不同放牧强度季节调控下荒漠草原主要植物种群点格局及空间关联性

种群空间格局是种群自身特性、种间相互关系及环境条件综合作用的结果。以短花针茅荒漠草原为研究对象,运用Programita软件,采用Ripley's K函数和Monte Carlo随机模拟方法,对短花针茅、无芒影子草和碱韭种群点格局及空间关联性进行了研究。结果表明:短花针茅在禁牧和过度放牧下集群分布的尺度在增加,禁牧和过度放牧两种草地利用方式下短花针茅种群的格局具有趋同的趋势;并且,随着放牧强度的增大或者是持续放牧的影响,使得随机分布尺度在逐渐的增大,短花针茅在更大的尺度上才可能为集群分布。春季重牧+夏季重牧+秋季轻牧和全年重度放牧利用下无芒隐子草在较大尺度上才表现为集群分布,并且尺度转化的临界点在放牧的影响下有增大的趋势;重度放牧下碱韭为了适应放牧干扰逐渐向集群分布方向发展,集群分布的尺度在减小以提高种群的稳定性从而抵御过度的干扰。在不同的放牧干扰强度下植物种群具有明显的响应策略,大致表现为物种的群居性在增强,物种集群分布的尺度在减小以提高种群的稳定性从而抵御过度的干扰。春季休牧+夏季重牧+秋季轻牧处理下种群斑块化的尺度较大,有利于群落的稳定,因此荒漠草原采用这种利用方法较为合理。

Point pattern and spatial association of primary plant populations in the seasonal regulation of grazing intensity in desert grassland

The spatial distribution pattern of a population demonstrates a combination of the unique characteristics of the population, and the interrelationship between species and the environment. In the present study, Stipa breviflora was used to examine the point pattern and spatial correlation of primary plant populations using Programita software, Ripley''s K function, and the Monte Carlo Method. The results showed that the scale of random distribution gradually increased with elevation of grazing intensity, or continuous grazing, and may be the primary explanation for the clustered distribution of populations at large scales. The clustered distribution scale of S. breviflora increased in the "grazing prohibited" and "overgrazed conditions". These two conditions were also associated with a convergence trend in S. breviflora. Increasing grazing intensity, or continuous grazing, gradually amplified the random clustered distribution scale of S. breviflora and may be the primary explanation for this clustered distribution. On a larger scale, Cleistogenes songorica showed a clustered distribution under "heavy grazing in spring+heavy grazing in summer+light grazing in autumn", and "heavy annual grazing". The critical point of the above scale conversion showed an increasing trend with grazing. Allium polyrhizum showed a trend of clustered distribution in response to grazing disturbance. The clustered distribution of this species was reduced to improve the population stability and avoid interference. Plant populations had specific response strategies under different grazing intensities, including enhancement of species sociality, and reduction of the clustered distribution, to improve population stability and avoid excessive disturbance. S. breviflora, C. songorica, and A. polyrhizum had either no correlation or a negative correlation at the small scale. At larger scales, primary plant species had either no correlation or a positive correlation. At a scale of 0-250 cm,S. breviflora and A. polyrhizum showed no correlation in conditions of "heavy grazing in spring+heavy grazing in summer+light grazing in autumn". However, at larger scales, S. breviflora and A. polyrhizum were positively correlated in the conditions of "zero grazing in spring+heavy grazing in summer+light grazing in autumn", and "zero grazing in spring+light grazing in summer+heavy grazing in autumn". Conditions of "spring grazing", "summer grazing", and "fall grazing" produced relatively lager-scale population patches that benefited the stability of the population. Thus, these methods are more suitable for the desert grassland.