Seeing the wood for the trees, irregular silviculture supports bat populations in conifer plantations
Author(s): Cook, P., Alder, D., Hordley, L., Newson, S.E. & Pengelly, D.
Published: June 2023
Journal: Forest Ecology and Management
Digital Identifier No. (DOI): 10.1016/j.foreco.2023.121214
Conifer woodland covers 1.6 million hectares of the UK and is an important source of economic revenue. There is increasing recognition that commercial forests should deliver other benefits beyond timber production, including the provision of ecosystem services and habitat for biodiversity.
Plantations are often considered to be poor for bats because they typically show only limited structural diversity - the trees typically being the same age and height, etc. Some woodland management practices - notably irregular silviculture - may improve structural diversity and benefit bats and other species. Irregular silviculture involves the selective removal of individual trees or the felling of small groups of trees, and the maintenance of a permanent and irregular canopy. The practice is likely to benefit species associated with mature forest, small scale disturbances and specific habitat features (such as open canopy).
Using passive acoustic monitoring, the authors were able to record bat activity at two sites in southern England. Alongside this, data were collected on the habitat characteristics of a series of woodland plots at these sites, the plots varying in the type of management used. Some 13 bat species were recorded, including rare species like Barbastelle and the two horseshoe bats (Greater and Lesser).
Bat species richness and the activity of individual bat species were significantly influenced by seven structural variables describing the woodland habitat. For example, the activity levels of Common Pipistrelle and Soprano Pipipistrelle were strongly associated with plots that had greater canopy openness, and also showed higher levels of activity in plots with more deadwood snags and greater quantities of fallen deadwood.
The study helps us understand how bats respond to different approaches to the management of conifer plantations, and again underlines the valuable role that acoustic monitoring can play in answering key questions about how we manage land and its implications for biodiversity.
NotesWe wish to thank the Stourhead Western Estate and National Trust Stourhead Estate for allowing access to conduct the research, in particular Nick Hoare, Henry Hoare and Kim Portnell. Forest manager, David Pengelly, provided important background information regarding the history of the stands, stand selection for the study and management of the stands.
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