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RECORD NUMBER: 27 OF 104

OLS Field Name OLS Field Data
Main Title Diurnal Water Relations of Walnut Trees: Implications for Remote Sensing.
Author Weber, J. A. ; Ustin., S. L. ;
CORP Author Corvallis Environmental Research Lab., OR. ;California Univ., Davis.
Publisher c1991
Year Published 1991
Report Number EPA/600/J-92/032;
Stock Number PB92-144047
Additional Subjects Remote sensing ; Trees(Botany) ; Moisture content ; Leaves ; Irrigation systems ; Hardwoods ; Dielectric constants ; Comparison ; Diurnal distribution ; Soil moisture ; Canopy ; Vegetation establishment ; Forests ; Evapotranspiration ; Reprints ; Walnut trees
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Status
NTIS  PB92-144047 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 08/28/1992
Collation 13p
Abstract
Leaf water content (LWC), relative water content (RWC) and water potential (LWP) were measured as indicators of diurnal change in tree water status in an experimental walnut orchard receiving two irrigation treatments: 100% and 33% of potential evapotranspiration (PET). LWP had the greatest magnitude of diurnal change throughout the experimental period with minima occurring each day in early to mid-afternoon and maxima between midnight and sunrise. The temporal discrepancy could be caused by cavitation of xylem elements in the vicinity of the DC (Dielectric Constants) probe. Microwave backscatter for L- and X-bands also measured diurnal variation that had local minima in the afternoon, but the pattern among wavelength and polarization signatures was complex. From these data it appears that radar backscatter can respond to diurnal changes in plant water status. Interpretation of diurnal patterns using a satellite sensor will require models that account for multiple sources of canopy and soil variance, including canopy architecture and soil moisture and more precise understanding of the basis of diurnal patterns in backscatter.