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Ditch cleaning (DC) is increasingly applied to facilitate forest regeneration following clear-cutting in Fennoscandinavia. However, its impact on the ecosystem carbon and greenhouse gas (GHG) balances is poorly understood. We conducted chamber measurements to assess the initial DC effects on carbon dioxide (CO2) and methane (CH4) fluxes in a recent forest clear-cut on wet mineral soil in boreal Sweden. Measurements were conducted in two adjacent areas over two pre-treatments (2018/19) and two years (2020/21) after conducting DC in one area. We further assessed the spatial variation of fluxes at three distances (4, 20, 40 m) from ditches. We found that DC lowered the water table level by 12 ± 2 cm (mean ± standard error) and topsoil moisture by 0.12 ± 0.01 m3 m−3. DC had a limited initial effect on the net CO2 exchange and its component fluxes. CH4 emissions were low during the dry pre-treatment years but increased particularly in the control area during the wet years of 2020/21. Distance to ditch had no consistent effects on CO2 and CH4 fluxes. Model extrapolations suggest that annual carbon emissions decreased over the four years from 6.7 ± 1.4 to 1.6 ± 1.6 t-C ha−1 year−1, without treatment differences. Annual CH4 emissions contributed <2.5% to the carbon balance but constituted 39% of the GHG balance in the control area during 2021. Overall, our study suggests that DC modified the internal carbon cycling but without significant impact on the carbon and GHG balances. [ABSTRACT FROM AUTHOR]

Even-aged management (rotation forestry, RF) involves ditch network maintenance (DNM) operations in peatlands. Although the DNM operations contribute tree growth, they have negative environmental effects on watercources. To avoid DNM, a strip cutting (SC) management has been proposed. SC management in peatlands relies on natural regeneration by trees growing on the edge stand next to a clear-cut strip. The width of a cut strip varies, and here 20, 35 and 50 m strip width were applied in three locations in Finland: Akaa (southern), Kuopio (central), and Oulu (northern Finland). Tree growth of an edge stand and sapling stand was modeled with a stand-level model which accounted for the effect of dominant height of the edge stand and variation of shading among alternative strip widths. In southern location, RF financially outperformed SC management with interest rates 2–4%, but with a 5% interest rate and strip with of 35 or 50 m SC management was more beneficial than RF. In central and northern locations RF was better only with a 2% interest rate and with a 20 m strip width. Our results demonstrate that SC management is a financially valid option to apply in pine-dominated peatlands, particularly in northern regions. [ABSTRACT FROM AUTHOR]

Peatland forest management is an important source of human-induced additional nitrogen, phosphorus, and organic carbon loads to surface waters in Finland. Ditch network maintenance (DNM) is typically used to ensure sufficient soil drainage for profitable timber production on peatland sites, but nutrient mobilization, particularly of phosphorus, and suspended sediment loads from ditches can cause harmful ecological effects on the quality of water courses. Various water protection structures have been developed to capture the loads released after treatments and to decrease the management impacts in forestry. Overland flow fields are efficient mechanisms for water purification, but they are rarely used in practice due to difficulties in finding suitable locations. In addition, leaving breaks between cleaned ditch sections is recommended wherever possible, as uncleaned sections decrease flow velocity and enhance sediment deposition from runoff water. To plan the most adequate protection methods in DNM, new GIS-based tools are needed to propose e.g. appropriate locations for water protection structures. We developed a spatial analysis to suggest locations for overland flow fields and uncleaned ditch sections within the catchment of lake Kovesjärvi (Parkano, Western Finland). Airborne lidar data consisting of 5 pulses m−2 enabled detailed terrain analysis and finding strictly specified terrain properties that satisfied the conditions of the water protection structures. Half of the field-reviewed overland flow fields were evaluated as good suggestions by forest management professionals and researchers. The model for uncleaned ditch sections worked well on the relatively flat study area, as 77% of the field-reviewed suggestions were rated good by expert opinions. Overall, the approach was evaluated to be useful in peatland forest management. Model parameters can be modified for various topographies, but more studies are needed prior to wider use of the model. • We developed a workflow to place water protection structures within a catchment. • Lidar data enable finding strictly specified terrain properties from the landscape. • Suggested locations for water protection structures were promising in the study area. • The method is useful for forest managers planning ditch network maintenance. [ABSTRACT FROM AUTHOR]