Measurement of Atmospheric Nitrogen Deposition and Nitrogen Leaching Rates in Several Forests in China

Abstract

By using ion exchange resin columns, nitrogen (ammonium and nitrate) deposition rates were measured in 6 forest areas in China (Hailar, Changchun, Chanbaishan, Beijing, and Guangdong (Heishiding and Dinghushan)) and at 6 forests in Nagano in Japan. The annual nitrogen deposition rates ranged from 2.5 to 20.7 kg N ha^-1 year^-1 by precipitation (without canopy), and from 1.4 to 39.2 kg N ha^-1 year^-1 by throughfall in forest areas in China. The rates were higher in southern parts of China, and significantly correlated with population density. The rates by throughfall exceeded those by precipitation in the forests having large nitrogen deposition. Dry deposition on tree leaves and twigs might contribute significantly to the nitrogen deposition in air polluted area. Ammonium nitrogen predominated the nitrogen deposition in forests having large nitrogen deposition. Nitrogen leaching losses measured by buried resin bags positively related with and mostly exceeded nitrogen deposition by throughfall in forest areas in China. Large nitrogen leaching loss (40 - 50 kg N ha^-1 9months^-1) observed by the buried bags was in accordance with the values estimated by a water budget approach in a small watershed in Dinghushan. High nitrate concentrations were observed throughout the rainy season there. Increase in nitrogen deposition accompanying with human activities might increase nitrogen leaching loss from forest areas in China.