Variation in leaf litter nutrients of a Costa Rican rain forest is related to precipitation

By assessing current leaf litter nutrient dynamics, we may be able to predict responses of nutrient cycling in tropical ecosystems to future environmental change. The goal of this study was to assess whether nutrient cycling is related to seasonal variation in rainfall in a wet tropical forest. We examined leaf litter of an old-growth tropical rain forest in N.E. Costa Rica over a 4-year period to explore seasonal and inter-annual changes in leaf litter nutrient concentrations, and to evaluate potential short- and long-term drivers of variation in litter nutrient concentration, particularly that of phosphorus (P) and nitrogen (N). We also examined the temporal dynamics of calcium, potassium, and magnesium in the leaf litter. Leaf litter [P] and %N changed significantly with time, both seasonally and inter-annually. Seasonal changes in leaf litter [P] were strongly positively correlated with rainfall from the previous 2 weeks; cations, however, were inversely related to this measure of current rainfall, while %N was not related to rainfall. We propose that the positive relationship between current rainfall and leaf litter [P] is due to a response by the vegetation to an increase in nutrient availability and uptake. In contrast, given the negative relationship between current rainfall and cation concentrations, leaching from live leaf tissue is a more likely driver of short-term changes in cations. Should global climate change include altered rainfall patterns in this biome, one class of ecosystem-level responses could be significant changes in P and cation cycling.