Plant Succession

Ecologists speak of plant succession, meaning an orderly, progressive series of changes in the type of plant community, one community type gradually replacing another until a stabilized condition called climax vegetation is achieved. Each community in the series alters the environment, thereby creating conditions favoring the next type of growth. Animals play a significant part in this process.

Some take the position that succession occurs because some species are more efficient than others, the survival of the fittest. Whether a plant thrives or fails is more likely related to its micro environment than to its genetic fitness, however. A seed may grow successfully in a certain spot but fail should it fall one inch to the side of that spot.

Plants having widely dispersed seeds may be “opportunists” that can grow well on denuded (stripped barren) soil. When a section of land is denuded, the first plants to reappear are those considered to be the fittest of all: weeds, grasses, and other herbaceous plants. In the eastern part of the United States, poplar and sumac would likely follow; gooseberries would likely come next in the western part of the country. Although the fittest may come first, they will in time be crowded out by other plants able to germinate and begin growth in the environment produced by the weeds, grasses, poplars, and sumac. The final, stabilized vegetation, called the climax forest, is determined by environment, climate, and soil. Maple and basswood is one kind of climax forest; oak and hickory is another. The soils deposited by the ice of the last glacier that came from the northeast support an oak-hickory climax. The soils deposited by the ice of the last glacier that came from the northwest support a basswood-maple climax.

The northern peninsula of Michigan is covered with coniferous forest. If these trees were to be cut down or destroyed by fire, the same species would not grow again. Rather, poplar trees would likely come first and would eventually be followed by other hardwood, deciduous trees. The climax forest of northern Michigan is said to be neither pine, spruce, nor hemlock but, rather, maple, oak, or hickory. So why are coniferous trees growing there now? The argument is that they have held on from the time that they were the climax vegetation after the retreat of the last glacier; but that if some event were to take them away, they would not return.