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

Abstract

Long-term nitrogen ( N ) loading on forest ecosystems can lead to " N-saturated forests " . Such ecosystems are likely to have high stream nitrate( NO − )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 NO − concentrations from 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 NO − concentration ranging from ． -． ㎎ N L − indicating that factors controlling stream NO − concentration were variable. High NO − 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.