We investigated the distribution patterns of senescent and green leaf litter patches on a streambed to evaluate the hypothesis that the different immersion times of senescent leaves in long-term benthic storage and newly retained green leaves affect streambed distribution patterns in summer (June, July, and August). We counted all the leaf litter patches in the streambed of the study reach, comparing the physical condition of patches and classifying the trapping obstacles associated with each patch type. The distribution patterns of senescent and green leaf litter patches differed. Green leaf litter patches were more numerous at every sampling date, with most trapped by cobbles, whereas senescent leaf litter patches were retained by twig obstacles, backwaters, and cobbles. In June and July, senescent leaf litter patches were located in significantly deeper stream areas than were green leaf litter patches. The distribution of senescent leaves would be primarily determined during spring snowmelt-driven floods. We speculate that senescent leaves were originally located at the edges of pools in the main flow pathway of the channel, which overflowed in the floods. We conducted flume experiments to clarify the transport characteristics of senescent and green painted maple and manchurian alder leaves in the water column. Our hypothesis was that the transport characteristics of each leaf type differ when they first enter the water, because of differing leaf properties. The flume experiments showed that duration of surface flotation differed for senescent and green leaves and for the two tree species. These differences in the duration of leaves on the streambed and in the floating time of green leaves of different trees ensure varied food resources for macroinvertebrates in various physical conditions.
<p>To promote sustainable water resource management through collaboration among multiple stakeholders including managers, water users, and residents, it is essential to understand place meanings that people attribute to the water environment. The water environment performs various functions, including flood control, water supply, habitat provision, recreation for people, and serving as an energy source, through the water cycle in the entire catchment. Therefore, it is important to understand which territories or ranges of the water environment within a catchment people find meaningful and to develop initiatives that correspond to these scales.</p> <p>In recent years, studies have used the concept of &#8220;sense of place&#8221; and have organized spatial perception patterns of landscape values at spot units using questionnaire surveys. Additionally, there have been attempts to evaluate and interpret the characteristics of cultural ecosystem services from spatial and geographical perspectives. However, the patterns and characteristics of spatial cognition with territoriality have not been clarified.</p> <p>To better understand the place meanings attributed to the water environment, here we study to clarify the characteristics of people&#8217;s spatial cognition with territoriality. Specifically, we conducted a questionnaire survey in Okazaki City, Aichi Prefecture, Japan, to visualize which areas of a tributary river basin people find meaningful. The survey was distributed to residents of various ages, positions, and places in Okazaki City. The municipal area generally coincides with the catchment area of the Otogawa River, a tributary of the Yahagigawa River. A total of 331 responses were received via web and mail.</p> <p>The questionnaire included two questions about the image of the water environment, and respondents were asked to fill in their answers of any size on the city map. One question asked respondents to describe areas of the catchment as it relates to their own lives and livelihoods, and the other asked respondents to describe familiar places. Respondents were also asked to indicate their attributes, such as residential history, daily river use, occupational history related to rivers, and the functions of rivers that they consider important.</p> <p>The results of the study showed typical patterns in the spatial perception of the water environment. There was a concentration of responses to certain river spaces corresponding to residential history in the perception of familiar places. On the other hand, for the perception of the range related to life and livelihood, even when respondents had similar residential histories, there were a variety of responses, including responses for several individual spots and a continuous range. It was suggested that these differences were influenced by the respondents&#8217; daily contact with the river and the functions they desired from the river. In the presentation, we will discuss the factors contributing to the formation of each pattern, focusing on spatial and social characteristics such as geographic or historical conditions, and discuss the potential application of these findings to water resource management in the future.</p>
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