Linear disturbances within boreal Canada (e.g., seismic lines) have the potential to significantly alter carbon cycling in Canada’s northern peatlands, creating the potential to switch these significant carbon stocks from long term carbon sinks to carbon sources. While efforts have been made to quantify the impacts of linear disturbance on ecosystem, vegetation, soil composition and GHG emissions, little is currently known about the specific interactions between the disturbance to peat hydrophysical structure and composition and the resulting alterations to CO 2 and CH 4 dynamics. To this end, 16 poor fen peat cores representing the top 10 cm of the peat profile were collected on and adjacent to a seismic line reflecting four degrees of disturbance complete mulch covering, partial mulch covering, mechanical roughing only, and undisturbed. In controlled laboratory conditions cores were then subjected to two subsequent static water table conditions (3 and 8 cm below core surface) for a period of ~30 days each with GHG flux measurements occurring 2-3 days. Cores were then subdivided into 5 cm segments and underwent detailed hydro physical (i.e., bulk density, porosity, water retention) and compositional (i.e., C:N, vegetational assemblage) analysis. Results show that both peat composition and hydrophysical structure were strong predictors of greenhouse gas emissions. Higher CO 2 emissions were related to both peat with high bulk density, low total and effective porosity and low C:N ratios, which occurred at depth in the undisturbed cores and at the surface where mechanical mulching and mixing occurred. Increased CH 4 emissions occurred in disturbed cores characterized by a reduction in macropores and effective porosity near the surface; these emissions were episodic in nature and occurred where trapped gas was released during pore desaturation when water tables were lowered. Additional work should therefore be conducted at field scale to further assess the interrelationships between direct changes to hydrophysical structure and these other impacts, to better determine the long-term changes to carbon cycling in systems disturbed by seismic line creation.