this presentation is designed to give you a feel for what ... · this presentation is designed to...

This presentation is designed to give you a feel for what tall, mixed and short grass prairie environments on North America look like. I hope that these pictures will help you understand more deeply when we talk about the ecology of these grassland ecosystems.

Prairies are found on all continents of the world, and they often have similar fire ecology. In many locations, people are restoring prairie ecosystems using fire, so we’ll be talking about that in our next lesson after you’ve seen some pictures.

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In the tall grass prairie, grasses can be up to 2 meters tall! This is tall grass prairie at a state park in Iowa.

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With rolling topography and a continuous bed of readily available fuels, there were few barriers to fire spread. Therefore, we think that fires were often large when they ignited when it was hot, dry and windy. In the tall grass prairie, as in most other prairies, there are many days each summer when the fuels are sufficiently dry to carry a fire with enough wind to spread the fire far and wide.

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The tall grass prairie was once extensive through the US Great Plains and north into Canada.

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Prairies are often dominated by grasses, but also can support a rich diversity of forbs. Although the forbs don’t contribute as much biomass as the grasses, they are important to many birds and animals.

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Trees were uncommon in the tall grass prairie and largely limited to riparian areas along rivers and streams, and to places where the topography was broken.

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When fires burn in tall grass prairie sites, they spread rapidly and burn very intensely. Grasses, shrubs, and forbs are often top-killed, yet many resprout, leading to rapid regrowth of biomass.

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The prairie grasses send up new tillers as soon as growing conditions are favorable after the fire.

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The grasses grow quickly and biomass rapidly accumulates.

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Slide 9

PM1 Penny Morgan, 8/23/2008

Managers of tall grass prairie preserves often use prescribed burning to consume accumulated biomass, maintain native species diversity, and to mimic what they believe were native fire regimes.

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We don’t know what the historical fire frequency was prior to Euro-American settlement. We do know that many of the different Indian tribes used fires, and that soldiers and early Euro-American settlers learned from the Indians about fire suppression and fire use.

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So much of the tall grass prairie is now converted to intensive agriculture that the tall grass prairie had been declared an endangered ecosystem.

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The intensive agriculture benefits from the high organic matter content of the prairie soils. The deep, finely textured soils are very fertile, thanks, in part to the organic matter accumulated over millenia in the prairie grasslands. In contrast, soils from the same parent material under what has long been forest are lower in organic matter (as indicated by their lighter color).

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There are many small preserves and reserves of tall grass prairie vegetation.

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Elsewhere, tall grass prairie still supports prairie grasses, but intensive grazing has altered the ecosystem.

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Let’s move on to the mixed grass prairie. These sites are intermediate between the more mesic tall grass prairie to the east and the dryer short grass prairie to the west. Grasses are not as tall here. Some of the dominant grasses found here are also found in the tall grass prairie, while others are found in the short grass prairies.

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Grasses are shorter in stature than in the tall grass prairie. As in other prairies, the terrain is often rolling, offering few barriers to fire spread if there is enough fuel available and fires ignite when it is hot, dry and windy.

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The Niobrara Preserve in Nebraska is one of the large preserves of native mixed-grass prairie. It is actively managed to promote native species diversity.

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Mixed grass prairie is widespread. Here is a site in Montana.

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On the Ordway Prairie, The Nature Conservancy uses prescribed fire, grazing by buffalo, and other active management to foster healthy prairie ecosystems rich in grasses and forbs.

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Here are several of the common grass species found in the mixed grass prairie.

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Compared to the tall grass prairie, less of the mixed grass prairie has been converted to agriculture. As a result, you can find good examples of mixed grass prairie in state parks and on private land.

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Here’s another picture of burned mixed grass prairie. Note how continuous the grass cover is just two months after burning. Again, the grasses are well adapted to regrow post-burn as long as the weather and soil conditions are conducive.

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Prairie grasslands are very important to many birds and small mammals. Migratory birds often stop briefly in prairie grasslands, especially those with water, on their way north and south. Many birds and small mammals make their homes in prairie grasslands as well. Many nest in the grass, which can make eggs and chicks vulnerable to fire.

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The mixed grass prairie has many associated forbs and shrubs. Patches of shrubs and forbs can add greatly to the plant diversity while also providing additional habitats and food for birds and animals.

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Forbs are very important to prairies in several ways. First, although they seldom dominate the grassland communities and seldom contribute the majority of the biomass, their foliage and seeds are disproportionately important to many insects and birds. Second, many organizations eager to gain donations and volunteer support find that the wildflowers are part of what attracts people to prairie ecosystems.

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Most prairie ecosystems, including the mixed grass prairie, have rugged, dry hills in some places. Fires spread less readily where terrain was broken.

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These “badlands” add to the visual diversity of prairie grasslands. They are ecologically important as well, for it is here that trees were more likely to survive when the surrounding prairies burned.

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Prairie grassland landscapes, like this one in Teddy Roosevelt National Park, often provide valuable wildlife habitat when streamside plant communities are located not far from grasslands and badlands. If you’ve never been to Teddy Roosevelt National Park, you should visit. It is very beautiful, never crowded with people, and offers great opportunities to see herds of buffalo. Besides, you can tell people that you’ve been to southwestern North Dakota and impress them with you ability to use directional adjectives.

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Young buffalo are cinnamon colored. Once abundant, buffalo were largely exterminated and now are found in isolated herds on mixed prairies and in some other locations.

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Eastern redcedar and other woody vegetation has increased in density and extent on many sites in mixed and tall grass prairies in recent decades. Here along the Platte River in Nebraska, the conifers have established in abundance under cottonwoods, a species of Populus. The Nature Conservancy on the Niobrara Preserve has instituted an aggressive campaign to remove eastern redcedar and to encourage the cottonwoods to regenerate.

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We can also find mixed prairie sites once dominated by grasses are now dominated by shrubs. Some such sites are burned or treated with herbicides to alter species composition in favor of grasses, but that depends upon the cost and management objectives.

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Many mixed prairie sites are grazed by domestic livestock, mostly cattle.

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The short grass prairie has even less annual precipitation than the mixed grass prairie. Here, droughts are so common that it is very difficult to farm.

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We have learned much about the ecosystem processes within short grass prairies from long term ecological research at the Pawnee National Grassland. Buffalo grass (Buchloe dactyloides) and blue grama (Bouteloua gracilis) are two very common grasses in short grass prairies.

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As you might guess from the name, the grass is short. There is more bare ground visible between the plants, especially in drought years. Most years are drought years.

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Here, blue grama, needle and thread, and wheatgrasses are the native grasses.

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Short grass prairie sites are often grazed, but even in the absence of grazing, there’s not much grass to fuel a fire.

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As in the other prairie ecosystems you’ve seen pictures of today, the intermixed forbs and shrubs add much to the species diversity and values to wildlife.

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In the “big sky” state of Montana, much of the native grasslands are short grass prairie.

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Agriculture has been tried and abandoned in many areas that once supported short grass prairie. Typically, intensive agriculture depends on irrigation in this ecosystem because the annual rainfall is not very abundant and the amount varies greatly from one year to the next. In the droughts of the Dust Bowl years of the 1930s, many homesteaders abandoned farms they had tried to establish in short grass prairie.

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Here, the crops are irrigated.

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Elsewhere, farmers often leave part of their land fallow in order to accumulate moisture in the soil for growing crops every other year. The brown strip in the middle of this picture will not be planted this growing season – the farmer will wait until next year for planting.

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Cattle grazing is a much more widespread use of short grass prairie than intensive agriculture.

This is the last of the slides of prairie grassland ecosystems from North America. We wanted you to learn from these pictures a little about the environment of the prairie grasslands. Our next presentation will be about fire ecology and restoration of prairie ecosystems.

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