What is Ecological Succession?
"Ecological succession" is the observed process of change in the species structure of an ecological community over time. Within any community some species may become less abundant over some time interval, or they may even vanish from the ecosystem altogether. Similarly, over some time interval, other
species within the community may become more abundant, or new species may even invade into the community from adjacent ecosystems. This observed change over time in what is living in a particular ecosystem is "ecological succession".
Why does "Ecological Succession" occur?
Every species has a set of environmental conditions under which it will grow and reproduce most optimally. In a given ecosystem, and under that ecosystem's set of environmental conditions, those species that can grow the most efficiently and produce the most viable offspring will become the most abundant organisms. As long as the ecosystem's set of environmental conditions remains constant, those species optimally adapted to those conditions will flourish. The "engine" of succession, the cause of ecosystem change, is the impact of established species have upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment. The original environment may have been optimal for the first species of plant or animal, but the newly altered environment is often optimal for some other species of plant or animal. Under the changed conditions of the environment, the previously dominant species may fail and another species may become ascendant.
Ecological succession may also occur when the conditions of an environment suddenly and drastically change. A forest fires, wind storms, and human activities like agriculture all greatly alter the conditions of an environment. These massive forces may also destroy species and thus alter the dynamics of the ecological community triggering a scramble for dominance among the species still present.
Ecological succession may also occur when the conditions of an environment suddenly and drastically change. A forest fires, wind storms, and human activities like agriculture all greatly alter the conditions of an environment. These massive forces may also destroy species and thus alter the dynamics of the ecological community triggering a scramble for dominance among the species still present.
How are humans affected by Ecological Succession?
Ecological succession is a force of nature. Ecosystems, because of the internal species dynamics and external forces mentioned above, are in a constant process of change and re-structuring. To appreciate how ecological succession affects humans and also to begin to appreciate the incredible time and monetary cost of ecological succession, one only has to visualize a freshly tilled garden plot. Clearing the land for the garden and preparing the soil for planting represents a major external event that radically re-structures and disrupts a previously stabilized ecosystem. The disturbed ecosystem will immediately begin a process of ecological succession. Plant species adapted to the sunny conditions and the broken soil will rapidly invade the site and will become quickly and densely established. These invading plants are what we call "weeds". Now "weeds" have very important ecological roles and functions (see, for example, the "Winter Birds" discussion), but weeds also compete with the garden plants for nutrients, water and physical space. If left unattended, a garden will quickly become a weed patch in which the weakly competitive garden plants are choked out and destroyed by the robustly productive weeds. A gardener's only course of action is to spend a great deal of time and energy weeding the garden. This energy input is directly proportional to the "energy" inherent in the force of ecological succession. If you extrapolate this very small scale scenario to all of the agricultural fields and systems on Earth and visualize all of the activities of all of the farmers and gardeners who are growing our foods, you begin to get an idea of the immense cost in terms of time, fuel, herbicides and pesticides that humans pay every growing season because of the force of ecological succession.
Does Ecological Succession ever stop?
There is a concept in ecological succession called the "climax" community. The climax community represents a stable end product of the successional sequence. In the climate and landscape region of the Nature Trail, this climax community is the "Oak-Poplar Forest" subdivision of the Deciduous Forest Biome. An established Oak-Poplar Forest will maintain itself for a very long period of time. Its apparent species structure and composition will not appreciably change over observable time. To this degree, we could say that ecological succession has "stopped". We must recognize, however, that any ecosystem, no matter how inherently stable and persistent, could be subject to massive external disruptive forces (like fires and storms) that could re-set and re-trigger the successional process. As long as these random and potentially
catastrophic events are possible, it is not absolutely accurate to say that succession has stopped. Also, over long periods of time ("geological time") the climate conditions and other fundamental aspects of an ecosystem change. These geological time scale changes are not observable in our "ecological" time, but their fundamental existence and historical reality cannot be disputed. No ecosystem, then, has existed or will exist unchanged or unchanging over a geological time scale.
catastrophic events are possible, it is not absolutely accurate to say that succession has stopped. Also, over long periods of time ("geological time") the climate conditions and other fundamental aspects of an ecosystem change. These geological time scale changes are not observable in our "ecological" time, but their fundamental existence and historical reality cannot be disputed. No ecosystem, then, has existed or will exist unchanged or unchanging over a geological time scale.
Types of Ecological Succession
Primary succession is the series of community changes which occur on an entirely new habitat which has never been colonized before. For example, a newly quarried rock face or sand dunes.
Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. For example, after felling trees in a woodland, land clearance or a fire.
Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. For example, after felling trees in a woodland, land clearance or a fire.