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

We aimed to quantify the variation of leaf delta C-13 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 delta C-13 in northern grasslands and Tibetan Plateau, China. We 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 delta C-13 data in Tibetan Plateau and northern grasslands in China were also compiled from studies in literature. Along the transect, leaf delta C-13 for C-3 plants ranged from -28.0aEuro degrees to -23.3aEuro degrees, and from -16.3aEuro degrees to -13.8aEuro degrees for C-4 plant Cleistogenes spp.. The change in leaf delta C-13 ranged from -0.26aEuro degrees to -3.51aEuro degrees with every 100mm increase of annual precipitation, and leaf delta C-13 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 delta C-13 to climatic changes. The most important factor regulating spatial variations of leaf delta C-13 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 delta C-13 depended on the most limiting factors in arid grassland (precipitation) and Tibetan grasslands (atmospheric CO2 concentration).