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

- Above ground biomass (AGB) for 3.5 m tall hedges amounted to 42.0 ± 3.78 t C ha−1.
- Hedge C stocks of 38.2 ± 3.66 t C ha−1 below ground almost equalled that for AGB.
- Farm management practices could focus on wider, taller hedges to sequester more C.
- Developing a hedge C stock inventory would strengthen national C accounting.

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.