A. The Principal Focus.
Mature, southeastern, hardwood forest is primarily structured by the older trees; these contribute most of the biomass to the more-or-less continuous canopy (Level D). The understory is comprised of the near vertical trunks and stems of the taller trees as well as younger trees and smaller tree species adapted to lower light levels (Level C). Below this is the shrub layer that includes small tree saplings as well as shrubs (Level B). Level A comprises the herbs of the forest floor but includes ferns, and the vital tree seedlings that are the forest of the future (see Kricher & Morrison, 1988, for a simple introduction to southeastern forest).
Invasive vines climb into the trees of the understory and canopy. They compete with the trees for soil nutrients and water, cause mechanical damage, contribute to a higher risk of disease, and a higher risk of being knocked down by the wind (‘wind-blow’).