Individual study: The restoration of neglected hedges using pollarding and coppicing, Monks Wood, Cambridgeshire, England
Croxton P.J., Franssen W., Myhill D.G. & Sparks T.H. (2004) The restoration of neglected hedges: a comparison of management treatments. Biological Conservation, 117, 19-23
Hedgerows are important semi-natural habitats, providing food and acting as corridors, nesting and roosting sites. Furthermore, hedgerows may be species rich in flora and fauna. Consequently, hedgerows have been designated as a priority habitat in the UK's Biological Action Plan, and they received legal protection in 1997.
For hedgerows to maintain structural integrity they must be managed, but between 1990 and 1998, linear features categorised as lines of trees/shrubs and relict hedges, increased by 35,000 km (31%), suggesting that many hedgerows had been left neglected. In this study, hedgerows that have been unmanaged for over 20 years were restored using coppicing or pollarding between the winters of 1998/9 and 2001/2, and the merits of these two techniques were compared.
Study site & hedgerows: In 1963, at the Monks Wood research station, Abbots Ripton in Cambridgeshire (southern England), 11 hedgerow types with four replicates each were planted. These were planted as double rows, 30 cm apart with 60 cm between plants, in 27 m long strips. Following cessation of research on these hedgerows, they remained unmanaged for 20 years. By 1998, only 25 hedgerows remained and they had grown into lines of trees, 5 to 8 m tall and 30 to 62 cm in girth at 20 cm above ground level. Furthermore, some species had produced suckers from roots and thus formed wide, dense thickets. This case study focuses on the twelve single species hedgerows that remained (field maple Acer campestre = 3; hornbeam Carpinus betulus = 2; hazel Corylus avellana = 2; hawthorn Crataegus monogyna = 2; elm Ulmus procera = 2; and blackthorn Prunus spinosa = 1).
Hedgerow management: Restoration management was conducted in the winters of 1998/9 (eight hedgerows), 1999/2000 (two hedgerows), and 2000/1 (two hedgerows). Half the length of each hedgerow was coppiced at ground level and the other half was pollarded at 60 cm above ground level. All brash was removed from each hedgerow. The lateral growth of hedgerows was contained by flail mowing.
Hedgerow regrowth: Hedgerows were recorded in February 2002. For both halves of each hedgerow, ten equispaced stools were selected and the number of shoots counted. The lengths of the five longest shoots from each of the stools were also measured.
Stool survival: The most tolerant species to cutting were field maple, hazel and elm, with some plots having complete survival (see Table 1, attached). There was a general trend of lower survival for coppiced stools than pollarded stools, particularly for hornbeam, as well as for one field maple and one hawthorn hedgerow.
Shoot number: For each species of hedgerow, pollarding produced more shoots per stool than coppicing (see Table 1, attached). Furthermore, ten of the twelve pollarded hedges produced more shoots per stool than coppiced hedges, four significantly.
Shoot length: For each species of hedgerow, pollarding produced longer shoots than coppicing (see Table 1, attached). Again, ten of the twelve pollarded hedges produced longer shoots per stool than coppiced hedges, eight significantly. Field maple, hazel and hornbeam hedges responded particularly strongly. Finally, both elm and field maple produced very high growth rates for both techniques.
Conclusions: From this study conducted at Monks Wood, it appears that pollarding is the most effective restoration strategy for hedgerows that have been neglected for over 20 years, and coppicing should certainly not be considered as a sole restoration technique.
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