This study clarifies relationship between characteristics of channel geomorphology of lowland river and of riparian forest, toward riparian forest management. We classified channels into braided (B), free-meandering (F), irregular-meandering preceding bottleneck (Irre), and meandering that are deep on one side but not the other (D). At bottlenecks there are in-growing meandering (Ing) and intrenched meandering channels (Int). On plains, the bed gradient is gentler and water level fluctuation is larger in order of (B), (Irre), (D) and (F). Channel-bed degradation after river improvement work is generally small in bottlenecks, where the ratio of pre-work length divided by post-work length is small; it is large on plains, where that ratio is larger. Channel-bed degradation is particularly great in (B), whose decrease in sediment transport due to river improvement work are larger than in the other types of channels. The channels were analyzed in terms of micro-topography, sedimentation, and stand distribution and structure. We categorized channels into two: (F) whose range and strength of disturbance are small and where stable development of stand is seen from the area adjoining the channel; and (B), where the area of disturbance is large but the strength of disturbance is moderate. Normally, little vegetation or only young trees are seen on the floodplains after river improvement work and double-row sandbars formed in (B). However, a decrease in flood frequency due to bed degradation and dam construction, and a reduction in the magnitude of disturbance due to streamline adjustment resulting from construction of the low-water revetment resulted in moderate stability of stand. It was thus thought that forest in (B) decay and re-grow repeatedly, and those in (F) develop into stable silva. These findings provide us with a key for better riparian forest management.

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We developed a method to estimate potential hunting areas of the Mountain Hawk Eagle, using data of seven pairs inhabiting Kyushu Island, Japan. Utilizing environmental data recorded where hunting behaviors were observed, we statistically identified those environmental factors that determined hunting areas. We concluded that estimating the distribution and amount of those environmental factors appropriate for hunting was the most effective method to define potential hunting area. We then, derived a method incorporating logistic regression analysis that allowed us to estimate the suitability for hunting of those areas not examined directly during the field survey. Using this method, we were able to estimate hunting areas of the Mountain Hawk Eagle in eight other regions in Japan quite accurately, thereby confirming the validity and general applicability of the method.

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Nature restoration projects are expected to fulfill integrated objectives, not only the restoration of ecosystem function but also reconstruction of human-nature relationship to resume the cultural transmissions of knowledge and techniques for sustainability. Upon setting project goals and implementation plans for nature restoration projects, therefore, integration of viewpoints from social and cultural sciences is required for the analysis of historical and cultural background and people's perception of natural environment. This paper describes an attempt of conservation ecological social survey to reveal the public commitment and past and present interactions between local residents and surrounding wetlands including river and rural agricultural environment around Azameno-se nature restoration project site in Kyusyu, Japan. In the survey we took a mixed approach of semi-structured interview and questionnaire method for 89 neighboring residents sampled according to the quota of sex and age classes of young (ages 10-29), middle class (ages 30-49), young-old (ages 50-69), and old-old (ages 70-89). The survey revealed the age-class-dependent perceptions of rural biodiversity and outdoor experiences, as well as differential commitment and expectations toward the restoration project. The survey results provided implications for vital elements of restoration projects in Japan; the consideration on the cultural and historical backgrounds of a locality and local community's preferences and perceptions of natural environment. The importance of incorporating interdisciplinary learning opportunities is reemphasized for the planning of nature restoration projects. As a catalyst for the communication between local community and practitioners, conservation ecological social survey may play an important role in building consensus on the focal project, and may facilitate the participation of the public. We also elucidated the merits and improvements of the conservation ecological social survey to promote further application of this approach in other sites of nature restoration projects.

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The gravel-bar restoration project, which is conducted in the Nagata district of the Tama River, was reported in this paper. The purpose of this project is to regenerate gravel-bar area and wildlife that is characteristics of gravel-bed river. In making a project execution plan, scholarship persons, citizens and administration discussed the goals of this project and its method together, taking account of both flood control and river environment. As a result, 1) Cutting down and uprooting Robinia pseudoacacia, one of exotic species, 2) Widening of low-water channel by excavating flood channel, 3) Making gravel-bar area by arranging gravel at comparatively high elevation above ordinary water-level, 4) Importation and supply of gravel and so on were carried out. After these works, researchers of the Tama River Research Group, the River Ecology Research Group have been monitoring the number of biological communities such as Aster kantoensis, Eusphingonotus japonicus, Charadrius placidus and riverbed topography as their habitat. The followings were confirmed as that result. 1) The number of the biological communities mentioned above increased in the widened area. 2) Sand accumulated at the time of the flood of about 700 m³/s in a part of the C-section of the widened area, which was planned and excavated not to make sand accumulate. 3) It has the possibility to control the degrading tendency of the riverbed, which goes on so far, by supplying gravel to the upstream end of the Nagata district. 4) Conysa sumatrensis and Erigeron Canadensis are washed out by flood, when the non-dimensional tractive force becomes greater than about 0.06.

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[in Japanese]

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[in Japanese]

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In streams, particulate organic matter (POM) serves as a pivotal link between dissolved nutrients, microbes and organisms at higher trophic levels. Especially in forested streams, such linkage with allochthonous POM is fundamental for saprophytic chain of stream ecosystems. Here, we reviewed current understanding of riverine POM by focusing its classification, dynamics, and ecological role in streams. Generally, coarse particulate organic matter (CPOM, >1mm) is broken down to fine particulate organic matter (FPOM, 0.45 μm-1mm) and dissolved organic matter (DOM, <0.45 μm) while providing essential energy and nutrients for microbes and aquatic fauna. Since input and transport of POM depend highly on season and discharge fluctuation, POM concentration in temperate streams shows wide ranges: 0.001 to 3mgC L^-1 for CPOM and 0.05 to 1mgC L^-1 for FPOM. For deposited POM density, channel unit such as riffle and pool is also influential. Major ecological roles of riverine POM are 1) habitat for aquatic fauna, 2) energy and nutrient supply for microbes, 3) energy and nutrient supply for aquatic fauna, and 4) material transport to downstream reaches and ocean. Colonization of fungi and bacteria on POM mediates carbon and nutrient uptake of aquatic fauna, especially macroinvertebrates. In stream ecosystems, therefore, POM is a major driving force and repeatedly experiences biological interaction and transformation, which is referred as organic matter spiraling. Thus, understanding of organic matter dynamics and its biological interaction is essential for conservation and restoration of stream ecosystems.

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