Analysis of spatial variability of the fractal dimension of soil particle size in Ammopiptanthus mongolicus' desert habitat

Quantitative analyses of soil texture with the help of the fractal dimensions of soil particle sizes show that fractal dimensions exhibit a significant linear negative correlation with the sand content (> 0.1 mm) and a significant power-law positive correlation with the content of clay and silt (< 0.05 mm) (P < 0.0001). However, results revealed that the range of spatial heterogeneity was not restricted to the range of the shrub canopies of the dominant Ammopiptanthus mongolicus communities in the desert region. These results did not support the theory of the fertile island effect arising from the interception of fine-grained materials including dust by the shrubs in a desert ecosystem. We hypothesize that the high spatial heterogeneity existing beyond the scope of the shrub canopies and the lack of proper soil substrate conditions required for the invasion of other species, lead to the steady dominance of A. mongolicus communities in these arid desert regions.