关键词: 掘根, 尖削度, 树冠特性, 林分密度, 土壤含水率

Abstract: The land use change in tropical forest area, as compared to that in other areas, is more vital to global carbon cycle. Taking the Naban River watershed in Xishuangbanna of Yunnan as study area, and by the methods of field survey and laboratory analysis, this paper studied the effects of the land use change from natural forest to dry farmland, paddy field, rubber plantation, or tea garden on the soil organic carbon (SOC) and soil microbial biomass carbon (SMNC) and nitrogen (SMBN). The results showed that after the natural forest changed into other land use types, the SOC, SMBC, and SMBN decreased significantly, with the greatest decrements of SOC and SMBC in paddy field. The SOC, SMBC, and SMBN were significantly higher in latosolic red soils than in latosols. The SOC was significantly positively correlated with SMBC, SMBN, and soil moisture, and significantly negatively correlated with soil bulk density and soil pH. The SMBN was significantly positively correlated with SOC and SMBC, and significantly negatively correlated with soil bulk density. The ratio of SMBC to SOC was significantly positively correlated with soil pH.

Key words: uprooting, taper degree, crown characteristics, stand density, soil moisture.