Agriculture affects the biogeochemical cycles of carbon, nitrogen, and phosphorus, leading to a deterioration of surface water quality. The increasing magnitude of climate change raises questions about potential additional or mitigating effects of climate change on this deterioration. One way to understand these potential effects is to cross‐analyze the dynamics of nutrient concentrations and hydroclimatic variables at multiple time scales. Here, we used a 16‐year data set, from a 5 km² agricultural watershed in France with a temperate oceanic climate, that contains a daily record of nutrient concentrations and hydroclimatic variables from 2002–2017. We calculated Mann‐Kendall and Theil‐Sen tests, Fourier transforms, and daily hydroclimatic distributions associated with extreme stream concentrations to investigate long‐term trends, seasonal dynamics and their interannual variations, and the daily time scale, respectively. Dynamics of dissolved organic carbon (DOC) and nitrate (NO₃) concentrations displayed opposite patterns at the three temporal scales, while soluble reactive phosphorus concentrations showed decoupled dynamics, related more to extreme hydrological events. Climate and past agricultural changes seem to have a synergetic effect that leads to long‐term NO₃ decrease and DOC increase. Precipitation and, to a greater extent, watershed wetness controlled seasonal and event‐driven dynamics.

中文翻译：

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小农业流域水气候与碳，氮，磷出口之间的多时相关系

农业影响碳，氮和磷的生物地球化学循环，导致地表水质量恶化。气候变化的幅度不断增大，引发了有关气候变化对这种恶化的潜在附加或缓解作用的质疑。了解这些潜在影响的一种方法是在多个时间尺度上交叉分析养分浓度和水文气候变量的动态。在这里，我们使用了一个5年²法国具有温带海洋性气候的农业流域，其中每天记录有2002-2017年的养分浓度和水文气候变量。我们计算了Mann-Kendall和Theil-Sen检验，傅立叶变换以及与极端溪流浓度相关的每日水文气候分布，以分别研究长期趋势，季节动态及其年际变化和每日时间尺度。溶解有机碳（DOC）和硝酸盐（NO ₃）浓度的动力学在三个时间尺度上显示出相反的模式，而可溶性反应磷浓度显示出解耦的动力学，更多地与极端水文事件有关。气候和过去的农业变化似乎具有协同效应，导致长期的NO ₃减少，DOC增加。降水以及更大范围内的分水岭湿度控制着季节和事件驱动的动态。