Abstract:

Background and Aims Artemisia ordosica is an important sand fixation plant in north China, whereas few studies were conducted on its population patterns. Population patterns of this species are therefore studied, and the aims are mainly: 1) how spatial scales are related to population patterns, 2) whether plant sizes effect population patterns, and 3) what roles environments play in the process of pattern formation?
Methods Two plots in the size of 50 m×50 m were established in the Mu Us sandy land, and all the A. ordosica plants were recorded and mapped. After that, the data were analyzed with the method of point pattern analysis.
Key results On the scales less than certain critical points, the population is usually characterized by non-random distribution (being clumped or regular), and their spatial association is considerably strong, but may be positive or negative. By contrast, if the scales enlarge beyond these points, the plants will disperse randomly, and their spatial association will loosen greatly. Small individuals are more likely to follow clumped distribution than those big ones. The spatial association between plants will turn from positive to negative if their size differences are enlarged increasingly. Unlike the A. ordosica plants growing in fixed sandy land, those plants in semi-fixed sandy land are easier to follow clumped distribution and associate with each other positively.
Conclusions Population patterns and spatial association of A. ordosica depend on spatial scales, individual sizes and environments, and so do their intra-specific relationships. If A. ordosica plants are transplanted into shifting sandy land for sand control and vegetation restoration, they ought to be arranged in the form of clumped distribution rather than regular distribution.

Key words: Artemisia ordosica, Point pattern analysis, Distribution pattern, Spatial association, Sand fixation