Prairie Ecology

Ecosystems

A quick glance at the plants and animals living in a place can tell you a lot about the local environment. The profligate plant life and riotous profusion of animals tell you the rainforest must have an abundance of water to support so much life. The sharp spines and thick skins of desert plants like cacti reflect the aridity of the environment, where the difficulty of survival puts a premium on protecting what one has. How have the plants and animals of the prairie adapted to their environment?

Great Spangled Fritillary Butterfly

Great Spangled Fritillary Butterfly

photo by Angie Babbit

Underground

Visit the prairie in early June or late September and you will see an impressive display of vivid blossoms rustling in the breezes. Look closer at the flowers and you may well glimpse the visit of a butterfly draped in striking orange and black tones or deep, bright blues. As you stroll, you will probably scare up many birds, some in cryptic browns and blacks and others decked out in loud yellows and blues. But, no matter how hard you look, you will end up missing most of the prairie. Why? Because most of the prairie is underground! To get an idea how much of a prairie lies hidden beneath your feet, imagine mowing down all its flowers and grasses and gathering the cuttings to weigh on a giant scale. This would tell you the prairie's aboveground biomass for plants. If you then did the same thing for all the roots, you would find that they outweigh the flowers and grasses by 200-400%!

Roots of Prairie Plants

Prairie plants need to invest so much in their underground infrastructure because of the challenges posed by the difficult environments they inhabit. Many prairies thrive in the arid Great Plains, where long, hot summers with limited rainfall dry out most plants. The long, branching roots of prairie plants allow them to reach water 10 or 15 feet deep in the soil and stay well-hydrated in scorching August heat

Illustration of the roots of prairie plant plants (PDF)

The roots also serve as reserve supplies of food that nourish quick re-growth. Prairies often need to regenerate because fires frequently sweep through, fueled by the layer of dead grass and dried out flower stalks created every autumn. A flashing strike from a bolt of lightning or a little dab of flaming diesel from the drip-torch of a prairie manager can quickly convert a quiet prairie into a raging conflagration. The seeming devastation is largely illusory, however, because less than a month after the blaze you can find new sprouts pushing up through the black soil, fueled by the energy stored away in the roots. By the end of the summer, lush grasses and lofty flowers will again tower over the landscape covering any signs of the fire's passage.

Role of Fire

This cycle of fire and quick recovery is a key feature of prairies. Without fires, prairies would find themselves quickly invaded by trees. Eventually, the wide canopies of the trees would absorb the sunlight and keep it from reaching the grasses and flowers below. The prairie would die, replaced by woodland. Trees don't do well around fires, however, because they invest so much energy in building their trunks and branches. Fires kill the most important part of a tree, but scarcely affect root-heavy prairie plants.

Burning Grass

Burning Grass

photo by Angie Babbit

Effects of Fire

Not surprisingly, massive walls of fire can strongly impact animals, too. Their mobility means animals can escape the immediate danger, but the burned landscape leaves them with the more long-term problems of finding something to eat and a place to hide from predators. For some, the solution lies in becoming even more mobile. Bison, the quintessential prairie animal, constantly move throughout the year in search of better grazing, water, or shelter from the weather. Fire plays a significant role in motivating bison to move, both as a repellant and an attractor. Obviously, the charred expanses left in the immediate wake of a fire force bison to find greener pastures. Within a few months, however, the once-blackened fields actually become the beckoning green pastures as the tender, nutrient-packed new shoots become a favored feeding ground for many grazers.

Animal Adaptations

The peripatetic habits of bison help them escape the dry weather that frequently afflicts the prairie. Smaller animals can't sustain the long marches of bison and have to learn how to survive with whatever they find in their immediate surroundings. Spadefoot toads exemplify a couple of different ways animals adapt. Like all amphibians, spadefoots prefer the damp environments that can be hard to find in arid prairies. Spadefoots meet this challenge by living below ground, away from the relentless summer sun, where the knobby "spades" on their hind feet help them carve through soil. Huge numbers of spadefoots do come to the surface following the periodic heavy rainfalls that strike the prairies and create ephemeral ponds and puddles that dot the landscape. These short-lived pools provide a breeding ground in which the toads can lay their eggs. The tadpoles that hatch must compress their development into a few weeks—much shorter than in other frogs—in order to become air-breathing adults before the puddles dry up.

The prairie abounds with more examples of adaptations to the climate and resources: the north-south orientation of compass plants to avoid the mid-day sun, the large, heat-dispersing ears of swift fox, or the underground habits of burrowing owls. The prairie is a demanding environment that leaves a mark on the plants and animals that survive there, but it is a mark that has created a striking ecosystem full of beautiful and fascinating creatures.

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