不同尺度下荒漠草原建群种短花针茅的空间分布对载畜率的响应

为探讨不同尺度下短花针茅种群密度空间分布对载畜率的响应特点及差异,本研究以内蒙古四子王旗短花针茅荒漠草原建群物种短花针茅为对象,分析了不同尺度(1 m×1 m小尺度和5 m×10 m中尺度)下对照、轻度放牧、中度放牧和重度放牧4种处理短花针茅种群的空间异质性。结果表明: 与小尺度相比,中尺度的对照与轻度放牧下短花针茅种群密度显著降低。在2种尺度下,与对照相比,放牧使得短花针茅种群密度显著增加。通过半方差函数进行模型拟合, 小尺度下,对照、轻度放牧、中度放牧及重度放牧样地短花针茅种群分布分别符合线性、指数、指数和指数模型,中尺度下分别为高斯、指数、高斯和指数模型。不同尺度和放牧强度下短花针茅种群空间结构发生改变,小尺度下,对照样地短花针茅分布格局较简单、空间结构较好;而重度放牧样地短花针茅分布格局较复杂、空间结构较差;中尺度下,重度放牧样地短花针茅分布格局较简单、空间结构较好,而中度放牧样地短花针茅分布格局较复杂、空间结构较差。中、小尺度下,中度和重度放牧使得短花针茅种群空间异质性降低且分布更为均匀;此外,对照、中度和重度放牧下中、小尺度短花针茅种群空间分布趋势基本一致,而轻度放牧则有所不同。

Responses of the spatial distribution of Stipa breviflora to stocking rate at different scales.

We conducted an experiment to test the characteristics and differences of the spatial distribution of constructive species Stipa breviflora at different scales under different stocking rates in the S. breviflora desert steppe in Siziwang Banner, Inner Mongolia. The spatial distribution of S. breviflora under four treatments (control, light grazing, moderate grazing, and heavy grazing) at different scales (small scale as 1 m×1 m and mesoscale as 5 m×10 m) were analyzed. The results showed that the population density of S. breviflora at mesoscale in the control and light grazing was significantly lower than that at the small scale. Grazing significantly increased the population density of S. breviflora in the meso- and small scales. At the small scale, the population distribution of S. breviflora in the control, light grazing, moderate grazing, and heavy grazing treatments conformed to linear, exponential, exponential and exponential models, respectively, and Gaussian, exponential, Gaussian and exponential models at mesoscale fitted by semi-variance function. The spatial distribution pattern at small scales in the control was simple and better but was more complex and poorer under the heavy grazing. At the mesoscale, it was simple and better under the heavy grazing but complex and poor under the moderate grazing. The spatial heterogeneity of S. breviflora population reduced and were more uniform under the moderate and heavy grazing at meso- and small scales. In addition, the trend of population distribution in the enclosure, moderate and heavy grazing were generally the same, while light grazing showed inconsistent trend at different scales.