Winter climate affects long-term trends in stream water nitrate in acid-sensitive catchments in southern Norway
Winter climate affects long-term trends in stream water nitrate in acid-sensitive catchments in southern Norway
复制标题
DOI：
10.5194/hess-12-393-2008
复制
发表时间：
2008-01-01
影响因子：
6.3
通讯作者：
Hole, L.
中科院分区：
文献类型：
--
作者：
de Wit, H. A.;Hindar, A.;Hole, L.
在山区和森林集水区的溪流水NO3的控制还没有彻底了解。溪流中NO3的长期趋势是积极的，中性和消极的，往往明显独立于N沉积的趋势。在这里，在挪威南部的四个小的酸敏感集水区的NO3的时间序列进行了分析，以确定可能的驱动程序的NO3的长期变化。在两个网站，溪流NO3出口下降了约50%，在一段时间内的25年，而在其他网站NO3出口增加了约20%。排放量和氮沉降单独是这些趋势的不良预测。冬季和春季NO3变化趋势最为明显。经验模型解释了每周NO3浓度变化的45%和61%之间，并描述了向上和向下的季节性趋势。关键的解释变量是雪深，流量，温度和氮沉降。所有集水区的积雪深度减少，冬季流量增加。在两个内陆集水区，位于中度N沉积区，这些气候变化似乎驱动冬季和春季浓度和NO3通量的显着下降。在一个沿海附近的山区集水区在低氮沉积区，这些气候变化似乎有相反的效果，即导致特别是冬季NO3的增加。这表明，减少积雪的影响可能会导致减少和增加集水区N淋溶取决于与N沉降，土壤温度制度和冬季排放的相互作用。
Controls of stream water NO3 in mountainous and forested catchments are not thoroughly understood. Longterm trends in stream water NO3 are positive, neutral and negative, often apparently independent of trends in N deposition. Here, time series of NO3 in four small acid-sensitive catchments in southern Norway were analysed in order to identify likely drivers of long-term changes in NO3. In two sites, stream water NO3 export declined ca 50% over a period of 25 years while in the other sites NO3 export increased with roughly 20%. Discharge and N deposition alone were poor predictors of these trends. The most distinct trends in NO3 were found in winter and spring. Empirical models explained between 45% and 61% of the variation in weekly concentrations of NO3, and described both upward and downward seasonal trends tolerably well. Key explaining variables were snow depth, discharge, temperature and N deposition. All catchments showed reductions in snow depth and increases in winter discharge. In two inland catchments, located in moderate N deposition areas, these climatic changes appeared to drive the distinct decreases in winter and spring concentrations and fluxes of NO3. In a coast-near mountainous catchment in a low N deposition area, these climatic changes appeared to have the opposite effect, i.e. lead to increases in especially winter NO3. This suggests that the effect of a reduced snow pack may result in both decreased and increased catchment N leaching depending on interactions with N deposition, soil temperature regime and winter discharge.