Change of spatial pattern of Potentilla fruticosa population along altitudinal gradient in Dongdahe forest area of Qilian Mountains Nature Reserve

The basic characteristics, coverage spatial pattern and the change along altitudinal gradient of Potentilla fruticosa population in Dongdahe forest areas of Qilian Mountains Nature Reserve were studied by using the methods of pattern indexes, accumulation intensity indexes and accumulation mean values. The results showed that the average population abundance, the average coverage and average height of Potentilla fruticosa reached their maximum values at an altitude of 2 842, 2 990 and 3 017 m, respectively. The appropriate altitude of P. fruticosa population distribution were about 2 900 ―3 100 m in the southeast slope.The population coverage was an aggregated distribution. With altitude elevating, the pattern index increased gradually and reached the maximum value at 2 990 m, and then fluctuated and declined. The change of accumulation intensity had the same pattern as the pattern index. The main reason for the aggregated distribution of P. fruticosa population was the survival environment of P. fruticosa population.