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Evaluating hedgerow and riparian buffer carbon storage potential in the Lower Fraser Valley from a field- and landscape-level perspective Dowell, Lyndsey


Hedgerows and riparian buffers have been promoted for their potential to increase carbon storage capacity of agricultural landscapes. However, there has been little quantification of this potential. Using the Lower Fraser Valley of British Columbia as a case study, I contextualized differences in carbon observed in hedgerows and riparian buffers and compared soil organic carbon (SOC) across five land use and land cover categories. Three SOC metrics were used to evaluate the below-ground carbon storage potential of each land use and land cover category. At the landscape-level I designed remote sensing methods to extract hedgerows and riparian buffers from 5m resolution RapidEye imagery. I reapplied methods to imagery collected in previous years to assess recent changes (2009 - 2017) in hedgerow and riparian buffer coverage. Greater species richness in hedgerows was highly correlated with greater SOC across all metrics. When measuring SOC using a mass-based approach approximating a 30 cm depth, or 0.4 t m⁻² of soil equivalent, high-diversity hedgerows and woody riparian buffers had greater SOC mass than managed grasslands. However, no differences were observed between either high-diversity hedgerows or woody riparian buffers and agricultural production land cover categories when using a depth-based approach. Carefully calibrated spectral, textural, and geometric rules developed from high spatial resolution remotely sensed imagery delineated and classified hedgerows and riparian buffers with a combined accuracy of 68% (kappa 0.63). In 2017, hedgerows and riparian buffers in the Lower Fraser Valley totaled 78.0 and 40.6 km², respectively. Change detection was less accurate (kappa 0.35), estimating increases in combined hedgerow and riparian buffer coverage from 2009 to 2017 by 72.7 % relative to the 2009 coverage and 2.3 % relative to the study area. Adequate broad scale hedgerow and riparian buffer maps, despite difficulties in temporal change detection, are a critical first step towards modelling carbon storage potential at a regional level.

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