Abstract
Spatial patterns and associations of plant species are important for revealing how species interact with each other and with the environment, and hence have important implications for the understanding of species interaction and underlying ecological processes with apparent patterns in temperate desert vegetation. In this paper, the function g (r) was used to characterize the spatial patterns and associations of four dominant woody species in three 1-ha desert plant plots in the desert–oasis ecotone of South Junggar Basin, NW China. The complete spatial randomness null model showed four species exhibited significant aggregations at small scales (<20 m). Anabasis aphylla and Nitraria roborowskii, Haloxylon ammodendron and Reaumuria songarica were spatially positive associations at small scales with the independent null model, while A. aphylla and H. ammodendron, A. aphylla and R. songarica, R. songarica and N. roborowskii species pairs exhibited negative associations at small or moderate scales (20–60 m) in our study. The random labeling null model showed that dead standing plants of A. aphylla were largely determined by the combined effects of intra- and interspecific competition. In addition, the results also indicated that the two main factors of habitat heterogeneity and sandy desertification play important roles in determining spatial distribution patterns and associations of woody species in the desert–oasis ecotone of South Junggar Basin. Thus, the differences of species features in spatial patterns and associations should be paid more attention when planning afforestation and developing conservation strategies.
Highlights
Spatial patterns of plants are important characteristics of vegetation and play a significant role in ecological processes, including competitive coexistence and transmission of mortality, and have impacts that scale up to ecosystem-level processes (Alekseev & Zherebtsov 1995; Arévalo & Fernández-Palacios 2003)
The study area was located on the desert–oasis ecotone spanning an elevation range of 258–265 m in South Junggar Basin, NW China (45°22′43.4′′N, 84°50′32.5′′ E), from July 2010 to September 2010, which is a transitional zone from the oasis to the desert
Contrary to the two spatial approaches, we investigated the spatial relation between the distributions of dead standing and living plants, and the random labeling null model was used to detect possible differences in the spatial distribution of dead standing plants compared with the distribution of living plants regardless of the underlying first-order process (Wiegand & Moloney 2004)
Summary
Spatial patterns of plants are important characteristics of vegetation and play a significant role in ecological processes, including competitive coexistence and transmission of mortality, and have impacts that scale up to ecosystem-level processes (Alekseev & Zherebtsov 1995; Arévalo & Fernández-Palacios 2003). Many factors play important roles in determining the spatial patterns of tree species distribution in a plant community. Theoretical models confirmed the coexistence of plant species based on habitat heterogeneity (Tilman & Pacala 1993). Both intra- and interspecific competition should be considered to understand the dynamics of the component species (He & Duncan 2000; Nishimura et al 2005). Regular patterns have been historically viewed as the result of intense competition for limited resources, such as available water or soil resources
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