Network-scale streamflow intermittence controls on dissolved organic carbon concentrations and processes

河流在碳的循环中很重要。流域中几乎一半的碳进入溪流和河流，在那里转化为碳气体或向下游输送。对这些过程的理解主要来自对连续流动的溪流和河流的研究。美国近60%的河流是间歇性的或短暂的，所有的河流和河流网络都有间歇性的径流。然而，人们对这些周期性干涸的河流在河流网络中碳的加工和移动中所起的作用知之甚少。该奖项将解决的问题，如何以及何时空间和时间模式的不稳定性影响碳浓度和特征。研究人员将探索流动阻力对溶解有机碳的影响，以及在瞬时过程控制溶解有机碳的条件下干燥的遗留效应的相对影响（例如，生长季节）和通过在溶解有机碳通常受流动控制的条件下与陆地源的连通性（例如，高流量）。更广泛的影响包括培训学生，与当地流域管理者合作，与研究网络协调，以及制作博物馆展览。理解河流碳循环的网络尺度方法通常会做出不适合间歇性网络的假设（例如，均匀的瞬时处理率），大陆和全球河流碳循环评估忽略了这些河流的作用，可能会错过全球碳循环的一个主要组成部分。该奖项将通过整合网络思维和河流对地球化学的影响，改变思考河流流动阻力及其对碳循环和运输的影响的方法。该奖项将发展概念和经验基础，以了解何时，何地以及如何流量波动影响瞬时过程速率，与上游碳源的连接，以及碳浓度和出口。本研究有两个具体的目标：目标1：评估空间和时间的影响，径流阻力的空间格局的溶解有机碳。这将通过结合空间上广泛的连续流存在/不存在的监测与详细的天气特征的溶解有机碳浓度和特性跨越间歇性流网络来实现。目标2：评估透明度如何以及何时影响溶解有机碳浓度的瞬时工艺速率和瞬时工艺控制。研究人员将使用高频监测流量，溶解有机碳浓度和瞬时代谢。该研究将为将异质性整合到河流碳循环网络模型中奠定基础。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Streams are important in the cycling of carbon. Almost half of the carbon in watersheds enter streams and rivers where it is converted to a carbon gas or transported downstream. Understanding of these processes come largely from studying continually flowing streams and rivers. Nearly 60% of streams in the United States are intermittent or ephemeral, and all stream and river networks have intermittent streamflow in their contributing networks. Yet little is known about the role that these periodically dry streams play in the processing and movement of carbon through the stream network. This award will address the question of how and when do spatial and temporal patterns of intermittence affect carbon concentrations and characteristics. The researchers will explore flow intermittence effects on dissolved organic carbon and the relative influence of legacy effects of drying during conditions when instream processes control dissolved organic carbon (e.g., growing season) and via connectivity to terrestrial sources during conditions when dissolved organic carbon is typically controlled by flow (e.g., high flows). The broader impacts include training of students, working with local watershed managers, coordinating with research networks, and producing a museum exhibit.Network scale approaches to understanding stream carbon cycling often make assumptions that are not appropriate for intermittent networks (e.g., homogeneous instream processing rates), and continental and global assessments of stream carbon cycling ignore the role of these streams, potentially missing a major component of the global carbon cycle. This award will transform approaches to thinking about streamflow intermittence and its effects on carbon cycling and transport by integrating network thinking and intermittency effects on biogeochemistry. This award will develop the conceptual and empirical basis for understanding when, where, and how streamflow intermittence affects instream process rates, connectivity to upstream carbon sources, and carbon concentrations and export. The research has two specific aims: Aim 1: Assess spatial and temporal effects of streamflow intermittence on spatial patterns of dissolved organic carbon. This will be accomplished through combining spatially extensive continuous flow presence/absence monitoring with detailed synoptic characterization of dissolved organic carbon concentrations and characteristics across an intermittent stream network. Aim 2: Assess how and when intermittence affects instream process rates and instream process controls on dissolved organic carbon concentrations. The researchers will use high-frequency monitoring of streamflow, dissolved organic carbon concentrations, and instream metabolism. The research will lay the groundwork for integrating heterogeneity into network models of stream carbon cycling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.