若尔盖草甸退化对土壤碳、氮和碳稳定同位素的影响

Effects of alpine meadow degradation on soil carbon,nitrogen,and carbon stable istope in Zoige Plateau

为了解不同退化阶段高寒草甸土壤碳、氮和碳稳定同位素的差异,对若尔盖湿地内沼泽草甸、草原化草甸、退化草甸3个阶段土壤的碳、氮和碳稳定同位素进行了分析.结果表明:若尔盖湿地草甸土壤δ^(13)C值介于-26.21‰^-24.72‰之间,土壤δ^(13)C值随土层加深而增大.土壤δ^(13)C值与有机碳含量对数值呈线性负相关.表层土壤(0~10 cm)δ^(13)C值大小顺序为草原化草甸>退化草甸>沼泽草甸,β值大小顺序为草原化草甸>沼泽草甸>退化草甸.沼泽草甸、草原化草甸、退化草甸0~30 cm土壤碳含量分别为105.32、42.11和31.12 g·kg^(-1),氮含量分别为8.74、3.41和2.81 g·kg^(-1),C/N分别为11.26、11.23和10.89.随着草甸的退化,土壤碳、氮呈降低趋势,退化草甸C/N值低于沼泽草甸和草原化草甸.随着土层深度加深,碳、氮含量呈现降低趋势.草甸退化导致的土壤δ^(13)C值差异主要发生在表层0~10 cm.3个退化阶段中,退化草甸土壤的β值和C/N最低,表明退化草甸土壤矿化作用较强.

To investigate the differences of soil carbon,nitrogen,and carbon stable isotopes in Zoige wetland,we analyzed the abundance of carbon stable isotopes and the contents of carbon and nitrogen in soils of three kinds of retrogressive successional grasslands(swampy meadow,steppe meadow,and degraded meadow）. The results showed that the δ13C values in the meadow soil of Zoige alpine wetland ranged from-26.21‰ to-24.72‰. The abundance of δ13C increased with the depth of soil. There was a significantly negative relationship between δ13C values and logarithm of soil organic carbon content across the soil profile. The δ13C values in the surface soil(0-10 cm）followed the order of grassland meadow degraded meadow swampy meadow,and the β values followed the order of grassland meadow swampy meadow degraded meadow. Soil organic carbon content was 105.32,42. 11 and 31. 12 g·kg^（-1）,while nitrogen content was 8.74,3.41 and 2.81 g·kg^（-1）,and C/N was 11.26,11.23 and 10.89,in the swampy meadow,grassland meadow and degraded meadow,respectively. The soil C/N was lower in degraded meadow than that in swampy meadow and grassland meadow. The total organic carbon and nitrogen content decreased obviously with increasing soil depth. The variations of soil δ13C among meadows with different degradation stages were mainly restricted to the 0-10 cm soil layer. The β values and C/N were the lowest in degraded meadow among three stages,suggesting that the mineralization rate of degraded meadow soil organic matter was relatively fast.