Abstract: Spatial distribution pattern and association of plant populations are important means to understand the interaction of plant populations and the relationship between plant populations and environment. In this study, the spatial distribution characteristics and the association of Reaumuria songarica (Pall.) Maxim. and Caragana roborovskyi Kom., two main species on different slopes in Laohutai arid desert area of Gaolan County, Gansu Province, were analyzed by using Ripley’s K function, aiming to reveal the changes of competition relationship, survival, and reproduction strategies of dominant populations during vegetation succession in the arid desert area. The results showed that the distribution of R.songarica and C. roborovskyi significantlydifferedin three slope aspects. The number of individuals and coverage of R.songaricashowed a decreasing trend, while theC. roborovskyi showed an increasing trend from northwest to southwest slope. On the northwest slope, R. songaricashowed a random distribution at 0-5 m scale, while C. roborovskyi was in aggregated distribution. On the west slope, both R. songarica and C. roborovskyi showed random distribution at all scales. On the southwest slope, R. songaricashowed an aggregated distribution at 0-5 m scale, while C. roborovskyishowed a random distribution. R. songarica and C. roborovskyi showed a negative correlation at various scales on the northwest slope. Both species showed no association at 0-5 m scale on the west slope. On the southwest slope, R. songarica andC. roborovskyishowed a negative association at 0-1.3 m scale, and had no association at 1.3-5 m scale. Our results were helpful to the understanding of the intraspecific and interspecific competition, diverse ecological strategies of plant species, and community succession in the study region.

Key words: Black soil region, Paddy field, Fertilizer nitrogen