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

溪流在碳的循环中很重要。流域中近一半的碳进入小溪和河流，在那里被转化为碳气或向下游输送。对这些过程的理解在很大程度上来自于对源源不断的溪流和河流的研究。在美国，近60%的河流是间歇性的或短暂的，所有的河流和河流网络在其贡献的网络中都有间歇性的溪流。然而，人们对这些周期性干燥的溪流在河流网络中碳的处理和移动中所起的作用知之甚少。该奖项将解决间歇的空间和时间模式如何以及何时影响碳浓度和特征的问题。研究人员将探索水流间歇对溶解有机碳的影响，以及在河流过程控制溶解有机碳的条件下(例如，生长季节)，以及在溶解有机碳通常由水流控制的条件下(例如，高流量)，通过与陆源的连通性，干燥遗留效应的相对影响。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。了解河流碳循环的网络规模方法往往做出不适合间歇性网络的假设(例如，同质的河流处理速率)，大陆和全球对河流碳循环的评估忽视了这些河流的作用，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间歇性对生物地球化学的影响，改变思考溪流间歇性及其对碳循环和运输的影响的方法。这一奖项将为理解径流间歇何时、何地以及如何影响入河过程速率、与上游碳源的连通性以及碳浓度和出口奠定概念和经验基础。本研究有两个具体目标：目标1：评估径流间歇对溶解有机碳空间格局的时空影响。这将通过将空间上广泛的连续水流存在/缺失监测与间歇河流网络中溶解有机碳浓度和特征的详细天气学特征相结合来实现。目标2：评估间歇性如何以及何时影响INSTREAM过程速率和INSTREAM过程对溶解有机碳浓度的控制。研究人员将使用高频监测径流、溶解有机碳浓度和河流新陈代谢。这项研究将为将异质性整合到河流碳循环的网络模型中奠定基础。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.