The plant microbiome significantly influences plant health and ecosystem functions, yet its response to environmental change and links to plant diversity are not fully understood. We investigated the impacts of climate warming and nitrogen deposition on leaf epiphytic and endophytic bacterial communities in Stipa breviflora and Cleistogenes songorica over an 18-year field experiment in temperate desert steppe. Results showed increased diversity in both leaf bacterial types, with epiphytic biomass rising and endophytic biomass falling due to distinct mechanisms. Epiphytic diversity and biomass increased with leaf temperature and transpiration rate, endophyte diversity increased with leaf carbon and nitrogen concentrations, and endophytic biomass related to leaf nitrogen and phosphorus levels. Structural equation modeling revealed both epiphytic and endophytic bacterial diversity correlated with reduced plant diversity, which in turn was linked to increased leaf bacterial diversity, indicating a complex response of phyllosphere bacteria to global changes in perennial grassland ecosystems.

Foliar herbivory is known to directly affect phyllosphere microbiomes through altering plant phenotypes. However, how plant evolutionary responses to herbivory shape phyllosphere microbiomes is unclear. Here we use different invasive populations of the plant Ambrosia artemisiifolia that vary in reassociation timespan with a native specialist herbivore, to test whether renewed selection imposed by the herbivore is accompanied by evolutionary shifts in leaf chemistry and correlated changes in phyllosphere microbial communities. In common garden experiments we found directional changes in phyllosphere fungal communities with increasing duration of reassociation, accompanied by increased phyllosphere fungal alpha diversity and community complexity. These changes were associated with shifts in concentrations of plant metabolites, expression levels of their underlying biosynthetic genes, and increased plant herbivore resistance. Invasive plant reassociation with specialist insects can thus reshape phyllosphere fungal communities via changes in plant chemistry, demonstrating the role of plant evolutionary responses to herbivores in modulating microbial communities.

Anthropogenic environmental changes are influencing the structure and function of many ecological communities, but their underlying mechanisms are often poorly understood. We conducted a seven-year field experiment to explore the ecological consequences of nitrogen (N) and phosphorous (P) enrichment in a high-altitude Tibetan alpine grassland. The enrichment of both N and P, but not either alone, resulted in increased plant above- and below-ground biomass. By contrast, N, but not P, enrichment reduced species richness, and altered plant phylogenetic diversity and structure. The observed decline in species richness under N addition was driven by the loss of species characterized by high leaf nitrogen content, and associated with higher soil manganese level and greater belowground competition. Our study highlights resource co-limitation of community biomass but not structure of the study grassland, while also identifying soil metal toxicity and belowground competition as important mechanisms driving community changes after nutrient amendment.

Nitrogen deposition and land use are known to influence various ecosystems, but how these anthropogenic activities influence community and ecosystem responses to disturbance remains poorly understood. Here we investigated the effects of increased nitrogen deposition and mowing on the resistance and recovery of a temperate semiarid grassland experiencing a three-year drought. Nitrogen addition reduced grassland biomass resistance and increased biomass recovery, whereas annual mowing reduced grassland structural resistance and increased structural recovery. The treatment effects on community biomass resistance and recovery were largely modulated by the stability of the most dominant species, whereas the treatment effects on community structural resistance and recovery were largely modulated by the structural stability of dominant species assemblages. The discrepancy in the response of biomass and structural stability emphasizes the need to study changes across levels of ecological organization for a more complete understanding of ecosystem responses to disturbances under widespread environmental changes.