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Forests in Flux

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Published on: Jun. 2, 1996

Last revision: Oct. 21, 2010

an earlier successional stage. All forests exist in a state of perpetual disturbance.

In this view of a forest, succession may proceed toward the climax forest, but the true climax is seldom, if ever, achieved. Disturbances to forests are so many in number and so frequent in the forests of the midwest that there may be no such thing as a perfect, stable forest.

Which forests did the first explorers and settlers in Missouri see? Probably more disturbed forest than climax forest. The same natural disturbances are present today. Some of these disturbances are quite obvious, while others are much more subtle.

Flood, Erosion, Siltation

In 1993 and 1995 thousands of acres of forests were under water along the major rivers.

Less obvious are the thousands of less severe flooding events that occur after smaller, more localized thunderstorms. Ice dams, beaver dams, rivers changing course and man's activities also cause localized flooding, erosion and siltation.

The impact of a flood on a forest can be minimal or major. Floods carry floating wood which batters, scars and otherwise physically disturbs growing vegetation.

Flood waters deposit gravel, sand and silt as waters slow down and remove various particles and solutions. Flood waters may warm or cool the soil or displace soil air, affecting growth of plants. Flood waters typically contribute seed to a regenerating forest. Flooding rivers can change channels, leaving behind sloughs, marshes and poorly drained land. The mere presence of water or saturated soil has an effect on germination of seeds and growth and development of plants.

Some species can tolerate high levels of moisture for long periods of time, while others will disappear after a few days. The effects of flooding can range all the way from total destruction of a forest, reverting it to the earliest stages of succession, to minor changes in species composition or the death of individual trees.

Fire

The effects of fire on forest are well known. Much was written about the Yellowstone fires of 1988 and the numerous fires of the western United States of 1994. Missouri has its share of fires today, and has had fires for the past thousands of years.

Natural fires in Missouri are rare - Missouri forests experience less than one lightning-caused fire per million acres, compared to almost 40 in parts of Florida, California and the mountains of Idaho and over 60 in areas in Arizona and New Mexico.

Indians reportedly burned the forests of what is now Missouri

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