Evidence for a 'plant community economics spectrum' driven by nutrient and water limitations in a Mediterranean rangeland of southern France

1. Plant species composition and cornmunity functional structure (Le. trait composition at the COffimunity level) result fram a hierarchy of envÍronmental filters that constrain which species and traits tend to be dominant in a given habitat. 2. We quantified variation in cornmunity functional structure along natural gradients of soíl resources using several aboveand below-ground parameters and explored links among these attl;butes to detennine whether plant resource econornics can be applied at the cornrnunity level in a Mediterranean rangeland of southern France. 3. Limitation by nitrogen, soíl water and soil depth were the maio ecological factors driving the fuoctional response at the community level. Most of the community functional parameters considered in this study were more dependent on nitrogen limitation than on the other two factors, mostIy reIated with the acquisitioll~conservation trade-off at both the leaf and the root level. 4. We found a strong coordination between above-ground and below-ground compooents, with a high level of coocordance along the resource gradients explored. As an example, tissue dry matter content both in leaves and roots was positively related to oitrogeo limitation. These findings indicate that the lea! ecollomic spectrum paradigm (resource cooservation io resource-poor habitats versus resource acquisition in resource-rich habitats) can be extrapolated to the below-ground component and extends to a plant community spectrum. 5. Changes in the functional structure of communities were promoted by two complementary components of variation: (i) the replacement of species with highly contrasting resource-use strategies and, to a lesser extent, (ii) the intraspecific variation in severa! above-ground traits. 6. Synthesis. This study showed that soil water and nutrient limitations are the main drivers controlling functional community structure in the Mediterranean rangelands studied and that shifts in this structure were mainly due to species turnover. In addition, we provided evidence for a plant community ecollomics spectrum, based on a strong coordinatioo between aboveand below-ground components in these resource-limited communities.