DOI: 10.6073/pasta/7099a8c876e998b53959ac541b381850
title: Bisley rainfall and throughfall, and chemistry of rainfall and throughfall

description: This data set contain summaries and analyses mean of collected weekly measurements expressed as mm per day, and calculation of fluxes, rates and means calculated after water chemistry analyses are conducted. Rainfall and throughfall are collected weekly at the Bisley LEF site. These data sets begin March 1988 and ends December 2003. Rain and throughfall samples are the total catch for the week, and are exposed to field conditions for that time. No event sampling is conducted on a routine basis. Rainfall Collected in Bisley (RCB) are bulk or always-open collectors that receive dry deposition by sedimentation. All samples are measured for pH and conductivity, and then filtered (pre-combusted Whatman GF/F glass fiber filter) prior to further analysis. From 1983-1994 samples were cooled and returned to the San Juan chemistry laboratory for analysis. During those years, samples for NH4 and NO3 analyses were refrigerated continuously until analysis. Sub samples for NH4 analysis were also preserved with 1 molar HCl. From 1994 on, samples for NH4 and NO3 were frozen until analysis, were not acidified, and all analyses were conducted at the University of New Hampshire. Nutrient fluxes in rainfall and throughfall were measured weekly in a mature subtropical wet forest in NE Puerto Rico over a 15-year period that included the effects of five hurricanes and several prolonged droughts. Annual inputs of K, Ca, Mg, Cl, Na, and SO4-S are similar to those reported from other marine-influenced tropical forests. Rainfall input of nitrogen is comparatively low and reflects the relative isolation of the air shed. Mean annual rainfall and throughfall were 3482 and 2131 mm yr-1 respectively. On average, rainfall, throughfall, rainfall pH, and rainfall flux NH4-N and NO3-N had small but significant decreases throughout the study period. More nutrients fluxes had seasonal differences in rainfall (6 out of 12) than throughfall (4 out of 12). All volume weighted enrichment ratios calculated for the 15-year period were greater than one. However, median weekly enrichment ratios were less than 1 for sea salts and dissolved organic carbon and between 1 and 2 for Mg, Ca, SiO2 and SO4-S. In contrast, median weekly enrichment ratios were greater than 10 for NH4-N, PO4-P, and K and reflect biological enrichment within the canopy. Droughts reduced enrichment ratios of cations and sea-salts, but increased enrichment ratios for NH4-N, PO4-P and K. In the weeks following hurricanes relative throughfall tends to be higher and enrichment ratios tend to be lower. These long-term observations indicate that physical and biological processes associated with water passing through the canopy act to buffer internal nutrient cycles from inter-annual, and seasonal variations in rainfall inputs. Support for this work was provided by grants BSR-8811902, DEB-9411973, DEB-9705814 , DEB-0080538, DEB-0218039 , DEB-0620910 , DEB-1239764, DEB-1546686, and DEB-1831952 from the National Science Foundation to the University of Puerto Rico as part of the Luquillo Long-Term Ecological Research Program. Additional support provided by the University of Puerto Rico and the International Institute of Tropical Forestry, USDA Forest Service.