Spatial and Temporal Variability of Soil Pore Water Chemistry and Stable Isotopes at Tropical Three Hillslopes: El Yunque National Forest, Puerto Rico
Abstract
The Luquillo Mountains in the El Yunque National Forest in Puerto Rico offer an ideal opportunity to study coupled hydrological and biogeochemical behavior in mountainous tropical rain forests. Data have been collected from three Luquillo sites utilizing a wide range of chemical and isotopic analytes. Soil water samples within the most biologically active horizon (10-70 cm) have been collected quarterly from three hillslopes in the Sabana, Icacos, and El Verde watersheds since spring 2016 and analyzed for concentrations of 24 major ions, as well as stable isotopes of water and nitrate. Most ion concentrations show substantial temporal variability with a large shift that began in April/June of 2016. K, Mg, and Ca concentrations decreased at Sabana and Icacos. The shift may be related to the recovery from a severe island-wide drought in the summer and fall of 2015. Nitrate stable isotopes show some seasonality effects with the influence of atmospheric N inputs during the winter and spring, likely linked to anthropogenic sources. Differences in concentrations of key nutrients are apparent between each of the three sites. Icacos has a unique geology and vegetation, and consistently shows higher PO4 and lower NO3 and K concentrations than El Verde or Sabana. Sabana appears to be relatively NO3 rich and K poor. El Verde has higher K and lower PO4 concentrations. Topography- and depth related intra-site differences are also present, with statistically higher concentrations of manganese and iron suggesting more reducing conditions near the base of the hillslope at Icacos and at valley sites in El Verde. This comprehensive study of key chemical and isotopic species in soil water across three sites spanning a range of geology and vegetation types provides valuable insight into scaling of processes in the Luquillo and supports development of better representations of Tropics nutrient processes in Earth System Models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B51C..09N
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0468 Natural hazards;
- BIOGEOSCIENCES