祁连山不同海拔土壤有机碳库及分解特征研究

依据三库一级动力学理论,通过室内土样培养实验,研究了祁连山不同海拔高度土壤总有机碳库(Csoc)、活性碳库(Ca)、缓效性碳库(Cs)和惰性碳库(Cr)特征及有机碳(SOC)的分解特征.结果表明,祁连山不同海拔A、B层土壤总有机碳库含量分别为7.606～89.026 g·kg-1,5.804～84.267 g·kg-1;活性碳库含量分别为0.180～1.328 g·kg-1,0.159～1.273g·kg-1;缓效性碳库含量分别为3.650～35.173 g·kg-1,3.703～43.623 g·kg-1;惰性碳含量分别为3.776～65.298 g·kg-1,1.942～48.121 g·kg-1.总有机碳库随海拔表现出"增加-减少-增加-减少"的变化趋势,3种组分碳库未表现出海拔高度上的明显变化规律,大致呈现中高海拔>高海拔>中低海拔.土壤总有机碳库和惰性碳库含量在海拔之间有极显著差异(P<0.01),缓效碳库有显著性差异(P<0.05),活性碳库间无显著性差异.培养结果显示土壤有机碳分解速率也未表现出随海拔高度的明显变化规律,与碳库变化几乎一致.不同海拔土壤有机碳日释放速率峰值与整个培养过程土壤有机碳释放速率变化一致,可以用以代表有机碳分解的快慢特征.活性碳库与有机碳日释放速率峰值满足线性关系(P<0.01).培养结果显示土壤有机碳按活性碳库、缓效性碳库、惰性碳库的顺序进行周转.多项式方程能很好表达有机碳累积释放量与时间的关系,三次多项式已能达到较好的精度(R2>0.99).

Study on Soil Organic Carbon Pools and Turnover Characteristics Along an Elevation Gradient in Qilian Mountain

On the basis of the first order dynamic model combining with the laboratory soil incubation experiment, characteristics of soil organic carbon pools(C_soc), active carbon pools(C_a), slow carbon pools(C_s), passive carbon pools(C_r) and their turnover in Qilian Mountain were studied. It has been showed that the size of C_soc in horizon A and B ranges from 7.606-89.026 g·kg^-1and 5.804-84.267 g·kg^-1, which shows tendency of "increase-decrease-increase-decrease" with elevation. The size of C_a, C_s and C_r in horizon A and B under different elevations respectively ranges from 0.180-1.328 g·kg^-1, 0.159-1.273 g·kg^-1; 3.650-35.173 g·kg^-1, 3.703-43.623 g·kg^-1; 3.776-65.298 g·kg^-1, 1.942-48.121 g·kg^-1,which incarnates no obvious variation law with elevation.The contents of C_soc, C_r and C_ssignificantly differ with different elevation gradients. There is no significant difference in the C_a content between different elevation gradients. Decomposition rate of C_soc also has no evident change law in elevation. The peak of daily carbon release rate varies with carbon release rate in the whole incubation process, which could be used to present character of SOC turnover rate. It has been also showed that C_a and peak of daily carbon release rate have a significant relationship, and they follow the linear relationship. The incubation reveals that C_soc turns over in sequence of C_a, C_s and C_r. Polynomial equation presents relation between total SOC release amount and time, of which cubic polynomial has achieved preferable precision(R²>0.99).