Patch‐burn management affects grassland butterfly communities in cattle‐grazed rangelands

Abstract

Abstract Grassland butterflies are undergoing worldwide population decline due to habitat loss and degradation. Rangelands in the Southern Great Plains can provide a habitat for grassland butterflies depending on management practices. Patch‐burn grazing is a management regime that involves burning portions of grazed pastures at different times. The combination of rotational fire and grazing creates a shifting mosaic of recently burned to older burned areas and lightly grazed to heavily grazed areas. However, the impact of fire and grazing on butterfly communities is complex and the effects of different management regimes on butterfly communities are not clear. We investigated the impact of time since prescribed fire and season of fire on butterfly communities in eight cattle‐grazed pastures, each with three burn units, in northern Oklahoma. Treatments included units burned in spring 2018, summer 2018, summer 2019, and spring 2020, with three replicates of each for a total of 12 burn units. Surveys were conducted three times per year in each burn unit in 2019 and 2020 using two standardised Pollard transects. A total of 909 butterflies and 35 species were observed. Species diversity varied by time since fire and season of fire, with spring‐burned sites having the lowest species diversity and summer‐burned sites having the highest. Dominant vegetation cover and blooming forb presence differed with time since fire and season of fire. Patch‐burn grazing creates a mosaic of successional vegetation stages which can benefit different butterfly species and support the overall community. Some species such as Cercyonis pegala, Danaus plexippus, and Atrytone arogos may benefit from fire every 1–2 years, while other species such as Echinargus isola may need longer times between fire treatments. Patch‐burn grazing regimes can support butterfly communities with species that need different fire return intervals by providing a mosaic of areas with different times since fire and associated grazing intensities.