Affiliations: MOE Lab.for Earth Surface Processes,Department of
Urban and Environmental Sciences,Peking University,Beijing 100871,China | Management Bureau of Anxi Extremely-Arid Desert
National Nature Reserve,Anxi County 736100,China
Note: [] Corresponding author; Nomenclature:List of vascular plants of
Anxi District (Zhang,1990).E-mail:lhy@ urban.pku.edu.cn
Abstract: Anxi County is located in the northwestern part of the Hexi Corridor
in Gansu Province and has the sole national level nature reserve of
extremely-arid desert in China.Phytosociological methods (Braun-Blanquet,1964)
are used to classify plant community types in this area.Eleven are
distinguished,including six of deserts,four of oases and one transitional type
between deserts and oases.Direct gradient analysis ( DCA ) is employed to
correlate the distribution of plant communities to physiogeographic
conditions.This study makes clear that water is the most important ecological
factor for the distribution of plant species and communities in this area.The
effects of water have been demonstrated in different ways.A vegetation gradient
from lower altitude to higher altitude in the southern part of the reserve is
driven by a precipitation gradient.The effects of the depth of ground water
table contribute to the differentiation of vegetation from desert to oasis in
the flat area.In a finer scale,the washed gullies have obviously higher species
richness and also higher vegetation cover than the surround gobi
surfaces,possibly caused by the effects of floods.The vegetation patterns
demonstrate that the area of Anxi County is a complete landscape unit.The range
of the current nature reserve is not large enough for the purpose of conserving
the unique biodiversity in this area.
Keywords: extremely-arid desert, vegetation pattern, nature reserve, Central Asia, gobi
