Greenhouse Gas Emissions Are Affected By Land Cover Type in Agroforestry Systems.

Agroforestry systems play an important role in sequestering carbon and mitigating greenhouse gas (GHG) emissions. We measured soil CO₂, CH₄, and N₂O emissions in forest and herbland (areas without trees) components of three agroforestry systems (hedgerow, shelterbelt, and silvopasture) over two growing seasons (2013 and 2014). We studied 36 agroforestry sites (12 sites for each system) located along a south-north oriented region in central Alberta, Canada. Over the two seasons, forest soils had 3.4% greater CO₂ emission, 36% higher CH₄ uptake, and 66% lower N₂O emission than adjacent herbland soils. As a result, forested areas had a smaller global warming potential (129) than their herbland counterpart (157 kg CO₂ ha^-1) based on all three GHGs. Emissions of CO₂ were silvopasture > hedgerow > shelterbelt. The temperature sensitivity of CO₂ emissions was greater in herbland (4.4) than in forest (3.1), but was not different among the agroforestry systems. Soils in the silvopasture system also had 15% greater CH₄ uptake and 44% lower N₂O emission rates as compared with the other two agroforestry systems. The global warming potential in the silvopasture system was similar to that in the hedgerow, but was 18% greater than that in the shelterbelt system due to greater CO₂ emissions from the silvopasture system. Our results suggest that establishment and retention of perennial vegetation provide substantial opportunities for minimizing GHG emissions in the agricultural landscape in western Canada.