| In this study, taking Populus euphratica population in the oasis of lower reaches of Heihe River as the research object, through field observation and indoor data analysis, using spatial point pattern analysis method, combined the micro spatial distribution pattern with macro processor geographical environment, to analyze spatial distribution pattern of P. euphratica population in different gradient and different distances from the riverat different scales; combining with the data of high resolution QuickBird image,analyzed the population spatial associations of intraspecies(P. euphratica population in differentage class) and interspecies(P. euphratica population and Tamarix chinensis population); application maximum entropy models and geographic information systems, selected 158 of P. euphratica population actual distribution point data, combined with the growth of P. euphratica six climate-related factors, three terrain factors, two soil factors and a water factor, to predicte the distribution of P. euphratica population in the study area and classifiy the level of appropriate growth areas, analysis of the main environmental factors affecting their growth distribution. Conclusions are as follows:(1)The distribution pattern of P. euphratica population in lower reaches of Heihe River at different spatial scales exist significant changes, mainly at mesoscale scale of 5-12 m were aggregated distribution, at small-scale of 0-2 m and large-scale of 38-40 m were randomly distributed, very few were uniformly distributed. It reflects that the interaction between individuals of P. euphratica population is weak mainly in less than scale of 2 m and greater than scale of 38 m.Along the river from top to bottom, P. euphratica population are mainly aggregated distribution, the aggregation intensities and scales show the first increase and then decrease. At different distances from the river, P. euphratica population are mainly aggregated distribution and aggregation intensities with distance from the river increases tended to increase. Flowing down the river, the farther the distance from the river lots, river recharge little, there is little P. euphratica can be grown in the lot, and showed a tendency to spread, P. euphratica population were random distributed. At the same belt with a defined distance from the river, the aggregation intensities and scales of P. euphratica population which along the East River on the whole are less than the West River’ s.(2)Based on high resolution QuickBird image data, analyzed the spatial distribution pattern and spatial correlation of P. euphratica and Tamarix chinensis populations at different scales: P. euphratica and Tamarix chinensis populations showed a uniform distribution within the range of 0-4 m smaller scale, and between them have significant spatial correlation, indicating that is fierce competition between intraspecies and interspecies in a small space scales. When the spatial scalelarger than a critical dimension tend to random distribution, the spatial correlation between the two is also reduced, indicating ecological linkages within and between species populations on the spatial scale has a strong dependence. The aggregation intensities of Tamarix chinensis population is higher than the P. euphratica population.P. euphratica population of each age class in the space-foot range studied mainly distributed randomly. When L(t)> 0, the maximum aggregation intensities of young age of trees was the strongest; increases with plants, the aggregation intensities of P. euphratica population decline, the middle and old age of P. euphratica population mainly distributed randomly. Young and old age of P. euphratica population, middleand old age of P. euphratica population only within the range of 0-9 m scale were significantly negatively associated, was not associated with spatial scales in the other; young and middle age of P. euphratica population were not associated within the studied spatial scales of 0-50 m. Shows that the P. euphratica population of each age class individuals are independent of each other in spatical distribution.(3)The predicted results of the potential distribution area of P. euphratica population show that: the most suitable areas of P. euphratica population mainly near the coast of Heihe River, where optimum area is 0.16 × 104 km2, representing suitable area is 0.24 × 104 km2, the core distribution area accounts for about 38.32% of buffer area along the river 15 km, accounting for about 6.44% of the total area of the lower reaches of Heihe River. The main environmental factors of affect the P. euphratica population distribution have groundwater level(59.8%), the average annual temperature(22.5%), the average annual rainfall(5.1%), January rainfall(3.2%), available soil water(2.4%) and so on. |
