为研究土壤有机碳库极其稳定性对高寒生态系统碳的源汇效应,通过物理—化学方法对不同海拔高度(3 400～4 100 m)高寒土壤不同活性有机碳进行连续分级分离,研究了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:(1)海拔梯度上高山土壤主要以粗颗粒为主(0.25～2 mm); 在>0.02 mm的物理分级中,土壤有机碳含量随海拔的增加先增加后减小; 在<0.02 mm土壤化学分级的有机—无机复合体中,土壤有机碳占总有机碳比例为2%左右,低于一般低海拔土壤,且随海拔升高有增加的趋势,但在4 100 m海拔处显著降低。(2)有机—无机复合体中的有机碳主要以腐殖质形式存在,随海拔增高有增加的趋势。因此,川西高山海拔梯度上土壤有机碳库以不稳定的颗粒态有机碳(POC)形式存在,在全球气候变化进程中随着温度升高,土壤有机碳矿化速率将加快。
In order to explore the effect of soil organic carbon storage and stability on the source and sink of carbon in alpine ecosystems, soil samples were collected along the altitudinal gradients ranging from 3 400 m to 4 100 m in the western Sichuan Province, and organic carbon in these samples were fractionated according to a physio-chemical sequential extract method to evaluate changes in soil carbon stability at different elevations of alpine. The results showed that:(1)the soils along the alpine elevation gradient was dominated by coarse particles(0.25～2 mm), in the physical classification(>0.02 mm), the soil organic carbon content increased at first and then decreased with the increase of the altitude, that was, the soil organic carbon mainly existed in the form of particulate organic carbon; organic-inorganic carbon(carbon in organic-inorganic complex <0.02 mm)increased with altitude except at the highest altitude(4 100 m), the ratio of which was around 2% in total organic carbon and lower than that in lowland soil;(2)humus carbon was the major form of carbon in the organic-inorganic complex, and concent of humus also increased with altitude. Therefore, soil organic carbon of alpine was mainly sequestrated as liable organic carbon in the form of particulate organic carbon in western Sichuan Province, and organic carbon mineralization would be accelerated due to soil warming in the cold area of alpine in scenario of global climate change.
