Do leaf traits and nitrogen supply affect decomposability rates of three Mediterranean species growing under different competition levels?

The effects of nitrogen addition on rates of litter decomposition of plants growing under different competition levels were assessed in a multifactorial glasshouse experiment. We established a two nitrogen-level treatment (control and fertilization) and three competition-level (plants growing alone, intra- and interspecific competition) experiment for Pinus pinea L., Pistacia lentiscus L. and Cistus salvifolius L. during one year. We collected leaves from different combinations at 3, 6 and 12 months and we established a 2-month microcosm experiment. We measured Kpot and different leaf and litter traits in order to test the hypothetical relationships between these traits and litter decomposability among the target species. Leaf nitrogen concentration was higher in plants growing under N-supply treatments but this supply only affected decomposition rates in the cases of P. pinea and P. lentiscus when grown alone. For P. pinea and C. salvifolius decay rate was higher in the fertilized treatment when growing alone. Leaf dry matter content was the leaf trait best related to litter decomposability. The results derived from the microcosm experiment provided evidence of the effect of some leaf and litter traits on litter decomposability and how some traits can give information about some important processes in ecosystems, such as decomposition.