Soil is the largest terrestrial organic carbon reservoir and is critical for climate change mitigation and adaptation. Mineral-organic associations play an important role in soil carbon storage, but the global capacity for this form of storage has never been quantified.
The first spatially-resolved global estimates of mineral-associated carbon and the carbon-storage capacity of soil minerals have been produced by Lawrence Livermore National Laboratory (LLNL) and an international team of collaborators.
The study, led by LLNL Lawrence fellow Katerina Georgiou and published in Nature Communications, collected data from 1,144 globally distributed soil profiles to better understand the role of climate and management in driving current mineral-associated carbon stocks and soil departure from their mineralogical capacity.
The study discovered that regions under agricultural management and deeper soil layers have the greatest mineral-associated carbon undersaturation; the degree of undersaturation can help inform sequestration efficiency over years to decades.
The researchers discovered that soils farthest from their mineralogical capacity are more effective at accruing carbon in 103 carbon accrual measurements spanning management interventions worldwide. Sequestration rates are three times higher in soils that are one-tenth their capacity than in soils that are half their capacity.
Soil organic carbon is an essential component of terrestrial ecosystems, contributing to ecosystem resilience and productivity. Human land-use and land-cover change have resulted in a significant net loss of soil carbon over the last two centuries.
“Improved soil management practises that promote soil carbon sequestration, particularly in stable carbon pools, are required to reverse this trajectory and contribute to climate change mitigation,” said Georgiou, the paper’s lead author.
“Our findings provide insights into the world’s soils, their capacity to store carbon, priority regions, and soil carbon management actions,” she added.