Structure and function of ecosystems in a river for applying to environmental assessment.

1)整理了定期的河床断面数据作为数据库。阐明了该河床近30年来的地貌变化。在最初的15年里，由于上游修建的大坝和下游挖砾石的大坝的淤积，河床地形起伏很大。在第二个15年中，它变得稳定，沙洲上植被所占的面积扩大了。2)芦苇群落内仅有6种藤科和5种亚科的分布。实验结果表明，两种葡萄属之间存在无竞争排斥的共存机制。3)大型底栖动物种类的分布与盐度、沉积物大小等环境因素相对应。利用多元回归分析、Logistic回归分析和/或数量化理论(类型II)对物种的生物量或发生可能性进行了一定程度的预测。4)从时间和空间上比较了平纹夜蛾斑块的分布、大小和密度。2001年的斑块大小比1999年大大减少，特别是分布在河口周围和最高处(距河口约14公里)的种群。在盐度较高和/或粗石沉积的地点，新梢生长和产种量较小。种群的扩张主要由根茎类植物所拥有，而种子则有助于向新的地点定居。5)建立了模拟平纹夜蛾种子扩散过程的水力学模型。

1) Periodical cross-sectional data of the riverbed was arranged as the data-base. Then geomorphologic change of the riverbed was clarified for past 30 years. The riverbed topography had greatly fluctuated during first 15 years due to sedimentation in dams which were constructed upstream and gravel digging downstream. It has become stable during the second 15 years, and area occupied by vegetation on bars has expanded. 2) Distribution of six species of Grapsidae and five species of Assimineidae has been restricted within reed communities. From an experimental treatment, it was suggested that coexisting mechanism without competitive exclusion existed for two species of Grapsidae. 3) The distribution of macro-benthic species corresponds with environments, such as salinity and sediment size. Biomass or occurrence possibility of the species was predictable in some extent by using multi-regression analysis, logistic-regression analysis and/or quantification theory (type II). 4) Distribution, size and shoot density of Bolboschoenus planiculmi patches was compared temporally and spatially. Patch size in 2001 was greatly decreased from 1999, particularly in populations distributed around river-mouth and uppermost area (ca.14 km from river-mouth). Shoot growth and amount of seed production were small at sites with high salinity and/or coarse-stony sediment. Expansion of the population is mainly owned by root-sucker, while seeds contribute to colonize to new sites. 5) Hydraulic model to simulate dispersal process of Bolboschoenus planiculmi seeds was developed.