The origin and reactivity of dissolved organic matter (DOM) have received attention for decades due to the key role DOM plays in global carbon cycling and the ecology of aquatic systems. However, DOM dynamics in river networks remain unresolved, hampered by the lack of data integrating the spatial and temporal dimensions inherent to riverine ecosystems. Here we examine the longitudinal patterns of dissolved organic carbon (DOC) concentration and DOM chemical diversity along a temperate river network under different hydrological conditions, encompassing small headwater streams to the river mouth and base flow to storm events. We show that, during nonstorm conditions, the concentration of DOC and the chemical diversity of DOM exhibit their maxima in the middle section of the network, depicting a bell‐shaped pattern along the river continuum. In contrast, DOM shows a homogeneous longitudinal pattern during storm events, with highly concentrated and diverse DOM along the river network. We posit that these emerging patterns result from changes in the relative influence of catchment versus in‐stream biogeochemical processes along the river continuum and that the degree of influence is modulated by river network hydrology. Based on these findings we put forward the “Bending DOM Concept,” a new conceptual framework around which testable hypotheses on the spatiotemporal dynamics of DOM and the functioning of temperate river networks may be formulated.

中文翻译：

---

描绘温带河网中溶解有机物的连续体

由于DOM在全球碳循环和水生生态系统中所起的关键作用，溶解有机物（DOM）的起源和反应性已受到关注数十年。但是，由于缺乏整合河流生态系统固有的时空维度的数据，阻碍了河流网络中DOM的动态化。在这里，我们研究了在不同水文条件下，沿着温带河网的溶解有机碳（DOC）浓度和DOM化学多样性的纵向模式，包括流向河口的小源头水流和暴雨事件的基流。我们表明，在非暴风雨条件下，DOC的浓度和DOM的化学多样性在网络的中间部分表现出最大值，描绘出沿河流连续体的钟形模式。相反，DOM在暴风雨期间显示出均匀的纵向模式，沿河网的DOM高度集中且变化多样。我们认为，这些新兴模式是由于沿河连续流域的集水区与河内生物地球化学过程的相对影响的变化所致，并且影响程度受到河网水文学的调节。基于这些发现，我们提出了“弯曲的DOM概念”，这是一个新的概念框架，围绕该框架可以制定关于DOM时空动态和温带河网功能的可验证假设。我们认为，这些新兴模式是由于沿河连续流域的集水区与河内生物地球化学过程的相对影响的变化所致，并且影响程度受到河网水文学的调节。基于这些发现，我们提出了“弯曲的DOM概念”，这是一个新的概念框架，围绕该框架可以制定关于DOM时空动态和温带河网功能的可验证假设。我们认为，这些新兴模式是由于沿河连续流域的集水区与河内生物地球化学过程的相对影响的变化所致，并且影响程度受到河网水文学的调节。基于这些发现，我们提出了“弯曲的DOM概念”，这是一个新的概念框架，围绕该框架可以制定关于DOM时空动态和温带河网功能的可验证假设。