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The notes from Yang et al., 2011
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The notes from Yang et al., 2011- Variation in carbon isotope discrimination in Cleistogenes squarrosa(Trin.) Keng: patterns and drivers at tiller, local, catchment, and regional scales
Shan Xu
A 13C natural tracer method was applied in many studies to separate root-derived CO2 from SOM-derived CO2 (Cheng et al., 2003; Kuzyakov & Cheng., 2004). The principle of 13C natural tracer method is based on the differences in δ 13C values between C3 species, whose mean δ 13C value is -27‰, and C4 species, whose mean δ 13C value is -12 ‰ (Smith and Epstein, 1971). This is because C4 plants incorporate more 13C than do C3 plants during photosynthesis (Chapin, 2002). The value of 13∆ commonly denotes the 13C fractionation and it can be obtained from δ13Cplant and δ13Cair in which it grows:
13∆ of C4 plants is often considered to be less responsive to environmental changes than that of C3 plants (Van de Water et al., 2002; Murphy & Bowman, 2009). However, a number of studies also suggested the 13∆ of C4 species could vary with environmental variables (Buchman et al., 1996; Wang et al., 2005).
Yang et al. (2011) investigated the 13∆ variations of a C4 perennial bunchgrass, Cleistogenes squarrosa (Trin.) Keng, and its potential drivers across a range of ecological scales (i.e. tiller, local, catchment, and regional scale) on the Mongolian plateau. They hypothesized that Nleaf is an important controlling factor of 13∆ variability in C. Squarrosa due to its influence on Ci/Ca and Φ.
According to Farquhar (1983), 13∆ variations of C4 plants during photosynthesis mainly depend on Ci/Ca and Φ. Nleaf could be one of the most important controlling factors that influence Ci/Ca and Φ. Leaf age, grazing pressure, soil properties and weather conditions are some factors that may influence Nleaf. Therefore, this study examed how Nleaf correlated with 13∆ of the C. Squarrosa from four different ecological scales, namely, tiller, local, catchment and regional, which represented the different leaf ages, grazing pressure, soil properties and weather conditions.
The results of this study showed Nleaf could averagely explained 23% of the variation in 13∆ and found 13∆ of C. Squarrosa varied from 5‰ to 9‰ across the Inner Mongolian steppe. Due to the large 13∆ variation of C. Squarrosa (4‰) at a region scale, they suggested C. Squarrosa could be a model species for studying the effect of environmental conditions on the 13∆ of C4 plants.
Dec.23, 2011
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