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Estimating the effects of understory removal from a Douglas Fir forest using a two‐layer canopy evapotranspiration model
Author(s) -
Kelliher F. M.,
Black T. A.,
Price D. T.
Publication year - 1986
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr022i013p01891
Subject(s) - understory , evapotranspiration , transpiration , bowen ratio , canopy , eddy covariance , environmental science , atmospheric sciences , penman–monteith equation , tree canopy , hydrology (agriculture) , soil science , geography , photosynthesis , ecology , botany , physics , ecosystem , geology , geotechnical engineering , biology , archaeology
W. J. Shuttleworth's (1979) development of the Penman‐Monteith evaporation equation for multilayer, partially wet forest canopies was modified for application to the hypostomatous canopies of Douglas fir and salal. This theory was combined with standard hourly micrometeorological measurements, eddy diffusive, boundary layer and stomatal resistance functions, and canopy and root zone water balance equations to calculate evapotranspiration rates ( E ) from a Douglas fir forest with salal understory over extended periods during two growing seasons. Calculated values of E agreed to within 0.2 mm d −1 of values determined using Bowen ratio‐energy balance measurements. The courses of average root zone volumetric water content (θ) calculated for two extended periods agreed well with neutron probe measurements. Salal understory removal resulted in measured values of θ being only 0.01–0.03 m 3 m −3 higher over the two periods, in close agreement with calculations. This corresponded to calculated tree transpiration rates being 0.4 mm d −1 higher on average, during the second half of both periods. These higher rates were confirmed by stomatal resistance measurements.