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Effects of sediment removal on nitrogen uptake by riparian plants in the higher floodplain of the Chikuma River, Japan |
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| Authors: | Fumikazu Akamatsu Koji Shimano Masatoshi Denda Koichi Ide Masatsugu Ishihara Hideshige Toda |
| Institution: | 1. Department of Environmental Sciences, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan 2. Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami Osawa, Hachioji, Tokyo, 192-0397, Japan 4. River Restoration Team, Water Environment Research Group, Public Works Research Institute, 1-6 Minami Hara, Tsukuba, Ibaraki, 305-8516, Japan 3. River Restoration Team, Water Environment Research Group, Public Works Research Institute, 1-6 Minami Hara, Tsukuba, Ibaraki, 305-8516, Japan |
| Abstract: | Riparian plants can use nitrogen (N) from soil and river water, but the use of river water N might be limited in higher floodplain environments of the Chikuma River. The purpose of this study is to reveal the relationship between N uptake by riparian plants and the floodplain topography (relative height and distance from a river channel). We examined the hypothesis that surface sediment removal from the higher floodplain increases river water N uptake by riparian plants by using a stable isotope analysis. The δ15N value of river water samples (ca. 8‰) were significantly higher than those of the soil extracts (ca. 3‰) in the study area. The δ15N value of riparian plants increased from +3.0‰ (standard deviation, SD ±2.1‰) before sediment removal to +9.6‰ (±2.1‰) after sediment removal, although there was no significant change in the δ15N value in N sources of soil and river water. The sediment removal enhanced frequency of flood disturbance, relative ground water level, and river water N uptake by riparian plants on the floodplain. |
| Keywords: | Ecotone Nitrogen dynamics Nitrogen stable isotope ratio Restoration Topography |
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