LCZO -- Stream Suspended Sediment, Streamflow / Discharge, Precipitation -- riverine particulate organic matter export -- Rio Mameyes and Rio Icacos -- (1991-2015)

Erosion, transport and deposition of riverine suspended load are pivotal processes in the terrestrial carbon cycle and function of the critical zone. In order to better understand the response of these drivers to changes in land cover and climate, it is critical to characterize these drivers. In montane rivers, such as the Luquillo Mountains, Puerto Rico, extreme storm events erode and transport clastic and organic material from mountain slopes to rivers, dominating annual export. Riverine particulate organic carbon (POC) and particulate nitrogen (PN) exports are not as well understood, especially at high runoff rates. Over 25 years, river POC export was 75±20 tC km-2 yr-1 for Rio Icacos and 22±8 tC km-2 yr-1 for the Mameyes. Caribbean river POC yields were higher in relation to their SS yields, suggesting that these rivers have greater terrestrial OM supply on the landscape to be eroded and transported into rivers, than what is expected based on data for world rivers. Additionally, we determined that 50% of the suspended load flux occurred during extreme rainfall events, spanning just over 2 days a year, but only exporting < 10% of the annual runoff and rainfall. These results emphasize the important role of extreme rainfall events as drivers of POM export from the Luquillo Mountains.