Boreal peatlands are carbon sinks but emit methane (CH4), creating trade-offs between carbon dioxide (CO2) uptake and CH4 release. Seismic lines, linear clearings created for geologic exploration, disrupt peatland hydrology, microtopography, and vegetation, potentially shifting the ecosystem carbon balance. Restoring these lines with inverted mounding is intended to return forest cover, but response of carbon fluxes remains unclear. We assessed understory-scale carbon dynamics by quantifying CH4 fluxes together with net CO2 exchange (NEE) using chamber measurements across untreated seismic lines, mounded seismic lines, and adjacent natural peatlands at two sites (Lidea-1 and Kirby) in northern Alberta. Untreated seismic lines acted as enhanced carbon sinks but substantially stronger CH4 sources, with mean emissions an order of magnitude higher than the understory of natural peatlands. Elevated CH4 emissions coincided with high understory productivity (up to ≈25-30 g CO2 m-2 d-1) and more negative NEE, reflecting graminoid and shrub expansion under warmer, wetter conditions. Inverted mounding reduced CH4 emissions by ≈40% relative to untreated lines but also reduced understory CO2 uptake, with GPP declining to approximately -8 g CO2 m-2 d-1 at Kirby. Microtopographic controls were site-specific: hollows dominated CH4 emissions at LiDea-1, whereas hummocks were the primary CH4 source at Kirby following disturbance. Water table depth was the dominant control on CH4 emissions, with peak fluxes near surface saturation. These results indicate that while mounding mitigates CH4 forcing on seismic lines, restoration planning must consider short-term reductions in understory carbon sequestration as vegetation communities re-establish.