HR: 15:05h
AN: B23E-06 [Abstracts]
TI: Dynamic Responses and Controlling Factors of Evapotranspiration in a Sagebrush-Steppe Ecosystem in North America
AU: * Ewers, B E
EM: beewers@uwyo.edu
AF: University of Wyoming, Department of Botany
1000 East University Avenue, Laramie, WY 82071, United States
AU: Kwon, H
EM: hkwon@uwyo.edu
AF: University of Wyoming, Department of Botany
1000 East University Avenue, Laramie, WY 82071, United States
AU: Pendall, E G
EM: pendall@uwyo.edu
AF: University of Wyoming, Department of Botany
1000 East University Avenue, Laramie, WY 82071, United States
AU: Naithani, K
EM: Kn77@uwyo.edu
AF: University of Wyoming, Department of Botany
1000 East University Avenue, Laramie, WY 82071, United States
AU: Cleary, M
EM: meagank@uwyo.edu
AB:
Current and future changes in precipitation in North America will alter key ecosystem such as water cycling and
surface energy balance. Although sagebrush-steppe is the largest ecosystem in North America, observations of
ET at ecosystem-level have been limited. We used eddy covariance and associated above- and belowground
micrometrolgy techniques to determine the dynamics and controlling factors of ET. Measuring occurred in a
sagebrush-steppe ecosystem in south-central Wyoming, USA for two growing seasons (2004 and 2005). 2004
had a dry spring while 2005 had an unusually high amount of precipitation in late spring. During the
measurement years, the highest rates of daily ET (1.7 mm day-1) occurred in the early summer season
(June, 2005) driven by high soil moisture and contribution from developing grasses and forbs. The general
pattern of daily ET was more strongly correlated with the deep soil moisture (15 – 45 cm) than the shallow soil
moisture (4 cm). Net radiation was a major driver of ET regardless of soil moisture availability while vapor
pressure deficit (D; atmospheric drought) was a major driver of ET when the ecosystem was not limited by soil
moisture reflecting stomatal closure in response to atmospheric drought. The influence of D was also reflected
in the decoupling factor (Ømega ranged from 0.2 to 0.7), showing the lowest values (near 0.2) when D was
high. Penman-Monteith model ET was calculated using surface conductance estimated from a Jarvis-type model
which included functions of D, light, and soil moisture. Model results indicate that interactions of soil moisture,
light and D components are critical predictive understanding of ET in the sagebrush-steppe ecosystem.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0476 Plant ecology (1851)
DE: 0495 Water/energy interactions (1878)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting