Niche and Spatial Distribution Pattern Analysis of the Main Populations of the Tarim Desert-Oasis Ecotone

Exploring the spatial patterns and niche characteristics of desert plant populations is helpful in elucidating the community dynamic mechanisms and vegetation restoration in desert-oasis ecotones. Based on vegetation investigation data of three transects (50 m wide and 900 m length), the spatial distribution patterns, interspecific associations, and niche characteristics of the main plant populations in the desert-oasis ecotone of Tarim basin were analyzed using spatial point pattern analysis and niche indexes. Results showed that Populus euphratica Oliv., Tamarix ramosissima Ledeb., and Glycyrrhiza inflate Bat.had higher importance values and niche widths, indicating better ability to compete for resources against other species with narrow niches, stronger ecological adaptability, and dominance of community structure dynamics and the environment. The values of niche overlap among the main plant populations were generally high, especially among herbaceous species. The distribution pattern indicated that desert plants in drought habitats had convergent adaptation, a low tendency of niche differentiation and intense interspecific competition for resources. The spatial patterns of dominant populations were different; T. ramosissima and G. inflate populations showed random distribution and aggregation distribution at the 0-25 m scale, respectively; P. euphratica populations showed an aggregated distribution at short distances (≤ 5 m) and random distribution with scale increase; P. euphratica vs T. ramosissima, P. euphratica vs G. inflate, and T. ramosissima vs G. inflate showed significantly negative spatial associations at the < 4 m, ≤ 16 m, and ≤ 25 m scales, respectively, and interspecific competition exclusion was significant. Convergent adaptation and interspecific competition were the main driving factors for community succession and restricted species coexistence under the condition of scarce resources.