Disturbance Drives Leaf Litter Leachate Dynamics in a Tropical Stream Ecosystem

Tropical rainforests in many regions are experiencing an increased frequency of severe hurricanes and droughts due to climate change, which can alter the quantity and quality of organic matter inputs entering tropical freshwater ecosystems through inputs of leaf litter. This study leached dried senesced and freshly abscised leaves in a controlled laboratory setting as proxies of drought- and hurricane-induced changes to leaf litter inputs, respectively. The nine species that were leached are representative of the dominant riparian vegetation across most of the Luquillo Mountains of Puerto Rico. Leachate analytics, including forms of carbon, nitrogen, and major cations and anions, were analyzed across leaf condition and species to assess relationships between climatic events, species type, and leaf leachate composition. Total accumulation of solutes and concentrations of dissolved organic matter and major ions were about 2–4 times higher in leachate from dried senesced leaves (i.e., drought litter inputs) than freshly abscised leaves (i.e., hurricane litter inputs); however, the magnitudes of these differences were highly variable across species, potentially connected to leaf tissue chemistry. These data allow for scaling the impact of riparian leaf litter inputs to further our understanding of the biogeochemical and metabolic response of tropical streams to increasingly frequent climatic disturbances.