Plant litter input has important influences on soil CO2 emission and soil organic carbon (SOC) formation in terrestrial ecosystem. However, it is not well known for the fate of carbon when exogenous organic matters with different chemical structures are added to soil with different textures. In this study, we added the uniformly 13C-labelled substrates of glucose, starch, and cellulose to red soil and sandy soil, and compared the net 13C accumulation and recovery and its proportions in soil releasing CO2, SOC, dissolved organic carbon (DOC) and microbial biomass carbon (MBC) pools. The results showed that δ13C values increased after exogenous substrate additions in CO2, SOC, DOC, and MBC, and that the peaks of δ13C in CO2 pool appeared delay with increasing chemical structure complexity. The fate of exogenous C and its contributions of different C pools were significantly influenced by exogenous C types, soil types, and incubation times. In sandy soil, the added exogenous C was more mineralized as CO2, with the net accumulation and recovery of 13C in CO2 pool decreasing in the order of glucose>starch>cellulose. In red soil, more exogenous C was transferred to SOC pool, with the net accumulation and recovery of 13C in SOC pool decreasing in the order of glucose>starch>cellulose. Our results implied that the chemical structure of exogenous substrates and soil texture together controlled the fate and accumulation of exogenous organic carbon.
植物凋落物碳输入显著影响陆地生态系统土壤CO2排放和有机碳(SOC)形成,然而,针对不同质地土壤添加不同化学结构外源碳去向依然不清楚。本研究将13C标记的葡萄糖、淀粉和纤维素添加至红壤和风沙土,比较2种质地土壤添加不同化学结构外源碳在土壤释放的CO2、SOC、可溶性有机碳(DOC)和微生物生物量碳(MBC)库的净累积量、回收率及贡献比例上的差异。结果表明: 添加外源有机碳显著提高了CO2、SOC、DOC和MBC的δ13C值,且随着外源有机碳化学结构复杂性的增加,CO2的δ13C峰值依次延迟出现;外源有机碳种类、土壤类型和培养时间均显著改变外源碳去向及其在各碳库的贡献比例;在风沙土中,外源有机碳更多被矿化为CO2,且CO2库的外源碳净累积量和回收率大小依次为葡萄糖>淀粉>纤维素;红壤添加外源碳转变为SOC的累积量和回收率显著高于风沙土,且红壤SOC库的外源碳净累积量和回收率大小顺序也为葡萄糖>淀粉>纤维素。可见,外源有机碳化学结构和土壤质地共同调控外源碳去向及累积贡献。.
Keywords: 13 C isotopic tracing; SOC accumulation; carbon recovery; exogenous organic carbon; soil texture.