Puerto Rico Leaf Litter Leachate

Tropical rainforests in many regions are experiencing an increased frequency of severe hurricanes and droughts due to climate change. These disturbance events alter the quantity and quality of organic matter inputs entering tropical freshwater ecosystems, including leaf litter and dissolved organic matter. We investigated how climatic disturbance events affect leaf litter leachate entering streams to explore watershed carbon cycling across the terrestrial-aquatic interface. This study used dried senesced and freshly abscised leaves from nine different tree species as proxies of drought- and hurricane-induced changes to leaf litter inputs, respectively. These nine species are representative of the dominant riparian vegetation across most of the Luquillo Mountains of Puerto Rico. Leachate analytes, including forms of carbon, nitrogen, and major cations and anions, were used to determine relationships between climatic events, species type, and leaf leachate composition. Disturbance conditions affected leaching dynamics of dissolved organic carbon and nitrogen. Concentrations of dissolved organic matter were higher in leachate from dried senesced leaves than freshly abscised leaves; however, the magnitudes of these differences were highly variable across species, potentially connected to C:N ratios. We also evaluated the leaching of potassium and other nutrients that can influence freshwater biotic communities. Determining the magnitude of altered carbon inputs following major disturbances will further our understanding of the biogeochemical and metabolic response of tropical streams to drought- and hurricane-based disturbances.