CHARACTERISTICS OF VIETNAM MONSOON TROPICAL FOREST

The researches are carried from 1989 to 2012. On a base of uniform biogeocoenosis (appr. ecosystem) approach the forest plant species composition, vertical and horizontal structure, the biological aspects some forest trees, the forest plant litter dynamic, the morphology and hydrology of forest soils and forest microclimate were studied. The forest flora of Vietnam, except for moos and lichens, comprises more than 7050 species of different life forms: trees-3140, herbs- 1660,   vine   species-1310,   epiphytes-844,   semi-epiphytes-31   and   66   species-parasites. The top of forests is formed by app. 330 tree species, the canopy - 2460 and less than 320 species-the understorey. Approximately 53 species from 34 genera and 19 families are representing the main trees forming the tropical monsoon forests. For representation of vertical structure of forests, we use a method of the profile diagrams. In total, profile diagrams for more than two hundred flat and mountain forest stands are prepared. Category of complexity of vertical structure for lowland forests is determined both the type of soil, and ability of soil to filtrate and accumulate an atmospheric water. There is a complication of forest stands vertical structure by a process of optimization soil and hydrological conditions. In mountain forests there is a simplification of forest stands vertical structure by a process of change forest soils from deeply drainage on a vector to easing of drainage and reduction of root zone. The changes in spectrum of environment forming trees in different forests occur mainly at a level of a rank of family, whereas in subordinated layers - in the greater degree at a level of species and genus inside family. Native tropical forest ecosystems represent a climatic climax. There is a dynamic balance in functioning of these ecosystems. This dynamics is determined by endogenous infringements, which are characteristic for forest ecosystems in general. The Man has introduced to the tropical nature new types of destructions. The apotheosis of destruction is the use of phytotoxicants and napalm, which were used to destruction of Vietnamese forests during the War. The occurrence not forest open territories has resulted in change of a microclimate, hydrological regime, properties of soils and development of erosive processes. It’s extremely important, that forest tree species, in natural conditions renewing under the primary forest canopy or in gaps and by virtue of their biological features, can not develop in open territories. Forest trees and the ecoton trees, are not evolutionary adapted to development on new, changed by the man, territories. This effected in the interruption of the series of successional changes of the vegetation. Complex, species-rich and evolutionary formed forest communities are substituted by simple in structure and species composition new or evolutionary alien communities with grass domination. It is obvious, that at progressing rates of deforestation various and weekly prognosis changes of climate will occur. The man should deal with new realities, when the economic benefits will appear temporary.