祁连山高寒草原主要植物种群格局对冬季放牧的响应

以肃南裕固族自治县鹿场冬季牧场为研究对象，采用偏离系数及t检验方法结合Ripley''s K函数及蒙特卡罗随机模拟对紫花针茅种群与醉马草种群进行格局分析，进一步采用计盒维数与信息维数对紫花针茅种群与醉马草种群进行分形分析，揭示在放牧系统中优势植物的种群变化。格局分析结果表明：牧场植物的种群格局出现5种变化规律。紫花针茅种群的偏离系数在放牧率3.64 AUM/hm²时^#，出现最小值。醉马草种群的偏离系数在放牧率4.16AUM/hm²时，出现最大值。在0-1 m的研究尺度内，紫花针茅种群与醉马草种群的Ripley''s K函数结果均在蒙特卡洛随机模拟区间内，呈随机分布格局。分形分析结果表明：伴随放牧率增大，紫花针茅种群的计盒维数区间为1.596，1.962]，醉马草种群的计盒维数区间为1.831，1.945]；紫花针茅种群的信息维数区间为1.590，1.899]，醉马草种群的信息维数区间为1.633，1.913]。在放牧率4.34 AUM/hm²时，紫花针茅种群与醉马草种群空间占据差值达到最大，信息维数相对较低，种群分布相对均匀，格局变化相对缓慢，经济效益与生态效益相平衡，最适合管理牧场。

Response of main plant population pattern to winter grazing in alpine steppe of the Qilian Mountains

The experiment was conducted in early August in the winter pastures of Sunan deer farm, Sunan Yugur Autonomous County, Gansu Province. Through observation of grazing behavior and the growth of vegetation, the main feeding path of Cervus elaphus kansuensis grazing is confirmed, and the grazing rate from high to low is formed from the import and export of the pasture. Three main paths were selected to set the sample plots at the entrance of 0 m, 300 m, 600 m, 900 m, 1200 m, and 1500 m, respectively. Each sample area is about 1 hm². According to the calculation formula of stocking rate, the grazing rates were 6.90, 4.85, 3.45, 2.45, 1.45, and 1.00 AUM/hm², respectively. Ten continuous quadrats with 0.25m² were set up for pattern analysis, and a 4 m² quadrat was used for fractal analysis. Using the deviation coefficient and the t-test method, Ripley''s K function and Monte Carlo stochastic simulation were used to analyze the pattern of the population of Stipa purpurea and Achnatherum inebrians, and the fractal statistics of box counting dimension and information dimension were used to analyze the population of the dominant plants including S. purpurea and A. inebrians in the grazing system. The pattern analysis showed that there were 5 changes in the population pattern of pasture plants. (1) A part of the plant population showed a cluster distribution pattern under all the herding rates. (2) Another part of the plant population showed a random distribution pattern under all herding rates. (3) The distribution pattern gradually shifted from random to cluster distribution as the stocking rate increased; (4) the distribution pattern gradually shifted from cluster distribution to random distribution as the stocking rate increased. (5) The population cluster distribution and the random distribution appeared alternately on the grazing gradient. The deviation coefficient of S. purpurea population was the lowest when grazing rate was 3.64AUM/hm². The coefficient of variation of the population of A. inebrians was the highest when the grazing rate was 4.16AUM/hm². In the scale of 0-1 m, the results of Ripley''s K function of S. purpurea population and A. inebrians population were in random distribution pattern in Monte Carlo stochastic simulation interval. The fractal analysis showed that with the increase of grazing rate, the box counting dimension interval of the population of S. purpurea and A. inebrians were1.596,1.962] and1.831,1.945], respectively. The information dimension interval of the population of S. purpurea and A. inebrians were1.590,1.899] and1.633,1.913], respectively. When the grazing rate was 4.34 AUM/hm², the difference between the population space of S. purpurea and the population of A. inebrians was the largest and the information dimension was relatively low. At the same time, the population distribution was relatively uniform while the change of the pattern was relatively slow. The economic and ecological benefits were balanced, which was the most suitable for the management of pasture.