The influence of topography on the stream N concentration in the Tanzawa Mountains, Southern Kanto District, Japan
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The water chemistry of 51 headwater streams was studied in the Tanzawa Mountains, western fringe of Southern Kanto Plain, Japan. The relationships to soil N processes and catchment topography were also evaluated using a geographic information system with fine-scale map data. The average concentration of total dissolved N was 0.74 mg-N L−1, of which 95% consisted of NO3 −-N. Stream N concentrations were not different among bedrock geologies and among vegetations of the catchments. Stream NO3 −-N marginally correlated to soil nitrification. Stream NO3 −-N also tended to be high in areas with steep and south-facing slopes. These results imply that N transport from Tanzawa forest ecosystems is related to hydrological and biological processes associated with catchment topography.
KeywordsCatchment topography Forest watershed Geographic information system (GIS) Nitrate Water quality
We are grateful to Makoto Arima, Eiko Nakamura, Keiich Ohno, Masamichi T. Ito, Masahiro Ishikawa, Yoshiyuki Kaneko, and Akiko Sakai at Yokohama National University for their assistance. This study was supported financially by the 21st Century COE Program of Japan Society for the Promotion of Sciences, a scientific research fund of Ministry of Education, Culture, Sports, Science and Technology (No. 18710035), and a fund for Enhancement of Education and Research in Yokohama National University.
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