Nitrogen lost from agriculture has altered the geochemistry of the biosphere, with pronounced impacts on aquatic ecosystems. We aim to elucidate the patterns and driving factors behind the N fluxes in lowland stream ecosystems differing about land-use and climatic-hydrological conditions. The climate-hydrology areas represented humid cold temperate/stable discharge conditions, and humid subtropical climate/flashy conditions. Three complementary monitoring sampling characteristics were selected, including a total of 43 streams under contrasting farming intensities. Farming intensity determined total dissolved N (TDN), nitrate concentrations, and total N concentration and loss to streams, despite differences in soil and climatic-hydrological conditions between and within regions. However, ammonium (NH4+) and dissolved organic N concentrations did not show significant responses to the farming intensity or climatic/hydrological conditions. A high dissolved inorganic N to TDN ratio was associated with the temperate climate and high base flow conditions, but not with farming intensity. In the absence of a significant increase in farming N use efficiency (or the introduction of other palliative measures), the expected farming intensification would result in a stronger increase in NO3−, TDN, and TN concentrations as well as in rising flow-weighted concentrations and loss in temperate and subtropical streams, which will further exacerbate eutrophication.

中文翻译：

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耕作强度和气候对低地溪流氮的影响

农业损失的氮改变了生物圈的地球化学，对水生生态系统产生了显着影响。我们旨在阐明在土地利用和气候水文条件不同的低地河流生态系统中 N 通量背后的模式和驱动因素。气候水文区代表潮湿寒冷的温带/稳定的排放条件和潮湿的亚热带气候/闪光条件。选择了三个互补的监测采样特征，包括对比耕作强度下的总共43条河流。尽管区域之间和区域内的土壤和气候水文条件存在差异，但耕作强度决定了总溶解氮 (TDN)、硝酸盐浓度以及总氮浓度和河流流失。然而，铵（NH4+）和溶解有机氮浓度对耕作强度或气候/水文条件没有显着响应。高溶解无机氮与 TDN 的比率与温带气候和高基流条件有关，但与农业强度无关。在农业氮利用效率没有显着提高（或引入其他缓解措施）的情况下，预期的农业集约化将导致 NO3−、TDN 和 TN 浓度的更强增加以及流量加权浓度的上升温带和亚热带河流的损失，这将进一步加剧富营养化。高溶解无机氮与 TDN 的比率与温带气候和高基流条件有关，但与农业强度无关。在农业氮利用效率没有显着提高（或引入其他缓解措施）的情况下，预期的农业集约化将导致 NO3−、TDN 和 TN 浓度的更强增加以及流量加权浓度的上升温带和亚热带河流的损失，这将进一步加剧富营养化。高溶解无机氮与 TDN 的比率与温带气候和高基流条件有关，但与农业强度无关。在农业氮利用效率没有显着提高（或引入其他缓解措施）的情况下，预期的农业集约化将导致 NO3−、TDN 和 TN 浓度的更强增加以及流量加权浓度的上升温带和亚热带河流的损失，这将进一步加剧富营养化。