Evapotranspiration partitioning, stomatal conductance, and components of the water balance: A special case of a desert ecosystem in China

Evapotranspiration partitioning, stomatal conductance, and components of the water balance: A special case of a desert ecosystem in China

Wenzhi Zhao^a*, Bing Liu^a*, Xuexiang Chang^a, Qiyue Yang^a, Yuting Yang^b, Zhiling Liu^c, James Cleverly^d, Derek Eamus^d

a. Linze Inland River Basin Research Station, Laboratory of Heihe River Eco-Hydrology and Basin Science, Cold and Arid Regions Environmental and Engineering Research

Institute, Chinese Academy of Sciences, Lanzhou 730000, China

b. CSIRO Land and Water, Canberra, ACT, Australia

c. School of Public Administration, China University of Geosciences, Wuhan 430074, China

d.  School of the Environment, University of Technology, Sydney, NSW, Australia

s u m m a r y

Partitioning evapotranspiration (ET) into its components reveals details of the processes that underlie ecosystem hydrologic budgets and their feedback to the water cycle. We measured rates of actual evapotranspiration(ET_a), canopy transpiration (T_c), soil evaporation (E_g), canopy-intercepted precipitation (E_I), and patterns of stomatal conductance of the desert shrub Calligonum mongolicum in northern China to determine the water balance of this ecosystem. The ETa was 251 ± 8 mmduring the growing period, while E_I, T_c, and E_g accounted for 3.2%, 63.9%, and 31.3%, respectively, of total water use (256 ± 4 mm) during the growing period. In this unique ecosystem, groundwater was the main water source for plant transpiration and soil evaporation, T_c and exceeded 60% of the total annual water used by desert plants. ET was not sensitive to air temperature in this unique desert ecosystem. Partitioning ET into its components improves our understanding of the mechanisms that underlie adaptation of desert shrubs, especially the role of stomatal regulation of T_c as a determinant of ecosystem water balance.