A STUDY ON SOIL-PHYSICAL PROPERTIES AND CHANGE OF SOIL MOISTURE CONTENT IN MAN-MADE FORESTS OF CUNNINGHAMIA LANCEOLATA AND PINUS MASSONIANA

This study was made in the yellow-red earth of man-made forests Cunninghamia lanceolata and Pinus massoniana in 1984-1988. There is a loam in soil texture. The depth of soil is thinner. The volume weight of soil ranges 0.78-1.35. The total porosity of soil is about 55%-77%, including capillarity porosity about 40%-50%.The coefficent of soil premeability 3.18-5.37mm/mun. The mean annual soil moisture content in 5 years is about 21%-32% of water. The soil moisture content in forests is more than that in the clear-cutting land, but the seasonal variation of soil moisture content in the forest is less than that in the clear-cutting land. The effect of climatical factors on soil moisture content is obvious. According to the mathematical statistics analysis, soil moisture(y) approximates precipitation (x1), air temperature (x2), air humidity (x3), air evaporation (x4) in polyromial regression, its equation is Y=a1x1 + a2x2 + a3x3 + a4x4 + a5. According to the analysis of this polyromial regression, the depth of soil moisture content, obviously effected by climatical factors, reaches to 20 cm of the soil in the forests and reaches to 40 cm of the soil in the clear-cutting land.