坡地黑土侵蚀区和沉积区不同有机碳库分配特征

Distribution Characteristics of Different Organic Carbon Pools of Sloping Black Soil in Erosion and Deposition Areas

试验采用Stewart物理-化学联合分组方法,以东北黑土区长期耕作坡耕地为研究对象,探讨坡上侵蚀-坡下沉积区不同稳定机制碳库(游离未保护、物理保护、生物化学保护、化学保护)分配特征。结果表明:坡上侵蚀区减少活跃碳库(游离未保护),但同时促进中等稳定机制碳库(物理保护)的更新,并富集惰性碳库(生物化学和化学保护);被侵蚀土壤有机碳(SOC)在坡下沉积区埋藏、固存,显著增加沉积区各碳库质量分数。坡上侵蚀区碳积累速率,从大到小依次为生物化学保护SOC(61.5%)、化学保护SOC(27.8%)、物理保护SOC(5.9%);坡下沉积区碳积累速率,从大到小依次为化学保护SOC(20.4%)、物理保护SOC(10.7%)、游离未受保护SOC(5%)。侵蚀区游离未保护SOC和沉积区生物化学保护SOC,对总有机碳的变化无明显响应。

With a typical sloping farmland from black soil region of Northeast China, we analyzed the distribution characteristics of different carbon pools(free unprotected organic carbon, physical protected organic carbon, biochemical protected organic carbon and chemically protected organic carbon) in erosion and deposition position, separately, by using the Stewart physical-chemical fractionation method. The results showed that soil erosion area reduced the easily degradable active organic carbon(free unprotected), while promoted the turnover of medium stable mechanism organic carbon(physical protection) and enriched inert organic carbon(biochemical and chemical protection). The eroded soil organic carbon(SOC) was buried and stored in the deposit area, leading to an increase of each carbon pool calculated in mass fraction(g·kg-1) in the deposit area. The rate of carbon accumulation from large to small in erosion area were biochemical protected organic carbon(61.5%), chemically protected organic carbon(27.8%), physically protected organic carbon(5.9%);and which in deposition area were chemically protected organic carbon(20.4%), physically protected organic carbon(10.7%), free unprotected organic carbon(5%). In addition, free unprotected organic carbon in erosion area and biochemical protected organic carbon in deposition area did not significantly response to the change of total organic carbon.