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The University of Southampton
Geography and Environmental Science

Research project: The role of lakes in the arctic carbon cycle (LAC) (NERC funded)

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The Arctic is changing rapidly, and it is predicted that areas which are today tundra will become tree-covered as warming progresses, with, for example, forest spreading northwards to the coast of northern European Russia by 2100. In some parts of the Arctic, such as Alaska, this process, commonly referred to as “greening”, has already been observed over the past few decades: woody shrubs are expanding their distribution northwards into tundra. Such vegetation changes influence nutrient cycling in soils, including carbon cycling, but the extent to which they will change the storage or release of carbon at a landscape scale is debated. Nor do we fully understand the role that lakes play in this system - but it is known that many lakes in the tundra and northern forests are today releasing carbon dioxide (and methane) into the atmosphere in significant amounts, and a proportion of this carbon comes into the lake from the vegetation and soils of the surrounding landscape.

This NERC funded project will bring a state-of-the-art approach to understanding the interactions between vegetation changes in arctic catchments and biogeochemical cycling in lakes over long time scales (decades, centuries), with particular attention on changes in carbon (C) cycling. Ourchosen study sites are representative of major pan-Arctic biomes (vegetation types) past and present, e.g., moist shrub tundra, boreal forest (European Russia, Norway, Alaska), dry shrub tundra (W. Greenland); these are characterized by different dominant plant functional types and nutrient regimes. Using data collected from regionally-replicated radiocarbon-dated lake-sediment profiles we will address the role that vegetation compositionplayed in determining lake metabolic state and how this affects lake biological structure.

The project will address the following critical questions:

  1. What role has vegetation composition (and hence dissolved organic C [DOC] export) played in determining lake metabolic state (auto- versus heterotrophy)?
  2. Have Arctic lakes always been important sites of C mineralization or have they been C-sinks for part of their history?
  3. To what extent are in-lake C dynamics a function of lake biological structure (trophic interactions, biodiversity)?
  4. What is the effect of transitions between regional plant functional types [PFTs] on (a) lake C and N processing, (b) aquatic production, and (c) biodiversity?
  5. Do changes in catchment PFTs cause tipping points in lakes (i.e. in metabolic state or biological structure); and if they do, does the system behave in a similar way ecologically when moving in the opposite direction (heterotrophy to autotrophy or vice versa)?

Staff

  • Mary Edwards
  • Peter Langdon
  • Maarten van Hardenbroek
  • Emma Hopla (PhD student, Southampton Geography)
  • Prof John Anderson (Loughborough)
  • Dr Viv Jones (UCL)
  • Dr Suzanne McGowan (Nottingham)
A key site in the Brooks Range, Alaska that we have investigated within the LAC project
Ruppert lake – Arial view of Ruppert lake
Interspersed with clay layers of varying thickness, thought to represent phases of strong catchment inwash into the lake.
Rupert lake sediments – Image shows the organic sediments

Related research groups

GeoData
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