AbstractForests can play a key role in the mitigation of climate change, although there have been limited regional scale assessments that account for variations in soil type and tree species. Most of the focus has been on their ability to sequester atmospheric CO2, while there is less information on the two other major greenhouse gases (GHGs), N2O and CH4. We examined the GHG budgets of ten forest soils in Poland, considering all three major GHGs, where no previous long-term measurements had been made, which encompassed different tree species, stand age, and contrasting edaphic conditions. In addition to the quantification and assessment of seasonal variability in the major soil GHG fluxes over two years, the aims of the present study were (i) the identification of the main drivers of the soil-based GHG fluxes, (ii) the determination of the contribution of each gas to the Global Warming Potential (GWP), and (iii) to assess the mitigation potential of these fluxes over different forest systems. All the forest soils were sources of CO2 and N2O and sinks for atmospheric CH4 with pronounced seasonal variations in CO2 and CH4 driven by soil moisture and temperature. The soils showed significant differences in annual GHG fluxes, with average values of 16.7 Mg CO2 ha−1, − 3.51 kg CH4 ha−1, and 0.95 kg N2O ha−1. The annual total GWP ranged from 13.1 to 22.0 Mg CO2 eq ha−1 with CO2 making the highest contribution, and forest-specific CH4 uptake resulting in a reduction in GWP, ranging from − 0.08% (in the youngest forest) to -0.97% (in the oldest forest). Mixed forests showed the greatest potential for climate change mitigation, with the highest soil C sequestration, and the lowest GWP values when compared to sites with monocultures. The results suggest that a mixture of tree species could eventually be incorporated into management plans to increase the effectiveness of forests in climate change mitigation.
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