A Comparison Of Hydrological Flowpaths And Nutrient Export In Three Small Tropical Forest Catchments
Hoalst Pullen, Nancy 1 ; Hamann, Hillary B. 2 ; Stallard, Robert F 3
1 Geography, INSTAAR, University of Colorado at Boulder
2 Geography and Environmental Sciences, University of Colorado - Colorado Springs
3 USGS (Boulder, CO); INSTAAR, University of Colorado at Boulder; Smithsonian Tropical Research Institute
The Center for Tropical Forest Research (CTFS) of the Smithsonian Tropical Research Institute (STRI) has coordinated a global network of 17 tropical forest dynamics plots of approximately 50ha to collect baseline data and to monitor spatial and temporal forest changes. Missing from most CTFS plot studies is an integrated soil hydrology and water chemistry component. To fill this gap, we developed and are testing rapid assessment methods to measure soil and hydrological properties for tropical forest catchments. This assessment includes rainfall, throughfall, and overland flow collection, as well as gaging and sampling first to third order headwater streams over several storm events within a 2-4 week period.
Data from storm events on Barro Colorado Island (Panama) demonstrate that Na+ and Si decrease in concentration with increasing discharge, while nutrients K+ and NO3- show the opposite trend. Results from the 25 ha catchment in Yasuni National Park (Ecuador) show a similar pattern during several small events on relatively impermeable soils. Data collected from the more permeable 50 ha catchment in Lambir Hills National Park (Malaysia) indicates rainfall amount, intensity and duration influences the magnitude of stream nutrient concentrations. K+/Si ratios test Elsenbeer's [1] continuum for tropical soils and indicate more open nutrient cycling in tropical forest environments than suggested from earlier radioactively-labeled isotopes [2].
[1] Elsenbeer, H., 2001, Hydrologic flowpaths in tropical rainforest soilscapes – a review: Hydrological Processes, v.15, p.1751-1759.
[2] Stark, N.M., and C.F. Jordan, 1978, Nutrient retention by the root mat of an Amazonian rain forest: Ecology, v.59(3), p.434-437.