Format: ORAL

Josep Padulls Cubino1,2, Albert Vil-Cabrera1, Javier Retana1,2

1 Centre for Ecological Research and Forestry Applications (CREAF), 08193 Cerdanyola del Vallès, Spain 2 Autonomous University of Barcelona, 08193 Cerdanyola del Vallès, Spain

Climate change is expected to exert an amplified influence on the climate edges of species distribution owing to their proximity to ecological tolerances. However, a notable ambiguity persists regarding the interplay between climate change, plant functional traits, and their collective role in driving shifts in plant abundance at climate edges. Furthermore, the influence of historical land-use legacies in moderating this interaction remains unclear. Leveraging data from approximately 300,000 monitored trees spanning 66 widely distributed species in Spain, we quantified shifts in tree species abundance at aridity edges (i.e., cold and wet vs. warm and dry conditions) over 25 years. We also examined the relative significance of the interplay between climate change and tree traits in driving these abundance shifts. To evaluate the shifts in tree species abundance at aridity edges, we used a null model to test the hypothesis that such shifts occur randomly concerning gains and losses of trees across the entire aridity gradient. Our investigation revealed an overall increase in tree species abundance over time across the studied region. Notably, a non-random increase in tree species abundance was observed at the cold and wet edge, while the increase at the warm and dry edge appeared to follow a random pattern. Furthermore, shifts in tree species abundance across the entire aridity gradient, including its edges, correlated with forest densification within the surveyed plots. The influence of climate change on shifts in tree species abundance was notably mediated by the traits of these species at the aridity edges. Consequently, our study offers species-specific insights into the dynamics of tree abundance at climatic edges, presenting valuable information pertinent to informed decision-making in formulating conservation, management, and restoration strategies within the context of anthropogenically-induced global environmental changes.