Climate Warming Can Accelerate Carbon Fluxes without Changing Soil Carbon Stocks

What is it about?

This paper describes a multi-year study of ecosystem carbon fluxes to and from boreal forest soils along a latitudinal gradient of replicated, similar forest stands. We observed significant increases in the carbon fluxes into and lost from these soils with the warmer and wetter climate of forests located in the lower latitudes. Despite this significant increase in mobilization of carbon to and from these soils no change in carbon stocks and little change in the chemical signatures was observed in these soils. Combined our results indicate that when boreal forests are not limited by water they are likely able to maintain their soil carbon stocks in the face of projected climate change.

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Why is it important?

Current Earth System Models (ESMs) used to predict terrestrial-atmospheric carbon exchange (i.e. net uptake or production of CO2 released to the atmosphere) exhibit very high uncertainties hampering efforts to constrain key climate feedbacks required in climate projections. Soil carbon is an important store of carbon globally and in many terrestrial ecosystems it is the result of a current net sink of carbon taken from the atmosphere. High latitude regions of the world contain a large part of this global soil carbon store but they are also projected to undergo some of the largest changes in climate. Therefore, we need to better understand how soil carbon stores in these regions are likely to respond to a future warmer climate. Recent studies have indicated that productivity of the boreal forest in response to warming depends greatly upon water availability, and that in regions with sufficient water forests appear to maintain or evenr increase productivity, and therefore carbon uptake. Our study takes these findings one step further by providing evidence that these moist high latitude ecosystems are also able to maintain longer-term soil carbon stores critical to maintaining terrestrial carbon sinks. Our work also highlights the need to better understand the limitations on these stores posed by water limitations and lateral transport of carbon to the aquatic environment.

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