PARENT SESSION
Poster Session #46: Riparian Ecology.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Comparison of transpiration rates among riparian trees using sap flow and leaf temperature methods.

Nagler, Pamela^*,1, Glenn, Edward², Thompson, Lew³, ¹ University of Arizona, Tucson, Arizona² University of Arizona, Tucson, Arizona³ University of Arizona, Tucson, Arizona

ABSTRACT- We measured transpiration rates of three Sonoran Desert riparian trees (Populus fremontii, cottonwood, Salix gooddingii, willow, and Tamarix ramosissima, saltcedar)) using sap flow and canopy and air temperature differential (Tc-Ta) for 11 days on constructed canopies, in which 6 potted plants formed a single, dense canopy over the summer. Six canopies (n = 2 species) were measured; for the first 8 days, all canopies were kept continuously moist with fresh water; for the last 3 days, plants were subjected to either water stress or salt stress. The first objective was to test the strength of the relationship between transpiration (Et) and Tc-Ta to determine if Tc-Ta can be a useful remote sensing method to measure Et for these species. The second objective was to compare Et rates among species, to determine if the invasive species, saltcedar, has higher Et rates or ecophysiological advantages over the native trees species. Et and Tc-Ta had significant (p<0.05) correlations for all species. These improved when a radiation term was included in the equation predicting Et from Tc-Ta. Saltcedar maintained higher Et rates than the native trees under water or salt stress. We conclude that the Tc-Ta method could be useful in estimating Et over riparian corridors, and that native trees are not at an ecophysiological disadvantage to saltcedar so long as sufficient non-saline soil moisture is available to support Et.

KEY WORDS: riparian vegetation, transpiration, sap flow, percent cover