Transpiration in cottonwood and willow riparian forests at perennial and ephemeral stream sites
AdvisorWilliams, David G.
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PublisherThe University of Arizona.
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AbstractSap flow, leaf gas exchange, and micrometeorological parameters were evaluated during 1997 in riparian forest at perennial and ephemeral stream sites on the San Pedro River in southeastern Arizona, USA. At the perennial stream site, measurements of sapwood area based transpiration and sapwood area/canopy area of clusters of Populus fremontii and Salix goodingii were used to estimate transpiration across the stand. Stand structural heterogeneity resulted in as much as 30% variation in mean transpiration across the stand. Transpiration of cottonwood was more dependent upon vapor pressure deficit at the ephemeral stream site which had an open, less dense canopy compared to that at the perennial stream site. This may be due to differences in advection properties and canopy feedback processes between sites. Conversely, transpiration in willow was less dependent upon vapor pressure at the ephemeral stream site than that at the perennial stream site. This may be due to water stress associated with deeper depth to groundwater.
Degree ProgramGraduate College
Renewable Natural Resources