To clarify relationships between leaf size and the environment variables, we constructed an energy balance model for a single leaf incorporating Leuning's stomatal conductance model and Farquhar's leaf photosynthesis model. We ran this model for various environmental conditions paying particular attention to the leaf boundary layer. The leaf size maximizing the rate of photosynthesis per unit leaf area (A) at a high irradiance differed depending on the air temperature. In warm environments, A increased with decrease in leaf size, whereas in cool environments, there was the leaf size maximizing A. With the increase in leaf size, the CO2 concentration inside the leaf (Ci) decreased and the leaf temperature increased, both due to lower boundary layer conductance. At low air temperatures, the negative effect of low Ci on A in large leaves was compensated by the increase in leaf temperature towards the optimum temperature for A. This balance determined the optimum leaf size for A at low air temperatures. With respect to water use efficiency, large leaves tended to be advantageous, especially in cool environments at low‐to‐medium irradiances. Some temperature‐dependent trends in leaf size observed in nature are discussed based on the present results.
Unexpected torrential rains have occurred recently due to global warming. There is “limits of public help” in such a disaster. Therefore, “self-help” and “mutual help” become more important to protect lives. Improving these helps enhances disaster resilience. The purpose of this research is to propose initiatives utilizing geospatial information in recovery and rehabilitation phases and to indicate the effects of using geospatial information in the initiatives. The initiatives have conducted for rehabilitation in Toho village, which was damaged by the Northern Kyushu Heavy Rainfall Disaster in July 2017. One initiative is formulating a rehabilitation plan. Meetings are held to reflect residents’ opinions to the plan; using the map is useful to collect and share the opinions. Residents could discuss concrete future visions by using a map, and the rehabilitation plan reflected the opinions of residents could be published. The other initiative is Risk Communication. Many kinds of geospatial information are collected in it, and the Risk Map is published. The map shows the dangerous places and evacuation sites, and residents could understand their location, then the map enhanced disaster resilience.
In Japan, the management of sediment in dam reservoirs has become challenging owing to heavy rain. Unexpected increase of sediment volume in dam reservoirs can increase flood risk owing to a rise in the level of the riverbed. It is therefore necessary to conduct sediment management to clarify the area of sediment production to control the amount of sediment transported and the timing of its movement. Sediment discharge from tributaries is often calculated based on catchment area and the deposited sediment volume already present in the dam reservoir. However, our preliminary surveys have implied that it is also necessary to consider regional geology in the evaluation of sediment transport. Moreover, variations in sediment deposition should be evaluated for each site where the geology changes.
In this study, we observe in detail changes in the riverbed in two tributaries with different regional geologies. Changes in the shape of the riverbed were analyzed from unmanned aerial vehicle observation data, following which the effects of erosion and sedimentation on the riverbed were quantitatively evaluated. Finally, sediment discharge was calculated by a one-dimensional numerical model of sediment transport. These results indicate that the tributary that is mostly composed of mudstone produced considerably more sediment than the tributary composed mainly of sandstone. This suggests that an understanding of regional geology is necessary in the evaluation of sediment dynamics and should be considered in addition to the catchment area.
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