Evapotranspiration in a cottonwood (Populus fremontii) restoration plantation estimated by sap flow and remote sensing methods

Pamela Nagler, Amity Jetton, John Fleming, Kamel Didan, Edward Glenn, Joseph Erker, Kiyomi Morino, Jeff Milliken, Steven Gloss

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Native tree plantations have been proposed for the restoration of wildlife habitat in human-altered riparian corridors of western U.S. rivers. Evapotranspiration (ET) by riparian vegetation is an important, but poorly quantified, term in river water budgets. Native tree restoration plots will potentially increase ET. We used sap flow sensors and satellite imagery to estimate ET in a 8 ha, cottonwood (Populus fremontii) restoration plot on the Lower Colorado River. Biometric methods were used to scale leaf area to whole trees and stands of trees. This technique was used to validate our estimates of ET obtained by scaling from branch level to stand (or plot) level measurements of ET. Cottonwood trees used 6-10 mm day-1 of water during the peak of the growing season as determined by sap flow sensors, and annual rates scaled by time-series MODIS satellite imagery were approximately 1.2 m year-1. Although irrigation was not quantified, the field had been flood irrigated at 2 week intervals during the 3 years prior to the study, receiving approximately 2 m year-1 of water. A frequency-domain electromagnetic induction survey of soil moisture content showed that the field was saturated (26-28% gravimetric water content) at the 90-150 cm soil depth under the field. Trees were apparently rooted into the saturated soil, and considerable saving of water could potentially be achieved by modifying the irrigation regime to take into account that cottonwoods are phreatophytes. The study showed that cottonwood ET can be monitored by remote sensing methods calibrated with ground measurements with an accuracy or uncertainty of 20-30% in western riparian corridors.

Original languageEnglish (US)
Pages (from-to)95-110
Number of pages16
JournalAgricultural and Forest Meteorology
Issue number1-2
StatePublished - May 14 2007


  • ET
  • ETM+
  • Heat pulse method
  • Riparian vegetation

ASJC Scopus subject areas

  • Forestry
  • Global and Planetary Change
  • Agronomy and Crop Science
  • Atmospheric Science


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