农田营造早竹林后土壤有机碳的变化

Changes in Soil Organic Carbon after Bamboo Afforestation in Cropland

对农田营造早竹林后不同年限土壤有机碳变化规律的研究结果表明：（1）竹林3年生时，各层次土壤有机碳含量都呈现下降的趋势，其中表土层（0～30em）下降幅度最大；竹林满园后，由于采取了集约经营措施，竹林土壤有机碳含量迅速回升，至9年生时，各层次土壤有机碳含量都超过了农田相应层次水平，但是12年生时竹林各层次土壤有机碳含量又呈现下降趋势。（2）土壤有机碳密度变化和土壤有机碳含量相似，竹林3年生时各层土壤有机碳密度均呈现下降趋势；6年生时，除了0～30cm土层继续下降外，其余各层次有机碳密度都增加；至9年生时，有机碳密度都超过相应农田各层土壤有机碳的密度；12年生时，各层土壤有机碳密度都呈现下降趋势。（3）3年生竹林土壤有机碳储量下降了近22％；以后土壤有机碳储量均逐渐增加，9年生竹林，土壤有机碳储量要超过农田土壤有机碳的储量；12年生时竹林有机碳储量下降，但是依然高于农田土壤有机碳的储量。

This paper deals with the changing regularity of soil organic carbon （ SOC ） after afforestation in cropland, which showed ： （ 1 ） in three years after afforestation, the contents of SOC were decreased in different soil profiles and the top soil profile（ 0 ～30 cm） was decreased more than that of the others; Three years later, due to the intensive management, the contents of SOC were increased quickly and up to nine years, the contents of SOC being larger than those of cropland ; but twelve years later, the contents of SOC were decreased again because of the less intensive management. （2） The density of SOC showed almost the same tendency as the content of SOC ; In three years, the density of SOC were decreased, later, the density of SOC was increased and in nine years, the density of SOC became larger than that of cropland; after nine yeas, the density of SOC were decreased again, but still more than those of cropland ; （ 3 ） Three years after afforestation, the storage of SOC was decreased by 22%. After three years, the storage of SOC was increased gradually and in nine years, the storage of SOC became larger than that of cropland ; In 12 years old stand, the storage of SOC was decreased, but larger than that of cropland. The content, density and storage of SOC all showed the tendency of decline, rising gradually, excessing and then decreasing.