Functional Plant Diversity: Traits, Evolution, Biodiversity Conservation and Ecosystem Restoration

Plant communities are being reassembled by drought, warming, nutrient enrichment and land-use intensification at the same time as the ecosystem functions they support are expected to remain dependable. Functional plant diversity, understood as the variety and distribution of plant traits within a community, is frequently invoked as the property that links biodiversity to the stability and resilience of these functions. This critical narrative review evaluates how far that expectation is supported by evidence. The review draws on theory, controlled biodiversity experiments, coordinated distributed experiments, long-term observational networks, forest inventories, tree-ring studies, eddy-covariance synthesis and satellite analyses, identified through structured searches of open scholarly indexes, supplemented by citation tracking, for work published between January 1994 and July 2026. The synthesis indicates that plant diversity generally increases the temporal invariability of biomass production and its resistance to climatic extremes, chiefly through species asynchrony, overyielding and the stability of dominant species. Evidence that trait dissimilarity itself generates asynchrony is weaker and more context-dependent than commonly assumed. Community-weighted trait composition, particularly the prevalence of resource-conservative strategies, often predicts invariability and resistance as well as or better than trait diversity, whereas acquisitive strategies tend to favour rapid recovery. Hydraulic trait diversity provides the most mechanistically coherent link between functional diversity and drought resilience in forests, although its support rests largely on a small number of multi-site syntheses and simulation studies. Eutrophication and land-use intensification consistently weaken diversity-mediated stabilisation, and stabilising mechanisms strengthen over decadal timescales and across spatial scales through beta diversity. Major uncertainties concern the selection of response traits, the neglect of intraspecific and belowground variation, the scarcity of explicit response-diversity measurements, the confounding of mean and variance in stability metrics and the geographical concentration of evidence in temperate grasslands and forests. Functional plant diversity is best regarded as a conditional rather than universal driver of resilience, whose effects depend on the stability dimension examined, the character of the perturbation and the traits that are measured. Management that conserves both diversity and conservative dominant species is supported by current evidence, but predictive, trait-based forecasting of resilience remains an unmet objective.