Effects of tree species diversity on leaf litter decomposition process in semi-arid Mediterranean oak forests

Many studies have been conducted on the effects of changes in plant diversity and species composition on ecosystem functioning and plant productivity due to climate change. However, a few studies have been conducted on the effects of species shifts on litter decomposition. In this context, we tested (i) the influences of litter species diversity on decomposition, (ii) deviation of litter mixtures decomposition from expected patterns (non-additive effects), and (iii) tree species loss or gain impact on the decomposition process. We performed a complete factorial decomposition experiment in a gradient of tree litter species diversity in a semi-arid Mediterranean oak forest for 550 days. Among species, only C, lignin, and water holding capacity (WHC) values varied significantly in initial litter characteristics. The litter mass loss at the end of the experiment differed significantly between Q. brantii and P. glabra. Initial lignin content and C/N ratio had the main effects on the decomposition rate. Lignin content was the best predictor of the overall decomposition rate in this region. Contrary to other ecosystems where synergistic non-additive effects are dominant, we observed 82% of additive and 18% of non-additive effects on litter mass and chemical components loss. Turnover of plant species due to climate change could negatively affect the litter decomposition and nutrient release from litter mixture in the semi-arid Mediterranean region.