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Plant and Environment Interactions

Quantification of Intrinsic Water Use Efficiency along a Moisture Gradient in Northeastern China

^a Laboratory of Quantitative Vegetation Ecology, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, P.R. China
^b Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904
^c Institute for Geospatial Research and Education, Eastern Michigan University, Ypsilanti, MI 48197

^* Corresponding author (meiyu{at}ibcas.ac.cn)

Received for publication September 13, 2004. Water use efficiency (WUE) is an important ecophysiological characteristic of plants, especially in semiarid and arid regions. At the scale of community or ecosystem, WUE is difficult to quantify because the amount of water used per unit dry mass production is a function of microclimatic variables and species composition. In this study, we analyzed corrected intrinsic water use efficiency (IWUE_s) of grass and shrub species along the western segment of the Northeast China Transect (NECT) and the relationship between IWUE_s and mean annual rainfall, habitat degradation status, vegetation type, and plant functional type (C3 versus C4) at 22 survey sites. Site intrinsic water use efficiency (IWUE_v) and its relationship with the aforementioned site variables were analyzed based on species frequencies at each site. First, it was concluded that photosynthetic pathway played a very important role in determining species IWUE_s. Mean IWUE_s for C4 species was approximately double that of C3 species. Second, mean annual rainfall, vegetation type, and site degradation status significantly affected IWUE_s (p < 0.01). Mean IWUE_s at degraded sites was twice as high as that at nondegraded sites. The mean IWUE_s for meadows was significantly higher than those for other vegetation types (p < 0.05). Third, the frequency of occurrence of C4 plants explained 36% of the variance in IWUE_v across the survey sites. The mean frequency of C4 occurrence at degraded sites was more than double that at nondegraded sites. Consequently, mean IWUE_v at degraded sites was more than double that at nondegraded sites. Dominant C4 species in saline–alkaline areas tended to have higher intrinsic WUE than dominant C4 species in sandy shrub communities.

Abbreviations: IWUE, intrinsic water use efficiency • IWUE_s, corrected intrinsic water use efficiency • IWUE_v, site intrinsic water use efficiency • NECT, Northeast China Transect • WUE, water use efficiency