Collaborative Research: How do hydrology and biogeochemistry control carbon flux from headwater streams to the atmosphere?

众所周知，溪流收集、处理和释放了盆地的大部分水。河流也收集、处理和释放盆地的大部分碳，这一点鲜为人知。碳以各种形式被流收集，其中一些碳被河床中的微生物加工成二氧化碳（CO2），并且大部分CO2在下游流动期间被排放到大气中。 这些过程在小型源头河流中尤为重要。 由于源头流域流失大量的陆地表面，这些耦合的水碳过程可能是全球性的。 该项目将通过深入研究俄勒冈州西部一个96公顷流域的源头河流内的河流碳循环来测量、建模和理解这种耦合的水碳循环。通过使用HJ安德鲁斯实验森林的分水岭1，本研究将利用详细数据收集的历史和大量现有的测量。 该项目团队将与奥杜邦协会合作，在实地教授1000名学童河流水文学和生态学。第一个是开发一个集成的建模框架，以模拟碳循环的流，是广泛转移到模拟地下和地表过程的地球系统模型中的流。第二是测试和提出一个综合理论的河流和地下水水文，碳地球化学，和CO2生产和流出的流。这些目标将通过开发一个模拟水文过程（例如，运输，潜流交换）和地球化学过程（例如，颗粒和溶解有机碳之间的转化，这些碳“池”的有氧呼吸速率）。建模将结合直接测量地下水输送的土壤呼吸的CO2，生物和物理过程控制碳循环，溶解氧，水文测量和CO2流出流到树冠下呼吸测量在流量塔以上的流。将使用原地潜流中围来操纵和监测反应性运输沿着流动路径参数化地球化学速率表达式中使用的综合模型。最后，该项目将扩大范围尺度的过程，以流域尺度来解释从河流网络的碳通量。

It is known that streams collect, process, and release much of a basin's water. It is less known that streams also collect, process, and release much of a basin's carbon. Carbon is collected by streams in various forms, some of that carbon is processed by microbes in the streambed into carbon dioxide (CO2), and much of that CO2 is vented to the atmosphere during downstream flow. These processes are particularly important in small, headwater streams. Since headwater basins drain significant land surface, these coupled water-carbon processes may be globally significant. This project will measure, model, and understand this coupled water-carbon cycle via intensive study of the stream carbon cycle within one headwater stream draining a 96-hectare basin in western Oregon. By using the Watershed 1 of the HJ Andrews Experimental Forest, this study will leverage a history of detailed data collection and a large number of existing measurements. The project team will partner with the Audubon Society to teach 1000 school children stream hydrology and ecology in the field.This project has two main goals. The first is to develop an integrated modeling framework to simulate carbon cycling in streams that is widely transferable to model subsurface and surface processes of streams in earth system models. The second is to test and present an integrated theory of stream and groundwater hydrology, carbon biogeochemistry, and CO2 production and efflux in a stream. These goals will be accomplished by developing an integrated carbon model for headwater streams that simulates hydrologic processes (e.g., transport, hyporheic exchange) and biogeochemical processes (e.g., transformation between particulate and dissolved organic carbon, aerobic respiration rates of these carbon "pools"). Modeling will be coupled with direct measurements of groundwater delivery of soil-respired CO2, biological and physical processes controlling carbon cycling, measurements of dissolved oxygen, hydrology, and CO2 efflux from the stream to subcanopy respiration measured at a flux tower above the stream. In situ hyporheic mesocosms will be used to manipulate and monitor reactive transport along flow paths to parameterize biogeochemical rate expressions for use in the integrated model. Finally, the project will upscale the reach-scale processes to watershed scale to explain carbon fluxes from river networks.