Abstract: Caryopteris mongolica is a scarce resource shrub, distributed mainly in typical grassland, desertification grassland and desert. Different from conventional methods, the study combined the spatial distribution pattern with branching architecture to reveal the ability of using space resources of the shrub. We choose a C. mongolica community in Daliuta, Shenmu, Shaanxi as the object. The spatial distribution pattern type, scale and intensity of the plant population were determined with the methods of adjacent lattice. Branching pattern characteristics, bifurcation ratio and fractal dimension was also studied. The results show that the population of C. mongolica distribute aggregately with highly pattern intensity on 20 m×20 m scale. The pattern scale was 8 m×16 m(128 m²). There is a very significant negative correlation relationship between plant height and density. Therefor the relationship between crown breadth and diffusion coefficient shows significant positive correlation. Competition for resources increases with density, made C. mongolica to a spheroidicity dwarf shrub. And the population density of C. mongolica was 2.79 plants per square meter. Crown fractal dimension of C. mongolica was 7.58, branch fractal dimension of the plant was 2.75, overall bifurcation ratio of the plant was 4.31, and the difference between stepwise bifurcation of plant was significant. Because the branch way of the shrub is pseudo-dichotomously branched, the fractal dimension and bifurcation ratio values were higher. Combine fractal dimension with bifurcation ratio provided scientific evidence of C. mongolica branching pattern was complex. There were a lot of branches in this shrub, and the branches grades were up to fifth-grade. While the branch grade increased, the branch number in each grade decreased significantly. This plant showed short length and large angle of the branches. Overall, C. mongolica has strong ability of spatial extension. It can use natural resources sufficiently through reasonable spatial distribution pattern and complex branching pattern.

Key words: Caryopteris mongolica, spatial distribution pattern, branching patterns, bifurcation ratio, fractal dimension