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

1)定期的河床断面数据作为数据库。阐明了近30年来河床地貌的变化。由于上游建坝和下游挖砾的淤积，河床地形在前15年中波动很大。在第二个15年，它已经变得稳定，并在酒吧植被所占的面积有所扩大。2)六种方蟹科和五种拟蟹科的分布仅限于芦苇群落内。实验结果表明，两种方蟹存在共存机制，但不存在竞争排斥。3)大型底栖物种的分布与盐度和沉积物大小等环境相对应。利用多元回归分析、逻辑回归分析和数量化理论（II型），可以在一定程度上预测该物种的生物量或发生概率。4)比较了扁叶草斑块的时空分布、大小和枝条密度。斑块面积在2001年大大减少，从1999年，特别是在人口分布在河口和最高的地区（约14公里，从河口）。芽生长和种子生产量小，在高盐度和/或粗石沉积物的网站。种群的扩展主要由根吸器负责，而种子则有助于定殖到新的地点。5)建立了扁叶土瓜螺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.