Transformation of organic carbon in the terrestrial-aquatic interface

我们的建议的总体目标是了解从土壤到lotic和lentic沃茨的陆生-水生界面的有机碳（OC）转化的调节，重点是短暂的溪流。这些系统大大扩展了陆地-水生界面，因此是密集OC转化的潜在场所。尽管陆地、半水生和水生地点的环境条件不同，但所有地点有机碳转化的可能主要因素是有机物的质量、氧气和营养物的供应以及水状况。我们的目标是（1）OC质量和启动，（2）流沉积物的性质，控制平流供应的潜流沉积物与氧气和营养物质，和（3）水制度的影响。沉积物相关的代谢活动，C周转，C-流动的微生物食物网的响应，以及陆地和水生OC的组合转换将进行量化和特征在于在补充实验室和现场实验。将在实验鸡溪集水区的陆地土壤，短暂和常年溪流和池塘海岸进行类似的围隔实验。这个研究地点是理想的，因为它有一个广泛但定义明确的陆生-水生过渡区，而且不稳定有机碳的背景浓度很低。这些研究将受益于新的方法和技术，包括开发潜流流径管，以及用土壤和水生科学的方法对土壤和河流沉积物呼吸进行比较评估。我们将结合联合收割机示踪技术来评估沉积物的平流供应、呼吸测量、温室气体通量测量、同位素标记和同位素天然丰度研究。我们的研究将有助于了解OC矿化，从而在陆地和水生系统的CO2排放。更深入地了解OC-转化在陆地-水生界面是高度相关的碳流通过景观的建模和全球C循环的理解。

The overarching goal of our proposal is to understand the regulation of organic carbon (OC) transformation across terrestrial-aquatic interfaces from soil, to lotic and lentic waters, with emphasis on ephemeral streams. These systems considerably expand the terrestrial-aquatic interface and are thus potential sites for intensive OC-transformation. Despite the different environmental conditions of terrestrial, semi-aquatic and aquatic sites, likely major factors for the transformation of OC at all sites are the quality of the organic matter, the supply with oxygen and nutrients and the water regime. We will target the effects of (1) OC quality and priming, (2) stream sediment properties that control the advective supply of hyporheic sediments with oxygen and nutrients, and (3) the water regime. The responses of sediment associated metabolic activities, C turn-over, C-flow in the microbial food web, and the combined transformations of terrestrial and aquatic OC will be quantified and characterized in complementary laboratory and field experiments. Analogous mesocosm experiments in terrestrial soil, ephemeral and perennial streams and pond shore will be conducted in the experimental Chicken Creek catchment. This research site is ideal due to a wide but well-defined terrestrial-aquatic transition zone and due to low background concentrations of labile organic carbon. The studies will benefit from new methodologies and techniques, including development of hyporheic flow path tubes and comparative assessment of soil and stream sediment respiration with methods from soil and aquatic sciences. We will combine tracer techniques to assess advective supply of sediments, respiration measurements, greenhouse gas flux measurements, isotope labeling, and isotope natural abundance studies. Our studies will contribute to the understanding of OC mineralization and thus CO2 emissions across terrestrial and aquatic systems. A deeper knowledge of OC-transformation in the terrestrial-aquatic interface is of high relevance for the modelling of carbon flow through landscapes and for the understanding of the global C cycle.