Affiliations: Xinjiang Institute of Ecology and Geography, Chinese
Academy of Sciences, Urumqi 830011, China | Graduate School of Chinese Academy of Sciences,
Beijing, 100039, China
Abstract: To investigate the relationships between the degradation of plant
community and groundwater level in the lower reaches of the Tarim River, nine
monitored sections were set along the main stream, where there had been no
runoff for nearly 30 years. The characteristics of plant communities were
analyzed. It was found that the coverage of trees gradually decreased along the
groundwater depth gradient, while the coverage of shrubs slightly increased
rather than decreased at first and then gradually decreased, and the coverage
of herbs steadily decreased at the beginning and then quickly decreased. The
species diversity and species richness of both herbs and woody plants showed
obvious degrading trends, while the variations in species evenness were slight.
The degrading sequences of species were related to their physiological and
ecological characteristics, especially their sensitivity to changes of
groundwater table. The herbs with shallow roots first degenerated or
disappeared when the groundwater table fell, and then did the deep-rooted
herbs, and finally the trees and shrubs with strong tolerance to drought
degenerated. The Populus euphratica communities showed typical degrading
characteristics, namely the dominant species Populus euphratica remained its
dominant status during the degradation. Overall, the existence of strongly
tolerant-drought species was the obvious indication of plant species
degradation; while simplification of community structure and the decrease of
species richness were the obvious indication of plant community
degradation.
Keywords: degradation, plant community, coverage, species diversity, Tarim River
