Individual study: Effects of clearcutting and wildlife corridor retention on abundance and diversity of small mammals in pine Pinus plantations in the Mead Westavaco South Region, South Carolina, USA
Constantine N.L., Campbell T.A., Baughman W.M., Harrington T.B., Chapman B.R. & Miller K.V. (2004) Effects of clearcutting with corridor retention on abundance, richness, and diversity of small mammals in the coastal plain of South Carolina, USA. Forest Ecology and Management, 202, 293-300
In response to environmental concerns in the USA and elsewhere, some forestry companies have altered their logging methods so rather than clear-cutting large areas, they may employ various selective harvesting techniques retain strips of trees to act as wildlife corridors. The idea behind corridor retention is to provide links between remaining patches of woodland that would otherwise be isolated and in so doing create a greater habitat heterogeneity.
A study was undertaken to examine how pine tree corridors in harvested stands influenced the abundance, richness and diversity of the small mammal fauna in some loblolly pine Pinus taeda plantations in the eastern USA.
Study sites: The study was conducted in six loblolly pine Pinus taeda plantations in the Mead Westavaco South Region on the coastal plain of South Carolina. The midstory vegetation within the plantations comprised mainly of sweetgum Liquidamber styraciflua and red maple Acer rubrum, while wild grape Vitis sp., greenbrier Smilax rotudifolia, poison ivy Toxicodendron radicans, and Virginia creeper Parthenocissus quinquefolia dominated the understory.
The pine plantations were divided into three harvested stands with 100 m pine tree corridors retained to maintain a woodland link with late successional stands and three non-harvested stands.
Small mammal live-trapping: Live-traps were baited and set in rectangular grids (112 traps/grid). The grids overlapped the harvested stands and the pine corridor, these were paired with non-harvested stands with the same rectangular trapping grid. Trapping took place over five consecutive nights during each monthly sampling period over 27 months (June 1998 to August 2000).
Captured individuals were identified, weighed, sexed and an age class allocated (adult, subadult, or juvenile), marked with a numbered ear tag and released at their capture location.
For each of the two treatments (havested and non-havested), data from each months trapping sessions was pooled into 3-month long periods based on time since timber harvest.
For each three-month period, relative abundance, species richness and species diversity were determined. For the pre-harvested period, capture rates, species richness and species diversity between the two treatments (harvested with corridor retention and non-harvested) were compared. For the post-harvested period, rodents and shrews were analysed separately in order to identify differences between treatments and among each three month period, within these two small mammal groups.
Small mammal caught: A total of 844 small mammals were caught: 60% were rodents (the majority being cotton mice Peromyscus carolinensis and cotton rats Sigmodon spp.); 40% were shrews (southern short-tailed shrew Blarina carolinensis was the most commonly caught species).
Pre-harvest trapping: During the pre-harvest period, live-trapping indicated that abundance, species richness and species diversity of rodents and shrews was approximately the same in both sets of pine stands i.e. those that would be cut with corridor retention and those that were not going to be felled.
Post-harvest trapping: Post-harvest abundance data is summarised in Table 1 (attached). Capture of rodents was greatest in harvested stands with corridor retention, compared to the uncut stands during several post-harvest trapping periods. Shrews did not differ in abundance between the two treatments, although capture rates declined in the post-harvested period.
Species richness and diversity: Species richness and diversity data is summarised in Table 2 (attached). Both richness and diversity were greater in the harvested stands with corridor retention than in the non-harvested ones, though richness did differ among periods while diversity did not.
Among the species caught, cotton mice and cotton rats were the most commonly found in the harvested stands. Southern short-tailed shrews and golden mice Ochrotomys nuttalli were the most common species in the non-harvested stands and also the pine corridors of the harvested stands (Table 3, attached).
Eastern harvest mice were more common in clearcut habitat, although they were also found in the interface between the clearcut and corridor habitats. Marsh rice rat Oryzomys palustris were only found in the clearcut habitat.
Conclusions: In terms of small mammals, corridor retention had a positive impact on the their abundance and diversity by creating a succession of habitats and niches suitable for a range of species. Corridor retention in harvested pine plantations probably act as refugia for woodland specialists from which they can spread into replanted areas as conditions became suitable.
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