The export of dissolved organic carbon (DOC) from a watershed is a key component of the terrestrial biosphere carbon cycle. There is a need to improve our understanding of how and by how much various environmental factors are driving the temporal patterns of DOC export in order to accurately model and evaluate terrestrial carbon storage and fluxes. In this synthesis, we compiled observational data sets from 14 watersheds in the conterminous United States spanning the time period from 1981 to 2017. We used these data sets to examine the relative impacts of various climate, atmospheric deposition, and land cover factors on the temporal patterns of DOC export across watersheds of different sizes and landscape conditions, as well as the time‐series autocorrelation of DOC export. Our results suggest that the dominant factor on an annual scale was the amount of precipitation, which had a positive correlation with DOC export from a watershed. Overall increasing nitrogen deposition was coincident with increasing DOC export, and increasing sulfur deposition was coincident with declining DOC export. The seasonal pattern of DOC export was strongly regulated by air temperature, the long‐term trend was negatively influenced by increasing sulfur deposition, and no obvious autocorrelation was detected in DOC export. In addition, higher rates of DOC export were positively correlated with greater area of wetlands within a watershed, but was not found to be strongly related to any of the other land cover types.

中文翻译：

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确定关键环境因素，以解释美国本土流域DOC出口的时间模式

流域中溶解有机碳（DOC）的出口是地球生物圈碳循环的关键组成部分。有必要增进我们对各种环境因素如何以及在多大程度上驱动DOC出口的时间模式的理解，以便准确地建模和评估陆地碳储量和通量。在此综合报告中，我们从1981年至2017年的时间段内，收集了来自美国本土14个流域的观测数据集。我们使用这些数据集来检验各种气候，大气沉积和土地覆盖因子对时间的相对影响不同大小和景观条件下的小流域的DOC出口模式，以及DOC出口的时间序列自相关。我们的结果表明，年尺度上的主要因素是降水量，这与流域的DOC出口呈正相关。总体上氮沉积增加与DOC出口增加同时发生，而硫沉积增加与DOC出口减少同时发生。DOC出口的季节性模式受气温的强烈调节，长期趋势受到硫沉积增加的负面影响，并且在DOC出口中未发现明显的自相关。此外，DOC出口量的增加与流域内更大的湿地面积呈正相关，但未发现与其他任何土地覆被类型密切相关。总体上氮沉积增加与DOC出口增加同时发生，而硫沉积增加与DOC出口减少同时发生。DOC出口的季节性模式受气温的强烈调节，长期趋势受到硫沉积增加的负面影响，并且在DOC出口中未发现明显的自相关。此外，较高的DOC出口率与流域内更大的湿地面积呈正相关，但未发现与其他任何土地覆被类型密切相关。总体上氮沉积增加与DOC出口增加同时发生，而硫沉积增加与DOC出口减少同时发生。DOC出口的季节性模式受气温的强烈调节，长期趋势受到硫沉积增加的负面影响，并且在DOC出口中未发现明显的自相关。此外，DOC出口量的增加与流域内更大的湿地面积呈正相关，但未发现与其他任何土地覆被类型密切相关。并且在DOC导出中未检测到明显的自相关。此外，DOC出口量的增加与流域内更大的湿地面积呈正相关，但未发现与其他任何土地覆被类型密切相关。并且在DOC导出中未检测到明显的自相关。此外，DOC出口量的增加与流域内更大的湿地面积呈正相关，但未发现与其他任何土地覆被类型密切相关。