Plant–Soil Relationships Diminish Under Major Versus Moderate Climate Change in Subalpine Grasslands

Plant communities and soil microbial communities influence each other directly and indirectly via the resource pools they modify. Despite apparent sensitivities of plants and microbes to climate, little is known concerning how climate change will affect plant–soil relationships. We conducted a downslope translocation of intact soil–plant mesocosms in subalpine grasslands to mid- and low-elevation sites to determine how climate change (warmer and drier conditions) influences plant–soil relationships. While soil nutrient pools and microbial composition were key determinants of plant community characteristics under control and moderate climate change (+1°C, +8 days growing season), these relationships diminished under major climate change (+3°C, +21 days growing season). Positive correlations of fungi and nitrogen-fixing bacteria for plant growth emerged under moderate climate change and diminished under major climate change. Our findings indicate that climate change effects do not solely impact plant community metrics, soil nutrient pools, and soil microbial community composition, but also a breakdown in the ecological coupling among them. We found evidence of threshold-like behavior for plant–soil relationships in response to major versus moderate environmental change and that plant community metrics and soil microbial dynamics may become more independent in subalpine grasslands following environmental shifts that accompany climate change.