Relationship between carbon and nitrogen in degraded alpine meadow soil

The distribution of soil organic carbon (SOC), labile organic carbon (LOC), and available nitrogen, as well as, the corresponding relationships between carbon and nitrogen were analyzed among meadows with varying degrees of degradation (normal, slight and severe) in Dangxiong, Tibet. The increasing severity of meadow degradation corresponded with decreasing soil organic carbon, LOC and available nitrogen. The SOC distributions in the 0 to 10 cm soil layer of the slightly degraded and severely degraded meadows were lower than that of the normal meadow by 13.2 to 27.5% and 39.5 to 78.6%, respectively. The LOC distribution in the two areas decreased by 11.1 to 50.9% and by 31.2 to 77.2%. The corresponding available nitrogen decreased by 25.6 to 38.2% and 48.8 to 68.0%, whereas the SOC decreased by 6.0 to 29.7% and 53.2 to 73.2%. The degradation of soil carbon and nitrogen occurred first in the 0 to 10 cm layer. In the 0 to 10 cm and the 10 to 20 cm layers, the relationship between soil available nitrogen and LOC was more significant than that between soil available nitrogen and SOC. Grassland degradation caused a decrease in the ratio of soil LOC to available nitrogen. The average proportions of LOC and available nitrogen in the normal, slightly degraded, and severely degraded meadows were 24, 19, and 17. These values showed that the nitrogen loss caused by grassland degradation is faster than LOC loss. During degradation, organic carbon was more stable than soil available nitrogen.