Study on the compensatory growth of alpine meadows along a degradation gradient in northwestern Yunnan Province

To identify the compensatory growth ability of alpine meadows and the mechanisms underlying the process of land degradation in northwestern Yunnan province (NYP), this study specified three degradation levels, i.e., heavy degradation (HD), moderate degradation (MD), and control (CK). An in situ mowing experiment was conducted to test the strength of alpine meadow compensatory growth across these three degradation levels from July to September 2018. Meanwhile, soil samples were collected and soil physical and chemical properties, such as bulk density, moisture, average particle size, pH, total organic carbon, total nitrogen, available nitrogen, and available phosphorus, were measured. The results showed that the total coverage, average height, and aboveground biomass of alpine meadows decreased along the degradation gradient. Regarding soil variables, the soil bulk density, soil moisture, average particle size, total nitrogen, and total organic carbon decreased along the degradation gradient. There were no significant differences in soil pH or available nitrogen content among degradation gradients, while the order of available phosphorus was MD > CK > HD. Additionally, the over-compensatory phenomenon was detected across all degradation levels, and there was no significant difference in the strength of over-compensatory growth among the degradation levels. The strength of over-compensatory growth of Gramineae and forbs did not change significantly across the degradation gradient, whereas the strength of over-compensatory growth of Cyperaceae increased as degradation level increased, i.e. CK < MD < HD. Compared to Gramineae and Cyperaceae, the over-compensatory growth of forbs was less affected by soil physicochemical properties. Finally, the effects of soil physicochemical properties on the over-compensatory growth of alpine meadows in HD were stronger than in those in CK and MD. This study suggests that although the plant communities and some soil physicochemical properties could be negatively affected by land degradation, the over-compensatory growth of plant communities could remain stable if the negative changes of soil physicochemical properties do not restrict the over-compensatory growth of plants in the alpine meadows of NYP.