| Summary: | Hedgerows have potential to help mitigate greenhouse gas emissions from agricultural activities by sequestrating carbon in woody biomass and in soil. In the Fraser Valley of British Columbia, a hedgerow stewardship program supports farmers to plant hedgerows to create habitat for biodiversity conservation and to improve ecosystem services, but it is unclear how much hedgerows contribute to climate change mitigation.
This study evaluated components of the mitigation potential of two types of hedgerows, those planted by the stewardship program, and those that are remnant in the region. We quantified the carbon stored in woody biomass and soil, and greenhouse gas emissions of these two hedgerow types relative to neighbouring production fields used for cultivation of annual crops. There was no significant difference in the biomass carbon in the two hedgerow types despite age differences. Woody vegetation species diversity was significantly greater in planted hedgerows than remnant hedgerows for richness, Shannon, and Simpson measures. Planted hedgerows stored greater soil carbon than remnant hedgerows to 1.2 t m-² standard soil mass. Soil carbon was significantly correlated with the Shannon, and Simpson diversity of the hedgerow shrubs and trees indicating that planting a diversity of woody species likely has a positive effect on the mitigation potential of hedgerows on farmland.
Carbon dioxide, nitrous oxide, and methane effluxes from soil, measured bi-monthly for one year indicate that the mitigation potential is not straightforward. For the 6-month production and non-production seasons, carbon dioxide was significantly greater in hedgerows than production fields. Relative emissions, emissions from hedgerows relative to their neighbouring production fields, from planted hedgerows were significantly greater than remnant hedgerows. For the 6-month production season, nitrous oxide emissions were significantly lower in hedgerows than productions fields, while no difference were observed in the non-production season or between hedgerow types. No significant differences were observed between seasons or hedgerow types for methane fluxes.
These findings suggest that planting hedgerows may be an important management option to store carbon on agricultural land in the Fraser River delta relative to remnant hedgerows, but their net impact on climate change mitigation is still unclear. === Land and Food Systems, Faculty of === Graduate
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