Comparing greenhouse gas dynamics and soil conditions in a newly restored wetland and a long-established natural site

Wetland restoration often aims to re-establish native vegetation and improve ecosystem functions, including greenhouse gas (GHG) regulation and biodiversity support. This study compares a newly restored spruce plantation, where managed vegetation was recently removed to encourage the return of native species, with a control site restored over a decade earlier, where natural vegetation and ecosystem functions have achieved greater stability. The objective was to assess how restoration stages influence GHG fluxes and associated soil conditions. Over one year, methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes were measured bi-weekly using closed chambers with a LI-7810 trace gas analyzer (LICOR Biosciences). Sampling focused on five key zones: three sections within the newly restored site (one near a water channel (NS), an area adjacent to a closed ditch (NCD), and an area far from the ditch (FDC)), one partly dominated by old-native vegetation (Wood), and a mature, naturally vegetated control site (Control). GHG measurement results revealed significant variations among the sampling sites. The control site showed the lowest CH 4 emissions, ranging from -3.62 to 0.47 nmol CH 4 m⁻² s⁻¹, and Reco ranging from 0.05 to 3.93 µmol CO 2 m⁻² s⁻¹. In contrast, the unrestored site with old vegetation and the newly restored site showed greater variability, with CH 4 fluxes ranging from -0.68 to above 84.88 nmol CH 4 m⁻² s⁻¹, while Reco ranged from 0.01 to above 28.49 µmol CO 2 m⁻² s⁻¹. Additionally, soil parameters, including pore water electrical conductivity, temperature, moisture content, and soil carbon (C%) and nitrogen (N%) concentrations, were measured at each sampling site. The control site showed the highest soil nutrient levels (C% = 12.7, N% = 0.73), indicating greater organic matter accumulation. By contrast, the other sites showed lower and variable nutrient levels, with C% ranging from 3.7 to 10.5% and N% from 0.21 to 0.61%. Other measured parameters also varied significantly across the sampling sites. These findings highlight the significant impact of restoration stages on GHG dynamics and soil properties. The control site, with its mature vegetation, represents a stable ecosystem. Meanwhile, the newly restored areas are characterized by higher GHG emissions and variable soil parameters, likely driven by ongoing ecological transitions. This study provides valuable insights into the processes that guide ecosystem recovery by comparing an established ecosystem to a site in the early stages of restoration. The results can inform future restoration strategies to enhance wetland functionality, improve biodiversity, and support climate regulation.