Leaf functional traits as browsing indicators in understory woody species of Mediterranean forests

Abstract

Herbivory by vertebrate browsers plays a critical role in shaping the structure and dynamics of understory communities of Mediterranean forests. However, understanding how browsing intensity is influenced by environmental factors remains a challenge. This study aimed to estimate the effect of aridity on browsing in understory communities of Mediterranean forests and analyse the role of leaf functional traits to explain browsing intensity. Using field data collected from 70 plots of Spanish National Forest Inventory (IFN), distributed across four forest types depending on the dominant tree species (Pinus halepensis Mill., Pinus pinaster Ait., Quercus faginea Lam., and Quercus ilex subsp ballota L.) in Spain, we assessed browsing intensity in 102 different woody understory species and analysed its relationships with aridity, forest type and plant functional traits. Our results indicate that forest type significantly affects browsing, with highest intensity in P. pinaster stands (∼24 %) and lower levels (∼10 %) in P. halepensis, Q. faginea and Q. ilex. Also, we found that aridity and functional richness had an important positive effect on browsing intensity. Among the functional traits analysed, leaf shape index (LSI, length/width of the leaf), leaf carbon content (C) and leaf dry matter content (LDMC) were negatively associated with browsing in most understory communities. This study highlights the interplay between environmental gradients, functional traits and its diversity in shaping browsing patterns, providing valuable insights for the management and restoration of Mediterranean forest under the impact of climate change.