Abstract:

This study investigated the plant communities in alpine meadow gullies with differing degrees of erosion and analysed the changes in species diversity and the key factors influencing it in gullies with different erosion levels. We used a quadrat method and randomly selected 1 m×1 m sample plots in mildly， moderately and strongly eroded alpine meadows， sampling alternate erosion gullies， and using no erosion as a control. It was found that the proportion of high-quality forage grasses with Carex moorcroftii as the dominant species gradually decreased with increasing severity of erosion and gradually evolved into a community dominated by poisonous weeds such as Artemisia hedinii. Along the gradient of increasing erosion in the studied alpine meadows， above-ground biomass initially decreased and then increased， and vegetation coverage and species diversity gradually decreased. Compared to the non-eroded sample site， the mildly， moderately， and strongly eroded sample sites showed， respectively， a decrease in above-ground biomass of 38%， 69%， and 16%， a decrease in vegetation coverage of 20%， 46%， and 65%， and a decrease in the Shannon-Wiener index of 11%， 17%， and 76%. A linear negative correlation was observed between the slope gradient and the species diversity within the alpine meadow plant community （P<0.001）. Soil erosion leads to changes in soil texture that affect plant growth and plant community diversity. Plant community diversity indices were highly significantly correlated with soil organic matter， particulate organic carbon， pH， and soil sand and clay contents （P<0.01）. Shannon-Wiener， Simpson and Margalef indices were all highly significantly negatively correlated with soil pH （P<0.001）， while Shannon-Wiener and Simpson indices were both highly significantly positively correlated with soil organic matter （P<0.01）. Plant growth indicators were significantly correlated with bulk density （P<0.05）. Aboveground biomass was highly significantly and positively correlated with total porosity （P<0.01）， but highly significantly and negatively correlated with bulk density of the soil （P<0.001）. Vegetation coverage was highly significantly negatively correlated with pH （P<0.01） and sand content （P<0.01）， but highly significantly positively correlated with soil organic matter （P<0.001）， particulate organic carbon （P<0.01）， silt content （P<0.01） and clay content （P<0.01）. In summary， with increasing severity of erosion， the vegetation coverage and plant diversity of alpine meadows gradually decreased， and the community structure tended to become more homogeneous. Slope， soil organic matter and pH are the main environmental factors influencing changes in community structure in erosion-affected alpine meadows.

Key words: alpine meadows, species diversity, biomass, erosion