of such data is emphasized. For example,
it is possible to distinguish savannas which can be reclaimed.
A consideration of all the facts involved indicates how this reclamation
can best be done. It is clear that agricultural methods
used in temperate regions are inappropriate when applied to tropical
lowland soils. Such practices disturb the water balance of tropical
soils, favor serious surface erosion, cause internal, leaching of
soils, and there is evidence that they produce an irreversible degradation
of soil fertility.
Raymond, M. Carices Indochinenses Necnon Siamenses. Memoires du Jordan
Botanique de Montreal, No. 53. 125 pp. Montreal. Feb. 1959.
ReinJeing, O.A., and G.W. Gross. The kao pan seedless Siamese pummelo
and its culture. Philippine Journal Science. 19: 389-^37. 1921.
Rich, R. W. Aerial photography as a means of measuring plant Tver
and composition. In Techniques and Methods of Measuring Understory
Vegetation. Proceedings of a Sympos.ium at Tifton, Georgia, pp.
79-81. Oct. 1958.
Richards, P.W. The Tropical Rain Forest - An ecological study. 5^0 pp.
%3 text figs, and 15 places. Univ. Press, Cambridge. 1952.
This is probably the most authoritative and comprehensive reference
on this vast and complicated subject. It contains 17 chapters,
divided into 6 parts. Part 1 - Treats with structure and
•physiognomy of the Tropical Rain forest; Part 2 - The Environment;
Part 3 - Floristic composition of Climax communities; Part 4 -
Primary successions; Part 5 - Tropical Kain forest under limiting
conditions; and Part 6 - -Man and the Tropical Rain forest.
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