Water and Nutrient Sources for Floodplain Trees: Model-Based Inference
Abstract
Hydrologic connectivity between floodplain forests and their rivers affects forest productivity, habitat quality, and river chemistry and function. Here we focus on one aspect of connectivity, plant water uptake from the shallow alluvial aquifer, as a key aquatic-terrestrial link and as a clue to nutrient uptake from the aquifer. We infer a depth profile of water accessed by trees by applying a one-dimensional hydrologic model to observations of sapflow, soil moisture, and meteorological variables at contrasting sites on the Nyack Floodplain of the Middle Fork Flathead River, Montana. Combined model simulations and field observations suggest that shallow groundwater access regulates the active growing season and spatio-temporal patterns of NPP. In the early summer, trees access water in the aquifer at each of the three instrumented sites despite differences in soil type and tree growth form. During the late summer simulations are especially sensitive to modeled rooting depth, with trees becoming either (1) increasingly dependent on the alluvial aquifer for water as surface soils dry or (2) fully disconnected from the aquifer. Ultimately, we plan to incorporate these results in the coupling of a hydrologic/biogeochemical model of the aquifer (WREN, Water-Borne Resource Exchange Network) with a forest growth model (Biome-BGC). With the coupled model we will investigate spatially explicit effects of forest nutrient uptake on the biogeochemistry of alluvial aquifers and floodplain- flanked river channels.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H11B0742A
- Keywords:
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- 1813 Eco-hydrology;
- 1820 Floodplain dynamics;
- 1830 Groundwater/surface water interaction;
- 1852 Plant uptake;
- 1866 Soil moisture