Effects of local interactrions on the dynamics and diversity of populations

本研究的目的是探讨放牧与周围植物相互作用对周围植物空间结构的影响。实验池采用无螺、5螺和10螺3个。通过图像处理分析，估计了周围植物的空间分布动态。然后，用半变异函数对结果进行分析。此外，还建立了以个体为基础的模型，探讨了影响蕨类植物空间分布变化的因素。实验结果表明，一个焦点区域的周围植物生物量的生长受到该区域生物量的负向影响，而受到邻近区域生物量的正向影响。在不放牧的情况下，空间斑块很少或没有形成。随着蜗牛放牧量的增加，斑块的形成更加明显。基于个体的模拟结果表明，当邻近区域的周边植物生物量对周边植物生物量的影响为正时，可以形成斑块。中等程度放牧压力形成较为清晰的斑块。此外，当蜗牛在曾经吃过草的地方吃周围植物时，斑块的大小有变大的趋势。这表明实验中的蜗牛倾向于在同一区域吃草。研究表明，蜗牛与周围植物之间以及邻近周围植物之间的相互作用会导致周围植物的空间结构分布。

The purpose of this study is to examine the effect of grazer-periphyton interactions on the spatial structure of periphyton. Three experimental tanks with no snail, 5 snails, and 10 snails were used. The dynamics of spatial distribution of periphyton was estimated by image processing analysis. Then, the results were analyzed using semivariogram. In addition, individual-based models were conducted to examine the factors affecting the change in spatial distribution of pheriphyton.The results of the experiments show that the growth of periphyton biomass in a focal area was negatively affected by the biomass in the area, but positively affected by the biomass in the neighboring areas. For the case of no grazing, little or no spatial patches were formed. With increase of snail grazing, the more conspicuous patches were formed. The results of individual-based simulation suggested that when the effects of the periphyton biomass in neighboring areas on the periphyton biomass were positive, the patches could be formed. The intermediate degree of grazing pressure form more clear patches. In addition, when snails grazed periphyton in area where the snails once grazed, the size of patches tended to become larger. This suggests that snails in the experiments tended to graze the same area. The present study indicats that the interactions between snails and periphyton and among neighboring periphyton would cause the structured spatial distribution of periphyton.