The impact of grazing exclusion on phosphorus dynamics in alpine grassland ecosystems

Background and aims

Grazing exclusion (GE) is widely implemented in alpine regions to restore habitats degraded by livestock. However, the effects of GE on phosphorus (P) dynamics in different alpine grassland ecosystems remain unclear.

Methods

We selected plots in alpine meadow and alpine steppe with both free grazing (FG) and GE. Plant community traits, plant P uptake, soil P fractions, soil physicochemical properties, enzyme activities, and microbial biomass were measured across all plots.

Result

GE significantly increased aboveground biomass P uptake in both alpine grasslands and belowground biomass P uptake in alpine steppe but had no significant effect in alpine meadow. Total soil P pools were not altered by GE in both alpine grasslands. However, GE increased the labile P fraction NaHCO₃-Pi and the non-labile P fraction c.HCL-Po in alpine meadow but decreased the NaHCO₃-Pi and non-labile P fractions c.HCL-Pi and c.HCL-Po in alpine steppe. The changes in the soil P pools in alpine meadow were primarily driven by soil organic carbon, whereas in alpine steppe, the changes were driven by soil properties (pH, ammonium, and nitrogen) and plant biomass.

Conclusion

The impact of GE on the plant P uptake in alpine meadows is less pronounced than in alpine steppe. Moreover, GE had opposite effects on soil P fractions in the two grasslands. These findings imply that GE may not have uniform benefits for P dynamics in all alpine grasslands, and management strategies should consider the distinct responses of different grassland types to optimize grassland restoration efforts.