The leaf economic spectrum drives leaf litter decomposition in Mediterranean forests

Background and aims: Leaf litter decomposition is an important process controlling nutrient cycling in most terrestrial ecosystems. We evaluated the relationships among traits of green leaves and decomposition rates of leaf litter (k) at different environmental scales and organisational levels (species and community). We also assessed the relationships at community level between k and the Leaf Economic Spectrum (LES) and between k and different soil variables. Methods: We measured leaf traits in 38 woody species distributed in nine sampling sites along a topographic gradient in southern Spain. Leaf litter was collected for each species in each sampling site and incubated in a microcosm experiment with soil collected from the top 20 cm of each site. Results: We found positive relationships between k and specific leaf area (SLA), leaf N, K and P and negative relationships with leaf dry matter content (LDMC) and leaf C isotopic composition (δ C), both at species and community levels. Decomposability was positively related with the first PCA axis describing the LES and the relationships were consistent across all sites and within different zones or topographic positions. In addition, community weighted mean values of leaf traits (LES ) were stronger predictors of litter decomposition than soil variables. Conclusions: A major finding of the present study is the main role that leaf traits, and the covariation among them (LES), play on decomposition process in Mediterranean ecosystems both at the species and community levels. In summary, our results support the idea that the suites of leaf traits have a strong control on the pace of C cycling, being the best drivers of decomposition processes under similar climatic conditions.