Acta Geographica Sinica ›› 2006, Vol. 61 ›› Issue (9): 919-928.doi: 10.11821/xb200609003

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Standardization of Qilian Juniper Ring-width Series in the Eastern Margin of the Qaidam Basin

XU Yan1,2, SHAO Xuemei1,3   

  1. 1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Graduate School of the Chinese Academy of Sciences, Beijing 100049, China;
    3. Institute of Tibetan Plateau Research, CAS, Beijing 100085, China
  • Received:2006-03-09 Revised:2006-07-12 Online:2006-09-25 Published:2010-09-01
  • Supported by:

    National Natural Science Foundation of China, No.40371118; Knowledge Innovation Project of the Chinese Academy of Sciences, No.KZCX3-SW-321

Abstract:

Standardization of tree-ring data is one of the most important procedures in dendroclimatology. We used abundant Qilian juniper (Sabina przewalskii Kom) tree-ring samples along the eastern margin of the Qaidam Basin to approximate the growth trend to generate a total growth trend curve. We used samples that contained complete pith reaching to a growth culmination in 40-60 years to estimate the total growth trend curve, and then employed the generalized negative exponential function to fit the curve. Usually, most sample cores cannot reach the tree pith for various reasons and it is difficult to determine the trees' cambial ages. An empirical model of initial radial growth (IRG) was developed to estimate the number of rings missing from the pith based on the same tree-ring data and the IRG model explained 90.9% of the variance. When constructing the chronology, the cambial age of the first ring from the pith is regarded as 1 year. Then the ages of the rings in samples without piths were determined by the estimated numbers of missing rings in the cores. Standardization was accomplished by dividing each tree-ring series by the corresponding values of the total growth trend curve. The chronologies developed by this method can preserve more low-frequency variability. This method helps to construct more reliable tree-ring width chronologies.

Key words: Qaidam Basin, Qilian juniper, tree-ring width, growth trend