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

点击翻译按钮获取中文摘要

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.