不同载畜率对典型草原大针茅种群点格局的影响

Effect of Different Stocking Rates on Spatial Point Patterns of Stipa grandis Population in Typical Steppe

基于点格局分析理论,使用成对相关函数并选择完全空间随机模型,结合大针茅种群地上数量特征,对不同载畜率下典型草原大针茅种群的空间格局变化特征予以分析。结果表明:(1)除平均枝条密度外,大针茅种群整体数量特征随着载畜率的增加表现出先升后降的趋势;平均高度、平均分盖度、地上现存量干重和重要值在轻度载畜率最高,在重度载畜率最低。(2)放牧条件下的大针茅种群空斑总面积显著高于未放牧(P<0.05),种群领地面积、分布密度和领地密度显著低于未放牧(P<0.05)。(3)在中等载畜率条件下,大针茅种群分布格局随着空间尺度的增加趋于均匀分布,在其他载畜率条件下呈随机分布模式。由上述结果得出,与未放牧相比,大针茅种群对放牧的适应性表现为:轻度载畜率下,在空间上采取收缩策略,以株丛个体内部调节为主;中度载畜率下,种群在空间格局上仍以聚集分布为主,种群数量特征上无显著变化;重度载畜率下,空间上由集聚分布向随机分布转变,株丛数量调节失灵,导致斑块破碎化。

In order to study the effect of grazing on the spatial pattern of Stipagrandis population in a typical steppe,the spatial pattern of S.grandis population was analyzed by the point pattern analysis theory,using the pair correlation function and selecting the complete spatial randomness.The results showed that：（1）In addition to the average density of tillers,the overall quantitative characteristics of S.grandis showed a tendency of rising and then decreasing with the increase of the stocking rate;the average height,the average coverage,the dry weight of the above ground and the important value were the highest at light stocking rate and the lowest at heavy stocking rate.（2）Under the condition of grazing,the total area of the hole of S.grandis population was significantly higher than that under the non-grazing conditions（P〈0.05）;The population density,territory density and population territory area of S.grandis population in grazing was significantly lower than no grazing（P〈0.05）.（3）Under the condition of medium stocking rate,the population distribution pattern of S.grandis tends to be evenly distributed with the increase of scale,and it showed the aggregation distribution and random distribution pattern under the conditions of other stocking rates.From the above results,the adaptability of the S.grandis population to grazing compared to the non-grazing conditions was as follows：under the light stocking rate,the contraction strategy was adopted in space,and the internal regulation of individual strains was dominant;Under the medium stocking rate,populations were still mainly clustered in the spatial pattern,and there was no significant change in population characteristics;Under heavy stocking rates,the spatial distribution changed from agglomeration to random distribution,and the number of clusters failed to regulate,resulting in plaques.