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Waterman and Hill-Traveller's Companion that you were reading.
Savanna is the name given to the transitional area that bridges the boundary between Prairie and Forest and is characterized by grassland interspersed with widely spaced trees with a canopy cover of less than 50% - 80%. Once thought to be merely a meeting of the Prairie and Forest communities it has recently been shown to be a distinct biological community in its own right - as different from Forest or Prairie communities as Forest and Prairie communities are from each other - with its own unique set of plants and animals.
As this realization has taken hold and ecologists have begun studying Savannas as communities in their own right numerous different kinds of Savanna have been discovered. These differences are caused by both soil types (clay, sand, black soil, shale, etc.) and exposure (which direction the Savanna faces and how much sunlight it receives).
Savannas were considered prime real estate by the earliest settlers since they were easily cleared, had (usually) rich soil, and were within easy reach of the raw materials of the forest. As a result they are the rarest ecological community in the United States. Former Savanna can often be recognized by local place names in that they usually contain the word "Grove" indicating small groups of trees which once differentiated the area from surrounding forest or prairie.
Role of Fire
Savanna habitats were dependent on and maintained by fire. Prairie fires, both natural and manmade, would sweep up to the edges of forests and destroy any vegetation that wasn't pre-adapted to cope with it. The aboriginal inhabitants of this continent were instrumental in the creation and maintenance of the Savannas encountered by the earliest European settlers and probably greatly expanded the range of the Savanna community in the millenia prior to the arrival of European settlement.
Some Savanna species
Some of out rarest - as well as most common - plants and animals were dependent on this community for their survival. Among the (currently) rare inhabitants are: Milbert's Tortoiseshell and Compton's Tortoiseshell Butterflies, Harris' Checkerspot Butterfly, Cooper's Hawk, and Rose- Breasted Grosbeaks.
Other animals have been able to adapt to changing conditions and have adopted suburban America (a region noted for grassland with scattered trees) as their home. Among these are the Cardinal, the Robin, the Rubythroated Hummingbird, and the Blue Jay. The most important (and indicative) plant species were the oaks - notably the Bur and Post Oak - under whose wide spreading branches and resulting shade large numbers of plant species found refuge.
The information on this page is tailored to Southern Illinois, Southwest Indiana, Western Kentucky, and Southeast Missouri
Copyright © 2004 Jim Jung