Ecosystem Succession Paper

Ecosystem Succession Paper

A community of organisms does not evolve instantly, but instead progresses steadily by way of a succession of species. The method of gradual community development involving the species of one period being replaced by unlike species is called succession. A landscape can originally be occupied by specific organisms that will eventually be replaced by new organisms, and these new organisms will ultimately be replaced by even newer organisms.

On page 87 in the text Environment, figure 5-4 illustrates the primary succession on a glacial moraine. Primary succession is the gradual transformation of species' configurations in an environment that until that time was never occupied by organisms. In addition, no soil is present when primary succession starts. Primary succession can take hundreds or even thousands of years to transpire. On exposed and desolate rock, the primary succession's transition from a pioneer community to a forest community will frequently transpire in the following order: lichens to mosses to grasses to shrubs then to trees. (Berg & Raven, 2004)

Letter A of figure 5-4 illustrates the exposure of the bare rock remaining after the retreat of the glacier, no soil exists. Lichens first occupy the exposed and desolate rocks. Lichens may be the most significant organism in the pioneer community. The pioneer community is the original community that evolves during primary succession. "Abundant pioneer plant communities are Oxyrietum digynae and Androsacetum alpinae with the following species : Oxyria digyna, Geum reptans, Cardamine resedifolia, Ranunculus glacialis, Arabis alpina, Saxifraga oppositifolia, Cerastium uniflorum; Androsace alpina, Poa laxa, Gentiana bavarica, Leucanthemopsis alpina and Saxifraga bryoides" (Burga, Frauenfelder, Ruffet, Hoelzle, & Kaab, 2004). Lichens release acids that assist in breaking the bare rock apart; as a result, this starts the method of soil creation. Eventually, mosses and drought enduring ferns can take the place of the lichen community, which will then be followed by tough grasses and herbs. After a sufficient amount of soil accumulates, small shrubs can take the place of the tough grasses and herbs. Letter B of figure 5-4 illustrates the period after letter A. After lichens, mosses, droughts enduring ferns, tough grasses, herbs, and small shrubs have established a sufficient soil base, small trees and larger shrubs can begin to inhabit the same community. Letter C of figure 5-4 illustrates the period after letter B. After small trees and larger shrubs have had a sufficient amount of time to be established, large trees will start to dominate, and eventually completely dominate, the same community. (Berg & Raven, 2004)

On page 88 in the text Environment, figure 5-5 illustrates secondary succession on an abandoned field in North Carolina. Secondary succession is the transformation of species' configurations that transpires after some kind of disruption has demolished the existing vegetation. In addition, soil is already present when secondary succession starts. Secondary succession can take more than 100 years to transpire in a specific area. On abandoned farmland in the southeastern United States, secondary succession will frequently transpire in the following order: crabgrass to horseweed to broomsedge and other weeds to pine trees then to hardwood trees. (Berg & Raven, 2004)

Figure 5-5 illustrates how abandoned farmland in North Carolina is occupied by an inevitable succession of communities. After cultivation of the field ends, during the first year the abandoned field is dominated by crabgrass. During years, two through four, annual and perennial weeds such as horseweed, broomsedge, ragweed, and aster dominate the abandoned field. Horseweed is the dominant plant on the abandoned field during the second year after cultivation of the field ends. However, horseweed will not dominate for more than one year. Weeds such as broomsedge, ragweed, and aster will become the dominant plants on the abandoned field during the third and fourth year after cultivation of the field ends. During years five through 15, pine seedlings and saplings such as shortleaf pines and loblolly pines will dominate the abandoned field. "One example of divergence in species composition occurs in old-field succession, the woody plants that replace the meadow species can vary from thickets of mostly shrubs to thickets of mostly trees" (Gardescu & Marks, 2004). The pine trees create soil litter, such as pine needles and branches, which generate circumstances that cause the previously dominant plants to diminish in significance and quantity. During years 25 through 50, a young pine forests and a developing community of hardwoods will dominate the abandoned field. Eventually, the pines trees will no longer be the dominant plant on the abandoned field. Instead, hardwoods such as oak trees and hickory trees will become the dominant plants on the abandoned field. The transformation from pine trees to oak and hickory trees depends