Small catchments of the Andes-Amazon: zooming in to understand the big picture

Tuesday, 7 June 2016
Emily Burt1, A. Joshua West1, Kathryn E Clark2 and Mark Torres3, (1)University of Southern California, Los Angeles, CA, United States, (2)University of Pennsylvania, Philadelphia, PA, United States, (3)California Institute of Technology, Pasadena, CA, United States
Abstract:
The Madre de Dios region of Peru hosts a transition from Andean tropical montane cloud forest to Amazonian rainforest, making it a compelling site to study catchment hydrology. We have been working in this region for several years, seeking to address fundamental questions regarding the interplay of hydrologic and biogeochemical cycles across mountain-floodplain systems. In work to date, we have constructed a hydrologic balance of the Kosñipata tropical montane cloud forest, which not only constrained the relative amounts of and methods by which water enters and exits a catchment, but also demonstrated the significant degree to which wet-season rain sustains dry-season runoff (Clark et al, 2014).

In addition, we are using concentration-discharge relationships of major elements to contribute to understanding of weathering and behavior of rock-derived nutrients and fluid flow paths across the Andes-Amazon. Previous work by Torres et al (2015) shows that the relationship between solute concentration and river discharge varies across the mountain to floodplain transition. Steep Andean catchments show relatively constant solute concentrations despite order of magnitude changes in discharge (“chemostatic behavior”). In the more shallowly sloping foreland-floodplain, solute concentrations decrease with increasing discharge. More recent work involving additional Andean tributaries with variable slope angles does not show the same contrast as seen between the Andean and foreland-floodplain catchments of Torres et al (2015).

 As part of a new field campaign we are currently initiating, bi-monthly sampling campaigns targeting five small catchments spanning gradients in elevation and slope will generate data to constrain plant water sources and nutrient and water fluxes. Water transit time models will be explored in detail, comparing both steady-state and time-varying models in tropical cloud forest vs. lowland rain forest. Detailed analysis of the stable isotope composition of plant xylem and soil waters is expected to generate information about potential soil water partitioning and plant-soil interactions.

<< Previous Abstract | Next Abstract >>