Importance of perennial and non-perennial streams for carbon dioxide and methane emissions during rain events and drying-rewetting cycles (StreamFlux)

溪流和河流在很大程度上促进了有机碳的全球循环，并向大气排放了与气候有关的气体-二氧化碳（CO2）和甲烷（CH 4）。CO2排放的动态与溪流排放和集水区水文学有关，而CH 4则与溪流生物群落和周围土地利用有关。然而，这些研究中的大多数都是在常年河流和稳定的河流流量下进行的，只包括有限的高流量事件（降雨事件）。因此，非常年（间歇性和短暂性）河流的气体排放也没有充分纳入地方和区域碳预算。目前对气候变化的预测还表明，洪水和干旱等严重气候事件的规模和频率可能会增加。拟议的项目旨在通过调查常年和非常年河流中CO2和CH 4排放的驱动因素以及季节与年度的相关性，填补一个重要的知识空白。该项目的第一个目标是量化常年河流事件驱动的CO2和CH 4排放的当地相关性。这一目标将通过以下几个方面的结合来探索：i）用于量化流经河流水-空气界面的气体通量的尖端技术，ii）最先进的传感器和原位气体测量，以及iii）用于评估微生物群落和潜在代谢活动的既定程序。该项目的第二个目标是调查当地河流中的碳循环和大陆非常年河流的气体排放，重点是干燥-再湿润循环。该项目的重点是德国莱茵兰-普法尔茨的奎克河流域（271平方公里）。河流在天然水库（Palatinate森林生物圈保护区）内上升，并沿着明显的景观梯度（自然到强烈的生态影响）流动;这种设置提供了一个理想的研究区域，以评估水文，河流生物群落和土地利用在推动河流碳相关气体排放中的作用。该项目的总体目标是量化和描述偶发（基于事件）和干燥-再湿润周期对当地和区域碳预算的贡献。项目数据将与辅助性水文和地球化学数据以及现有地理信息系统相结合，以便能够制定升级程序，将上述贡献纳入大规模碳循环预算。

Streams and rivers contribute substantially to the global cycling of organic carbon and to the emissions of the climate-relevant gases carbon dioxide (CO2) and methane (CH4) to the atmosphere. Dynamics of CO2 emissions have been linked to stream discharge and catchment hydrology, while CH4 were found to correlate with stream biome and surrounding land use. Yet, the majority of those studies have been performed in perennial streams and under stable stream discharge, with limited inclusion of high discharge episodes (rainfall events). As a result, gas emission from non-perennial (intermittent and ephemeral) streams are also not adequately included in local and regional carbon budgets. Current climate change projections also indicate that the magnitude and frequency of severe climatic events, such as floods and drought will likely increase. The proposed project aims at filling an important knowledge gap by investigating drivers and the seasonal to annual relevance of CO2 and CH4 emissions in perennial and non-perennial streams. The project’s first objective is to quantify the local relevance of event-driven CO2 and CH4 emission from perennial streams. This objective will be explored using a combination of i) cutting-edge techniques for the quantification of gas fluxes across the stream water-air-interface, ii) state-of-the art sensors and in situ gas measurements, as well as iii) established procedures for the assessment of microbial community and potential metabolic activity. The project’s second objective is to investigate local in-stream carbon cycling and gas emissions from continental non-perennial streams, with emphasis on drying-rewetting cycles. The project will focus on the catchment of River Queich (271 km2) in Rheinland-Pfalz, Germany. The river rises within a natural reservoir (Palatinate Forest Biosphere Reserve) and flows along a marked landscape gradient (natural to strongly anthropogenically-impacted); this setting provides an ideal study area to assess the role of hydrology, stream biome and land use in driving carbon-relevant gas emission from streams. The project’s overarching goal is to quantify and characterize contributions of episodic (event-based) and drying-rewetting cycles to the local and regional carbon budget. Project data will be combined with auxiliary hydrological and biogeochemical data, and existing geographic information systems to enable the development of upscaling procedures to include the above contributions into large-scale carbon cycling budgets.