[Point pattern analysis of Populus euphratica population in the lower reaches of Heihe River]

Taking Populus euphratica population in the lower reaches of Heihe River as the research object, through field investigation, using spatial point pattern analysis method of Ripley's K function, and combined the macro geographical environment with micro point pattern, we analyzed the spatial distribution pattern of P. euphratica population at different scales. The results showed that P. euphratica density decreased with the increasing distance away from the river, and its density was higher along the East River than along the West River on the whole. The distribution pattern of P. euphratica population varied with spatial scale which was mainly aggregated at mesoscale of 5-12 m, randomly distributed at small-scale of 0-2 m and large-scale of 38-40 m, and very few was evenly distributed. P. euphratica populations were mainly aggregated away from the river, and the aggregation intensity tended to increase with the distance, while it tended to spread and turned into a random distribution at the farther distance. Research showed that the ecological linkages of P. euphratica populations strongly depended on space scale, and the surface soil moisture and groundwater depth were the main factors influencing the spatial distribution of P. euphratica populations.