黄土丘陵区不同有机碳水平侵蚀坡面土壤微生物量碳的分布特征

Distribution of soil microbial biomass on eroded sloping land with different organic carbon contents in the hilly loess plateau region

通过分析5种不同有机碳水平侵蚀坡面上土壤微生物量碳的空间分布特征及其影响因素,探究了不同土壤有机碳水平下侵蚀和土壤微生物量碳的＂压力-响应＂关系.结果表明：10-20 cm土层土壤微生物量碳含量随土壤有机碳水平的增加而增加.0-10 cm土层土壤微生物量碳含量比10-20 cm土层更易受坡面有机碳背景的影响,且对侵蚀的响应较敏感;2土壤微生物碳含量随着土层深度的加深而减少,当坡面有机碳水平为5.68 g·kg-1时,土壤微生物量碳的剖面分布差异最大.土壤微生物量碳的水平分布表现为沉积区〉对照区〉侵蚀区,当坡面有机碳含量在4.92-5.65 g·kg-1范围内,其水平分布差异较大.即在中等有机碳水平的侵蚀坡面上,土壤微生物量碳的空间分布差异较大,对侵蚀的响应较敏感;3土壤微生物量碳的空间分布主要受坡面土壤有机碳水平的影响;其次受坡位、土壤平均含水量、土壤容重等的影响.

Spatial distribution of soil microbial biomass carbon（ SMBC） in eroded sloping land is critical for understanding erosion effects on soil carbon emission. In this paper＂S＂-shaped sloping land was constructed in the field with 5 soil organic carbon levels. The ＂S＂-slope was divided into control zone,erosion zone and sediment zone from the top to the bottom of the slope based on the slope gradient. Soil samples were taken from different positons of the slope after a raining season. We studied the ＂pressure-response＂relationship between soil erosion and SMBC on sloping land to reveal how SMBC responded to the＂pressure＂of erosion through analysis of the spatial distribution of SMBC and its interrelationships with different organic carbon levels.Results showed that： 1 SMBC content in the 0 - 20 cm soil layers increased with the increasing soil organic carbon（ SOC） levels on sloping land,however,SMBC content in the 0 - 10 cm soil layer was more susceptible to erosion and subsequent SOC changes than the 10 - 20 cm soil layer; 2 The vertical distribution of SMBC showed a decline with depth. The biggest differences of SMBC between the 0 - 10 cm and the 10 - 20 cm soil layers were observed when the SOC content was around 5.68 g·kg-1,a moderate level of the background SOC; Horizontal distribution of SMBC on the sloping land adhere to a consistent rule that sedimentary zonecontrol zoneerosion zone.A higher variation of the horizontal distribution of SMBC on the sloping land was observed when the background SOC was at moderate levels ranged 4.92 g·kg-1to 5.65 g·kg-1,suggesting greater sensitivity to erosion at moderate SOC,compared to low or high SOC; 3 The spatial distribution of SMBC was mainly affected by different levels of SOC in the sloping land,followed by slope position,average soil water content and soil bulk density. The results implicated that the＂pressure-response＂relationship between soil erosion and SMBC on sloping land was dominant by background SOC. More attention should be paid to the land with moderate SOC in evaluating erosion effects on soil carbon emission.