Point pattern analysis of different life stages of Haloxylon ammodendron in desert-oasis ecotone

The Haloxylon ammodendron natural desert forest is an important vegetation formation and has a large distribution area in Junggar Basin, Xinjiang Province, China. In this paper, H. ammodendron populations were mapped, characterized and the spatial distribution patterns and spatial associations of H. ammodendron among different life stages (seedlings – S, juveniles – J, mature – M, overmature – O) were analyzed using O-ring univariate O11(r) and bivariate O12(r) statistics. We found that: (1) H. ammodendron was a regenerating population. (2) H. ammodendron (S), H. ammodendron (J), and H. ammodendron (M) showed significant aggregations at scale 0-8 m, 0-27 m, and 0-35 m, respectively, whereas H. ammodendron (O) tended to have random distributions at almost all scales. (3) The spatial associations between different life stages of H. ammodendron tended to turn from positive to negative if their size differences are enlarged increasingly. Strongly positive associations were found at small scales for only two pairs: H. ammodendron (S)-H. ammodendron (J), H. ammodendron (J)-H. ammodendron (M).

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