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Knowledge of the response of thinning implementation on forest soil–atmospheric greenhouse gas (GHG) (CO2, CH4, N2O) fluxes exchange system in Mediterranean region is limited because of the high heterogeneity of both soil properties and forest biomass. The novelty of this study is grounded predominantly in evaluating for the first time the response of annual GHG fluxes to thinning in a coniferous peri-urban forest soil in Greece, thus contributing significantly to the enrichment of the GHG fluxes database from the Mediterranean forest ecosystem. Results suggest that CH4 uptake increased with increasing thinning intensity. The reduction in CO2 emissions in both thinning treatments was possibly related to an indirect effect of soil heterotrophic and autotrophic respiration. Coniferous peri-urban forests in Greece can act temporally as sinks of atmospheric N2O in the coldest months and a weak source of N2O fluxes in summer. The GHG variation depended largely on soil environmental factors with soil temperature representing the dominant factor for CO2 and CH4, whereas soil moisture correlated, albeit weakly, with N2O variability. Reduction in global warming potential was observed in both thinning treatments, markedly in selective treatment, giving an initial indication that high-intensity thinning in coniferous peri-urban forests in Greece presents a high potential for global change mitigation.

The contribution of litterfall (dead leaves, twigs, etc., fallen to the ground) and forest floor (organic residues such as leaves, twigs, etc., in various stages of decomposition, on the top of the mineral soil) is fundamental in both forest ecosystem sustainability and soil greenhouse gases (GHG) exchange system with the atmosphere. The effect of different thinning treatments (control-no thinning, traditional-low thinning, selective-intense thinning) on litterfall and forest floor nutrients, in relation to soil GHG fluxes, is analyzed. After one year of operations, thinning had a significant seasonal effect on both litterfall and forest floor, and on their nutrient concentrations. The intense (selective) thinning significantly affected the total litterfall production and conifer fractions, reducing them by 46% and 48%, respectively, compared with the control (no thinning) sites. In the forest floor, thinning was able to significantly increase the Fe concentration in traditional thinning by 59%, and Zn concentration in the intense thinning by 55% (compared with control). Overall, litterfall acted as a bio-filter of the gasses emitting from the forest floor, acting as a GHG regulator.

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