干热河谷不同利用方式下土壤活性有机碳含量及其分配特征

对比研究了干热河谷新银合欢林地、大叶相思林地、旱耕地和荒地土壤有机碳(SOC)、易氧化有机碳(ROC)、微生物生物量碳(MBC)和可溶性有机碳(DOC)含量及其分配比例.结果表明,4类利用方式下SOC含量在4.22～5.19g·kg-1之间,其差异不显著.新银合欢(2.14g·kg-1)和大叶相思林地ROC含量(2.03g·kg-1)显著高于旱耕地(1.38g·kg-1)和荒地(1.34g·kg-1);4类利用方式下,旱耕地MBC和DOC含量均最高,荒地最低.林地ROC分配比例是荒地和旱耕地的1.3～1.6倍;旱耕地MBC和DOC的分配比例均高于其他3类利用方式,林地和荒地MBC、DOC分配比例接近.植被凋落量和管理措施是不同利用方式下ROC含量差异的主要原因,而土壤含水量和植被凋落性质是4类利用方式下MBC、DOC含量变异的主要影响因素.干热河谷ROC含量变化可以敏感地指示SOC动态,但MBC、DOC含量变化则不能反映SOC动态.

Soil Labile Organic Carbon Contents and Their Allocation Characteristics Under Different Land Uses at Dry-hot Valley

Soil organic carbon(SOC), readily oxidation organic carbon(ROC), microbial biomass carbon(MBC)and dissolved organic carbon(DOC)contents and their allocation ratios were comparatively investigated under Leucaena leucocephala woodland, Acacia auriculiformis woodland, dry cropland and wasteland in dry-hot valley. Results showed that SOC contents were not significant differences among the four land uses with the range of 4.22-5.19 g·kg^-1. ROC contents under L. leucocephala(2.14 g·kg^-1)and woodland(2.03 g·kg^-1)were both significantly higher than those under dry cropland(1.38 g·kg^-1)and wasteland(1.34 g·kg^-1). The highest MBC and DOC contents both presented under dry cropland among the four land uses, whereas the lowest occurred under wasteland. ROC allocation ratios under woodlands were 1.3 to 1.6 times to those under dry cropland and wasteland. MBC and DOC allocation ratios under cropland were higher than those under other three land uses, and the ratios were closely among woodlands and wasteland. Plant residue amounts and management were primarily determined ROC contents, and soil water content and plant residue quantity were mainly affected the variation of MBC and DOC contents under the four land uses. The change of ROC contents could sensitively indicate SOC dynamics in dry-hot valley, but the change of MBC or DOC could not.