Individual study: Burning and grazing management of prairie grassland effects different butterfly species in varying ways, Broken Kettle Grasslands Preserve and Five Ridge Prairie, Iowa, USA
Vogel J.A., Debinski D.M., Koford R.R. & Miller J.R. (2007) Butterfly responses to prairie restoration through fire and grazing. Biological Conservation, 140, 78-90
The effects of three restoration practices (grazing only, burning only, and burning and grazing) on butterfly communities and vegetation characteristics of remnant prairies in Plmouth County, Iowa (northern USA) was assessed.
Study areas: A total of 69 survey sites were located on prairies at Broken Kettle Grasslands Preserve, Five Ridge Prairie and adjacent land.
Management: The areas were divided into 29 management units (from 10 to over 100 ha; average 40 ha) according to restoration practice (burned only, grazed only, or burned and grazed). Burned units (n = 10) were managed with prescribed fires during the autumn or spring in 2–6 year rotations. Grazed units received low intensity rotational cattle grazing (stocking rate c.1 cow–calf pair/ 4 ha).
Butterfly and vegetation surveys: At each site, two butterfly surveys were conducted each year between 1 June and 15 August in 2004 and 2005. Vegetation was also surveyed twice each year, in June and July.
Nearly 4,000 individuals of 51 butterfly species (28 habitat-generalists, 16 habitat-specialists and 7 woodland species) were observed during the 2004 and 2005 surveys.
Average butterfly abundances were highest in units managed by burning and grazing (31.5), grazed only (27.8), and burned only (20.2). However, average butterfly species richness and diversity was highest on the burned only units (8.6; 2.3); on burned and grazed units (8.5; 2.0) and lowest on grazed only units (7.4; 1.9).
Importantly, responses of individual species to management were highly variable. Predictive modelling suggested total butterfly abundance was negatively associated with the cover of bare ground whilst positively associated with forb cover. Butterfly communities in each of the three restoration practices were equally species rich but different practices resulted in compositionally different butterfly communities.
Conclusions: Butterfly species richness did not differ among the three restoration practices. Butterfly diversity was highest in the burned only units but was similar between the grazed only, and burned and grazed, units. The authors conclude that, due to the variation in butterfly species responses to different restoration practices, there is no single practice that will benefit all species, or all species within habitat-specialist or habitat-generalist habitat guilds.
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