- Introduction
Learn- Task
Learn
As any population increases in size, the same resources must be shared by a greater and greater number of individuals. The decreasing supply of resources may lower the population's birth rate, increases its death rate, or both until birth and deaths are in balance. At that point of balance, and as long as the resource supply remains constant, the population should stabilize at some equilibrium size. Ecologists call this balance point of a population's equilibrium the carrying capacity of the environmental system inhabited by that particular species.
Ecologists use the term carrying capacity to define the maximum population of a particular species that a given area of habitat can support over a given period of time. The ecological principles that govern a habitat's carrying capacity are the same for all species. A sustainable supply of resources - including nutrients, energy, and living space - defines the carrying capacity for a particular population in a particular environmental system.
Acorns, produced by oak trees, are a favorite food for deer, squirrels, jays, quail, crows, woodpeckers, raccoons, rabbits, and foxes. In areas with mild winters, acorns may be available for eight months of the year and constitute about 75% of the diet of deer. Acorns are higher in fat and easily-digested carbohydrates than other food sources, such as leaves, twigs, small green plants, and fungi.
In areas with hard winters, reproductive success of deer decreases with greater snow cover, when acorns may be harder to find. In cases when acorns are less available, deer have reduced birth weights and lower survival of fawns. In areas with mild winters, such as the Southeastern United States, deer appear to be better able to survive years of low acorn production by shifting to other foods.
In the task section of this lesson, you will create a model of an oak forest and estimate the number of deer that can be supported by the forest. This lab is modeled after a forest in Virginia which covers 19,535 acres (metric equivalent = 7906 hectares).
 |
 |