Greenhouse gas emissions are affected by land use type in two agroforestry systems: Results from an incubation experiment
2020
Li, Ping | Lang, Man | Zhu, Sixi | Bork, Edward W. | Carlyle, Cameron N. | Chang, Scott X.
In order to better understand factors affecting greenhouse gas (GHG) emissions in Canadian agroforestry systems, we conducted a laboratory incubation study to assess N₂O, CO₂ and CH₄ emissions from soils in response to land use (forestland vs. cropland) and agroforestry system type (hedgerow vs. shelterbelt) in central Alberta, Canada. Emissions of N₂O were lower in soils from forestland than cropland, and forest soils acted as a net sink of atmospheric CH₄ while cropland soils were weak sources of CH₄. However, the forest soil had higher CO₂ emission rates than the cropland soil within both agroforestry systems. Soil CH₄ oxidation was higher in soil from hedgerow (consisted of natural forest vegetation) than from shelterbelt system (planted forest vegetation), while the former also had lower N₂O emissions. Overall, soil CO₂ emissions were significantly higher from hedgerow than from shelterbelt systems. Emissions of N₂O were positively related with gross nitrification rates and soil pH, and negatively related with gross N immobilization rates. The CO₂ emissions were positively related with water‐soluble organic C contents, while CH₄ emissions were positively related with clay content, but negatively with gross N immobilization rates and soil organic C content. The global warming potential was higher in forestland soil than in cropland soil within agroforestry systems, and higher in forestland soil of the hedgerow compared to that in shelterbelts. Our results suggest that we need to select land uses or agroforestry systems that have a higher potential of mitigating GHG emissions from soils.
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