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

Plant functional traits are measurable morphological, physiological and phenological characteristics that influence performance and, through performance, the dynamics of populations, communities and ecosystems. Over three decades, trait-based ecology has moved from regional strategy schemes to global analyses suggesting that much interspecific variation in plant form and function is organised along a small number of axes, principally a resource-economics continuum contrasting acquisitive and conservative tissues and a size continuum spanning plant height, seed mass and leaf area. These spectra are widely used to infer community assembly processes and to predict ecosystem properties, yet their explanatory reach has been questioned. This critical narrative review evaluates the evidence connecting evolutionary trait trade-offs, community assembly and ecosystem functioning. Literature published between January 1995 and the final search date was identified through multidisciplinary scholarly indexes, supplemented by backward citation searching, and was appraised for design, scale, measurement quality and consistency. The synthesis indicates that the leaf economics and size dimensions are robust at global interspecific scales, whereas belowground variation adds at least one partly independent axis linked to mycorrhizal collaboration. Trait covariation weakens, disappears or reverses within species and local communities, which limits the transfer of global spectra to local prediction. Evidence that traits predict demographic rates is consistent in direction but modest in explanatory power and strongly dependent on environmental context. Pattern-based inferences of environmental filtering and limiting similarity are frequently confounded, whereas approaches grounded in coexistence theory and predictive assembly models provide more defensible tests but remain geographically and taxonomically narrow. Community-weighted mean traits often explain ecosystem properties better than functional diversity indices, although traits alone explain only part of ecosystem variation, particularly across years. Major unresolved questions concern belowground and hydraulic integration, trait-by-environment interactions in fitness, temporal dynamics and the scaling of species-level trade-offs to ecosystem fluxes. A multidimensional, scale-explicit and mechanistic trait framework, rather than a single fast–slow axis, is therefore the most defensible basis for predicting vegetation responses to environmental change.