Forest and grassland cover types reduce net greenhouse gas emissions from agricultural soils

Science of The Total Environment

Available online 20 July 2016

In Press, Corrected Proof — Note to users

• Mark Baah-Acheamfour^a,
• Cameron N. Carlyle^b,
• Sang-Sun Lim^a,
• Edward W. Bork^b,
• Scott X. Chang^{a, ,}

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doi:10.1016/j.scitotenv.2016.07.106

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Highlights

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Canada's prairie region is a significant source of GHGs due to extensive agriculture.

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Agroforestry (AF) systems are common features and could reduce GHG emissions.

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Chamber measurements of CO₂, CH₄, and N₂O emissions were done in three AF systems.

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Forest and grassland cover types in agricultural lands reduce emission of non-CO₂ GHGs.

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Establishment of perennial vegetation in agriculture provide benefit to mitigate GHGs.

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Abstract

Western Canada's prairie region is extensively cultivated for agricultural production, which is a large source of greenhouse gas emissions. Agroforestry systems are common land uses across Canada, which integrate trees into the agricultural landscape and could play a substantial role in sequestering carbon and mitigating increases in atmospheric GHG concentrations. We measured soil CO₂, CH₄ and N₂O fluxes and the global warming potential of microbe-mediated net greenhouse gas emissions (GWP_m) in forest and herbland (areas without trees) soils of three agroforestry systems (hedgerow, shelterbelt and silvopasture) over two growing seasons (May through September in 2013 and 2014). We measured greenhouse gas fluxes and environmental conditions at 36 agroforestry sites (12 sites for each system) located along a south-north oriented soil/climate gradient of increasing moisture availability in central Alberta, Canada. The temperature sensitivity of soil CO₂ emissions was greater in herbland (4.4) than in forest (3.1), but was not different among agroforestry systems. 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. Combining the CO₂ equivalents of soil CH₄ and N₂O fluxes with the CO₂ emitted via heterotrophic (microbial) respiration, forest soils had a smaller GWP_m than herbland soils (68 and 89 kg CO₂ ha^− 1, respectively). While emissions of total CO₂ were silvopasture > hedgerow > shelterbelt, soils under silvopasture had 5% lower heterotrophic respiration, 15% greater CH₄ uptake, and 44% lower N₂O emission as compared with the other two agroforestry systems. Overall, the GWP_m of greenhouse gas emissions was greater in hedgerow (88) and shelterbelt (85) than in the silvopasture system (76 kg CO₂ ha^− 1). High GWP_m in the hedgerow and shelterbelt systems reflects the greater contribution from the monoculture annual crops within these systems. Opportunities exist for reducing soil greenhouse gas emissions and mitigating climate change by promoting the establishment of perennial vegetation in the agricultural landscape.

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Graphical abstract

Keywords

• Agroforestry;
• Agriculture;
• Canada;
• Climate change;
• Hedgerow;
• Shelterbelt;
• Silvopasture;
• Temperature sensitivity

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