Scaling sap flux measurements of grazed and ungrazed shrub communities with fine and coarse‐resolution remote sensing

摘要: We measured transpiration by black greasewood (Sarcobatus vermiculatus) (SAVE) and fourwing saltbush (Atriplex canescens) (ATCA) over a nitrate-contaminated aquifer in Monument Valley, Arizona, on the Colorado Plateau. Heat balance sap flow sensors were used to measure shrubs 2006 2007 results scaled larger landscape units longer time scales using leaf area index (LAI), fractional vegetation cover, meteorological data, enhanced (EVI) from MODIS Terra satellite. Transpiration was high depending (2·95–6·72 kg m−2 d−1) controlled vapour pressure deficit (D) atmosphere. SAVE tended have higher rates than ATCA had steeper response D, but both exhibited midday depression of conductance. Over most site, cover (fc) area-wide LAI low (0·10 0·37, respectively) due heavy grazing cattle sheep. However, portion plume that been protected for 10 years fc = 0·75, 2·88. ground-area basis varied with LAI, midsummer daily values ranging 1·44 mm d−1 (LAI 0·36) 13·1 2·88 mm) corresponding projected annual 159–1447 year−1. Controlling could, theoretically, slow or halt movement contamination allowing shrub community extract more water is recharged aquifer. Copyright © 2008 John Wiley & Sons, Ltd. This article published online 26 September 2008. An error subsequently identified. This notice included print versions indicate corrected (29 2008)