Abstract:

This paper introduced a grid-based point pattern analysis method and analyzed the spatial pattern of Nitraria tangutorum sand mounds in desert-riverine ecotones，Ordos Plateau，using pair correlation function and Ripley L function. The results showed that the total mounds and different size mounds were clumped，which might result from the nursing effects of the desert ecosystem on plants. Grid-based method showed stronger aggregating tendency at small scale than point approximation method. Bivariate analysis results showed there existed different degree of competition between mounds with different sizes in two climatic zones，and a stronger competition appeared in arid Balagong area. The two methods produced different results at large scale, which cannot be explained clearly yet. Grid-based method，as a new analysis method for spatial pattern，was more suitable for sparse plant pattern analysis in arid and semi-arid areas using remote sensing data.

Key words: Nitraria tangutorum sand mounds, grid data sources, spatial pattern analysis, pair correlation function, Ripley L function, arid and semi-arid areas