THE EXPLOITATION OF TROPICAL RAINFOREST IN RELATION TO SOIL AND WATER CONSERVATION IN SOUTHERN YUNNAN
Wang Hui-hai Ma Wei-jun Deng Chun-zhang Li De-hou(Yunnan Institute of Tropical Botany,Academia Sinica)
In order to study laws of soil and water loss of tropical rainforest andthe exploitation and utilization of its land.We have carried out the field-plotexperiment of water loss and soil erosion in southern Yunnan for six yearsfrom 1962 to 1967. The results of the study are summarized as follows: 1. The seasonal variation of soil and water loss in southern Yunnan isvery obvious,it may be divided into three different periods on the basis of soiland water loss during six years. (1) The period of slight soil and "water loss in hot and dry season(Feb.to May). (2) The period of severe soil and water loss in rainy season(Jun.toAug.). (3) The period of slight soil and water loss in cold and cool season(Sep.to Jan.of next year). 2. The general law is that the runoff,the soil erosion and the runoffcoefficient increase with every increase of rain capacity and rainfall intensity in this region. 3. In different exploitation,the soil and water loss of the rubber-teacommunity is 22.3％ and 29.7％ 1ower than that of a pure rubber plantation,and 95.7％ and 93.9％ lower than that of farm crop.Therefore,to transformfarm land into rubber-tea community or economic forest land of two storiesis a better way to utilize tropical mountainous area rationally and to decreaseloss of soil and water. 4. The results of the study still shows that the loss of soil and water onthe farm land of shifting cultivation is the most serious.It is 778.3 times and34.5 times that of tropical rainforest,and 6.6 times and 5.7 times that ofbench terrace respectively.In order to restore the function of tropicalrainforest ecosystem and to prevent the loss of soil and water on farm land inthis region,wé must safeguard tropical rainforest against deforestation.Wemust change of the slope land to contour terrace,and reform step by stepthe cropping system of shifting cultivation into that of rational rotation ofcrops,these are efficient measures to raise soil fertility,keep water and soil,fix farm land and obtain high yield of crops.