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Woodland recovery after suppression of deer: cascade effects for small mammals, wood mice (Apodemus sylvaticus) and bank voles (Myodes glareolus).

Bush ER, Buesching CD, Slade EM, Macdonald DW - PLoS ONE (2012)

Bottom Line: In this study, we tested whether recovery in the vegetative habitat of a woodland due to effective deer management (from a peak of 0.4-1.5 to <0.17 deer per ha) had translated to the small mammal community as an example of a higher order cascade effect.Using the multi-state Robust Design method in program MARK we found survival and abundance of both voles and mice to be equivalent between the open woodland and the experimental exclosures with no differences in various metrics of population structure (age structure, sex composition, reproductive activity) and individual fitness (weight), although the vole population showed variation both locally and temporally.We conclude that the response of small mammal communities to environmental disturbance such as intense browsing pressure can be rapidly reversed once the disturbing agent has been removed and the vegetative habitat is allowed to increase in density and complexity, although we encourage caution, as a source/sink dynamic may emerge between old growth patches and the recently disturbed habitat under harsh conditions.

View Article: PubMed Central - PubMed

Affiliation: Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Oxford, United Kingdom. emmie.bush@gmail.com

ABSTRACT
Over the past century, increases in both density and distribution of deer species in the Northern Hemisphere have resulted in major changes in ground flora and undergrowth vegetation of woodland habitats, and consequentially the animal communities that inhabit them. In this study, we tested whether recovery in the vegetative habitat of a woodland due to effective deer management (from a peak of 0.4-1.5 to <0.17 deer per ha) had translated to the small mammal community as an example of a higher order cascade effect. We compared deer-free exclosures with neighboring open woodland using capture-mark-recapture (CMR) methods to see if the significant difference in bank vole (Myodes glareolus) and wood mouse (Apodemus sylvaticus) numbers between these environments from 2001-2003 persisted in 2010. Using the multi-state Robust Design method in program MARK we found survival and abundance of both voles and mice to be equivalent between the open woodland and the experimental exclosures with no differences in various metrics of population structure (age structure, sex composition, reproductive activity) and individual fitness (weight), although the vole population showed variation both locally and temporally. This suggests that the vegetative habitat--having passed some threshold of complexity due to lowered deer density--has allowed recovery of the small mammal community, although patch dynamics associated with vegetation complexity still remain. We conclude that the response of small mammal communities to environmental disturbance such as intense browsing pressure can be rapidly reversed once the disturbing agent has been removed and the vegetative habitat is allowed to increase in density and complexity, although we encourage caution, as a source/sink dynamic may emerge between old growth patches and the recently disturbed habitat under harsh conditions.

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Composition of the undergrowth layer.Mean percentage cover of constituent plant species; U.diocia (Nettles), C. Avellana (Hazel), D. Filix-mas (Male fern), R. Fruticosus (Bramble). Bramble dominates the exclosures.
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pone-0031404-g005: Composition of the undergrowth layer.Mean percentage cover of constituent plant species; U.diocia (Nettles), C. Avellana (Hazel), D. Filix-mas (Male fern), R. Fruticosus (Bramble). Bramble dominates the exclosures.

Mentions: The percentage cover of plants in the undergrowth was much reduced in the open woodland for the sites SF and FB compared to the exclosure, but showed no difference for ML (Figure 4) (Undergrowthex = 53.5, undergrowthow = 24.5, N = 3, W = 6, p = 0.11, Wilcoxon rank sum test). There were also compositional differences between the exclosures and open woodland. The mean values showed a consistent pattern across all sites; Male fern (Dryopteris filix-mas (L.) Schott), and Hazel (Corylus avellana L.), made up a greater proportion of the vegetation in the undergrowth height zone in the open woodland, whereas bramble (R. fruticosus), nettles (U. diocia) and other species dominated in the exclosures (Figure 5). The fruiting index of bramble in the open woodland was low, with three times fewer floral apices observed per unit bramble cover than in the exclosures (fruitex = 0.42±0.05, fruitow = 0.14±0.08, N = 3, W = 6, p = 0.11, Wilcoxon rank sum test).


Woodland recovery after suppression of deer: cascade effects for small mammals, wood mice (Apodemus sylvaticus) and bank voles (Myodes glareolus).

Bush ER, Buesching CD, Slade EM, Macdonald DW - PLoS ONE (2012)

Composition of the undergrowth layer.Mean percentage cover of constituent plant species; U.diocia (Nettles), C. Avellana (Hazel), D. Filix-mas (Male fern), R. Fruticosus (Bramble). Bramble dominates the exclosures.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3275623&req=5

pone-0031404-g005: Composition of the undergrowth layer.Mean percentage cover of constituent plant species; U.diocia (Nettles), C. Avellana (Hazel), D. Filix-mas (Male fern), R. Fruticosus (Bramble). Bramble dominates the exclosures.
Mentions: The percentage cover of plants in the undergrowth was much reduced in the open woodland for the sites SF and FB compared to the exclosure, but showed no difference for ML (Figure 4) (Undergrowthex = 53.5, undergrowthow = 24.5, N = 3, W = 6, p = 0.11, Wilcoxon rank sum test). There were also compositional differences between the exclosures and open woodland. The mean values showed a consistent pattern across all sites; Male fern (Dryopteris filix-mas (L.) Schott), and Hazel (Corylus avellana L.), made up a greater proportion of the vegetation in the undergrowth height zone in the open woodland, whereas bramble (R. fruticosus), nettles (U. diocia) and other species dominated in the exclosures (Figure 5). The fruiting index of bramble in the open woodland was low, with three times fewer floral apices observed per unit bramble cover than in the exclosures (fruitex = 0.42±0.05, fruitow = 0.14±0.08, N = 3, W = 6, p = 0.11, Wilcoxon rank sum test).

Bottom Line: In this study, we tested whether recovery in the vegetative habitat of a woodland due to effective deer management (from a peak of 0.4-1.5 to <0.17 deer per ha) had translated to the small mammal community as an example of a higher order cascade effect.Using the multi-state Robust Design method in program MARK we found survival and abundance of both voles and mice to be equivalent between the open woodland and the experimental exclosures with no differences in various metrics of population structure (age structure, sex composition, reproductive activity) and individual fitness (weight), although the vole population showed variation both locally and temporally.We conclude that the response of small mammal communities to environmental disturbance such as intense browsing pressure can be rapidly reversed once the disturbing agent has been removed and the vegetative habitat is allowed to increase in density and complexity, although we encourage caution, as a source/sink dynamic may emerge between old growth patches and the recently disturbed habitat under harsh conditions.

View Article: PubMed Central - PubMed

Affiliation: Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Oxford, United Kingdom. emmie.bush@gmail.com

ABSTRACT
Over the past century, increases in both density and distribution of deer species in the Northern Hemisphere have resulted in major changes in ground flora and undergrowth vegetation of woodland habitats, and consequentially the animal communities that inhabit them. In this study, we tested whether recovery in the vegetative habitat of a woodland due to effective deer management (from a peak of 0.4-1.5 to <0.17 deer per ha) had translated to the small mammal community as an example of a higher order cascade effect. We compared deer-free exclosures with neighboring open woodland using capture-mark-recapture (CMR) methods to see if the significant difference in bank vole (Myodes glareolus) and wood mouse (Apodemus sylvaticus) numbers between these environments from 2001-2003 persisted in 2010. Using the multi-state Robust Design method in program MARK we found survival and abundance of both voles and mice to be equivalent between the open woodland and the experimental exclosures with no differences in various metrics of population structure (age structure, sex composition, reproductive activity) and individual fitness (weight), although the vole population showed variation both locally and temporally. This suggests that the vegetative habitat--having passed some threshold of complexity due to lowered deer density--has allowed recovery of the small mammal community, although patch dynamics associated with vegetation complexity still remain. We conclude that the response of small mammal communities to environmental disturbance such as intense browsing pressure can be rapidly reversed once the disturbing agent has been removed and the vegetative habitat is allowed to increase in density and complexity, although we encourage caution, as a source/sink dynamic may emerge between old growth patches and the recently disturbed habitat under harsh conditions.

Show MeSH
Related in: MedlinePlus