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

Aims We aimed to quantify the variation of leafδ^(13)C 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 leafδ^(13)C in northern grasslands and Tibetan Plateau,China.Method 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 semiarid grassland transect in northern China.Leafδ^(13)C data in Tibetan Plateau and northern grasslands in China were also compiled from studies in literature.Important Findings Along the transect,leafδ^(13)C for C_(3)plants ranged from−28.0‰to−23.3‰,and from−16.3‰to−13.8‰for C_(4)plant Cleistogenes spp..The change in leafδ^(13)C ranged from−0.26‰to−3.51‰with every 100 mm increase of annual precipitation,and leafδ^(13)C 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 shrubδ^(13)C to climatic changes.The most important factor regulating spatial variations of leafδ^(13)C 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 leafδ^(13)C depended on the most limiting factors in arid grassland(precipitation)and Tibetan grasslands(atmospheric CO_(2)concentration).