南方红壤丘陵区不同土地利用方式下土壤有机碳分布特征及其与草本生物量的关系

Effects of land use type on the distribution of organic carbon in different sized soil particles and its relationships to herb biomass in hilly red soil region of South China

不同土地利用方式下不同粒径土壤有机碳含量的变化可以在一定程度上反映土壤碳的变化,对揭示土壤有机碳循环过程具有重要意义.本研究在长期水土流失监测的基础上,采用土壤颗粒分级的方法,以南方红壤丘陵区不同土地利用方式(荒地、松林、草地)坡地土壤为研究对象,探讨了不同土地利用方式对不同粒径土壤有机碳分布特征的影响及其与草本生物量的关系.结果表明:土地利用方式和坡位对不同粒径土壤有机碳含量的影响较明显,研究区不同粒径土壤有机碳含量均表现为草地>松林>荒地;不同粒径土壤有机碳所占比例主要取决于土地利用方式,与坡位关系不大;由颗粒有机碳/矿物结合态有机碳(POC/MOC)值可知,草地土壤有机碳较易矿化,而荒地和松林土壤有机碳较稳定;红壤丘陵区坡地土壤砂粒有机碳对草本生物量的影响较大.

The changes in organic carbon content in different sized soil particles under different land use patterns partly reflect the variation of soil carbon,being of significance in revealing the process of soil organic carbon cycle.Based on the long-term monitoring of soil erosion,and by the methods of soil particle size fractionation,this paper studied the effects of different land use types（wasteland,pinewood land,and grassland） on the distribution of organic carbon content in different sized soil particles and its relationships to the herb biomass.Land use type and slope position had obvious effects on the organic carbon content in different sized soil particles,and the organic carbon content was in the order of grassland﹥pinewood land﹥wasteland.The proportion of the organic carbon in different sized soil particles was mainly depended on the land use type,and had little relationships with slope position.According to the analysis of the ratio of particle-associated organic carbon to mineral-associated organic carbon（POC/MOC）,the soil organic carbon in grassland was easily to be mineralized,whereas that in wasteland and pinewood land was relatively stable.On the slopes mainly in hilly red soil region,the soil organic carbon in sand fraction had great effects on herb biomass.