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Dryad

Data from: Foliar N content parallels increasing aridity in a Mediterranean-Saharan transition zone: Evidence from regional and global trends

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Sep 03, 2024 version files 214.78 KB

Abstract

Aim Warm deserts are characterized by water shortages and high-temperature extremes. A common adaptive strategy in such environments is the maximization of photosynthetic capacity, which allows plants to achieve positive carbon budgets by taking advantage of short periods of water availability and non-inhibitory temperatures. Assuming that photosynthetic capacity is approximated by leaf N concentration, we tested the hypothesis that environmental aridity is related to an elevated leaf nitrogen content.

Location 53 locations in the transitional zone spanning the Mediterranean and the Sahara Desert in Morocco. The mean maximal temperature (Tmax) within the area varied between 35.7 and 43.5 °C, and the mean annual precipitation (MAP) was between 12 and 246 mm.

Taxon 225 vascular species representative of local vegetation

Methods Leaf samples were collected along a regional aridity gradient and preserved in herbarium presses. The leaf mass per area (LMA) and N concentrations expressed on leaf mass (Nmass) and area (Narea) basis were determined. We also obtained LMA and Nmass values for 6711 species from a worldwide database for comparative analysis.

Results Significant increases in mean LMA, Nmass, and Narea accompanied the increase in Tmax and the decrease in MAP in woody species and in non-graminoid herbs, but not in graminoids. Considering that the climate in our sampling area as a whole was arid, we compared the Nmass values of Moroccan plants with those from a worldwide database and found that at a common LMA, the Moroccan plants showed on average elevated Nmass relative to the global values.

Main conclusions These two lines of evidence: regional gradient and global comparison confirm that hot deserts select for high leaf N content. This result predicts the direction of natural selection that will accompany future climate warming.