Prairies are subtle but amazing
The citizens of Marshall County are very fortunate to have a wide variety of natural habitats conserved within our borders. Whether it be forestlands, wetlands, fishing waters, trails, Iowa River access points for boats or canoes, a wide array of opportunities await. Making the effort to travel to these fine natural areas is worth your time. Using handy brochures from the MCCB office located at the Grimes Farm and Conservation Center, you can plan an excursion to fit your schedule and interests.
One interest of this scribe is PRAIRIES, those natural grasslands holding numerous varied species of tall grasses seemingly reaching for the clouds. Lower to the ground and tucked away between the tall grasses are forbs, or flowers, of many types, colors and sizes. Investigating what they are, how they got there and the history of how they came to survive in spite of all the odds against them is an amazing story. I’ll try to hit a few highlights today about native grasslands. So get comfortable, enjoy the read and get inspired to go the prairie yourself this summer.
Why should we be interested in grasslands? Because they are one of the most productive ecosystems in the United States. Why have they not been preserved? Because they were too productive, being quickly transformed to croplands, and, because of their vastness, they were considered a prime example of monotony and were taken for granted. However, when you take the time to let a native grassland introduce itself, you will meet a lifelong friend. This new friend can teach you a lot about nature and the schemes she uses to thrive and survive.
After the most recent glaciation of all of Canada and northern portions of the United States, the slow and inevitable growth of plant materials followed in time on ice-free land surfaces. Since nature abhors a vacuum, soil, air and water were going to grow something. At first it was low-lying tundra mosses and sedges. The northern progression of the ice margin created bands of vegetation similarities such as boreal forests of spruces, then an intermixing of spruces and hardwoods. As natural climatic shifts brought warmer temperatures and less rain, hardwood forests got thinner. Within those gags grasses emerged to fill the voids. Given even more time, grasses came to dominate.
For Iowans, for just one state within the Midwest, which botanists called the tallgrass prairie region, grasses grew well. Grasses, in effect, built the thick, organic dark soil layers and held the soil together with extensive root systems that were many feet deep. Above the ground grew the likes of big bluestem, little bluestem, switchgrass, Indian grass, prairie cordgrass and many others. All the grass types grew is vast concentrations, an almost solid cover over the ground. However grasslands are more than just grass. Within their clutches grow many kinds of wildflowers. All provide cover, food and habitat for birds, mammals, reptiles, insects, amphibians and countless microscopic soil organisms.
Native grasslands in North America are called prairies. In Asia they are known as steppes. South Americans call their grasslands pampas, while in South Africa they are titled veld. The existence of North American grasslands is marked by irony. After millennia of adaptations to survive, they were transformed within half a century by European settlers. The rich soils and unbroken spaces lured hungry settlers and were quickly exploited for human use. The result is that native prairies in Iowa account for only one-tenth of 1 percent of our land area. They are rare. Nationally native grasslands have also taken a big hit. But some areas still exhibit on a grand scale, notably the north central part of Nebraska, the Sand Hills area.
All grasslands have several things in common. First, they exist on relatively flat or gently rolling topography. Second, all occur on similar soils those rich in organic matter, slightly alkaline and very fertile. Third, grasslands exist in areas where rainfall is between 10 and 30 inches per year. This quantity of rain is not the whole story. The time of year when it falls is important. Rain usually falls during peak periods with drought a frequent player in this fourth; grass plants can tolerate and minimize the evaporation their leaves will give off. Small, long and very narrow leaves do this. Since there tend to be no tall trees in prairies, wind is the fifth factor. Wind is moving air, and we all know winds can be very generous at times in open country. Constantly blowing winds take evaporated water with them.
Now enter the next big factor for maintaining prairie grasslands fire. Dry grasses provide plenty of fuel for fires to eat away at. In some areas where forests may try to “invade” grasslands, fire is the mechanism by which trees are killed or weakened and thus held back. Winds push fires along steadily, and quickly if winds speeds are high. Fires do not hurt the growing points of grass.
Grass composes the third largest family of flowering plants in the world. It can be found from pole to pole and contains more species that are distributed worldwide than any other family of plants. As a group, it is easy to call them grasses. A lack of showy flowers seem to make them dull and difficult to distinguish. Botanists specializing in grass thus have a niche all to their own. A prejudice against grass is unfortunate given the importance of it to the survival of mankind.
Leaf surfaces of grasses must be big enough to allow sunlight to work its magic of photosynthesis. Yet at the same time the smaller the leaf the less transpiration of water from the plant. Leaf arrangement is vertical for maximum photosynthesis efficiency. However, it the root system underground that does the bulk of the work. A seven-day-old Big Bluestem seedling is barely visible above ground, but is extensively branching root system is already 2 feet long! Fully grown prairie grass has enormous fibrous root systems, sometimes reaching a depth in the soil of twice its height above ground. As for biomass above ground during a growing season, a forest is about 90 percent above and 10 percent below. For prairie grasses, biomass percentage is about 50 above and 50 below.
Grass with extensive root systems is a hedge against drought and a hedge against grazers. Bison eat grass, and modern-day cattle eat grasses as well. When cutting or grazing happens, the growth point of grasses is at the base of the plant near soil level. Give it just a bit of time and new growth springs forth. In addition, young shoots are hidden inside older shoots in a series of wraparound tubes. Grasses also produce shoots called tillers, offshoots from the base. Clumps of tillers help build the mound effect of a grass clump. Underground is where the magic happens because grass, a perennial, can live for long periods of time, surviving the coldest of winters due to a root system that “sleeps” until next spring.
ANIMALS of the prairies are associated with iconic megafauna such as bison. But prairie regions further west include pronghorns, elk, mule deer, white-tailed deer, coyote, jack rabbits and a host of rodents including prairie dogs. Locally the prairie dog is not one we see. We do see (if very lucky) its cousin the pocket gopher. Add to the mix many grassland birds, snakes, insects of a huge variety, and badgers. Each of these animals can run away from fire or predators, or go into an underground burrow for safety. Animals of the prairie tend to be more social also, a defense strategy employing more eyes, ears and noses to detect danger. In the long run this is safer for the group than living alone.
Hidden deep in the soil are countless microscopic organisms where they feed on dead plants and animal matter. These tiny critters actually do most of the real work of the prairie. In spite of overwhelming above ground herbivores, it appears they consume only a small portion of the green matter available. Even insects waste a huge amount of the leaf material they nibble on. Bacteria and fungi eat wasted plant matter. How much do these tiny organisms weigh? According to botanical estimates, the things we cannot see are about equal to the total weight of the vegetation.
Big animals eat grass. Cattle are the obvious choice here. Their bodies can eat grass and convert it into food we can eat: beef and dairy products. Humans depend on grasses of all kinds in the long run. Our nation’s history, its landscapes and our economy have connections to grasses that we take for granted. The next time you stroll through a grassland or native prairie, as you watch the tall grass waving in the wind, reflect upon today’s story. Remember that prairies are subtle and amazing.
Here is your funny bone fix for the day: A mouse trap placed on top of your alarm clock will prevent you from rolling over and going back to sleep after you hit the snooze button.
Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at PO Box 96, Albion, IA 50005.