Introduction

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The Eastern Deciduous Forest occupies the eastern half of the United States and southeastern Canada. The northern boundary of the Eastern Deciduous Forest blends gradually into the Northern Boreal Forest (Taiga) in New England and southern Canada and there is never a point where one can say "This is where the Northern Boreal Forest becomes the Eastern Deciduous Forest." The western boundary is equally nebulous. A rough line of demarcation between the Eastern Deciduous Forest and the Prairie Biome is the Mississippi River. However this boundary really is ill-defined. Along the western margins of the Eastern Deciduous Forest patches of Forest and Prairie intermingle depending on purely local conditions. In fact small pieces of Prairie reach as far east as Pennsylvania and Maryland. The southern boundary of the Eastern Deciduous Forest lies in central Florida. Southern Florida is given over to a Subtropical Region.

The Eastern Deciduous Forest is defined by the dominance of deciduous trees in the ecosystem. Deciduous trees are almost all angiosperms such as oaks, maples, beech, hickories, and birches that drop their leaves. Evergreen conifers do live in the Eastern Deciduous Forest, but are rarely as common or dominant as the deciduous trees except under particular types of local conditions.

The Eastern Deciduous Forest develops under a particular set of climatic conditions. Winters are cold, but relatively mild compared to the winters further north in the regions of the Northern Boreal Forest and the Tundra. The summer is similarly longer than further north and temperatures are higher. Possibly the most important climatic feature of the Eastern Deciduous Forest is precipitation, both rain and snow. Total precipitation throughout the year is higher in the Eastern Deciduous Forest than anywhere else in North America except for the tropical and subtropical areas to the south and the isolated spots of Temperate Rain Forest found along the Pacific Coast. Almost as important is the relative constancy of precipitation throughout the year.

Examine the graph of temperature and precipitation for a typical year in Fort Wayne, Indiana. Temperature throughout the year is shown by the red line and the scale on the left. Precipitation is represented by a blue line and the scale on the right. Note the relatively high precipitation throughout the year and its constancy throughout the year. In comparison the Prairie Biome to the west has lower total annual precipitation and the winter is considerably drier than the summer. The Northern Boreal Forest to the north has both colder winters and less annual precipitation than the Eastern Deciduous Forest.

Although the Eastern Deciduous Forest is defined as a single biome, it is anything but homogeneous. There are suprising changes in the species at different localities. These differences in species composition depend upon large scale climatic differences across the length and width of the Eastern Deciduous Forest and also upon variation in local condition. The factors affecting the species composition of the forest are discussed in the following pages.

Large Scale Climate Differences

Local Variation in the Eastern Deciduous Forest

Soil Types

Local Temperature Differences

Succession

Aquatic or Periodically Flooded Habitats

The Problem with Mountains