西南喀斯特石灰土中钙的形态与含量及其对土壤有机碳的影响

【目的】研究钙对喀斯特地区典型土壤有机碳积累与转化的影响。【方法】采取野外取样分析与室内培养相结合的方法，采集两种喀斯特典型土壤（棕色石灰土、黑色石灰土）和一种对照土壤（红壤）共54个样品，检测了土壤中钙的形态与含量及有机碳含量等理化指标。在此基础上，选取3种土壤类型具有代表性的样品，设置不添加外源物质（CK）、添加碳酸钙粉末（T2）和同时添加14C标记的稻草与碳酸钙粉末（T3）3个处理，通过室内培养试验，对培养过程中土壤CO2释放量和4种形态钙的含量进行了检测及分析。【结果】土壤中4种形态的钙以交换态和有机结合态与有机碳关系更为密切。添加碳酸钙显著影响土壤有机碳矿化，有机结合态钙含量的增量均值在红壤、棕色石灰土和黑色石灰土中依次为2.14%、4.66%、10.23%。土壤有机碳矿化对添加钙的激发效应在红壤中最强烈，其次为棕色石灰土，最后为黑色石灰土。【结论】西南喀斯特地区土壤有机碳的稳定性因土壤类型不同而存在差异。土壤有机碳的稳定性为黑色石灰土＞棕色石灰土＞红壤，因此，3种供试土壤中，黑色石灰土最有利于土壤有机碳的积累。

The Speciation and Content of Calcium in Karst Soils, and Its Effects on Soil Organic Carbon in Karst Region of Southwest China

【Objective】 The effect of calcium on soil organic carbon(SOC) turnover was studied.【Method】 Two Karst soils(terra fusca and rendzina) and a contrast soil(red soil) were selected(54 samples) for the study.Both sampling in field to analyze and laboratory incubation were done.The contents of four speciations of calcium and SOC were tested.Three typical samples from three soil types were used to conduct a 100d incubation experiment,and no adding exogenous substrate(CK),calcium carbonate addition(T2),both 14C-labeled organic substrate and calcium carbonate addition(T3) were designed.Mineralization of SOC and the content of different calcium speciations were measured during the incubation experiment.【Result】 The result showed that the calcium speciation of exchangeable-Ca and bound to organic mater-Ca were more closely related with SOC.SOC mineralization was significantly affected by adding calcium carbonate.The increment of bound to organic matter-Ca in red soil,terra fusca and rendzina was 2.14%,4.66%,10.23%,respectively,and the priming effect of cumulative mineralization by adding calcium carbonate was in the order of red soil > terra fusca > rendzina(P<0.05).【Conclusion】 It was concluded that SOC stability has differences in different soil types.The stability of SOC was in the order of rendzina> terra fusca > red soil.Therefore,the soil type which is most beneficial to cumulate SOC is rendzina,the second is terra fusca and the last was red soil in Karst area.