Evapotranspiration (ET) and regulating mechanisms in two semiarid Artemisia-dominated shrub steppes at opposite sides of the globe
Understanding the regulation of ecosystem ET is crucial to comprehend present and potential future
vegetation and water availability in arid environments. We compared ET data from eddy-covariance flux
measurements in two semiarid shrub-dominated ecosystems. Located in the Kubuqi Desert (KD, Inner
Mongolia, China) and the Sierra Madre (SM, Wyoming, USA), the ecosystems shared similarities in
latitude, climate and vegetation.We analyzed ET at KD and SM for the years 2006-2007 and 2004-2005,
respectively, and tested regulatory functions of climate variables through modifications to the widely
used FAO-Penman-Monteith model. Important modifications included the insertion of soil water
potential (Js) and the removal of vapor pressure deficit (VPD) and wind speed (u). The modifications
improved daily estimates of growing season ET as they reduced deviations between model and
measurement to 1-33%. According to model results, available energy (Rn-G) and Js were the main
drivers of ET during growing seasons. VPD and u influenced ET mainly after precipitation events and at
low Js (i.e., Js close to zero). Although our empirical model still requires validation through data from
other sites, the results suggest that the regulatory power of Js and the conditional sensitivity to VPD are
characteristic of ET in shrub steppes.
Burkhard Wilske, Hyojung Kwon, Long Wei, Shiping Chen, Nan Lu, et al.
firstname.lastname@example.org (B. Wilske).
Journal of arid environments