The path toward a unified trait space: synthesizing plant functional diversity

Plant traits capture the remarkable diversity of ecological strategies, yet synthesizing this complexity into coherent frameworks remains challenging. Trait spaces have significantly advanced this effort, distilling numerous traits into meaningful ecological dimensions. Recent frameworks integrate above- and belowground characteristics, but other dimensions - such as reproduction, phenology, hydraulics, and mycorrhizal associations - remain poorly represented, facing conceptual and methodological hurdles. Resolving these issues requires addressing biases in trait databases, standardizing methodologies, and integrating complex or categorical traits. In this review, we propose the development of a fully unified trait space that is flexible, modular, and scalable, which would greatly enhance global comparisons, improve our predictive capabilities of plant ecological responses to global change, and ultimately strengthen biodiversity monitoring and management.