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Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater

Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater,10.1029/2010WR009797,Water Resources Research

Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater   (Citations: 1)
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Watersheds can be characterized as complex space-time filters that transform incoming fluxes of energy, water, and nutrients into variable output signals. The behavior of these filters is driven by climate, geomorphology, and ecology and, accordingly, varies from site to site. We investigated this variation by exploring the behavior of evapotranspiration signals from 14 different AmeriFlux sites. Evapotranspiration is driven by water and energetic forcing and is mediated by ecology and internal redistribution of water and energy. As such, it integrates biological and physical controls, making it an ideal signature to target when investigating watershed filtering. We adopted a paradigmatic approach (referred to as the null model) that couples the Penman-Monteith equation to a soil moisture model and explored the deviations between the predictions of the null model and the observed AmeriFlux data across the sites in order to identify the controls on these deviations and their commonalities and differences across the sites. The null model reproduced evapotranspiration fluxes reasonably well for arid, shallow-rooted systems but overestimated the effects of water limitation and could not reproduce seasonal variation in evapotranspiration at other sites. Accounting for plant access to groundwater (or deep soil moisture) reserves and for the effects of soil temperature on limiting evapotranspiration resolved these discrepancies and greatly improved prediction of evapotranspiration at multiple time scales. The results indicate that site-specific hydrology and climatic factors pose important controls on biosphere-hydrosphere interactions and suggest that plant–water table interactions and early season phenological controls need to be incorporated into even simple models to reproduce the seasonality in evapotranspiration.
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    • ...[4] While it is reasonable to suggest that rainfall timing, topography, vegetation dynamics, and moisture storage can be important controls on V, accurate quantication and modeling of these controls on V for the Earth’s diverse terrestrial plant ecosystems remains a daunting challenge and an area of intense focus for contemporary ecohydrologists [Thompson et al., 2011a, 2011b]...

    Hal Voepelet al. Quantifying the role of climate and landscape characteristics on hydro...

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