1. Introduction
Drylands of the Mediterranean basin, where precipitation
and temperature are out of phase, are particularly sensitive to the
intensification of aridity conditions (Giorgi and Lionello, 2008).
The response of aboveground net primary production (ANPP) to
precipitation represents an effective and straightforward approach
to evaluate drylands status and trends (Verón et al., 2006).
However, there exist differences between the spatial and temporal
models that relate ANPP to climate factors (e.g. Jobbagy et al., 2002;
Le Houérou et al., 1988), suggesting that other biotic and abiotic
factors are involved.