Shrublands are an important intermediary successional community. Shrubs, as the name suggests, dominate the canopy while small trees, snags, grasses, and herbaceous vegetation also contribute to the dynamic structural composition. Historically, shrublands were transitional habitats, succeeding to woodlands, or became shrubby prairies as a result of frequent drought-induced fire. Shrubland communities are a shifting mosaic across the landscape, and their structural uniqueness is important for many types of wildlife, especially birds.
Many small parcels of shrubland exist at Fermilab, mostly adjacent to woodlands and savannas but also in wetlands. Soil moisture determines the dominant shrubs present. Dry-mesic shrublands can be composed of grey dogwood (Cornus racemosa), hazelnut (Corylus americana), and American plum (Prunus americana), while blue-fruited dogwood (Cornus obliqua), meadowsweet (Spirea alba), and sandbar willow (Salix interior) might dominate in wet-mesic shrublands. The sparrow hedge area is classified as mostly unassociated woody growth. These areas support a variety of weedy native and non-native trees and shrubs, such as box elder (Acer negundo), grey dogwood (Cornus racemosa), common buckthorn (Rhamnus cathartica), autumn olive (Elaeagnus umbellata), and American plum (Prunus americana). While plant composition is not desirable, the structural heterogeneity is excellent for nesting and migrating shrubland birds such as Bell’s vireo (Vireo bellii) and yellow-breasted chat (Icteria virens). Prescribed fires are carried out every 3-5 years to maintain this successional community.