Greenhouse gas fluxes from temperate forest soils following eight years of free air CO2 enrichment at BIFoR-FACE.

Globally, forests are capture about 18% of the total human source carbon dioxide (CO2) emission into air, thus playing a pivotal role in climate change mitigation. However, forests are responsible for about 60% of the total nitrous oxide (N2O) gas emitted from soils, and consume ~25% of the total atmospheric methane (CH4). N2O and CH4 are potent greenhouse gases (GHG), playing a critical role in global warming. Previous research at the University of Birmingham Institute for Forest Research's Free Air CO2 Enrichment (BIFoR-FACE) Facility for mature forests showed an initial increase in CO2 fluxes from soils, followed by reduction in CO2 fluxes by the 7th year of elevated atmospheric CO2 (eCO2) enrichment. At the same time an increase in CH4 consumption and in potential N2O emission (Sgouridis et al. 2023) was observed. Will these greenhouse gas fluxes patterns persist over the next three years of eCO2 enrichment (year 8, 9 and 10) as stable state shift responses to eCO2 enrichment and what key environmental and soil factors affect these fluxes? Answering these questions are important to accurately predict global warming potential of forests under future climates.

Enhancement of photosynthesis rates of the forests (Gardner et al. 2021), a decrease in soil moisture, increase in fine roots biomass (Ziegler et al. 2022) and soil nutrient cycling processes (Sgouridis et al. 2023) in the first 5 years of under eCO2 enrichment are expected to persist and thus it is very likely to affect net greenhouse gas emission from soils. Therefore, unravelling the impacts of plant-soil-microbes interactions on greenhouse gas production and consumption processes is urgently needed to accurately model the net climate benefits of forests. The aim is to disentangle the impact of eCO2 on the dynamics of GHG production and consumption at the soil-atmosphere interface, reducing uncertainties in predicting the role of forests in global warming and climate change mitigation.

This research sits at the interface of on-going and planned research in soil science, plant physiology, and atmospheric sciences at BIFoR-FACE), UK to unravel previously unexplored pathways of GHG production and consumption under eCO2 in a mature oak-dominated forest ecosystem. The cross disciplinary outcomes of this research links to global scale modelling of carbon and nitrogen budgets of forests under future climates.