From observations of the plant communities that existed in these sites, Billings was able to construct a detailed successional sequence. The annuals were then quickly replaced in dominance in the next year by biennial plants and grasses . After about 3 to 4 years, the biennial and grass species gave way to perennial herbs and shrubs . These plants live for many years and have the ability to reproduce several times over their lifespans. Succession of plant species on abandoned fields in North Carolina.
Pioneer species consist of a variety of annual plants.
This successional stage is then followed by communities of perennials and grasses, shrubs, softwood trees and shrubs, and finally hardwood trees and shrubs. This succession takes about 120 years to go from the pioneer stage to the climax community. As the softwoods increased in their numbers and grew in height, they began forming a forest canopy. This canopy reduces the amount of light reaching the forest floor. The resulting shaded understory conditions caused the exclusion of many light loving perennial herb and shrub species.