外源碳酸钙和稻草对喀斯特地区土壤活性有机碳的影响

为了解喀斯特土壤活性有机碳在土壤有机碳周转中的特征,设置在干土中添加14C–稻草(每1 g干土添加500μg C)、14C–CaCO3粉末(每1 kg干土添加50 g C)和不添加任何外源物(CK)3种处理,对广西环江县2种典型类型土壤棕色石灰土、黑色石灰土和地带性红壤进行为期100 d的室内培养试验。结果表明,添加14C–稻草和14C–CaCO3后5 d,红壤、棕色和黑色石灰土中土壤总微生物生物量碳(MBC)含量均达峰值,红壤中总MBC含量分别为231.7、273.0 mg/kg,分别高于对照70.2%和100.5%;棕色石灰土中总MBC含量分别为288.1、307.7 mg/kg,分别高于对照23.0%和31.3%;黑色石灰土中总MBC含量分别为683.7、787.2 mg/kg,分别高于对照4.5%和20.3%。3种土壤总溶解有机碳(DOC)含量均达到最大值;黑色石灰土总MBC含量显著大于棕色石灰土和红壤,而红壤总DOC含量显著大于石灰土(P<0.05)。14C–稻草对3种土壤14C–MBC、14C–DOC含量的影响显著大于14C–CaCO3的影响(P<0.05)。添加外源碳酸钙和稻草均能增加土壤活性有机碳含量。喀斯特地区石灰性土壤较红壤稳定,有利于土壤有机碳的积累。

Influence of exogenous calcium carbonate and rice straw on active organic carbon of Karst soils

To elucidate the features of active organic carbon in Karst soils in the turnover of soil organic carbon,14C–labeled straw and 14C–labeled calcium carbonate were respectively added to each of the terra fusca,rendzina and zonal red soil of Huanjiang Guangxi for a 100 d incubation test.Soils with no addition were regarded as CK.Results showed that 14C–labeled straw exhibited obviously higher influence on 14C–MBC,14C–DOC in the three soils,compared to 14C–labeled calcium carbonate(P<0.05).After 5 d of incubation,total MBC(microbial biomass carbon) reached the peak in the three soils added with 14C–labeled straw or 14C–labeled calcium carbonate,and the MBC in red soils was 231.7,273.0 mg/kg,were respectively 70.2% and 100.5% higher than that in the CK;the MBC in terra fusca was 288.1,307.7 mg/kg,were respectively 23.0% and 31.3% higher than that in the CK while MBC in rendzina was 683.7,787.2 mg/kg,were respectively 4.5% and 20.3% higher than that in the CK;DOC(dissolved organic carbon) in the three soils also reached the maximum.The MBC in rendzina was obviously higher than that in terra fusca and red soil,but the DOC in red soil was obviously higher in terra fusca,rendzina(P<0.05).Exogenous 14C–labeled matters could promote the increase of soil active organic carbon and in the same condition,rendzina and terra fusca are more likely to accumulate organic carbon,compared to red soil.