Evaluation for ecological functions of the fragmented urban forests by landscape ecological methods and molecular ecological methods

分析了北九州北部城市森林破碎化的影响因素、木本植物群落的大小结构和遗传结构、小型哺乳动物群落的物种组成以及栖息地破碎化引起的种间关系变化。主要研究结果如下：1)调控系统有助于保护城市森林面积；2)某些立地条件容易遭到破坏；3)一些森林在被破坏的情况下仍可能成为保护区域生物多样性的关键；4)某些物种的种群结构可能受到严重影响。种群动态和遗传结构受生境破碎化的影响。综合上述结果，可以对这些破碎化森林所涉及的一些生态功能进行评价。例如，锥栗是该地区的优势树种之一，在以锥树为主的高度破碎化的森林中形成了丰富的苗木银行。这是因为在森林中，可以成为甜锥主要种子捕食者的小型啮齿动物的数量非常少。因此，这类森林的栖息地功能对于一些啮齿动物来说是较低的，而对于锥栗来说则是较高的。

Factors affecting fragmentation of urban forests, size structure and genetic structure of woody species communities, species composition of small mammal communities, and the changes of inter-specific relationships by fragmentation of their habitats were analyzed in the northern part of Kitakyushu City.Main results of the studies were as follow : 1)the regulation systems contributed to conserve the area of urban forests, 2)there were certain site conditions that were prone to be destructed, 3)some forests could become the key stones for conserving regional biological diversity even the forests had been fragmented, and 4)certain species might be severely affected on their population structure, population dynamics and genetic structures by the effects of habitat fragmentation.Some ecological functions involved in those fragmented forests could be evaluated by integrating above results. For example, Castanopsis cuspidate, which was one of dominant canopy species in the region, formed abundant seedling bank in the highly fragmented forests with canopy dominated by the Castanopsis. This is attributable to the fact that the number of small rodents that could become main seed predator of the Castanopsis was very few in the forests. Thus, the habitat function of this type of forests was lower for some rodent species, but higher for Castanopsis cuspidata.