Collaborative research: Turning on the lights - Photochemical and microbial processing of newly exposed carbon in arctic ecosystems

该项目将调查通过火灾、热岩溶破坏和永久冻土融化等扰动，越来越多的溶解有机物（DOM）释放到北极表面沃茨的命运。研究人员假设，新获得的土壤碳将不稳定的光化学和微生物的攻击，并会增加系统中的居民DOM的降解，导致质量较差的DOM输出到海洋。他们计划通过以下方式对这些过程进行机械理解：（A）确定光化学反应和微生物处理将如何快速改变地表沃茨中的常驻DOM和新释放的DOM，以及（B）测量地表沃茨中DOM的命运，无论是作为释放到大气中的CO2还是作为有机碳改变并运输到沿海海洋。这将通过一系列实验室实验来完成，以确定来自不同来源的DOM的光降解和微生物处理速率，并通过一系列景观比较和取样断面来描述从源头到北冰洋延伸250-300公里的小流域和大河的DOM降解特征。通过将这种基于过程的研究与正在进行的研究热岩溶破坏的形成以及燃烧对植物和土壤碳分配的影响的项目相结合，研究人员将解决一些问题，例如从苔原到海洋的碳出口是否会上升或下降，出口碳的反应性如何，以及即将发生的干扰（包括气候变化）的最终影响，北极的净碳平衡及其与全球碳循环的相互作用。调查人员将与几个既定的方案在密歇根大学和UM工作（1）招募妇女和少数民族学生参与和研究这个项目，特别是从历史上的黑人学院，（2）参加研讨会上辅导策略为少数民族，和（3）开发额外的推广活动，包括会谈，由PI，研究生和本科生的初中和高中。数据的介绍将与NSIDC和Arctic LTER数据管理协调。

This project will investigate the fate of dissolved organic matter (DOM) released in increasing amounts to Arctic surface waters through such disturbances as fire, thermokarst failure, and thawing of permafrost. The investigators hypothesize that newly available soil carbon will be labile to photochemical and microbial attack, and will enhance the degradation of resident DOM in the system resulting in poorer quality DOM exported to the ocean. They plan to develop a mechanistic understanding of these processes by: (A) Determining how fast photochemical reactions and microbial processing will alter resident DOM and the newly-released DOM in surface waters, and (B) Measuring the fate of DOM in surface waters, either as CO2 released to the atmosphere or as organic carbon altered and transported to coastal oceans. This would be accomplished with a series of laboratory experiments to determine rates of photodegradation and microbial processing of DOM from different sources, and a series of landscape comparisons and sampling transects to characterize DOM degradation in small basins and large rivers extending 250-300 km from the headwaters to the Arctic Ocean. By integrating this process-based research with ongoing projects studying the formation of thermokarst failures and the impacts of burning on plant and soil carbon allocation, the investigators will address questions such as whether carbon export from tundra to oceans will rise or fall, how reactive is that exported carbon, and what will be the ultimate impact of impending disturbances, including climate change, on the net carbon balance of the Arctic and its interaction with the global carbon cycle. The investigators will work with several established programs at UNC and UM to (1) recruit women and minority student participation and research in this project specifically from Historically Black Colleges, (2) participate in a workshop on mentoring strategies for minorities, and (3) develop additional outreach activities, including talks to middle and high schools by the PIs, graduate, and undergraduate students. Presentation of data will coordinate with NSIDC and Arctic LTER data management.