黑土坡耕地有机碳及其组分累积-损耗格局对耕作侵蚀与水蚀的响应

Responses of accumulation-loss patterns for soil organic carbon and its fractions to tillage and water erosion in black soil area

耕作与水蚀是黑土区坡耕地碳库退化的主导因素,为进一步探究土壤有机碳(SOC)及其组分对不同侵蚀驱动力(耕作、水力)的响应格局,基于该区耕作侵蚀与水蚀模型,在定量表达耕作侵蚀-沉积量与水蚀量的基础上,利用地统计学的方法,分析了东北黑土区典型漫岗地形坡面尺度SOC及其3种组分的空间分布特征.结果表明:耕作侵蚀与沉积速率分别表现为坡上>坡下>坡中>坡脚和坡脚>坡下>坡中>坡上;水蚀速率表现为坡下>坡脚>坡中>坡上;坡下陡坡位置耕作侵蚀与水蚀协同引起严重的土壤流失.虽然耕作侵蚀速率(0.02~7.02t·hm^(-2)·a^(-1))远小于水蚀速率(5.96~101.17 t·hm^(-2)·a^(-1)),但耕作侵蚀在全坡面范围均可对SOC产生不同程度的影响,而水蚀则主要在坡下径流汇集区显著影响SOC的累积-损耗.受水蚀与耕作侵蚀-沉积作用影响,SOC、颗粒有机碳、水溶性有机碳在侵蚀点含量低于沉积点,而微生物生物量碳变化趋势相反;耕作侵蚀通过影响颗粒有机碳参与SOC的积累-损耗过程.

Tillage and water erosion have been recognized as the main factors causing degradation in soil organic carbon（ SOC） pools of black soil. To further explore the response of SOC and its fractions to different driving forces of erosion（ tillage and water）,geostatistical methods were used to analyze spatial patterns of SOC and its three fractions at a typical sloping farmland based on tillage and water erosion rates calculated by local models. The results showed that tillage erosion and deposition rates changed according to the slope positions,decreasing in the order： upper-slope lowerslope middle-slope toe-slope and toe-slope lower-slope middle-slope upper-slope,respectively; while the order of water erosion rates decreased in the order： lower-slope toe-slope middle-slope upper-slope. Tillage and water erosion cooperatively triggered intense soil loss in the lower-slope areas with steep slope gradient. Tillage erosion could affect C cycling through the whole slope at different levels,although the rate of tillage erosion（ 0.02-7.02 t·hm^-2·a^-1） was far less than that of water erosion（ 5.96-101.17 t·hm^-2·a^-1） in black soil area. However,water erosion only played a major role in controlling C dynamics in the runoff-concentrated lower slope area. Affected by water erosion and tillage erosion-deposition disturbance,the concentrations of SOC,particulate organic carbon and dissolved organic carbon in depositional areas were higher than in erosional areas,however,microbial biomass carbon showed an opposite trend. Tillage erosion dominated SOC dynamic by depleting particulate organic carbon.