江汉平原不同土地利用方式下土壤团聚体中有机碳的分布与积累特点

论文探讨了江汉平原果园、旱地、水田、水旱轮作等利用方式下土壤团聚体的组成、有机碳与活性有机碳的分布与积累特点。结果表明:供试土壤团聚体的组成均以2～20μm粒径为主,其次为<2μm和20～50μm粒径,<50μm粒径团聚体的含量占团聚体总量的80.8%～94.1%。不同利用方式下有机碳含量的峰值均出现在200～2000μm团聚体中,且>50μm粒径团聚体中有机碳的含量比<50μm粒径的高;但69.8%～86.6%的有机碳分布在<50μm粒径团聚体中,其中以2～20μm团聚体中有机碳所占的比例最大(35.2%～45.9%),细微团聚体固碳能力较强,而粗粒径团聚体中的有机碳对土地利用方式的变化较为敏感。土壤团聚体中的活性有机碳以2～20μm粒径的最低,<2μm和20～50μm中有机碳的活性相差不大;不同粒径的团聚体中均为水耕利用方式下(水田和水旱轮作)土壤活性有机碳的含量比旱耕利用方式下(果园和旱地)的高,但随着土壤团聚体粒径的增加,由水耕利用方式下活性有机碳所占的比例较大逐渐过渡到以旱耕利用方式下活性有机碳的比例较大。由于供试样品中2～20μm团聚体中有机碳积累最大、固定的有机碳最多,可以考虑将2～20μm团聚体作为土壤固定有机碳的特征团聚体。这些结果可为我国区域土壤有机碳的循环提供科学数据。

Organic Carbon Distribution and Storage of Soil Aggregates under Land Use Change in Jianghan Plain, Hubei Province

Soil aggregates determine the fertility and productivity of soils,and possess the ability to protect soil organic carbon by physical entrapment.The land use change will affect the capacity of the soil to act as both a source and a sink of organic matter and nutrients.However,limited literature on soil organic carbon in aggregates with different sizes under land use change were reported.The objective of the present study was to elucidate aggregate composition,organic carbon(OC)distribution and storage of orchard soil,dryland soil,paddy soil,and dryland and paddy rotation soil from Jianghan plain.The results showed that the percentage of soil micro-aggregates in the following order:2-20μm,<2μm and 20-50μm.Soil micro-aggregates in <50μm size group occupied 80.8%-94.1% of the total soil micro-aggregates.The organic carbon contents under different land uses was the highest in 200-2 000μm fractions of aggregates.Furthermore,OC contents in >50μm fraction were higher than those in <50μm fraction.However,69.8%-86.6% of the total organic carbon was mainly found in the aggregates with a size of <50μm.Especially,35.2%-45.9% of the total organic carbon was concentrated in the aggregates with sizes of 2-20μm.So the fine micro-aggregates possessed the high ability of carbon sink,and the organic carbon content in coarse micro-aggregates responded easily to land use change.The content of active soil organic carbon in 2-20μm fraction of different aggregates was the lowest,and their differences between <2μm and 20-50μm was slight.The content of active soil organic carbon was higher in paddy field than that under dryland cultivation.It was proposed that 2-20μm fraction of aggregates was regarded as characteristic aggregates due to its high retention of soil organic carbon.These results will help to reveal the regional soil organic carbon sequestration.