Carbon isotope discrimination of C3 vegetation in Central Asian grassland as related to long-term and short-term precipitation patterns

摘要

The relationship between carbon isotope discrimination (13Δ) of C3vegetation and long-term (30 years) and short-term (growing period)precipitation was investigated. Different species of Stipa, adominant grass genus in the (semi-)arid Asian steppes, and other C3 specieswere collected along aridity gradients in Inner Mongolia in 2005 (11 sites,71 samples) and in the Republic of Mongolia in 2006 (40 sites, 45 samples).The data set was expanded with published and unpublished data ofStipa and other C3 species (11 studies covering 8 years, including64 observations of Stipa, and 103 observations of other C3 species)and C3 community bulk-samples (11 samples). Weather data weregeostatistically interpolated for all sampling sites and years. 13Δ of Stipa followed different relationships for the individual yearswhen related to mean annual precipitation due to large anomalies betweenannual and long-term average precipitation patterns. However, the13Δ response to rainfall converged when the (long-term) meanannual precipitation was replaced by year-specific mean daily precipitationduring the growing period ( style="border-top: 1px solid #000;">P_G). Remarkably, the 13Δ-response to ( style="border-top: 1px solid #000;">P_G) for C3 species as a whole (including herbaceousdicots, semi-shrubs and grasses) and also the C3 community-level responsewere virtually identical to that of Stipa. The relation was alsovalid outside the geographical and climatic range where it was developed,giving proof of its robustness.