Communities go through a process of development from youth to maturity similar to that seen in individual organisms. This developmental process is called ecological succession. If a community develops on a newly formed site, this is called primary succession. If a community develops on a site that previously had a community on it, but which was disturbed or disrupted in some fashion, it is termed secondary succession. Some species (pioneer species) do very well during the early stages of succession but tend to be replaced by other species as the community matures. These species tend to be ecological generalists and do not hold-up well in the face of competition from more specialized species.

Eventually a community matures to the point that it is largely composed of only those species that are best adapted to survive under the prevailing environmental conditions. At this point the community is stable and tends to undergo little further change. Such a community is called the climax community. In much of the eastern United States, hardwood deciduous forest is the climax community. If you cut this forest and then leave it alone, it will go through a secondary successional sequence leading back to the Climax State. As the new community in the ecological succession progresses, we begin to see new organisms emerge.

In a temperate deciduous forest, rocks and lichen give way to mosses, grasses, shrubs, confers, and deciduous woodland. These plant species begin to dominate this new community. They dominate in the sense that they are the most abundant source of food. This becomes useful when animal succession begins. Temperate forests support an abundance of animal life. Smaller mammals, such as chipmunks, voles, squirrels, raccoons, opossums, and white-footed mice, live mainly on nuts and other fruits-mushrooms and insects.

The wolves, bobcats, gray foxes, and mountain lions, in the areas where they have not been driven out by the encroachment of civilization, feed on these smaller mammals. Deer live mainly on the forest borders, where they browse on shrubs and seedlings. In terms of biomass, or total mass, the producers (grass, trees, shrubs... ) have more biomass than that of the consumers (fox, bear... ) which contain less. The Temperate Deciduous Forest has 32 kilograms of biomass per meter..