Regional Comparison of Nitrogen Export to Japanese Forest Streams
Regional Comparison of Nitrogen Export to Japanese Forest Streams
复制标题
日本森林溪流氮输出的区域比较
作者：
H. Shibata;K. Kuraji;H. Toda;K. Sasa
亚洲国家的氮(N)排放量预计将在未来几十年内增加。了解N向森林溪流输出的时空波动机制不仅对量化N、N饱和状态和土壤酸化N的临界负荷具有重要意义，而且由于缺乏对溪流N化学的区域比较研究，日本森林流域土壤酸化N的动态和收支尚不清楚。为了解决缺乏比较研究的问题，我们从2000年6月到2001年5月测量了日本群岛18个实验森林的溪流中无机氮(硝酸盐和铵)的浓度，这些森林属于日本大学森林联盟。监测了基流和丰水期溪水中的N浓度，并通过间歇培养实验测定了土壤中N的矿化潜力。日本中部的溪水中硝酸盐浓度较高，这是一个大气氮沉降率较高的地区。在日本北部，积雪融化导致溪水中硝酸盐浓度增加。表层土壤的潜在净N矿化速率高于次表层土壤，表层土壤的高N矿化潜力是暴雨期间溪水中硝酸盐浓度升高的部分原因。大气氮沉降的地区差异、降水和高流量的季节性是控制日本森林流域溪水中硝酸盐浓度和变化的主要因素。
Nitrogen (N) emissions in Asian countries are predicted to increase over the next several decades. An understanding of the mechanisms that control temporal and spatial fluctuation of N export to forest streams is important not only to quantify critical loads of N, N saturation status, and soil acidification N dynamics and budgets in Japanese forested watersheds is not clear due to the lack of regional comparative studies on stream N chemistry. To address the lack of comparative studies, we measured inorganic N (nitrate and ammonium) concentrations from June 2000 to May 2001 in streams in 18 experimental forests located throughout the Japanese archipelago and belonging to the Japanese Union of University Forests. N concentrations in stream water during base flow and high flow periods were monitored, and N mineralization potential in soil was measured using batch incubation experiments. Higher nitrate concentrations in stream water were present in central Japan, an area that receives high rates of atmospheric N deposition. In northern Japan, snowmelt resulted in increased nitrate concentrations in stream water. The potential net N mineralization rate was higher in surface soil than in subsurface soil, and the high potential for N mineralization in the surface soil partly contributed to the increase in nitrate concentration in stream water during a storm event. Regional differences in the atmospheric N deposition and seasonality of precipitation and high discharge are principal controls on the concentrations and variations of nitrates in stream water in forested watersheds of Japan.