Mixed plantings vs monocultures for carbon

When planting forests to offset carbon emissions, is it best to go with monocultures or a mix of species? Kris Hulvey and colleagues compiled and analysed data from existing forest studies to compare carbon storage in mixed tree plantings to carbon storage in monoculture plantings.

They found that mixtures of tree species stored at least as much carbon as monoculture plantings comprised of the single most productive species in the mixture. Additionally, at times, mixes outperformed monoculture plantings. In mixed-species stands, individual species, and in particular nitrogen-fixing trees, increased
stand biomass. Further motivations for incorporating tree richness into planted forests include the contribution of diversity to total forest carbon-pool development, carbon-pool stability and the provision of extra ecosystem services.

Although tree monocultures are one option for storing carbon in forests, this analysis suggests that increasing tree diversity in carbon plantings can increase carbon storage through the production of more above-ground biomass. What’s more, they found that including key species in these more diverse tree mixes can facilitate stand growth leading to higher carbon storage. Finally, tree diversity may also contribute to additional ecosystem functions and services. Based on their findings, they suggest a two-pronged strategy for designing carbon plantings which includes: (1) increased tree species richness; and (2) the addition of key species that contribute to carbon storage and provides other benefits.

Hulvey KB, RJ Hobbs, RJ Standish, DB Lindenmayer, L Lach & MP
Perring (2013). Benefits of tree mixes in carbon plantings.
Nature Climate Change 3: 869–874.

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