title: Pooled versus separate tree-ring δD measurements, and implications for reconstruction of the Arctic Oscillation in northwestern China.
abstract: Stable hydrogen isotope ratios (δD) in tree rings are an attractive but still rarely explored terrestrial archive of past climatic information. Because the preparation of the cellulose nitrate for δD measurements requires more wood and a longer preparation time than preparation techniques for other isotopes in cellulose (δ18O or δ13C), it is challenging to obtain high-resolution records, especially for slow-growing trees at high elevations and in boreal regions. Here, we tested whether annually pooled samples of Qinghai spruce (Picea crassifolia Kom.) trees from northwestern China provided results similar to those derived as the mean of individual measurements of the same trees and whether the resulting chronologies recorded useful climate information. Inter-tree variability of δD was higher than that of measured ring width for the same trees. We found higher and significant coherence between pooled and mean isotope chronologies than that among the individual series. It showed a logarithmic relationship between ring mass and δD; however, accounting for the influence of ring mass on δD values only slightly improved the strength of climatic signals in the pooled records. Tree-ring δD was significantly positively correlated with the mean, maximum, and minimum temperatures during the previous winter and with maximum temperature during the current August, and significantly negatively correlated with precipitation in the previous November to January and the current July. The winter climate signal seems to dominate tree-ring δD through the influence of large-scale atmospheric circulation patterns, i.e. the Arctic Oscillation. These results will facilitate reconstruction of winter atmospheric circulation patterns over northwestern China based on a regional tree-ring δD networks.
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: liuxh@lzb.ac.cn.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Liu
authors.affiliation: MOE, Key Laboratory for Coast and Island Development, School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China.
authors.forename: Wenling
authors.initials: W
authors.lastname: An
authors.affiliation: Swiss Federal Research Institute WSL, Dendro Sciences Unit, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Treydte
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Guobao
authors.initials: G
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Zeng
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Guoju
authors.initials: G
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Xuanwen
authors.initials: X
authors.lastname: Zhang
keywords: Dendrochronology; Hydrogen isotopes; Mass contribution; Pooling; Spruce; Winter atmospheric circulation