Ecological Characteristics of Ancient Semi-Natural Woodlands undergoing transformation to an Irregular High Forest silviculture in southern Britain

Alder, Daniel Carl (2023) Ecological Characteristics of Ancient Semi-Natural Woodlands undergoing transformation to an Irregular High Forest silviculture in southern Britain. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Ancient woodlands in lowland Britain are repositories of cultural and ecological histories which reflect a long association with human intervention since the Mesolithic. The interests of ancient woodland are valued by society yet demands on woodlands beyond providing woodland produce have increased. Uncertainties around anthropogenic climate change are driving land-use policies towards more resilient outcomes and sustainable forest management is part of the response. Irregular silviculture is one method to achieve continuous cover forestry in the United Kingdom and is promoted as an appropriate method of sustainable forestry management and has been practised at the study site, Rushmore estate since the 1980s. As an exploited resource ancient woodlands were significant in the development of European society providing fuel, building materials and furnace charcoal for metallurgy. Coppice management was prevalent over many centuries, at its height between the 13th and 19th centuries. Despite intensive exploitation, woodland species adapted alongside to form distinct communities against a backdrop of a farming landscape which was more benign than that which modern agriculture has created, causing woods to become isolated remnants of semi-natural habitats. Changes in the way woodlands were generally managed across Europe reflected the increasing sophistication of technology and demands on the types of wood resources required especially during the industrial revolution. The progression of Silviculture as a science ran parallel and many of the traditional coppice-based products became obsolete. High forest silviculture developed as coppice subsided alongside the arrival of plantation management with a focus on producing increasing quantities of timber for construction to meet national demands and security of supply. By the middle of the 20th century coppicing of most ancient woods ceased; woods became either neglected or converted to high forest often with non-native conifers planted which changed conditions for many of the ancient woodland species associated with continuity of coppice management. Under-management is a conservation threat to many species associated with a more heterogenous stand structure. Continued management by coppicing however, remains economically tenuous. This study in the Cranborne Chase with a long history of coppice management across its ancient woodlands provided a unique opportunity to compare habitat structures between active coppice silviculture, Irregular high forest, transitional stands in the early stages of silvicultural management and limited intervention stands, those neglected between 30-50 years previously. Using a combination of descriptive, multivariate analysis, correlations and modelling with pairwise tests between stand types of the effects of silvicultural management, or the lack of it, upon three different taxonomic groups; birds, bats and plants associated with ancient woodland. Irregular high forest was found to positively influence all three taxonomic groups. Significantly, Irregular silviculture retained many species of conservation interest including the conservation red-listed Marsh Tit Poecile Palustris and Barbastelle Bat Barbastella barbastellus which is listed internationally as near-threatened by the International Union for the Conservation of Nature. Both were found to occupy Irregular stands at greater levels of abundance and activity respectively compared to either coppice or limited intervention stands. For ancient woodland indicator plants and coppice-associated plants as derived by Rackham (2003), there was no significant difference between coppice and Irregular stands. Structural comparisons between Irregular and limited intervention stands were strikingly different with lower basal area, stand structural variation and developing understorey associated most strongly with the former. Irregular silviculture provides structural heterogeneity and complexity associated with early successional growth typical of the coppice cycle and more open woodland, but also older growth features, e.g., deadwood, of mature stands related to larger diameter trees. Both sets of attributes provide important functional resources for a range of woodland species analogous to a woodland successional gradient. This study has identified that Irregular high forest produces a broad ecological ‘bandwidth’ of environmental conditions for woodland species. Active silvicultural management that includes Irregular in ancient woodland is preferable to neglect associated with limited intervention because it appears to retain structural characteristics important to several groups of woodland species of intrinsic conservation value.