Abstract: To clarify the contents and ecological stoichiometric characteristics of soil carbon (C), nitrogen (N), and phosphorus (P) in alpine grasslands under different degradation degrees, we analyzed soil organic C (SOC), N, P, C∶N, C∶P and N∶P in undegraded (ND), lightly degraded (LD), moderately degraded (MD) and severely degraded (SD) alpine grasslands. The results showed that soil SOC, N, and P contents showed a decreasing trend with increasing degradation degree of grasslands. The average values of C∶N, C∶P, and N∶P were lower than the global level, all of which showed N-shaped changes with increasing degradation degree. Soil SOC, N, C∶P, N∶P, and N∶P were negatively correlated with soil pH and bulk density (P<0.05). Soil SOC, N, P, C∶P, and N∶P were positively correlated with soil water content (P<0.05). Soil P was not significantly correlated with soil bulk density (P>0.05). Soil C∶N was positively correlated with soil pH and bulk density (P<0.01), and negatively correlated with soil water content (P<0.01). Results of structural equation modeling indicated that grassland degradation directly affected soil physicochemical properties and thus soil SOC, N, and P content and their eco-stoichiometric ratio. In summary, grassland degradation changed soil microenvironment by reducing soil water content and increasing pH and bulk density, resulting in decreases in the contents of SOC, N, and P.

Key words: alpine grassland, degradation, eco-stoichiometric ratio, vertical distribution