Shades of Green: Earth's Forests -- Forests Through Time

Disturbances to forest ecosystems happen all the time; some create short-term havoc, others take several years to begin showing their effects. Some disturbance is necessary to create the diversity of habitats. For example, small, frequent fires in certain areas make it easier for pines to survive where oaks would otherwise grow. When fires happen regularly, species adapt, and some trees even depend on fire to release their seeds.

If forests change naturally, why worry about the disruptions humans cause? Because humans are fast. If the climate changes naturally, it takes a while. Forests have time to migrate, some species die out, new species develop. But humans are dramatically changing ecosystems all over the world at a rate at which animals and plants just can't keep up.

Seasons bring major changes to forests, but at predictable times. Plants and animals have adapted to take advantage of food sources and habitat available at different times of the year. Those that inhabit the temperate zone have to deal with the freezing temperatures of winter and the very different conditions of the other three seasons, while the tropical forests experience only two distinct seasons.

Weather can change forests in less dramatic ways as well. Temporary cold spells and droughts can seriously affect certain species, though don't usually change the entire composition of the forest. Other disturbances, such as pests, may also be confined to one or two types of trees, creating small gaps in the forest. Diseases can also be responsible for far more serious changes in forests. The effect of any given disturbance depends on its frequency, predictability, and magnitude.

forests through time -- page 5 of 5
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sub-topics
[humans & forests] [temperate regions] [tropical regions] [prehistoric forests & amber] [ecological succession] [seasons]

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