Canada’s northern boreal and tundra ecosystems sequester large amounts of carbon (C) but the effects of climate change on their C and nitrous oxide (N2O) fluxes are unclear. Climate warming is accelerating vegetation growth, driving northward boreal treeline expansion and increased dominance of N-fixing green alder (Alnus alnobetula) in the tundra. This study examined how Arctic vegetation influences greenhouse gas emissions by quantifying soil carbon dioxide (CO2) and N2O flux and their drivers (soil temperature, moisture, inorganic N, and C:N in vegetation and soils) within boreal forest and two tundra shrub types (dwarf shrub and green alder patches). Average boreal CO2 emissions (µmol CO2 m-2 s-1) were highest (3.23) compared to dwarf shrub (2.26) and green alder patch soils (2.24). Boreal N2O flux probabilities and magnitudes (µmol N2O m-2 s-1) were highest (50.2%; 0.11), followed by dwarf shrub (21.0%; 0.040), then green alder patch soils (2.6%; 0.0021). These results were attributed to C and N storage in vegetation. Although tundra soils exhibited favourable conditions for CO2 and N2O production (high temperature and moisture), ground vegetation displayed the highest C:N, suggesting that N limitation may slow C and N cycling, reducing emissions. Green alder had lower C:N than boreal spruce, indicating that, despite N fixation, more efficient uptake by green alder may limit microbial N availability and reduce emissions. These results provide evidence that CO2 and N2O emissions from Arctic soils are controlled by vegetation, emphasizing the importance of vegetation-soil interactions for understanding greenhouse gas fluxes under global change.