Acta Geographica Sinica ›› 2003, Vol. 58 ›› Issue (1): 90-100.doi: 10.11821/xb200301011

Previous Articles     Next Articles

Dating the 1000-year-old Qilian Juniper in Mountains along the Eastern Margin of the Qaidam Basin

SHAO Xuemei1,2, 1,3, FANG Xiuqi4, 1   

  1. 1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Institute of Earth Environment, CAS, Xi'an 710075, China;
    3. Beijing Normal University, Beijing 100875, China;
    4. National Climate Center, Beijing 100081, China
  • Received:2002-08-14 Revised:2002-11-11 Online:2003-01-25 Published:2003-01-25
  • Supported by:

    Knowledge Innovation Project of CAS, No. KZCX2-314, KZCX1-10-02; National Key Basic Research Special Fund, No. G1998040811

Abstract:

In this paper, the methods for developing the master chronologies for 1000-year-old Qilian Juniper (Sabina przewalskii Kom.) are introduced in detail. Since the studied sites are located in the arid region of northeast Qinghai-Xizang Plateau, the tree-ring cores sampled contain a certain number of missing rings and several false rings. To assure the proper placement in time of each growth layer for the 1000-year-old trees, some improvements were made in the practice of master chronologic development. Firstly, trees with a variety of ages were sampled besides very old trees. The large sample depth benefited the identification of missing rings for cores from old trees and avoided the possibility that all collected specimens could be missing a ring for any one year. Secondly, cores from younger trees and from trees that exhibit a little width variation were selected to do the skeleton plot first and cores with many missing rings were done last when the ring-width pattern was known. Thirdly, inferring where rings may be missing was made based on the agreement among the narrow rings as well as among the wide rings. If the agreement of wide rings is not so good and there were some missing rings, the chronology from nearby sites was used to infer the year of missing ring occurrence. Finally, several methods, such as the computer program COFECHA and the line plots were used to examine the dating and the measurements of ring width for a site. The number of cores without missing rings and time span covered by them were also inspected to avoid the possibility that all collected specimens were added a missing ring for any one year. The Gleichlaufigkeit statistics was used to examine the dating agreement between master chronologies of different sites.

Key words: the Qaidam Basin, dendrochronology, ring-width pattern, tree-ring chronology