Premium
WATER BALANCE DELINEATES THE SOIL LAYER IN WHICH MOISTURE AFFECTS CANOPY CONDUCTANCE
Author(s) -
Oren Ram,
Ewers Brent E.,
Todd Philip,
Phillips Nathan,
Katul Gabriel
Publication year - 1998
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/1051-0761(1998)008[0990:wbdtsl]2.0.co;2
Subject(s) - evapotranspiration , canopy , water content , transpiration , environmental science , throughfall , canopy interception , canopy conductance , interception , vapour pressure deficit , soil water , water balance , hydraulic conductivity , hydrology (agriculture) , water potential , soil science , stomatal conductance , groundwater recharge , botany , ecology , geology , groundwater , aquifer , biology , photosynthesis , geotechnical engineering
To link variation in canopy conductance to soil moisture in the rooting zone, measurements of throughfall ( P T ), volumetric soil moisture (θ) to 0.7 m, transpiration from trees >10 mm in diameter ( E C ), and vapor pressure deficit ( D ) were made in a forest dominated by Pinus taeda. Total evapotranspiration ( E T ) was estimated from P T , changes in volumetric soil water content within a defined soil volume (Δ S ), and drainage out of that volume ( Q ), calculated from unsaturated soil hydraulic conductivity and θ. Our calculations suggest that over 145 growing‐season days, Q was negligible, and most of P T , averaging ∼2 mm/d, was partitioned between soil moisture recharge (0.4 mm/d) and E T (1.6 mm/d, not including ∼0.4 mm/d of interception, I, by canopy trees), of which E C was estimated from direct measurements at nearly 1.2 mm/d. Evapotranspiration by the subcanopy component accounted for slightly over 0.4 mm/d, about a third of E T (a fourth if I is included). Most of the water used for E T (>90%) was taken from the upper soil layer (top 0.35 m, or less). Canopy leaf conductance, calculated from E C , D, and canopy leaf area, was strongly related to θ in the upper soil layer once θ decreased below 0.22.