Large trees play key role in tropical forest biomass storage

A large-scale study has found that a handful of big trees store up to half the above-ground biomass in tropical forests, raising implications for forest management and climate change mitigation.

Trees remove carbon from the atmosphere as they grow, storing it in leaves, woody tissue, roots and organic matter in soil, and playing a critical role in regulating the Earth’s climate and mitigating climate change.

Calculating above-ground biomass — which comprises all living biomass, or organic material, above the soil, including stem, stump, branches, bark, seeds and foliage — helps scientists measure the role of forests as carbon sinks in mitigating climate change.

The study ultimately involved some 60 scientists. They examined data on 192,308 trees at least 10 cm in diameter in 120 lowland moist old-growth forest locations in South America, Africa and Asia. Large trees were defined as those measuring at least 70 cm (28 inches) in diameter at breast height (dbh).

Among their results, the researchers determined that bigger trees play a larger role in storing biomass than previously thought. “Only 3 percent of the forests are made up of big trees, but these trees store up to half the biomass,” study said. “If just a few of these large trees die, it immediately has a major impact.”

They also concluded that climatic variables affect the density of large trees and above-ground biomass, which means climate change will affect the storage of tropical forest biomass. “If temperatures keep rising — a 2 to 6 degree (Celsius) rise is predicted over the next century — it will likely negatively affect these big trees,”.

The results have implications in several areas. Now we know these big trees are important for biomass, but we still don’t know much about the dynamics of these trees — how fast they grow, how old they get — because researchers have been concentrating on relatively small plots which contain few big trees due to their low density.

The importance of these large trees should also be a wake-up call for the forestry industry.

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