LESSON 2: FOREST DYNAMICS

Like any population of living things, a forest is always changing. In a forest, however, the change is so slow that most people don't even recognize it. Sometimes this leads to the erroneous belief that a forest is a static entity, one that needs only protection to make it last forever.

The living, changing nature of forests makes them unique among our natural resources they are renewable. They can be harvested, replenished, and harvested again forever. We don't have to preserve forests; we must conserve and manage them so the flow of environmental and material benefits from the forest will never be interrupted. Understanding and applying how forests live, grow, and change are the keys to managing this resource.

Discuss the differences between conservation (wise use) and preservation (keeping safe). Many people tend to use the words interchangeably.
Ask if all forests should be managed. Are there situations where it would be advisable to leave some forestland untouched and let nature take its course? What would happen if all of South Carolina's forests were handled this way?

The dynamics of change in a forest are a part of the natural order which may be modified but not arrested. All forests are inexorably moving toward a predetermined forest type. This is called the climax, and it is reached by a predictable series of steps called plant succession. In the Southeast, the climax forest type is one consisting primarily of oaks and hickories.

Plant succession can be observed in old fields which have been abandoned. During the first year the site will be dominated by grasses and some annual weeds. The second year sees the addition of perennial weeds and marks the advent of pine seedlings on the site. Hardwood sprouts also begin to appear during the second and third years, but the pines will assume dominance because they grow faster. Over a period of 12-20 years, many of the grasses and weeds will die out because of the shade produced by the pines. Most hardwoods are described as being shade tolerant and will survive as shrubs or small trees beneath the pine canopy.

The life span of southern pines is generally less than 200 years; most individuals within a population will die before they reach that age. As the pines succumb to natural causes, light is allowed to reach the forest floor. This stimulates the growth of the hardwoods which have survived, and they respond by growing to fill the places once occupied by the pines. Since pines are intolerant (cannot survive in shade), there are few young pines to compete with the hardwoods, and a predominantly hardwood forest, mostly oaks and hickories, is the result. 

Locate a nearby vacant lot, abandoned field, or unused garden spot. Help the students decide what stage of plant succession is evident. Then discuss how you might be able to modify the succession process. What would happen if you burned the area with a hot fire? What would be the effect if all of one species was killed with herbicide? How would an epidemic of disease or insects which preyed on one species change the succession process?


Reference Resources / Education

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