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HYDROLOGIC THRESHOLDS FOR BIODIVERSITY IN SEMIARID RIPARIAN ECOSYSTEMS: IMPORTANCE OF CLIMATE CHANGE AND VARIABILITY
Impact/Purpose:
We will determine region-wide sensitivity of riparian vegetation to climate change. Our hypotheses: i) Decadal scale climate change and variability alter riparian aquifer recharge through mechanisms that depend on the magnitude, frequency and seasonality of flooding, and exert the greatest change in reaches that receive minimal groundwater inflow from the regional aquifer. ii) Riparian vegetation structure responds non-linearly as riparian aquifers are dewatered and as key hydrologic thresholds for survivorship of plant species are exceeded. iii) Decadal scale climate variability and change alters riparian ecosystem water budgets that in turn changes vegetation structure and function and the ecosystem services provided to society.
Description:
Riparian ecosystems of the arid and semiarid Southwest are linear corridors of high productivity and diversity. These ecosystems are sensitive to even small changes in the riparian water balance, with sharp changes in vegetation as streams become intermittent and as groundwater declines below survivorship thresholds. As a result, riparian vegetation has declined on many rivers due to water abstraction or has been altered due to the hydrologic impacts of climate variability. Despite much disciplinary work on individual rivers, a regionally comprehensive and integrated understanding of how aquatic-terrestrial ecotones respond to hydrologic change, including those imposed by climate change, awaits development.