HR: 12:00h
AN: H52C-07    [Abstracts]
TI: Testing the Bouchet-Morton Complementary Hypothesis at Harvard Forest using Sap Flux Data
AU: * Pettijohn, J C
EM: geocory@bu.edu
AF: Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, MA 02215 United States
AU: Salvucci, G D
EM: gdsalvuc@bu.edu
AF: Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, MA 02215 United States
AU: Phillips, N G
EM: nathan@bu.edu
AF: Department of Geography and Environment, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 United States
AU: Daley, M J
EM: mdaley@bu.edu
AF: Department of Geography and Environment, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 United States
AB: The Bouchet-Morton Complementary Relationship (CR) states that at a given surface moisture availability (M_A), changes in actual evapotranspiration (ET_a) are reflected in changes in potential evapotranspiration (ET_p) such that ET_a + ET_p = 2ET₀, where ET₀ is an assumed equilibrium evaporation condition at which ET_a = ET_p = ET₀ at maximum M_A. Whereas ET_p conceptually includes a potential transpiration component, existing CR model estimates of ET_ {p are based upon the Penman combination equation for open water evaporation (ET_p,Pen). Recent CR investigations for a temperate grassland at FIFE suggest, however, that the convergence between ET_a and ET_p,Pen will only occur if a maximum canopy conductance is included in the estimation of ET_p. The purpose of this study was to conduct a field investigation at Harvard Forest to test the hypothesis that a CR-type relationship should occur between red maple ( Acer rubrum L.) actual transpiration and red maple potential transpiration, i.e., transpiration given unlimited root- zone M_A via localized irrigation. Just as pan evaporation (ET_p,Pen) is a physical gauge of ET_p, we therefore question whether a well- irrigated maple is a potential transpirator. Daily averages of whole-tree transpiration for our co- occurring irrigated red maple network and reference network were calculated using high-frequency constant-heat sap flux sensor (i.e., Granier-type) measurements. Soil moisture, temperature and matric potential parameters were measured using Campbell Scientific sensors. Preliminary results suggest that the relationship between potential and actual transpiration differs significantly from ET_a and ET_p,Pen in the context of CR, adding useful insight into both ET_p estimation and the understanding of physiological response to M_A variability.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1852 Plant uptake
SC: Hydrology [H]
MN: Fall Meeting 2005