Avian Use of Perennial Biomass Feedstocks as Post-Breeding and Migratory Stopover Habitat

Increased production of biomass crops in North America will require new agricultural land, intensify the cultivation of land already under production and introduce new types of biomass crops. Assessing the potential biodiversity impacts of novel agricultural systems is fundamental to the maintenance of biodiversity in agricultural landscapes, yet the consequences of expanded biomass production remain unclear. We evaluate the ability of two candidate second generation biomass feedstocks (switchgrass, Panicum virgatum, and mixed-grass prairie) not currently managed as crops to act as post-breeding and fall migratory stopover habitat for birds. In total, we detected 41 bird species, including grassland specialists and species of state and national conservation concern (e.g. Henslow's Sparrow, Ammodramus henslowii). Avian species richness was generally comparable in switchgrass and prairie and increased with patch size in both patch types. Grassland specialists were less abundant and less likely to occur in patches within highly forested landscapes and were more common and likely to occur in larger patches, indicating that this group is also area-sensitive outside of the breeding season. Variation in the biomass and richness of arthropod food within patches was generally unrelated to richness and abundance metrics. Total bird abundance and that of grassland specialists was higher in patches with greater vegetation structural heterogeneity. Collectively, we find that perennial biomass feedstocks have potential to provide post-breeding and migratory stopover habitat for birds, but that the placement and management of crops will be critical factors in determining their suitability for species of conservation concern. Industrialization of cellulosic bioenergy production that results in reduced crop structural heterogeneity is likely to dramatically reduce the suitability of perennial biomass crops for birds

Effects of Ants and An Ant‐Tended Herbivore on Seed Production Of a Neotropical Herb

This study examined a complex interaction among species, focused on (1) a neotropical perennial plant, Calathea ovandensis (Marantaceae), that produces extrafloral nectar, (2) ants that visit the nectaries, (3) an ant—tended specialist herbivore, Eurybia elvina (Lepidoptera: Riodiniadae), that feeds on buds, flowers, and fruits, and (4) other herbivores of reproductive tissues. We experimentally investigated: (1) to what extent seed production was influenced by ants and herbivores, and (2) whether spatial variation in seed production was influenced by spatial variation in the ant community. The lowest seed production (x = 6) was for inflorescences with Eurybia but without ants. Highest seed production (x = 21) was for inflorescences with ants, but without Eurybia. In the presence of ants, Eurybia lowered mean seed production by 33%. In the absence of ants, Eurybia lowered mean seed production by 66%. The eight ant species differed greatly in the magnitude of their beneficial effects on seed production. Ants were not equally distributed over sites, and spatial hetrogeneity in seed production by Calathea reflected differences in ant communities among sites. We concluded that variation and interdependence of various components of plant—animal interactions are likely to result in variation in the magnitude of their beneficial or detrimental impact on plants. Such variation should be incorporated into plant demograpic models as spatially varying alternate life history paths to yield insight into the evolutionary impact of plant—animal interactions