Greenhouse gas dynamics and soil conditions in restored wet moorlands in an upland managed spruce forest landscape

Ecosystem restoration often aims to re-establish environmental conditions required by specific habitat types and improve key ecosystem functions, including greenhouse gas (GHG) regulation and biodiversity support. This study compares two sites in a managed spruce forest landscape on drained wet moorlands in the Ardennes uplands in Belgium. A recently restored area, where spruce stands were cleared, and rewetting was encouraged by blocking drainage ditches to promote the development of moorland habitat, and a longer-established wet moorland site restored over a decade earlier, where vegetation and ecosystem functions have reached a more stable state. The objective was to assess how the restoration stage influences GHG fluxes, associated soil conditions, and biodiversity. From September 2023, methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) fluxes were measured bi-weekly using closed dark chambers with LI-7810 and LI-7820 trace gas analyzers (LI-COR Biosciences). From March 2025, transparent chambers were used during the growing season to quantify net ecosystem exchange (NEE). Sampling focused on five zones: three within the recently restored site (adjacent to a closed ditch, far from the ditch, and near a functional drainage ditch), one plot in the managed spruce forest, and one in a longer-established moorland site (Control). At each plot, we also measured soil pore water electrical conductivity, temperature, moisture content, bulk density, and concentrations of soil carbon (C%) and nitrogen (N%). Additionally, ground-dwelling carabid beetles were surveyed using pitfall traps to characterize local biodiversity. GHG measurements revealed large spatial differences among the sites. The Control showed the lowest CH₄ fluxes, ranging from −3.62 to 0.47 nmol CH₄ m^-2 s^-1, and ecosystem respiration (Reco) from 0.05 to 3.93 µmol CO₂ m^-2 s^-1. In contrast, the recently restored areas showed greater variability, with CH₄ fluxes from −0.68 to above 84.88 nmol CH₄ m^-2 s^-1 and Reco from 0.01 to above 28.49 µmol CO₂ m^-2 s^-1. Growing-season NEE indicated that all plots acted as net CO₂ sinks, with the control site reaching peak uptake around −29 µmol CO₂ m^-2 s^-1 and the restored plots showing weaker sinks. The control site also had the highest soil nutrient values (C% = 12.7, N% = 0.73) and the lowest bulk density, whereas the other sites showed lower and more variable C and N (C% = 3.7–10.5; N% = 0.21–0.61) and higher bulk density. N₂O and other measured parameters also varied substantially across the sampling sites. In total, over 772 individuals from 22 carabid beetle species were captured, with differences in richness, density, and biomass among sites. These findings indicate that the restoration stage has a large impact on GHG dynamics, soil properties, and biodiversity. The longer-established control site represents a relatively stable semi-natural moorland with low CH₄ and N₂O fluxes, strong net CO₂ uptake, higher soil C and N, and lower bulk density, while the recently restored areas are characterized by higher and more variable fluxes and denser soils. By comparing restoration stages, this study provides insight into ecosystem recovery and can inform strategies to enhance ecosystem functioning, biodiversity, and climate mitigation.