$title="Plants and Animals - Plant Adaptations"; include "/local/php/ismsite/midewin/header.php"; ?>
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grasses and forbs are adapted to drought, fire, and grazing. They
are perennials that grow back every year and have their growing
points underground. During a prairie fire, the above-ground portion
of the plant is destroyed, but the below-ground growing structures
are unharmed because the soil protects the underground structures.
Some trees and shrubs are also resistant to fire, but through
different mechanisms. Many of the oaks, especially bur oak
(Quercus macrocarpa), have very thick bark, which offers
high resistance to fire. Other trees such as aspen (Populus
tremuloides) and northern pin oak (Quercus
ellipsoidalis) have thin-barked above-ground parts that are
killed by fire, but they readily resprout following fire. Many
shrubs, notably hazel (Corylus americana), also resprout
readily after fire. In fact, the shrub prairie owes its existence
to the resprouting ability of shrubs.
Frequently burned tallgrass prairie suffers from nitrogen limitation, but many nitrogen-fixing legumes common in prairies show positive growth following fire, thus restoring nitrogen to the ecosystem.
The dominant grasses of the tallgrass prairie are adapted to withstand dry conditions and high daytime temperatures. The roots of big bluestem and Indian grass reach depths of 1.5-2.5 m, and those of switch grass, extend downward to a depth of 2.5-3.5 meters (Weaver, 1954). The roots of these grasses, which form thick networks beneath the prairie, effectively absorb moisture during dry periods. Prairie grasses have narrow leaves, which lose less water to evapotranspiration than flat, broad leaves.
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