不同水土保持林地土壤有机碳研究

研究了重庆四面山低山丘陵区不同水土保持林地0~20、20~40 和40~60 cm的土壤有机碳含量及不同深度的土壤有机碳密度。结果表明：0~20、20~40 和40~60 cm土层中土壤有机碳含量的平均值分别为3309、751和321 g/kg；0~20 cm的土壤有机碳密度介于497～1431 kg/m2，而0~60 cm的土壤有机碳密度介于784～1794 kg/m2，均值为1278 kg/m2；土壤有机碳含量和有机碳密度随土壤深度增加而显著减少，但其减少程度随水土保持林树种组成不同而异；不同水土保持林地60 cm深度的土壤有机碳密度存在显著差异，表现为：天然次生林>人工林>农耕地，其中，天然阔叶混交林土壤有机碳密度最大，为1794 kg/m2，农耕地的最小，仅为784 kg/m2。人工水土保持林中，阔叶混交林的土壤有机碳密度最大。从增加土壤碳的角度，建议营造阔叶混交林

SOIL ORGANIC CARBON UNDER DIFFERENT FORESTS FOR WATER AND SOIL CONSERVATION

Different forests for water and soil conservation in Simian Mountain of Chongqing were selected for field experiment to study soil organic carbon (SOC) content in 0~20,20~40 and 40~60 cm and SOC density to different soil depths.Results showed that the mean SOC content in 0~20,20~40 and 40~60 cm was 33.09, 7.51 and 3.21 g/kg,respectively.The SOC density to the depth of 20 cm ranged from 4.97 to 14.31 kg/m2,and that to 60 cm ranged from 7.84 to 17.94 kg/m2 with the mean of 12.78 kg/m2 in forest stands for water and soil conservation.With increasing soil depth,SOC content and density decreased significantly,but the decrease varied with tree species composition.Significant differences were found for SOC density to the depth of 60 cm in different forest stands,which decreased in the order of natural secondary forests > plantations for water and soil conservation > agricultural land.The highest SOC density (17.94 kg/m2) was found in the natural broad leaved mixed forest,and the lowest one (7.84 kg/m2) in the agricultural land.Among plantations for water and soil conservation,the highest SOC density was found in the broad leaved mixed plantation.Therefore,broad leaved mixed plantation is suggested to be established to increase SOC