Grassland species composition and morpho-functional traits along an altitudinal gradient in a Mediterranean environment:: Relationship with soil water availability and evaporative dynamic

We studied the relationship between soil water dynamics and plant spatial distribution in Mediterranean grasslands. We considered five sites along an altitudinal gradient of 1100 m in Central Spain, each one comprising plots in the upper and lower zones of a south-facing slope. Soil and vegetation variables were obtained for five subplots placed at random within each plot. The evaporative dynamics of soil and litter samples was studied under laboratory conditions at two extreme temperatures (12 and 30 degrees C). We used Detrended Correspondence Analysis and regression analysis to determine the relationship between the evaporation parameters of soil and the abundance and traits of the species. We related soil moisture and evaporation to the distribution of the herbaceous vegetation for plant species and morpho-functional traits, revealing a variation trend associated simultaneously with altitude and the geomorphological position. Water content at the end of the linear phase and parameters of total evaporation length showed linear relationships with the vegetation gradient, in both soil and litter. These relationships, however, depended on temperature setting and enabled us to examine hypotheses on the consequences of different climate change scenarios in Mediterranean grasslands. if global temperatures increase, soils at high altitudes will require higher water content in order to maintain their characteristic vegetation. (c) 2008 Elsevier Masson SAS. All rights reserved.