Climatic significance of the stable carbon isotope composition of tree-ring cellulose: Comparison of Chinese hemlock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast) in a temperate-moist region of China

In the reconstruction of past climate using stable carbon isotope composition (δ ¹³C) in tree ring, the responses of the stable carbon composition (δ ¹³C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ ¹³C series in annual tree rings for Chinese hemlock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast), and investigated the relationships between climatic parameters and stable carbon discrimination (Δ¹³C) series, and evaluated the potential of climatic reconstruction using Δ¹³C in both species, in a temperate-moist region of Chuanxi Plateau, China. The raw δ ¹³C series of the two species was inconsistent, which may be a result of different responses caused by tree’s inherent physiological differences. After removing the low-frequency effects of CO₂ concentration, the high-frequency (year-to-year) inter-series correlation of Δ¹³C was strong, indicating that Δ¹³C of the two tree species were controlled by common environmental conditions. The Δ¹³C series of the species were most significantly correlated with temperature and moisture stress, but in different periods and intensity between the species. During the physiological year, the impacts of temperature and moisture stress on Δ¹³C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature, respectively) than for alpine pine (March to May for moisture stress and April to July for temperature, respectively). In addition, in temperatemoist regions, the control on Δ¹³C of single climatic parameter was not strongly dominant and the optimal multiple regressions functions just explained the 38.5% variance of the total. Therefore, there is limited potential for using δ ¹³C alone to identify clear, reliable climatic signals from two species. Supported by the National Natural Science Foundation of China (Grant Nos. 90211018, 40501076 and 40371118), the International Partnership Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-2) and the Innovation Project of the Key Laboratory of Cryosphere and Environment, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences