Internal nutrient fluxes in a tropical rain forest

TitleInternal nutrient fluxes in a tropical rain forest
Publication TypeJournal Article
Year of Publication1998
AuthorsMcDowell, WH
JournalJournal of Tropical Ecology
Accession NumberLUQ.397
Keywordsdissolved organic carbon, nitrogen, nutrient cycles, Phosphorus, Puerto Rico, soil solution, throughfall, tropical rain forest

Throughfall and soil solution chemistry were studied for 1 y in atropical montane forest in the Luquillo Mountains of Puerto Rico. Passage of pre-cipitation through the forest canopy resulted in an increase in the concentrationand flux of all solutes except H+and NO3−. Throughfall chemistry showed no strongseasonal patterns, but concentrations of many solutes declined during weeks ofhigh rainfall. Enrichment in throughfall relative to precipitation was similar tovalues reported recently for several other tropical sites, with the exception of NH4+,which was particularly high at this site. Based on net throughfall deposition of Cl−,dry deposition of marine aerosols appears to be a relatively minor component(c. 15%) of total deposition. In soil solution, no seasonal patterns in concentrationwere evident and variability was highest for elements with high biological activity(especially N). Concentrations and fluxes of K+and dissolved organic carbon(DOC) showed the largest declines as throughfall passed through the soil profile;concentrations of most other elements increased or were relatively constant.Declining DOC flux through the soil profile appears to be due to sorption processessimilar to those observed in many temperate forests. Concentrations and fluxes ofHCO3−and SiO2increased substantially in soil solution, but never approachedthose observed in the stream. This suggests that additional weathering must occuras groundwater moves from this ridgetop site to the stream