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

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 δC values in the meadow soil of Zoige alpine wetland ranged from -26.21‰ to -24.72‰. The abundance of δC increased with the depth of soil. There was a significantly negative relationship between δC values and logarithm of soil organic carbon content across the soil profile. The δC 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, while nitrogen content was 8.74, 3.41 and 2.81 g·kg, 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 δC 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.