川西高寒山地灌丛草甸不同海拔土壤碳矿化特征

Mineralization characteristics of alpine shrub meadow soil carbon at different elevations in western Sichuan

研究不同海拔土壤碳矿化特征对深入认识不同海拔高寒灌丛草甸土壤有机碳动态变化有重要作用.以折多山3800 m、4000 m、4200 m的半阴坡和半阳坡土壤为研究对象,采用野外调查与室内分析相结合的方法对不同海拔土壤碳矿化差异进行探讨.结果表明:各海拔土壤有机碳矿化速率随着培养时间的推移逐渐降低,且前21 d降低幅度明显高于后21 d,土壤有机碳矿化速率和累积碳矿化量在坡向上和土层中大体呈现出半阴坡高于半阳坡,0-20 cm土层高于20-40 cm土层且差异显著(P<0.05),但在海拔上没有一致变化规律.一级动态方程均能很好地拟合各海拔土壤累积矿化量,各海拔土壤潜在可矿化有机碳量(C0)、C0/SOC值均表现出半阴坡高于半阳坡,且都在3800 m灰化土达到最大,表明在相同的环境温度背景下,半阴坡土壤固碳能力低于半阳坡,且灰化土固碳能力最弱.各海拔土壤活性有机碳含量占总有机碳含量比例呈现出半阴坡大于半阳坡,说明与半阳坡相比半阴坡土壤有机碳质量更高.除3800 m灰化土以外,土壤有机碳、活性碳含量均表现0-20 cm土层高于20-40 cm土层且差异显著(P<0.05).土壤碳矿化速率、累积矿化量与土壤有机碳、活性碳显著相关,且活性碳更能直接影响有机碳矿化.综上所述,高寒地区阴阳坡土壤有机碳矿化存在差异,阴坡有机碳矿化量高于阳坡.

Examining the variation in soil organic carbon(SOC)mineralization at different elevations is crucial to better understand organic carbon dynamics in soil.We selected semi-shady slopes and semi-sunny slopes of 3800 m,4000 m,and 4200 m in the alpine Zheduo Mountains as the study area and used field investigation and indoor analysis methods to evaluate the differences in carbon mineralization at different elevations.The SOC mineralization rate gradually decreased with cultivation time at each elevation,and the first 21-day reduction was significantly higher than the last 21-day reduction.There was no consistent change in the SOC mineralization rate or cumulative SOC mineralization with elevation,but semishady slopes and the 0-20 cm soil layer presented significantly higher values than semi-sunny slopes or the 20-40 cm soil layer(P<0.05).The dynamics of SOC mineralization could be described by first-order kinetics.The potential mineralizable organic carbon(C0)and C0/SOC values were significantly higher in the semi-shade slopes and reached maximum values at 3800 m,indicating that the carbon sequestration capacity of semi-shady slope soil was relatively lower than that of the semi-sunny slopes.The podzolic soil was weakest under the same ambient temperatures.The ratio of soil active organic carbon to total organic carbon was significantly higher in the semi-shade slopes,indicating that the quality of soil organic carbon was greater.Soil organic carbon and activated carbon content were significantly higher in the 0-20 cm soil layer than in the 20-40 cm soil layer(P<0.05),except in podzolic soil at 3800 m.Soil organic carbon was also significantly correlated with soil activated carbon.The soil carbon mineralization rate and cumulative mineralization were significantly correlated with SOC and activated carbon content,and activated carbon directly affected organic carbon mineralization.