Paper addresses breeding bird response to intercropping switchgrass in young loblolly pine plantations

One of several potential approaches for producing bioenergy feedstocks is intercropping herbaceous vegetation such as warm season grasses in young, managed forest stands during early rotation. Results were recently published from a study investigating breeding bird community response to intercropping of switchgrass (Panicum virgatum) in young loblolly pine plantations in Mississippi. The paper was written by Zachary G. Loman, Samuel K. Riffell, Bradley R. Wheat, and James A. Martin of Mississippi State University, Darren A. Miller of Weyerhaeuser NR Company, and Francisco J. Vilella of the U.S. Geological Survey. The abstract follows.

Intercropping switchgrass (Panicum virgatum L.) between tree rows within young pine (Pinus spp.) plantations is a potential method to generate lignocellulosic biofuel feedstocks within intensively managed forests. Intensively managed pine supports a diverse avian assemblage potentially affected by establishment and maintenance of an annual biomass feedstock via changes in plant communities, dead wood resources, and habitat structure. We sought to understand how establishing switchgrass on an operational scale affects bird communities within intercropped plantations as compared to typical intensively managed loblolly pine (Pinus taeda L.) forest. We conducted breeding bird point counts using distance sampling for three years (2011 ̶ 2013) following establishment of intercropped switchgrass stands (6 replicates), traditionally-managed pine plantations, and switchgrass-only plots (0.1 km2 minimum) in Kemper Co., MS. We detected 59 breeding bird species from 11,195 detections. Neotropical migrants and forest-edge associated species were less abundant in intercropped plots than controls the first two years after establishment and more abundant in year three. Short distance migrants and residents were scarce in intercropped and control plots initially, and did not differ between these two treatments in any year. Species associated with pine-grass habitat structure were less abundant initially in intercropped plots, but converged with pine controls in subsequent years. Switchgrass monocultures provided minimal resources for birds. If songbird conservation is a management priority, managers should consider potential reductions of some breeding birds for one to two years following intercropping. It is unclear how these relationships may change outside the breeding season and as stands age.  

Reference  

Loman, Z.G., S.K. Riffell, B.R. Wheat, D.A. Miller, J.A. Martin, and F.J. Vilella. 2014. Breeding bird community response to establishing intercropped switchgrass in intensively-managed pine stands. Biomass and Bioenergy 67:201 ̶ 211. http://dx.doi.org/10.1016/j.biombioe.2014.05.001