Diverse forests with mixed species store 70 per cent more carbon than monocultures which have only one variety, new research has found.
Complementary traits of the different species can increase overall carbon storage and thus, mixed forests are especially effective at storing carbon, the international study including researchers from the University of Oxford, UK, found after comparing carbon stocks in mixed planted forests and monocultures, including commercial ones.
Mixed forests are also more resilient to pests, diseases, and climatic disturbances, which further raises their long-term carbon storage potential, the researchers said in their study published in the journal Frontiers in Forests and Global Change.
"As momentum for tree planting grows, our study highlights that mixed species plantations would increase carbon storage alongside other benefits of diversifying planted forests," said Susan Cook-Patton, a collaborator on the study.
For the study, the researchers' dataset included studies published since 1975 that directly compared carbon storage in mixed and single-species forests and previously unpublished data from a global network of tree diversity experiments.
The team found that forest systems with two species had greater aboveground carbon stocks than monocultures and stored up to 35 per cent more carbon.
Further, forests having a mix of four species were found to be the most effective carbon sinks.
However, forests made of six species showed no clear advantage to monocultures, the researchers found.
Overall, they said, aboveground carbon stocks in mixed forests were 70 per cent higher than in the average monoculture and 77 per cent higher than in commercial monocultures, made up of species bred to be particularly high yielding.
The researchers acknowledged that their study had limitations, given the overall limited availability of studies addressing mixed vs monoculture forests, particularly studies from older forests and with higher levels of tree diversity.
"This study demonstrates the potential of diversification of planted forests, and also the need for long-term experimental data to explore the mechanisms behind our results," said Emily Warner, a postdoctoral researcher in ecology and biodiversity science at the Department of Biology, University of Oxford, and first author of the study.
"There is an urgent need to explore further how the carbon storage benefits of diversification change depending on factors such as location, species used and forest age," said Warner.