Bird conservation potential of fire and herbicide treatments in thinned pine stands

Abstract

Abstract Fire-maintained pine (Pinus spp.) forests, characterized by a diverse herbaceous layer, sparse midstory layer, and a dominant pine overstory, once covered approximately 30 million ha in the southeastern United States. Fire suppression, landscape changes, and land management changes have contributed to reduced suitability of many pine stands for fire-dependent species, including many avian species in regional decline. However, intensively managed loblolly pine (P. taeda) stands treated with prescribed fire and herbicide could help restore or maintain fire-dependent communities within working landscapes. Therefore, we investigated avian responses to combinations of prescribed fire and herbicide (imazapyr) treatments within a matrix of intensively managed pine stands in east-central Mississippi, USA. We used a randomized complete block design of 6 mid-rotation, thinned pine stands (blocks) each with 4 treatments (control, burn only, herbicide only, burn + herbicide) assigned to 10-ha experimental units. We applied imazapyr herbicide (Arsenal®) during fall 1999 and burned units during winter every 3 years, beginning in 2000. We conducted avian point counts from year pre-treatment (1999) through 9 years post-treatment (2000–2008) and summarized annual vegetation structure and composition. We used 34 of 64 observed avian species for analyses using mixed models, repeated measures ANCOVA. Across the 9-year post-treatment study period, fire and imazapyr differentially affected avian communities with our combination treatment (fire + imazapyr) favoring high-priority, open pine bird species most. However, remaining treatments (burn only, imazapyr only, controls) provided additional vegetation gradients for species preferring greater structure diversity or canopy coverage. Our results indicated that fire and herbicide treatments can maintain vegetation structure attractive to a bird community of high-conservation value, while concurrently meeting economic and sustainable forestry goals. Although primarily managed for economic gain, intensively managed forests can provide suitable habitat conditions for avian species of conservation concern helping land managers meet biodiversity objectives.