Individual study: Gopher tortoise Gopherus polyphemus response to prescribed burning habitat management at the Camp Shelby National Guard Training Site, Piney Woods, Mississippi, USA
Yager L.Y., Hinderliter M.G., Heise C.D. & Epperson D. M. (2007) Gopher tortoise response to habitat management by prescribed burning. Journal of Wildlife Management, 71, 428-434
The gopher tortoise Gopherus polyphemus is endemic to the southeast USA, where it inhabits sandy areas in the transition zone between woods and open grassland. Good natural habitat is declining throughout its range and it is considered threatened. In many south-eastern pine forests, the absence of frequent, natural fires can result in overstory canopy closure and shrub encroachment. In habitat occupied by gopher tortoise this reduces forage accessibility. As a result, gopher tortoises move into or increase use of anthropogenically maintained, open areas such as roadside verges, cultivation plots, pastures and cleared military training areas. This situation is detrimental to the species as it increases exposure to heavy machinery, chemicals, and predators, such as racoon Procyon lotor and red fox Vulpes vulpes. Prescribed burning of forest adjacent to open areas at a military site inhabited by gopher tortoises was carried out in an effort to re-instate suitable tortoise habitat thereby encouraging the tortoises to re-settle in the managed forest.
Study area: This study was undertaken at Camp Shelby National Guard Training site (52,067 ha) located within the Piney Woods sub-province of Mississippi, southeast USA. The eight areas selected for study consisted of military firing points (1.3-4.3 ha in area) comprising open areas with herbaceous ground cover and a 200 m buffer of adjacent mature longleaf pine forest (23.1-32.7 ha), with well-developed shrub midstories and minimal herbaceous groundcover. Sites were considered to be of similar habitat quality and had similar sandy soils. Prior to the commencement of prescribed burns, each area had 4-7 gopher tortoises.
Methods: Four of the eight study sites were burned in the winter 2001-2002 and again in April 2003, while the remaining four were left unburned as control areas. The application of fire at this time of the year occurred during the dormant and growing season (January/February and April, respectively). The primary firing technique was aerial ignition of fuels (vegetation) which included grasses, pine litter and shrubs.
Habitat data was collected along transects orientated from firing-point areas into the adjacent forest and around tortoise burrows, during May-June of 2001, 2002, 2003 and 2004. During the same period, 40 tortoises were fitted with radio-transmitters and tracked for >300 days or >70 times per year. Data collected was used to determine burrow use, movements and home range during the periods between prescribed burn treatments and after.
In 2002, 158 tortoise burrows were located within the eight study sites, by September 2004, a further 42 new burrows had been identified in the entire study area. In forested areas on burned sites, 33 active burrows were found in September 2004, compared to 11 in April 2002 (a 200% increase in the number of active burrows). This indicated that prescribed burning had temporarily improved habitat and encouraged tortoises to create new burrows
Although woody cover was initially reduced post-burn, changes in forest vegetation measured during 2001-2004 indicated that burn treatments did not increase herbaceous understorey vegetation. Woody stem densities in fact increased due to regrowth to 10.8 stems/m2 in 2004 compared to control plots (7.8 stems/m2).
The movement patterns, burrow use, and home range of tortoises radio-tracked from 2002-2004 did not differ between treatments.
Conclusions: Prescribed burning did not restore desired habitat conditions for gopher tortoises in shrub-encroached forest. The regrowth of woody shrubs indicates that successful restoration of degraded forest areas may require dormant-and-growing-season prescribed burning over a period of several years to reinstate suitable open conditions.
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