Abstract: Different types of spatial pattern and spatial association of plant populations can reflect their adaptive strategies in using environmental resources, and can reveal the population biology under disturbances. By using point pattern analysis, this paper studied the spatial pattern and spatial association of Stellera chamaejasme and Melilotoides ruthenicus var. inschanicus at their different succession stages on the northern slope of Qilian Mountains, Northwest China. With the degradation of natural grassland, the plant density, plant height, and aboveground biomass of S. chamaejasme population had a persistent increase, the spatial pattern transferred from aggregative into random or regular. In the meantime, the plant height of M. ruthenicus var. inschanicus population decreased gradually, its plant density and aboveground biomass decreased after an initial increase, and the spatial pattern transferred from aggregative or regular to random. The spatial association between S. chamaejasme and M. ruthenicus var. inschanicus populations transferred from increasingly positive to not significant. During the degradation of natural grassland, the decline of Stipa krylovii population at the upper layer of the community and the differences in the plant height between S. chamaejasme and M. ruthenicus var. inschanicus made an asymmetric competition of light resources, which led to the regulation of the resource allocation strategies of S. chamaejasme and M. ruthenicus var. inschanicus, and affected the spatial pattern and spatial association of the two plants.

Key words: Transgeic, Common carp, Environmental factor, Endurance capacity