A quantitative Study of Deadwood in 3 ancient woodland pasture sites in Derbyshire
A quantitative study of dead wood in
3 ancient wood pasture sites in Derbyshire
Monica Gillespie Msc
First published in The History, ecology and Archaeology of Medieval Parks and Parklands - Landscape Archaeology and ecology Volume 6, 2007.
Introduction
Dead wood is not a single uniform substrate it includes fallen wood, dead standing trees and it is also present in living trees as dead branches, decay, cavities and other dysfunctional wood. Ancient wood pasture sites and their associated ancient trees are important dead wood habitats for many specialised species because of their continuity with post-glacial wildwood (Harding & Alexander, 1993 and Kirby et al, 1995). Many studies have quantified fallen dead wood and standing dead trees in woodlands and forests (Kirby et al, 1998 and Humphrey et al, 2003), however there have been few attempts to quantify dead wood in wood pasture sites. Dead wood present in living trees has virtually been ignored in these previous studies.
The study
A study was undertaken to quantify the dead wood habitats of 3 ancient wood pasture sites in Derbyshire. All the sites have a long history of wood pasture management and many ancient trees, but management has varied between the sites in the last 100 years. At Calke Park there has been minimal intervention and dead wood in most areas is left where it falls. At Kedleston Parkdead wood has been moved from the main parkland areas to the woodlands, as it is not considered to be compatible with the C18th ideal of a ‘classical landscape’. Intervention at HardwickPark has been high with dead wood removed and many old oaks felled in the C20th.
Deadwood was recorded either as fallen dead wood (FDW) or standing dead wood (SDW). FDW on the site was measured using line-intercept sampling. There is no established methodology for measuring SDW in living trees and as such one was designed for this study. Comparison of the results between the sites shows a clear general trend; the volume, spatial distribution and the diversity of dead wood decreased with increasing intervention. SDW is a significant proportion (37.54%) of all dead wood recorded. Notably SDW in living trees recorded as decay, cavities and dysfunctional wood (excluding entirely dead trees and branches) on average accounted for 25.81% of all dead wood.
Comparison of the volume of dead wood with the species richness data for saproxylic invertebrates available for the sites (Alexander 2004 a, b & c) showed a positive relationship. Although this remains statistically unproven the results strongly suggest that increasing intervention has reduced the value of the sites for saproxylic species.
Impact of management of dead wood habitat
It takes around 100 years without intervention for FDW to reach semi-natural levels (Webster & Jenkins, 2005). SDW as decay and cavities in ancient trees reflects management on a much longer timescale than FDW, possibly several centuries. As such, long term planning is required to ensure the continuity of a diversity of habitats.
The past management of the sites has influenced their value for saproxylic species and there is evidence that local extinctions of some species have already occurred as a result, notably at Hardwick (Alexandra, 2004c). Improving the dead wood habitat on all sites could prevent further loss of species.
Management Challenges.
Ideally all FDW should be left where it falls and if necessary only moved short distances. On some sites, however, increasing FDW will be dependent on balancing landscape and biodiversity priorities by agreeing zones of minimal intervention in less visible areas. A wider recognition of the ecological as well as cultural heritage of these sites is required to secure their biodiversity value for the future.
Maintaining existing SDW volumes is dependent on the retention and sensitive management of existing ancient and veteran trees to ensure their longevity.
Increasing the level of SDW to ensure suitable habitats for species survival is more of a challenge given the timescales involved in the natural development of this habitat. ‘Veteranising’ trees by initiating premature decay and senility may bridge gaps in the habitat (Key & Ball, 1993 and Fay, 2002).
Protecting threatened species dependent on dead wood also depends upon extending positive management practices beyond the boundaries of these sites, increasing dead wood and protecting ancient and veteran trees in the wider landscape.
Key words: Dead wood, wood-pasture, ancient trees, saproxylic invertebrates.
Authors contact: monica@peaktreeconsultancy.com
References
Alexander, K.N.A. (2004a) Saproxylic Invertebrate Survey of Calke Park SSSI,
Derbyshire. Unpublished report for English Nature.
Alexander, K.N.A. (2004b) Saproxylic Invertebrate Survey of KedlestonPark, Derbyshire. Unpublished report for English Nature.
Alexander, K.N.A. (2004c) Saproxylic Invertebrate Survey of Hardwick Park, Derbyshire. Unpublished report for English Nature.
Fay, N. (2002), The Principles of Environmental Arboriculture. The Arboricultural Journal 26 (3).213-238
Harding, P.T. and Alexander, K.N.A. (1993) 'The Saproxylic Invertebrates of Historic
Parklands: Progress and Problems.' In Kirby, K. J. and Drake, C. M. (eds) Dead wood Matters: the ecology and conservation of saproxylic invertebrates in Britain. English Nature, Peterborough.
Humphrey, J., Ferris, R. and Quine, C. (eds) (2003) Biodiversity in Britain’s Planted Forests- Results from the Forestry Commission’s Biodiversity Assessment Project. Forestry Commission, Edinburgh.
Key, R.S. & Ball, S.G. (1993) ‘Positive management for saproxylic invertebrates' In Kirby, K. J. and Drake, C. M. (eds) Dead wood matters: the ecology and conservation of saproxylic invertebrates in Britain. English Nature, Peterborough
Kirby, K., Reid, C.M., Thomas, R.C. and Goldsmith, F.B. (1998) 'Preliminary estimates of fallen dead wood and standing dead trees in managed and unmanaged forests in Britain.' Journal of Applied Ecology, 35, 148-155.
Kirby, K., Thomas, R.C, Key, R.S., McLean, I.F.G., and Hodgetts, N. (1995) ‘Pasture-woodland and its conservation in Britain.’ Biological Journal of the Linnean Society 56: 135-153.
Webster, C.R. and Jenkins, (2005) ‘Coarse woody debris dynamics in the southern Appalachians as affected by topographic position and anthropogenic disturbance history.’ Forest Ecology and Management, 217(2-3) 319-330.
Commentaires