Climate change has altered the amount, timing, and form (rain vs snow) of precipitation in western montane forests, leading to both widespread forest decline and decreasing surface water supplies. It remains unclear how landscape characteristics interact with climate to affect the hydrological and ecological responses of ecosystems differently. Recent work has suggested that the diversity of responses arise from complex interactions between geology, topography, climate, and ecology that control the partitioning of precipitation available to plants. Addressing this challenge hinges on the data-model integration of relevant plant physiological mechanisms, hydrologic redistribution, and distributed observations of both catchment and ecosystem responses to climate variability. To understand processes that potentially influence plant water supply and plant response to drought, this study leverages a newly developed model, ParFlow-TREES, that integrates plant hydraulics with groundwater hydrology. We apply ParFlow-TREES to well-instrumented Critical Zone Observatories and related sites spanning a range of climatic, ecologic, geologic, and physiographic environments in the four-corner states. We hypothesize that the underlying geology and physiographic environment controls the extent of groundwater contributions to plant water supply. For example, forests in locations with lower groundwater storage and subsidy will exhibit larger interannual variability plant growth while larger groundwater reserves will dampen interannual variability in plant growth related to contemporaneous climate. These results will have implications for guiding resource management and upscaling predictions from specific sites to regional scale.
Tai, X., Brooks, P.D., Anderegg, W., Sperry, J., Mackay, D.S., Nesbitt, L. (2018): Quantifying groundwater contribution in mediating plant response to drought across various geology and climate conditions. Abstract H11W-1785 presented at 2018 AGU Fall Meeting, Washington, D.C., 10-14 Dec.