Quantifying carbon dioxide removals in Mediterranean oak-dominated ecosystems

Forests and soils play a significant part in controlling climate change with their ability to store carbon. Increasing forest carbon pools by climate-smart management is one of the suggested strategies for removing CO₂ from the atmosphere, which is known as carbon dioxide removal (CDR) and is an essential component of climate mitigation strategies. Within this study, our goal was to understand the carbon cycle in two typical Mediterranean ecosystems, the partitioning of carbon in aboveground (wood, litterfall) and belowground (roots, soil) pools and the estimation of carbon released back into the atmosphere as soil CO₂ emissions.

We quantified the CO₂ removals as CO₂ equivalents in six experimental plots in Greece. We studied two oak-dominated ecosystems, one deciduous dominated by Quercus frainetto Ten., followed by Quercus cerris L. and Quercus petraea (Matt.) and one broadleaf evergreen ecosystem dominated by Q. coccifera L. We explored their carbon allocation and soil CO₂ emissions within 2 years of measurements. The two ecosystems have different ecological responses that influence their carbon allocation to different components. Our results show higher belowground carbon allocation and soil inorganic carbon (SIC) stocks in evergreen oaks vs. higher soil organic carbon (SOC) stocks and aboveground carbon allocation in deciduous oaks. Moreover, evergreen oaks have a faster turnover rate of both aboveground and belowground litter that leads to faster carbon cycling than in deciduous oaks. However, this also led to higher soil CO₂ emissions in evergreen vs. deciduous oaks.

This work contributes to our understanding of patterns of carbon allocation and sequestration potential relative to carbon emissions across different oak-dominated ecosystems and may support improvements in CDR strategies.