Plant community of alpine steppe shows stronger association with soil properties than alpine meadow alongside degradation.

The interaction between soil properties and plant community determines the efficacy to restore the degraded grassland via improving soil properties. We conducted a field survey to investigate the relationship between plant community composition and soil physical and chemical properties alongside different degradation stages of alpine grassland. Results showed that with the increasing severity of degradation, the dominant plants shifted from sedge and graminoid species, respectively, to forbs species in alpine meadow (AM) and alpine steppe (AS). Species richness and diversity indices were unchanged until the severely degraded stage in both AM and AS. Forward selection showed bulk density (BD) and ammonia nitrogen (NH4+) at 10-20 cm, pH and the ratio of soil organic carbon to total nitrogen (C/N) at 0-10 cm were the four important variables being responsible for the species community variation alongside degradation of AS, which explained 18.7% of the total variance. Soil nitrate nitrogen (NO3-) and C/N at 20-30 cm, NH4+ at 10-20, and BD at 0-10 cm were the important variables in driving the community variance alongside degradation stages, which only explained 9.5% of the total variance of AM. The loss of dense root layer and the species community change induced change in BD, and difference in plant competition for available resources would lead to the stronger association between vegetation community and soil properties in AS than that in AM. Our results indicate that though improving soil nutrients and soil texture to restore the degraded AS may be more effective than to restore degraded AM.