Physiognomy and Structure: This group includes spontaneously formed exotic tree-dominated stands, with irregular structure, or abandoned forest plantations, which may still show some evidence of row planting. Dominant trees may be hardwood or conifer.

Floristics: The tree layer is dominated (>80% cover) by exotic tree species. The list of exotic tree species include Conifers: Pinus thunbergii and Hardwoods: Acer platanoides, Ailanthus altissima, Malus fusca, and Robinia pseudoacacia. Although Robinia pseudoacacia is a native in the central hardwoods region, it is so widely planted outside of its range that it is exotic in character. Understory shrub and herb species vary from exotic invasives to native generalists. Invasive shrub species include a variety of honeysuckles (Lonicera japonica, Lonicera morrowii, Lonicera tatarica, Lonicera x bella), Rhamnus cathartica, and others. Sites show evidence of former and heavy human use, particularly with extensive and intensive soil disturbances, including plowing, grading, skidding, etc. The most common exotic tree species found in abandoned plantations include Larix decidua, Picea abies, and Pinus sylvestris. They may be mixed with native tree species, including Picea glauca, Pinus banksiana, Pinus resinosa, Pinus strobus, and Pinus virginiana, particularly when these stands form from abandoned plantations.

Dynamics:  Stands most typically represent the tree-dominated stage in the development of vegetation on sites that were heavily disturbed by humans, including plowing, grading, skidding, etc. In these cases, earlier stages of vegetation include annual and perennial weeds, grasslands and shrublands [see ~Eastern North American Ruderal Meadow & Shrubland Group (G059)$$]. Because the extensive soil disturbances typically lead to a mix of weedy native and exotic shrub and herb species, the stands take on a ruderal composition. Exotic tree species may initiate establishment before natives or outcompete natives. Canopy cover may be as low as 10%, but eventually stands may have more-or-less continuous canopy, leading to a shift to a more shade-tolerant ground layer. The successional stages of this type have been described in many studies, particularly the early stages of tree invasion into old fields (e.g., Singleton et al. 2001). See also Wright and Fridley (2010) for the biogeographic variation among stands of this type.

This type may also form in other ways. First, exotic forest plantation stands (tracked in 7. ~Agricultural & Developed Vegetation Cultural Class (CCL01)$$)) could become exotic ruderal stands if not intensively managed and the planted trees begin to die out. But because exotic planted trees only rarely regenerate on sites where they are planted, these stands more typically are invaded by native generalist trees and succeed to ~Eastern North American Native Ruderal Forest Group (G030)$$. Second, native forest stands that have not been plowed or planted may be stressed to the point where the characteristic native combination of species is altered (Curtis 1959). These stands are probably best tracked as altered variants of native types until the overstory itself is substantially altered to the point where exotics tree species are the dominant.