Is 'irregular forestry' the way forward for UK's woodland biodiversity?

Posted by Danny Alder
 
A new approach to managing broadleaf woodland in lowland Britain is providing a unique opportunity for research into how well irregular forestry stands conserve woodland biodiversity as compared to traditional coppice systems and neglected stands. Danny Alder, a PhD student working on birds and bats, along with Dr Phil Sterling and Mike Jeffes (moth diversity) and Bryan Edwards (plant diversity), have embarked on a five year research programme at Rushmore estate in Cranborne Chase on the Dorset/Wiltshire border.

A well developed irregular stand with a mixture of understorey and canopy trees. The irregularity of both creates a patchy appearance with high complexity (Photo: Danny Alder).

Unlike even-aged high forest management, irregular forestry creates a mix of permanently irregular aged stands of trees that provide an economic return. Tree-felling is selective and stand development relies on natural woodland processes (Susse et al 2011). Continuous cover, irregular forestry enjoys something of a reputation in continental Europe as a ‘close to nature’ management type, yet, in this country, it’s almost unheard of in semi-natural woodlands. In UK, more often than not, coppice with or without standards, and high-forest are the most widely known and practiced. High forest relies on thinning regularly producing a rather even-aged structure of trees with little regard to the understorey, while coppicing is reliant on traditional niche markets or targeted grant aid for its viability.

Traditional coppicing at the Rushmore Estate (Photo:Danny Alder).

Much of the 440 hectares of semi-natural woodland at Rushmore was, until recently, managed as coppice. Now, only enough of a market for coppice products survives to keep one or two people employed. Since the 1980s, many stands have been converted to the irregular management system. As a result, and because many stands have been neglected, there are few places in Britain that provide the opportunity to compare the effects of each management type. Simple coppice, primarily of birch, is used to produce faggots used for either brooms or horse-racing jumps. This is cut on a 5-7 year rotation and produces very dense thickets between 3-5 years and is frequented by Willow Warbler Phylloscopus trochilus and Garden warbler Sylvia borin.

Don Taylor prepares hazel rods which he splits to form ‘sails’ (uprights) which he weaves to 
make hurdles for fencing (Photo:Danny Alder) .

Early stage irregular woodland stand (Photo:Danny Alder)

 
The above stand is in the early stages of transformation to irregular with a range of younger and only a few old growth trees. The canopy has been manipulated to allow the understorey to regenerate which protects tree seedlings which were evident. However, it is important not to ‘lose control’ of the understorey vegetation which can smother newly developing seedlings and patchiness is encouraged by cutting swathes through the bramble where necessary. 

One of 310 plots laid out across the woodland management types. During 2014, Danny 
conducted two rounds of timed bird point counts covering the early and late parts of breeding 
season (Photo:Danny Alder).

The project will examine the usage of the different woodland types by key birds - both in terms of overall abundance in the summer and winter, and during detailed investigation of birds foraging. The figure above shows that there has been a general decline in woodland birds with specialists, those reliant on all their resources within woodland suffering the most. In the first year, birds and habitat structure have been recorded at a total of 310 plots. Plants, bats, and moths will be recorded at a subset of these plots in 2015. 

Different age classes of trees and saplings were counted in each plot along with understorey 

density scores using a chequer board to estimate % obscuration (left), and canopy openness 

values using a spherical densitometer (right; Photos:Danny Alder).

  
By examining in detail, for the first time in British woodland, the congruence between vegetation structure, woodland plants, Lepidoptera, bats and birds we will be able to identify the strongest influences resulting from differing management types in broadleaf woodland.

The retention of standing and fallen deadwood within irregular management is encouraged 
and here the work of great spotted woodpecker Dendrocopos major can be seen in the ash 
Fraxinus excelsior stump (Photo: Danny Alder).

References: 

Susse, R, Allegrini, C., Bruciamacchie, M, and Burrus, R. (2011) Management of Irregular Forests: developing the full potential of the forest. Association Futaie Irreguliere. English translation P.Morgan 144pp.

Danny is a PhD student working with Stu and Huw Lloyd in the CEB group. Phil Sterling works with Dorset County Council, Mike Jeffes and Bryan Edwards with Dorset Environmental Records Centre.The project runs under the auspices of Dorset Environmental Records Centre, and is funded by the Golden Bottle Trust. Acknowledgements to Rhiannon Rogers DERC, Ian Burt Rushmore Estate and Andy Poore Rushmore Estate, plus Andy Taylor Freelance birch coppice worker and deer manager.