Variations in leaf carbon isotope composition along an arid and semi-arid grassland transect in northern China

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AimsWe aimed to quantify the variation of leaf δ13C along an arid and semi-arid grassland transect in northern China. We also evaluated the effects of environmental factors (i.e. precipitation, temperature and altitude) on the spatial variation of leaf δ13C in northern grasslands and Tibetan Plateau, China.MethodWe sampled leaves of plant species belonging to three herb genera (Stipa spp., Leymus spp. and Cleistogenes spp.) and three shrub genera (Caragana spp., Reaumuria spp. and Nitraria spp.) for carbon isotope analysis from 50 locations along a 3200-km arid and semi-arid grassland transect in northern China. Leaf δ13C data in Tibetan Plateau and northern grasslands in China were also compiled from studies in literature.Important FindingsAlong the transect, leaf δ13C for C3 plants ranged from −28.0‰ to −23.3‰, and from −16.3‰ to −13.8‰ for C4 plant Cleistogenes spp.. The change in leaf δ13C ranged from −0.26‰ to −3.51‰ with every 100mm increase of annual precipitation, and leaf δ13C of shrubs (Nitraria spp., Reaumuria spp. and Caragana spp.) responded more markedly to climatic factors (precipitation and temperature) than that of herbs (Stipa spp., Leymus spp. and Cleistogenes spp.), indicating higher sensitivity of shrub δ13C to climatic changes. The most important factor regulating spatial variations of leaf δ13C in Tibetan Plateau was altitude, while it was precipitation in northern grasslands. Our results suggested that shrubs are more adapted to increasing drought in arid and semi-arid grassland. Controls of environmental factors on leaf δ13C depended on the most limiting factors in arid grassland (precipitation) and Tibetan grasslands (atmospheric CO2 concentration).

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