Physiognomy and Structure: Stands are open to closed, and range from pure conifer to pure hardwood.

Floristics: These semi-natural forests are dominated by naturalized Acer platanoides, Ailanthus altissima, Paulownia tomentosa, Pinus nigra, or Pinus thunbergii. These are all exotic tree species that have locally established in the region. Pinus thunbergii stands occur in the northeastern coastal region and likely beyond. Stands are of variable canopy height and closure and dominated by Pinus thunbergii or Pinus nigra. A frequent canopy associate can be Pinus rigida. The shrub layer is not well-developed, and the herbaceous layer is of variable composition. Toxicodendron radicans is common in all strata of this community (Sneddon and Lundgren 2001). Ailanthus altissima is a native of eastern Asia. This forest occurs mostly in disturbed areas, along roadsides, urban abandoned lands, and on limestone clifftops. In some parts of the range, this forest is associated with calcareous soils. Acer platanoides stands often occur to the exclusion of virtually all other canopy species. Most documented stands are at low elevations, on flat or rolling topography both above and below the glacial boundary. Acer platanoides is the overwhelmingly dominant tree, typically forming a closed or nearly closed canopy. In some stands native trees, including Fraxinus americana and Acer saccharum (the latter especially susceptible to exclusion by Acer platanoides), may be present in very limited amounts. Other stands may have non-native associates, including Pinus nigra, Pinus sylvestris, or Robinia pseudoacacia. The deep shade cast by Acer platanoides limits understory growth, aside from regeneration of Acer platanoides, or incursions by non-native shrubs such as Rosa multiflora, Berberis vulgaris, Lonicera japonica, or Lonicera morrowii. Native herbs are few, especially compared to more natural deciduous forests in similar settings. A few native or exotic herbaceous species or vines may occupy the ground layer, such as Alliaria petiolata, Eurybia divaricata (= Aster divaricatus), Toxicodendron radicans, and Vinca minor (Patterson 1976). Paulownia tomentosa forests are found on disturbed, usually steep and rocky areas. This species is native to eastern Asia, where it is a minor component of deciduous mesophytic forests. It has become naturalized in portions of the eastern United States, where it occurs as small, scattered populations along roadsides, in disturbed woodlots, and in streamside forests (Williams 1993).

Dynamics:  The long-term persistence of these stands is not clear. They are not likely to become strongly invasive, since they require large-scale, substrate-scarifying disturbance for optimal establishment and maintenance (Patterson 1976, Williams 1993, Sneddon and Lundgren 2001).