Impacting Plant Succession

Plant succession normally occurs when plant communities are left alone to develop and may take hundreds of years to go from an early stage, like an abandoned farm field, to a climax forest community. However, in the real world, many of these plant communities are not left alone, and they may be influenced by a number of external factors. Often the changes that are made, either intentionally or unintentionally, suppress or “set back” plant succession.

If we stop mowing the lawn, a young meadow will develop that has several annual and biannual plants. Let’s assume, however, that we finally return from our 12-week trip, and resume mowing the lawn. If this is the case, the turf grass will persist, because plant succession was set back by mowing. Sometimes, however, it is desirable to retain an open field for wildlife or to maintain a wildflower meadow. If this is the case, then the meadow might be mowed once per season to prevent woody vegetation from becoming established.” Americans used fire to burn off meadows to retain this type of habitat; today, wildlife managers sometimes employ prescribed burns to perpetuate prairie grass communities. Foresters manipulate woodlands to make successional changes. In the south, a forester may prescribe an understory burn in a slash pine stand to help maintain this “fire dependent” timber type and reduce the fire hazard by preventing the very flammable palmetto from being established in the understory. In our region, it is sometimes desirable to perpetuate an oak-hickory forest for the inherent timber value, and to provide hard mast (acorns, nuts) for wildlife. This can be accomplished by creating openings during a logging operation that allow abundant sunlight to reach the forest floor. Increasing the amount of sunlight will promote development of young oak “advanced regeneration” now that the young oaks have a canopy opening to exploit. Sometimes management activities may speed up plant succession; an example of this might be the planting of oak, pine, maple, and beech trees in an abandoned farm field. Planting this combination of trees this will create an oak – hickory forest that might otherwise take 50 – 100 years to develop by natural means.

Besides human intervention, the process of succession can be influenced by living and nonliving forces. The spread of invasive plants can alter successional changes and adversely impact the community. Several non-native plants have been brought into the United States over the years, many of which have spread throughout our natural areas. These invasive plants can impact our natural communities by displacing the native plants and sometimes creating self sustaining communities that are difficult to eradicate. As an example: suppose a Homeowners Association decides to dedicate a large open area for wildlife and aesthetics, and a wildflower meadow is established throughout a vacant field. Unbeknownst to them, the field has a lot of autumn olive seed, and the native grasses and wildflowers are overrun with the very aggressive olive plant soon after planting occurs. This autumn olive community could persist for many years unless this invasive is controlled. A large deer herd can impact the development of a community. Sometimes large populations of deer can devour most native understory plants, leaving non-natives like barberry and stilt grass to populate the understory. Suppose deer strip the native plants in a young forest community, and all that is left is invasive plants in the understory. If this persists, then once the pioneer plants in the overstory begin succumbing to old age, what remains are the invasive lurking in the understory. Wildfires can also impact forest communities. A very destructive wildfire can destroy a western pine stand, leaving nothing but charred earth behind. This kind of disturbance will set back succession to its bare field beginnings. As stated earlier, fire can sometimes be used as a management tool to perpetuate fire dependent plant communities. In the Great Lake states, fire is used to consume mixed Jack Pine hardwood stands, resulting in charred earth. The serotinous pinecones, however, do not normally burn, and the high temperatures promote the opening of these cones and seed, resulting in the reestablishment of a solid Jack pine forest. Wildlife managers use fire to reinvigorate this fire dependent pine stands to preserve habitat for the rare Kirtland’s warbler, a bird that is highly dependent on Jack pine stands for its survival. The short-lived Jack pine will eventually change to a mixed hardwood forest unless succession is once again set back by fire.

Article by FCFCDB

Nature note for 12/11/2021