Chin J Plan Ecolo ›› 2005, Vol. 29 ›› Issue (5): 836-844.DOI: 10.17521/cjpe.2005.0111

• Research Articles • Previous Articles     Next Articles

PALAEO_BIODIVERSITY AT THE NORTHERN PIEDMONT OF TIANSHAN MOUNTAINS IN XINJIANG DURING THE MIDDLE TO LATE HOLOCENE

ZHANG Yun, KONG Zhao_Chen, YAN Shun, YANG Zhen_Jing, and NI Jian   

  1. Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences
  • Online:2005-08-30 Published:2005-08-30
  • Contact: ZHANG Yun

Abstract:

Palaeo_biodiversity and environmental characteristics in the Mid_ and Late Holocene were investigated in five profiles from Daxigou, Huashuwozi, Xiaoxi gou, Dongdaohaizi and Sichanghu, which are located at different elevations and in different vegetation zones on the northern piedmont of Tianshan Mountains, Xin jiang. Selected profiles were located at three vegetation zones. The first was the alpine and subalpine meadow vegetation zone (2 700-3 400 m). Thirty_eight genera and families were identified in the Daxigou profile (3 450 m).Pollen Simpson index was 2.72-7.67 with a mean value of 4.84. The forest_steppe ecotone was from 1 200-1 600 m elevation. Forty_two pollen genera and families were identified in the Huashuwozi profile and 39 in the Xiaoxigou profile at this vegetation zone. The pollen Simpson index of Huashuwozi profile was 4.2-12.4 with a mean value of 7.8, and that of Xiaoxigou profile was 4.13-12.06 with a mean value of6. 89. The last two profiles were located in the typical desert zone (400-600 m). Thirty_two pollen genera and families were identified in Dongdaohaizi profile and 35 in Sichanghu profile. The pollen Simpson index of Dongdaohaizi profile was 1 .8 - 18.8 with a mean value of 6.62. The pollen Simpson index of Sichanghu profile was 4.1 - 9.0 with a mean value of 5.55. These results showed that Holocene biodiversity and the pollen Simpson index were the highest in profiles from the desert_steppe vegetation zone. Our analysis also showed that four periods (3600-3200 aB.P., 1700-1400 aB.P., 1000-600 aB.P., and 450 aB.P.) had the highest pollen Simpson index and highest biodiversity on the northern piedmont of Tianshan Mountains in Xinjiang. Thus, the pollen Simpson index reflects climatic and environmental changes to a certain extent. However, biases exist due to the influence of buried pollen assemblages, low precision in pollen identification _ to genera and family levels only, influx of exotic pollen and human disturbances. Pollen that had low representation in the profiles was not taken into account in calculating the biodiversity index, which might underestimate overall palaeo_biodiversity. Due to different abilities o f pollen dispersal and transportation, there is high spatial variation in the number of pollen taxa at different sites within the same research district. In addition, sediment composition, strata chronology and human activities have great impacts on pollen preservation, which also affect our ability to estimate palaeo_ biodiversity. All in all, this research showed that the pollen Simpson index is an important index of palaeo_biodiversity and the paleoenvironment,but more research is needed.