Studies on the influences of large-scale landform transformation on remained forest community and planted tree population in residential development

自20世纪60年代S以来，大规模的住宅开发集中在以次生林为主的郊区丘陵，这些次生林包括锯缘栎林和其他落叶和常绿三种，直到20世纪50年代S所谓的燃料革命之前一直被用作草丛。典型的低起伏丘陵由新近纪或早更新世的半固结或松散沉积物组成。地貌和地质条件使重土石方的土地转化变得容易，本研究勾勒出丘陵的土地特征及其改造史。在仙台、东京和大阪的选定丘陵进行了实地研究，以衡量挖方和填方作业形成的保留地和开发地的自然潜力。在每个发达土地的部分地区，挖深和填土厚度超过20米。以保育和栽植锯缘栎树的生命力作为衡量自然潜力及其…的生物学指标土地流转带来的变化更多。在这里，低的树木生命力点表示树木生长良好，意味着土地潜力高，而高的生命力点数表示树木生长不良，潜力低。实地调查的主要结果如下：1)保护区内树木平均生命点较低。最低点的地区在仙台的富宫丘陵，可能是因为这些丘陵靠近锯缘栎林的分布中心，而且丘陵的土壤条件相当好，特别是物理性质。另一方面，大阪仙谷丘陵的地势相对较高，表明该丘陵固有的自然土地潜力较差。2)各调查丘陵发达土地的平均树木生命点和变异显著增加，表明土地潜力通过土地改造而降低。然而，根据场地特征的不同，可以观察到点的分布不均匀。例如，在东京的玉马山，人工填土上的树木生命点高于通过重型机械将风化的火山灰压实而成的挖方上的树木生命点，而且植物生长条件较差。较少

Since the 1960's, large-scale residential developments have concentrated on suburban hills covered mostly with secondary forests which, consisting of Quercus serrata and other deciduous and evergreen threes, had been used as coppice until the so-called fuel revolution of the 1950's. Typical hills with relatively low-relief are composed of semi- or unconsolidated sediments of Neogene or early Pleistocene age. The geomorphic and geologic conditions made the land transformation through heavy earthworks easy.Land characteristics of the hills and their modification history was out-lined in this study. Field study was carried out in the selected hills in Sendai, Tokyo and Osaka in order to measure the natural potential of conserved lands and developed lands which were made by cut and fill operations. Cut depth and fill thickness exceed 20m in parts of every developed lands. The tree vitality of conserved and planted Quercus serrata was used as a biological index of natural potential and its … More change caused by land transformation. Here low tree vitality point shows good tree growth and suggests high land potentiality, while high point shows poor tree growth and low potentiality. The range of point is between 1.00 and 5.00 Followings are the main results obtained from field study.1)Mean tree vitality points are low in conserved lands. The lowest-point area is in the Tomiya Hills in Sendai, probably because the hills are located near the distribution center of Quercus serrata forests and the soil condition of the hills is rather good particularly in physical property. On the other hand, the Senboku Hills in Osaka show relatively high points, which suggest the poorness of inherent natural land potentiality of the hills.2)Mean tree vitality points and variances remarkably increase in developed lands in every surveyed hills, suggesting the lowering of land potentiality through land transformation. However, uneven distribution of points can be observed according to the differences of site characteristics. For example, in the Tama Hills in Tokyo, tree vitality points on artificial fill are higher than those on cut which was made through the compaction of weathered volcanic ash by heavy machinery and provides worse plant growing conditon. Less