Effects of prairie and barrens management on butterfly faunal composition

Published source details Swengel A.B. & Swengel S.R. (2001) Effects of prairie and barrens management on butterfly faunal composition. Biodiversity and Conservation, 10, 1757-1785.
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This study is summarised as evidence for the following.

	Action	Category
	Use rotational grazing Action Link
	Use rotational mowing Action Link
	Use rotational burning Action Link
	Maintain species-rich, semi-natural grassland Action Link
	Cease grazing on grassland to allow early succession Action Link

Use rotational grazing

A replicated, site comparison study in 1990–1997 in 105 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001) found that rotationally managed prairies (grazed, hayed or burned) which were last managed longer ago had a higher abundance and species richness of specialist and grassland butterflies than more recently managed prairies. All data were presented as models results. Of 105 prairies (1.2–2,024 ha), seven areas within the Sheyenne National Grassland, North Dakota, were managed by rotational grazing (0.3–0.6 animal use months/ha/year), 77 prairies were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown), and 27 were managed by haying, mostly on a two-year rotation. From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Species were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).

(Summarised by: Andrew Bladon)
Use rotational mowing

A replicated, site comparison study in 1990–1997 in 105 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001) found that rotationally managed prairies (hayed, grazed or burned) which were last managed longer ago had a higher abundance and species richness of specialist and grassland butterflies than more recently managed prairies. All data were presented as models results. Of 105 prairies (1.2–2,024 ha), 27 were managed by haying, mostly on a two-year rotation, 77 areas were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown), and seven areas within the Sheyenne National Grassland, North Dakota, were managed by rotational grazing (0.3–0.6 animal use months/ha/year). From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Species were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).

(Summarised by: Andrew Bladon)
Use rotational burning

A replicated, site comparison study in 1990–1997 in 86 tallgrass prairies and 32 pine-oak barrens in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001, same experimental set-up as Swengel & Swengel 1997 and Swengel 1998) found that barrens had a higher abundance and species richness of specialist and grassland butterflies after more recent burning, but that prairies had a lower abundance and species richness of butterflies after more recent burning. In pine-oak barrens, the abundance and species richness of specialist and grassland butterflies was higher in recently burned areas than in unmanaged areas. However, in the first year after prairies had been burned, the abundance and species richness of specialist and grassland butterflies was lower than in areas which had not been burned in the last year. In addition, in Illinois, Wisconsin and eastern Iowa, the abundance of specialists, and the abundance and richness of grassland species, was lower in burned prairies of any age than in unmanaged prairies. However, apart from in the first year since burning, there were no differences between burned and unmanaged prairies in western Iowa, Minnesota and North Dakota. All data were presented as models results. A total of 77 prairies and 20 barrens were managed by rotational burning (every 2–5 years) in the cool-season, although some areas had not been burned for eight years. Nine prairies and 12 barrens had been unmanaged for many years. From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Butterflies were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).

(Summarised by: Andrew Bladon)
Maintain species-rich, semi-natural grassland

A replicated, site comparison study in 1990–1997 in 106 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001, same experimental set-up as Swengel & Swengel 1997 and Swengel 1998) found that in some states, prairies managed by haying had the highest abundance and species richness of specialist and grassland butterflies, but in other states grazing supported a higher abundance and species richness of butterflies compared to other management types. In Missouri, the abundance and species richness of specialist and grassland butterflies was higher in prairies managed by two-year rotational haying than in rotationally burned areas. In Minnesota, North Dakota and western Iowa, the abundance of specialist and grassland species was higher in hayed areas than in burned areas, and the abundance and richness of specialist species was lower in rotationally grazed areas. However, in eastern Iowa, Illinois, and Wisconsin, the abundance of specialist and grassland species, and the richness of specialists, was higher at a continuously grazed site than in other management types. All data were presented as models results. Across all prairies, specialist and grassland butterfly abundance and richness tended to be higher at rotationally managed sites (haying, grazing or burning) longer after they were last managed. Of 106 prairies (1.2–2,024 ha), 27 contained areas managed by haying, mostly on a two-year rotation, seven were managed by rotational grazing (0.3–0.6 animals/ha/year) and one by continuous grazing (3–6 animals/ha/year), 77 areas were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown), and nine had been unmanaged for many years. From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Species were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).

(Summarised by: Andrew Bladon)
Cease grazing on grassland to allow early succession

A replicated, site comparison study in 1990–1997 in 106 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA (Swengel & Swengel 2001, same experimental set-up as 4 and 6) found that in some states, abandoned, unmanaged prairies had a lower abundance and species richness of specialist and grassland butterflies than prairies managed by grazing, but a higher abundance and species richness than prairies managed by burning. In Illinois, Wisconsin and eastern Iowa, the abundance and species richness of specialist and grassland butterflies was lower in unmanaged prairies than in grazed prairies, but higher than in rotationally burned prairies. However, there were no differences in western Iowa, Minnesota, North Dakota or Missouri. All data were presented as models results. Across all prairies, specialist and grassland butterfly abundance and richness tended to be higher at rotationally managed sites (grazed, hayed or burned) longer after they were last managed. Of 106 prairies (1.2–2,024 ha), nine contained areas which had been unmanaged for many years (abandoned), eight were managed by grazing, 27 were managed by haying (mostly on a two-year rotation), and 77 areas were managed by rotational burning (every 2–5 years) in the cool-season (of which 24 were also hayed or mown). From May–September 1990–1997, butterflies were surveyed on parallel transects (5–10 m apart) at each site. Most sites were surveyed more than once/year, and in >1 year. Species were classified as “specialists” (of native plants), “grassland” (occurring widely in open habitat) and “generalist” (occurring in a range of habitats).

(Summarised by: Andrew Bladon)