Using hedgerow biodiversity to enhance the carbon storage of farmland in the Fraser River delta of British Columbia

Abstract

Hedgerows (also known as field margins, shelterbelts, or windbreaks) have the potential to help mitigate greenhouse gas emissions from agricultural activities through carbon (C) sequestration in the woody biomass of trees and shrubs as well as in the soil. A first step to understanding the sequestration potential is to quantify the biomass C and soil C storage. In the Fraser Valley of British Columbia, Canada, a hedgerow stewardship program incentivizes farmers to plant hedgerows to create habitat for biodiversity conservation and to improve ecosystem services such as climate change mitigation. This study evaluated the efficacy of hedgerows to store C in woody biomass and soil relative to remnant hedgerows (RH) and neighboring production fields with annual crops. We measured soil C (equivalent soil mass) and soil aggregate stability in both hedgerows and production fields, while biomass C and species diversity were calculated for the trees and shrubs in the two hedgerow types. There was no significant difference in the biomass C in the two hedgerow types, despite age differences with planted hedgerows (PH) having a mean total above- and belowground biomass of 76 ± 32 t C ha⁻¹ (33.8 ± 14.2 tn C ac⁻¹) and RH 124 ± 21 t C ha⁻¹ (55.3 ± 9.3 tn C ac⁻¹). Aggregate stability was similar in both hedgerow types, and was significantly greater than neighboring production fields. Woody vegetation biodiversity was significantly greater in PH than RH for richness, Shannon, and Simpson measures. Planted hedgerows stored significantly greater soil C than RH to 1.2 t m⁻² (1.1 tn yd⁻²) standard soil mass with values being 175.9 ± 13.2 t C ha⁻¹ (78.4 ± 5.8 tn C ac⁻¹) and 132.7 ± 7.3 t C ha⁻¹ (59.1 ± 3.2 tn C ac⁻¹), respectively. Soil C in PH was 40% greater than that of their neighboring production fields. Soil C was significantly correlated with the Shannon and Simpson diversity of the hedgerow shrubs and trees indicating that planting hedgerows, with improved woody vegetation biodiversity, may have a positive effect on their greenhouse gas mitigation potential on farmland.