Source, transformation and fate of organic matter in boreal forest watersheds

北方景观覆盖了加拿大的大部分地区，包括大部分为北极大河提供水源的分水岭，预计本世纪将经历一些全球最大的气候变化。北方寒带土壤和水生系统中的天然有机质是全球重要的碳储量，也是北方寒带生态系统养分和能量的来源。然而，在过去的几十年里，已经观察到由北方河流输送的陆源有机质的增加，这表明气候引起的这些高纬度景观的变化对下游水生和海洋生态系统产生了影响。例如，这种有机物质吸收光并结合金属——这两种特征都可以极大地影响水生和海洋环境中的藻类生产力。我的小组之前在NSERC的支持下进行的研究表明，加拿大潮湿的北方森林景观可以保持土壤碳的储存，尽管大气损失很大，并且随着气候变暖，这些生态系统中溶解的有机物的动员增加了。这些森林中气候驱动的变化似乎与更长期的生态系统效应密切相关，这些生态系统效应改变了苔藓和土壤的性质，这些性质与这些森林如何应对未来的变暖有关，进而影响对我们气候的关键反馈。我们的研究还使我们能够开发新的分析工具，通过淡水和海水跟踪这些森林来源的有机物，使我们能够从源头到汇跟踪重要的碳和营养储量。*** ***通过继续我们对北方森林流域气候梯度的研究，在接下来的五年里，这个项目将重点关注这些陆地来源的有机物质池在通往水生和进入海洋环境的道路上的转变和命运。通过研究这些有机物质池，从源头溪流到河流及其在沿海环境中的口，我们将把北方景观与下游的水生和海洋生态系统联系起来。在此过程中，本研究将提高我们对气候变化影响的理解：(1)北方生态系统功能（碳、养分循环和食物网）；(2)寒带流域及其相关沿海环境的气候-碳反馈。通过确定控制森林和海洋生产力的关键因素将如何响应气候变化，这种理解将提供与加拿大森林和渔业等自然资源管理相关的重要发现。

Boreal landscapes cover most of Canada, encompass the majority of the watershed feeding large Arctic rivers, and are predicted to undergo some of the largest climate changes globally this century. Natural organic matter in soil and aquatic systems of boreal regions represents an important global store of carbon as well as source of nutrients and energy for boreal ecosystems. However, increases in land derived organic matter transported by boreal rivers has been observed over the past few decades suggesting climate-induced alterations of these high-latitude landscapes with repercussions for downstream aquatic and marine ecosystems. For example, this organic matter absorbs light and binds metals - both features that can greatly impact algal productivity in the aquatic and marine environment. My group's previous research supported by NSERC has indicated that the moist boreal forest landscapes of Canada can maintain their stores of soil carbon despite large losses to the atmosphere and increased mobilization of dissolved organic matter that occurs with climate warming in these ecosystems. Climate driven changes in these forests appear to be tightly linked with more long-term ecosystem effects that alter both mosses and soil properties relevant to how these forests will respond to future warming and in turn impact critical feedbacks on our climate. Our research has also enabled the development of new analytical tools with which to track organic matter from these forest sources through both fresh and marine waters enabling us to following important carbon and nutrient stocks from source to sink.*** ***By continuing our research along a well establish climate gradient of boreal forest watersheds, over the next five years, this program will focus on the transformation and fate of these land derived organic matter pools on route to and through the aquatic and into the marine environment. By studying these organic matter pools from headwater streams through rivers and their mouths in the coastal environment we will connect the boreal landscape to downstream aquatic and marine ecosystems. In doing so this research will improve our understanding of climate change impacts on: (1) boreal ecosystem function (carbon, nutrient cycling and food webs); and (2) climate-carbon feedbacks within boreal watersheds and their associated coastal environments. This understanding will provide important findings relevant to the management of natural resources including forests and fisheries in Canada by identifying how key factors controlling forest and marine productivity will respond to climate change.