Investigating the effects of management in temperate broadleaved woodland on bats and their insect prey

  • Andrew Carr

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Woodland is an important natural resource providing wood-derived biomass for use as a carbon lean source of heating and electricity. The role of biomass in reducing our dependence on fossil fuels should not be underestimated, nor should the potential negative impacts on biodiversity as land managers are incentivised to bring under-managed woodland back into production to meet renewable targets. The effect of woodland management on wildlife needs more scientific research. In this thesis, I investigate the influence of the silvicultural practice involving selective thinning of woodland over time on bats and their insect prey, and use emerging technologies to identify the ecological requirements of a woodland specialist bat species at different spatial scales.

When compared to unmanaged woodland (minimal intervention and underutilised), bat species richness was higher in managed woodland (selective thinning) because uncluttered understory vegetation provided opportunities for edge and open foraging bats, in addition to woodland interior specialists. Common and adaptable edge foragers were more active in managed woodland. Interior foragers and tree-roosting bats were more active in unmanaged woodland and often absent from managed woodland. Bats responded positively to standing dead trees and tree cavities, and to a relatively open and heterogeneous canopy architecture. Standing dead trees were three times more abundant, and tree cavities five times more frequent in unmanaged woodland. Canopy architecture was similar between managed and unmanaged woodland. Bats and insects had contrasting non-linear temporal responses to time since last management with bat activity reducing, and insect numbers peaking in early stage successional woodland. The woodland-dwelling bat Barbastella barbastellus roosted primarily in ancient semi-natural broadleaved woodland which contained more tree cavities than adjoining younger plantation woodland. High energetic demands of pregnant and lactating bats influenced roost selection and behaviour. B. barbastellus specialises in feeding on moths. Linear landscape features such as hedgerows provide food for moth larvae and were used by B. barbastellus for feeding on adult moths.

Bats respond well to characteristics that form in old age woodland. The relatively low frequency of standing dead trees and number of cavities in shorter rotation production woodland limits its value to bats. Tree roost availability and canopy architecture characteristics can be encouraged in young woodland by minimal intervention management, or in production woodland through positive thinning management. Improving B. barbastellus roosting and foraging habitat will conserve habitat suitable for all developmental stages of their moth prey.
Date of Award6 Nov 2018
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorGareth Jones (Supervisor)

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