Restoration of degraded alpine meadows from the perspective of plant–soil feedbacks

Understanding the plant–soil feedbacks (PSFs) of dominant species of alpine meadow under different degradation status could provide insights into sustainable restoration. The direction, strength, and influencing factors of dominant species’ PSFs in nondegraded (Intact), moderately degraded (MD), and severely degraded (SD) alpine meadows were examined in a two-phase PSFs experiment. Species of Intact exhibited neutral conspecific PSFs, whereas those of MD and SD exhibited negative conspecific PSFs. The species of MD demonstrated neutral heterospecific PSFs to those of Intact, whereas that of SD negatively feedbacked to those of Intact and MD. The NO₃⁻-N and NH₄⁺-N of soil conditioned by the species of Intact were 66% and 58% higher than the control (mixture soil conditioned by all species); but they were 37% and 32% lower in soil conditioned by the dominant species of SD. The relative abundance of soil fungal pathotrophs was 57% and 74% higher in soil conditioned by the dominant species of MD and SD than in Intact soil. The conspecific and heterospecific PSFs of all species positively correlated with the plant conditioning and degradation induced changes of difference in NO₃⁻-N and NH₄⁺-N and negatively correlated with the difference in relative abundance of pathotrophs. Soil microorganisms and nutrients explained most of the variation in conspecific (43%) and heterospecific PSFs (60%). Our results indicated that the N addition would facilitate the sustainable restoration of degraded alpine meadows because the addition of available N could drive the heterospecific PSFs toward more positive.