Researchers looked at pine plantations in Scotland.
Forests should not be seen as a “silver bullet” against climate change as deep soils there may be less effective at storing carbon in the long term than previously thought, new research suggests.
Professor Jens-Arne Subke of the University of Stirling said we cannot “over-rely” on forests to mitigate the impacts of climate change.
He has co-authored a new commentary examining the findings of a BOKU University led study focused on European beech forests in Central Europe which suggested that ignoring deep soil carbon levels could lead to over optimistic estimates of how much carbon forests are able to store.
The commentary also builds on recent research by Professor Subke’s team which looked at pine plantations in Scotland.
It found that soils under mature pine forests had about half as much carbon as nearby soils that stayed as grassland, and that the carbon lost from the soil was equal to around a third of the carbon that the trees had absorbed from the atmosphere.
Prof Subke said: “Our findings emphasised that we cannot over-rely on forests to mitigate the impacts of climate change because there is still so much that we don’t understand.
“Despite accumulating tree biomass, we may be losing carbon capital – the carbon stored long term in soils and ecosystems – to the atmosphere.”
During the study, researchers took soil samples from 16 sites in the Scottish Lowlands where pines had been planted on former long-term grasslands – with the oldest planted 68 years ago.
They found that carbon left in forest soils was less stable, meaning that it could break down and be released more easily in the future.
Tree planting campaigns are taking place around the world using photosynthesis to store carbon in soil, roots and wood.
Dr Thomas Parker of the James Hutton Institute, who co-authored the commentary, said: “Forests are an essential for human and planetary well-being for a range of reasons, but we need to acknowledge that they are not a silver bullet for all our problems.
“There are complexities and trade-offs that need to be understood to maximise the net benefits that we gain from forests.”
The commentary, Uptake and release – what is driving change in the net carbon budget in forest soils? was published in the Global Change Biology.
The study about pine trees was published in the Journal of Environmental Management.
Work took place in collaboration with Colorado State University and Forest Research and was funded by a collaborative grant from the National Environmental Research Council (NERC) and National Science Foundation (NSF).
