Benefit of permanent non-fire refugia for Lepidoptera conservation in fire-managed sites

Published source details Swengel A.B. & Swengel S.R. (2007) Benefit of permanent non-fire refugia for Lepidoptera conservation in fire-managed sites. Journal of Insect Conservation, 11, 263-279.
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This study is summarised as evidence for the following.

	Action	Category
	Leave some areas unburned during prescribed burning Action Link
	Manage heathland by cutting Action Link

Leave some areas unburned during prescribed burning

A replicated, site comparison study in 1991–2005 in seven pine barrens and four prairies in Wisconsin, USA (Swengel & Swengel 2007) found that six out of nine specialist butterfly species were more abundant at sites with unburned areas than at sites without unburned areas. At one pine barren, Karner blue Lycaeides melissa samuelis and mottled duskywing Erynnis martialis abundance in the unburned refuge were higher 10–17 years after establishment (Karner blue: 10.2–17.3 individuals) than 3–9 years after establishment (2.4–14.9 individuals), while abundance in 10 burned areas remained similar (10–17 years after: 7.1–14.6; 3–9 years after: 4.7–9.2 individuals; data for mottled duskywing not presented). In addition, when the unburned refuge was older, relative abundances of gorgone checkerspot Chlosyne gorgone (47% of records in refuge) and dusted skipper Atrytonopsis hianna (49% of records) were higher than in 10 burned areas, compared to when the unburned refuge was younger (checkerspot: 9%, skipper: 19% of records in refuge). There was no significant difference in relative abundances between the refuge and burned areas for Olympia marble Euchloe olympia (older: 12%; younger: 4% of records in refuge) and Persius duskywing Erynnis persius (older: 13%; younger: 0% of records in refuge). At another pine barren, over 13 years, frosted elfin Callophrys irus abundance in the refuge increased, but was absent from a site after burning, and abundance decreased at 11 comparison sites (see paper for details). In two prairies, regal fritillary Speyeria idalia abundance in unburned refuges (15.9–53.5 individuals) was higher than in burned areas (2.7–11.1 individuals). At the prairie with the most recently established refuge, regal fritillary abundance began to increase once the refuge was 7-years-old. However, Ottoe skipper Hesperia ottoe abundance declined at two prairies managed with burning and unburned refuges (data presented as model result). Seven pine barrens (8–48,921 ha) and four prairies (25–4,766 ha) were managed with cool-season rotational burning, mowing, grazing and hand-cutting of woody vegetation, within which areas were unburned for up to eight years. Two barrens contained an unburned refuge (4–14 ha) last burned in 1988 and 2002. Three prairies had long-established unburned refuges (11–35 ha), while the 3-ha refuge at the fourth prairie was last burned in 1991. From May–August 1991–2005, butterflies were surveyed along transects at each site, but sites were not surveyed every year.

(Summarised by: Andrew Bladon)
Manage heathland by cutting

A site comparison study in 1992–2005 in a pine barren in Wisconsin, USA (Swengel & Swengel 2007) found that an area managed by mechanical cutting supported more Karner blue butterflies Lycaeides melissa samuelis than areas managed by rotational burning. Over 13 years, in an area managed by cutting, Karner blue abundance (28–32 individuals/year) was higher than in areas managed by rotational burning (9–11 individuals/year) or rotational burning and cutting (8–10 individuals/year). An unburned refuge supported a similar abundance of Karner blue (11–14 individuals/year). Within a 12,180-ha pine barren, six areas with a similar abundance of wild lupine Lupinus perennis were compared. One area was managed by mechanical cutting, one was managed with cool-season rotational burning, three were managed by burning and cutting, and one area was left as a 14-ha unburned refuge (last burned in 1988). From May–July 1992–1995 and 1997–2005, butterflies were surveyed once/year along transects in each area.

(Summarised by: Andew Bladon)