Litterfall mass and nutrient fluxes over an altitudinal gradient in the coastal Atlantic Forest, Brazil

Litterfall is one of the most important pathways through which nutrients are recycled in the terrestrial biosphere. In tropical soils, which are generally low in essential nutrients such as phosphorus and cations, the flux of nutrients through litterfall is particularly important to sustaining CO2-uptake capacity; however, questions remain over the role of altitude in altering litter nutrient cycling rates among tropical forest ecosystems. Here we examine litterfall, carbon (C), nitrogen (N) and phosphorus (P) fluxes through litterfall over an altitudinal gradient in the coastal Atlantic Forest located on the northern coast of the State of Sao Paulo, Brazil. Litterfall was collected twice a month for 1 y (April 2007-March 2008) using 30 litter traps placed in four different forest types arrayed by altitude - coastal forest (sea level), lowland forest (50-200 m asl), submontane forest (300-500 m asl) and montane forest (1000 m asl). Litterfall mass-fluxes decreased with increasing altitude, from similar to 9 Mg ha(-1) in lowland forests to 7 Mg ha(-1) in higher-altitude ecosystems. Contribution of reproductive organs to litterfall was significantly greater in lower than in higher altitudes. Litterfall N and P fluxes were higher in the lowland forest vs. other forest types, pointing to strong altitudinal controls over nutrient cycling. Furthermore, nitrogen-use efficiency (NUE) was lower and litter d15N was higher in the lowland site providing additional evidence for lack of N constraints to productivity in lowland of the south-eastern Atlantic Forest.