Mechanism of plant-soil feedback in a degraded alpine grassland, Tibetan Plateau

Abstract

Although biotic and abiotic factors have been confirmed to be critical factors that affect the community dynamics, their interactive effects have yet to be fully considered in grassland degradation. Herein, we tested how soil nutrients and microbes regulated plant-soil feedback (PSF) in a degraded alpine grassland. Our results indicated that, from non-degraded (ND) to severely degraded (SD), significantly (P<0.05) decreased soil total carbon (from 17.66 to 12.55 g/kg) and total nitrogen (from 3.16 to 2.74 g/kg) were detected. Despite higher nutrients in ND soil generating significantly (P<0.05) positive PSF (0.52) on monocots growth when the soil was sterilized, a high proportion of pathogens (36%) in ND non-sterilized soil resulted in a strong negative PSF on monocots. By contrast, the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes (70%) strongly promoted their survival and growth in SD with infertile soil. Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil. And the emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland.