Global environmental change affects the sustained provision of a wide set of ecosystem services. Although the delivery of ecosystem services is strongly affected by abiotic drivers and direct land use effects, it is also modulated by the functional diversity of biological communities (the value, range, and relative abundance of functional traits in a given ecosystem). The focus of this article is on integrating the different possible mechanisms by which functional diversity affects ecosystem properties that are directly relevant to ecosystem services. We propose a systematic way for progressing in understanding how land cover change affects these ecosystem properties through functional diversity modifications. Models on links between ecosystem properties and the local mean, range, and distribution of plant trait values are numerous, but they have been scattered in the literature, with varying degrees of empirical support and varying functional diversity components analyzed. Here we articulate these different components in a single conceptual and methodological framework that allows testing them in combination. We illustrate our approach with examples from the literature and apply the proposed framework to a grassland system in the central French Alps in which functional diversity, by responding to land use change, alters the provision of ecosystem services important to local stakeholders. We claim that our framework contributes to opening a new area of research at the interface of land change science and fundamental ecology.biodiversity ͉ land change ͉ mass ratio hypothesis ͉ plant functional traits G lobal environmental changes, including land use and land cover changes, have considerable impacts on the ecological properties of ecosystems and therefore on the ecosystem services (ES) that societies derive from them (1). Although links between ecosystem properties (EP) and ES are not always trivial, many ES and their changes can be reasonably quantified by EP that are routinely measured in ecological studies (2). Global change effects on EP can be direct, through their effects on physical and chemical processes and on the metabolism and behavior of organisms. Global change drivers can also influence EP indirectly through their impacts on biodiversity, either through their effects on local biota or by altering the ability of organisms to disperse through landscapes. Relevant changes in biodiversity are manifested through changes in plant functional diversity (FD), i.e., the value, range, and relative abundance of plant functional traits in a given ecosystem (2). Although often subtler than direct effects of global change drivers (3, 4), these indirect biotic effects remain a major source of uncertainty in predicting the impacts of global change on ES provision.Conceptual models accounting for links between the functional trait values of local plant communities and EP are scattered in the literature, and the conceptual connections between them are not always clear. We articulate the most important of those models i...

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies.