Advances in understanding forests and CO2

A new paper by our scientists helps to reduce some of the uncertainty in the estimates of the size of this carbon sink

News from Forest Research: October 2012

Sonic anemometer and infrared gas analyser

Globally, forests are a large sink for carbon and therefore have a fundamental role in helping to regulate atmospheric carbon dioxide (CO2) concentrations. Despite continued research, uncertainties still exist regarding the size of this carbon sink. A new paper recently published by Forest Research scientists helps to reduce some of the uncertainty in these estimates.

Alice Holt Research Forest in Hampshire hosts a long-term ‘flux site’ where CO2 and environmental data have been continuously recorded since June 1998. Forest Research scientists used these data to examine the relative contributions of photosynthesis and respiration to the overall carbon balance of the 80-year old deciduous oak forest. Furthermore, they were able to examine how natural variations in the weather and biological processes affected the size of this carbon sink.

The results showed leaf area to be the most important factor influencing the efficiency with which the forest was able to capture CO2 from the atmosphere. It is well recognised that forest respiration is largely controlled by temperature. However, an important new finding from this study is the role of summer soil moisture levels: there was a clear reduction in the effect of temperature on respiration during drier summers.

The research also highlighted the importance of biological factors in the forest carbon balance. For example, a major outbreak of defoliating moth caterpillars – mostly oak leaf roller moth (Tortrix viridana L.) and winter moth (Operophtera brumata L.) – in 2009 and 2010 caused considerable damage to the forest canopy and significantly reduced CO2 uptake.

The paper, entitled ‘Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England’ by Wilkinson et al., is published in the interactive open access journal, Biogeosciences Discussions.

More information about Forest Research’s Alice Holt CO2 flux site

For more information on this project please contact Matt Wilkinson or Ed Eaton.

Further work on this subject is detailed in a recent Research Report - Understanding the carbon and greenhouse gas balance of forests in Britain (PDF-7422K) -see page 9.

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