Spatial and temporal controls on watershed ecohydrology in the northern Rocky Mountains

Vegetation water stress plays an important role in the movement of water through the soil‐plant‐atmosphere continuum. However, the effects of water stress on evapotranspiration (ET) and other hydrological processes at the watershed scale remain poorly understood due in part to spatially and temporal...

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Bibliographic Details
Published in:Water resources research 2010-11, Vol.46 (11), p.n/a
Main Authors: Emanuel, Ryan E., Epstein, Howard E., McGlynn, Brian L., Welsch, Daniel L., Muth, Daniel J., D'Odorico, Paolo
Format: Article
Language:English
Subjects:
Atmosphere
Atmospheric boundary layer
Carbon
Evapotranspiration
Forests
Growing season
Hydrology
Investigations
Land
Low temperature
mass density
Moisture content
Mountain forests
Mountains
Plant growth
Precipitation
Radiation
Seasons
Snow
Soil moisture
Soils
Stream flow
Terrestrial ecosystems
thermosphere
Topography
Vapor pressure
Vegetation
Water
Water stress
Watersheds
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Summary:Vegetation water stress plays an important role in the movement of water through the soil‐plant‐atmosphere continuum. However, the effects of water stress on evapotranspiration (ET) and other hydrological processes at the watershed scale remain poorly understood due in part to spatially and temporally heterogeneous conditions within the watershed, especially in areas of mountainous terrain. We used a spatially distributed model to understand and evaluate the relationship between water stress and ET in a forested mountain watershed during the snow‐free growing season. Vegetation water stress increased as the growing season progressed, due to continued drying of soils, and persisted late into the growing season, even as vapor pressure deficit decreased with lower temperatures. As a result, ET became decoupled from vapor pressure deficit and became increasingly dependent on soil moisture later in the growing season, shifting from demand limitation to supply limitation. We found water stress and total growing season ET to be distributed nonuniformly across the watershed due to interactions between topography and vegetation. Areas having tall vegetation and low topographic index experienced the greatest water stress, yet they had some of the highest evapotranspiration rates in the watershed.
ISSN:0043-1397
1944-7973
DOI:10.1029/2009WR008890