Plant Succession

“Succession” describes the changes a community of plants undergoes over time. In most cases, plant communities change from a short lived, transitory grouping to a more permanent collection of plants. This may take a few short years, or it could take decades, depending on a number of variables.

To visualize this, think about a large, grassy lawn. Regular mowing and some weeding are necessary to maintain this grass community. Let’s say, however, that you discontinued mowing this site. The grasses will continue to grow, then “weeds” like pigweed, smart weed, sorrel, clover, goldenrod, honeysuckle, and poison ivy will begin to grow amongst the grasses. If the area in this example is not mowed for a season or two, the plant community will change from a lawn to a field or meadow, which is a different ecological community. Suppose that this meadow is allowed to continue to develop: in time, longer-lived, herbaceous and woody perennial plants, such as mullein, Queen Anne’s lace, ragweed, pokeweed, brambles, eastern red cedar, dogwood, sumac, hawthorns, locust, and cherry will begin to invade the area. These more advanced meadows are often called “old fields.” As the young trees and shrubs are allowed to grow, the old field becomes an old field in the shrub-sapling stage. This means that the meadow now has scattered trees and shrubs growing in it. After more time, the trees and shrubs grow larger, and more woody vegetation invades the field, the canopies beginning to close together. Once “canopy closure” begins, the grasses and field vegetation are covered in the shade of the canopy and begin to die out.

These young forest communities normally have relatively open understories, because much of the open-field vegetation can not survive in the shade. A young forest is normally composed of those “pioneer” species that have seed that can be spread over long distances by the wind: e.g. maple, pines, tulip poplar, aspen, and ash, or they have seed that is spread by birds like crabapple, cedar, cherry, dogwood, and persimmon. These pioneers typically exhibit rapid growth, need a lot of sunlight, and are relatively short lived, as far as trees go. As these young forests develop, vegetation that can develop and grow in shady areas becomes established in the understory of the forest. Once this occurs, typical forest understory vegetation such as mountain laurel, spicebush, witch hazel, iron wood, serviceberry, and black haw becomes established. Along with native shrubs and herbaceous material, many trees will also become established in the understory of a young forest. Much of these “shade tolerant” trees are well adapted to living in reduced sunlight, or they can germinate and hang around until a break in the overstory occurs that they can exploit. These older growth varieties have heavier seed that is the form of a nut or acorn, which need to be dispersed by animals such as squirrels or chipmunks. These tiny tree planters will gather up nuts and bury them for later consumption. Fortunately, they do not have a good memory, so they sow the seeds for many future nut-producing trees.

Article by FCFCDB

Nature note for 12/4/21