川西高山树线交错带海拔梯度上土壤有机碳稳定性特征

高山树线交错带是高海拔地带对环境变化最为敏感的生态系统之一，土壤有机碳库及其稳定性在生态系统变化中具有显著指示作用。通过物理-化学方法对土壤不同活性有机碳进行连续分级分离，研究土壤有机碳不同组分在海拔环境梯度下分布特征及稳定性。结果表明，高山树线交错带土壤有机碳主要集中在物理分级组分（≥0.02 mm），且粒径越大有机碳含量越高，即主要以颗粒态有机碳形式存在，占比均高于98%；在<0.02 mm有机-无机复合体中有机碳采用化学分级分离，这部分有机碳占比低于土壤总有机碳2%，且主要以腐殖质（胡敏素）形式存在（占土壤总有机碳0.6%~0.8%），腐殖质占有机碳比例远低于一般土壤；随着海拔升高，土壤有机碳总量上升，颗粒态有机碳（物理分级组分）比例升高，胡敏素类腐殖质比例下降。因此，川西高海拔树线交错带的高寒土壤有机碳，主要以不稳定有机碳（POC）形式存在，随着温度上升（海拔降低）将导致土壤矿质化和腐殖化加剧，有机碳总量下降，土壤不稳定性组分（物理分级组分）降低，土壤稳定性（腐殖化比例）上升。

Stabilization of Soil Organic Carbon in Alpine Treeline Ecotone along Altitudinal Gradient in the West of Sichuan Province

The alpine treeline ecotone(ATE)is one of the most sensitive ecosystems for environmental change at high altitudes.The soil organic carbon pool and its stability have significant indications in ecosystem changes.In this paper,the physio-chemical methods were used to continuously separate the different activities of soil organic carbon,and the distribution characteristics and stability of different components of soil organic carbon under the elevation of environmental gradient were studied.The results showed that the soil organic carbon in the interlaced zone of alpine tree line was mainly concentrated in the physical fractionation component(≥0.02 mm),and the bigger the soil particle size,the higher the organic carbon content,i.e.the organic carbon existed mainly in the particulate form with the proportion of higher than 98%.Organic carbon in<0.02 mm organic-inorganic composites was chemically fractionated,which accounted less than 2%of total organic carbon in soil,and mainly existed in the form of humus(humin)(organic carbon 0.6%-0.8%),the proportion of humus in organic carbon was much lower than that in general soil.Along with the increase of elevation,soil organic carbon increased,the total organic carbon and the proportion of particulate organic carbon(physical fractionation)increased,and the proportion of humin in humus decreased.It is conclude that the alpine soil organic carbon in the high-altitude tree line interlace zone in western Sichuan is mainly in the form of unstable organic carbon(particulate organic carbon,POC).As the temperature rises(decreases altitude),soil mineralization and humification will increase,and the total amount of organic carbon will increase.As the soil component(physical fractionation component)decreases,soil stability(humidification ratio)increase.