Carbon storage in hedge biomass—A case study of actively managed hedges in England

Abstract

Farmland hedges could be managed for carbon sequestration, but empirical data on their carbon (C) stock in the UK is lacking. Lowland hedges managed by hedge laying and triennial trimming using a mechanical flail formed a dense woody structure (mean 81 368 stems ha-1). Hedges untrimmed for 3 years (mean height 3.5 m, widths 2.6-4.2 m), contained an above ground biomass (AGB) C stock of 42.0 ± 3.78 t C ha-1 (14.0 ± 1.94 t C km-1); when trimmed to 2.7 m high, and subsequently 1.9 m high, AGB C stocks were reduced to 40.6 ± 4.47 t C ha-1 (11.4 t C km-1) and 32.2 ± 2.76 t C ha-1 (9.9 t C km-1), respectively. A 4.2 m wide hedge contained 9.7 t C km-1 more AGB C stock than a 2.6 m wide hedge (mean height 3.5 m). Below ground biomass (BGB) was 38.2 ± 3.66 t C ha-1 (11.5 t C km-1). Near horizontal stems, arranged by hedge laying, 12-18 years prior to sampling, accounted for 5.2 t C ha-1 (1.6 t C km-1) of AGB C. The empirical data demonstrated how changing management practices to wider/taller hedges sequestered C in AGB. These estimates of hedgerow C stocks fill a knowledge gap on C storage and identified the need for a more comprehensive biomass inventory of hedgerows to strengthen the national carbon accounting of agro-ecosystems in the UK.

Carbon sequestration in hedgerow biomass and soil in the temperate climate zone

“…2), with a correlation between years since last coppicing and hedgerow height (Pearson's correlation coefficient (r) = 0.38, p < 0.01). Below-ground biomass C stocks were only reported in two studies (Axe et al 2017;Crossland 2015). Axe et al (2017) measured three hedgerows down to 1 m depth.…”

“…Below-ground biomass C stocks were only reported in two studies (Axe et al 2017;Crossland 2015). Axe et al (2017) measured three hedgerows down to 1 m depth. These sampled hedgerows had a mean (± SD) root/shoot ratio of 0.94 ± 0.26 (Axe et al 2017).…”

“…Axe et al (2017) measured three hedgerows down to 1 m depth. These sampled hedgerows had a mean (± SD) root/shoot ratio of 0.94 ± 0.26 (Axe et al 2017). In contrast, Crossland (2015) derived below-ground C biomass stocks from above-ground biomass C stocks via a fixed root/ Fig.…”

“…This assumed root/shoot ratio was not specific for the sampled hedgerows and therefore seems to underestimate below-ground biomass compared with the empirical values. Therefore, we took the measured root/shoot ratio by Axe et al (2017) to estimate an average belowground biomass C stock. Axe et al (2017) included the root crowns and the stools in the below-ground biomass.…”

How do hedgerows influence soil organic carbon stock in livestock‐grazed pasture?

“…Position relative to hedgerows is also important, with SOC greater upslope of contour-planted hedgerows, where the hedgerow acts as a physical barrier reducing soil erosion and increasing A-horizon depth (Follain et al, 2007). Regular hedgerow management (via cutting with a tractor-mounted flail) increases the amount of surface litter adjacent to the hedgerow (Axe, Grange, & Conway, 2017) potentially increasing inputs to soil. Regular cutting also decreases the shoot-to-root ratio, which can influence fine root turnover and either increase (Peter & Lehmann, 2000) or decrease (Crossland, 2015) SOC storage.…”