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

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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.