Top‐down control of plant communities by consumers

Trophic interactions are widely recognized to be a fundamental force shaping plant populations and communities. However, our understanding of how different consumers (i.e. grazers, insect herbivores and pathogens) affect plant performance (i.e. biomass, diversity, reproduction and/or survival) is fragmentary, particularly across diverse ecosystems and environmental contexts. We conducted a global meta‐analysis of 3135 data comparisons from 296 papers to quantify the effects of removing plant consumers on plant biomass, diversity, reproduction and survival. We examined how these effects varied across ecosystem types (forest or grassland), levels of ecological organization (population or community) and study designs (field or pot experiment), as well as along environmental gradients (e.g. of temperature and precipitation) and across spatial scales (i.e. different plot sizes). Pathogen removal increased plant survival but reduced plant species diversity, supporting a role for pathogens in maintaining diversity through conspecific negative density dependence (CNDD). The removal of insect herbivores enhanced plant biomass, reproduction and survival, particularly at the population level and in field experiments. Grazing exclusion increased plant biomass, reproduction and survival, with legumes and trees showing particularly strong responses. The effects of pathogen removal on survival and grazing exclusion on biomass and reproduction were moderated by plot area, with stronger effects observed in larger plots. Synthesis . Our findings highlight the critical role of trophic interactions in shaping plant communities through top‐down regulation. Grazers, insect herbivores and pathogens differentially impacted plant performance, with pathogens playing a key role in maintaining plant diversity through CNDD, while herbivores and grazers strongly regulated plant biomass, reproduction and survival. Our results also underscore the importance of considering spatial scale and environmental context when assessing consumer effects on plant communities. Ongoing global change may amplify these effects, with significant implications for plant community structure and biodiversity conservation.