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Hedgerow agroforestry in England and Wales: increasing width to sequester additional carbon

Hedgerow systems are one of the more prominent agroforestry systems in temperate European 
agriculture, and the UK has the second largest extent of these in the European Union (Herzog 
2000; den Herder et al. 2016). An estimated 456 000 km of hedge in England and Wales has 
been actively managed (Carey et al. 2008); which limits hedge outward growth, and maintains an 
effective barrier to livestock (Pollard et al. 1974). This management consists of a short period 
trimming cycle every 1 - 3 years, and a long period structural restoration cycle, after approximately 
40 years growth (Staley et al. 2015). A mechanical flail is used for the short period trimming cycle 
by 92% of farmers in England and Wales (Britt et al. 2011). Typical ‘Enclosure’ hedges in England 
and Wales were planted with only hawthorn (Crataegus monogyna), in single, or double rows, 
from the 16th Century onwards (Maclean 2006). Hawthorn is still the dominant woody species, 
found within 90% of hedges in England and Wales, but a mix of woody species is common, and 
blackthorn (Prunus spinosa) is the second most frequent species, found within 50% of these 
hedges (Barr et al. 2000). 
The potential for temperate agroforestry to sequester carbon (C), and mitigate rising levels of 
Green-House Gasses (GHG), is beginning to receive more attention (Udawatta and Jose 2012). 
Axe et al. (2017) showed the potential to sequester C where wider managed hedges had greater 
C stocks (t C km-1 
). Allowing such hedges to grow wider from lateral branch growth only, without 
increasing planting density, may not be the most effective way to accumulate Above Ground 
Biomass (AGB) C. It also introduces uncertainty in using area C stock values (t C ha-1 
) to estimate 
AGB C (t C), as this parameter assumes a linear relationship with hedge width. 
Here new data on the contribution made by blackthorn to AGB C stock, and the correlation 
between hedge width and t C km-1 
, from the pilot study of triennially flailed hedge biomass (Axe 
et al. 2017), along with supporting evidence on shrub growth in unmanaged hedges (Kuppers 
1985), is examined to advance how atmospheric C could be sequestered by increasing hedge 
width.