Environment, Chinese Academy of Sciences

Stable carbon isotope composition (d13C) usually shows a negative relationship with precipitation at a large scale. We hypothesized that sampling method affects foliar d13C and its response pattern to precipitation. We selected 11 sites along a precipitation gradient in Inner Mongolia and collected leaves of Leymus chinensis with five or six replications repeatedly in each site from 2009 to 2011. Additionally, we collected leaves of L. chinensis separately from two types of grassland (grazed and fenced) in 2011. Foliar d13C values of all samples were measured. We compared the patterns that foliar d13C to precipitation among different years or different sample sizes, the differences of foliar d13C between grazed and fenced grassland. Whether actual annual precipitation (AAP) or mean annual precipitation (MAP), it was strongly correlated with foliar d13C every year. Significant difference was found between the slopes of foliar d13C to AAP and MAP every year, among the slopes of foliar d13C to AAP from 2009 to 2011. The more samples used at each site the lower and convergent P-value