Evaluating the Influence of Environmental Factors on Mountain Stream Nitrate Concentrations in Miyazaki Prefecture

• Published in: Journal of Environmental Conservation Engineering Vol. 51; no. 5; pp. 267 - 278
• Main Authors: MAKINO, Soyoka, MAUNG, Nay Lin, TOKUCHI, Naoko
• Format: Journal Article
• Language: Japanese
• Published: Osaka Society of Environmental Conservation Engineering 20.09.2022; Japan Science and Technology Agency
• Subjects: Agriculture; Ammonia; Annual precipitation; Catchments; Deposition; Ecosystems; Elevation; Emissions; Environmental factors; Forest ecosystems; Fossil fuels; Geology; Human impact; Livestock; Mountain streams; nitrate; Nitrates; Nitrogen; nitrogen deposition; stream; Terrestrial ecosystems
• ISSN: 0388-9459; 1882-8590
• DOI: 10.5956/jriet.51.5_267

Long-term nitrogen (N) loading on forest ecosystems can lead to "N-saturated forests". Such ecosystems are likely to have high stream nitrate (NO3-) concentrations. Recent increases in atmospheric emissions from livestock and agriculture activities and combustion of fossil fuels have changed the N cycle in terrestrial ecosystems. We investigated stream NO3- concentrations from 200 forest catchments free from human disturbances within Miyazaki Prefecture and assessed the relationships with N depositions and catchment properties (e.g., climate, topography, vegetation, geology, and soil). Stream NO3- concentration ranging from 0.01-1.07 ㎎ N L-1 indicating that factors controlling stream NO3- concentration were variable. High NO3- concentrations were more common for sites with low annual precipitation, high ammonia emission-based N depositions from livestock and agriculture, and high annual N deposition. Temperature, elevation, and radiation are also important factors. Our study is the first to show the influence of livestock and agriculture via N deposition on mountain stream chemistry in Japan.