- Explain how grazing contributes to the maintenance of Tallgrass Prairie at the expense of the forested vegetation.
Grazing is used as an agricultural tool used in the Great Plains and is important in the Mixed Grasslands, but less so in the Prairie because a lot of this has been largely converted to successful cultivation of row crops. However, both the Tallgrass covered Sandhills of Nebraska and the Flint Hills of Kansas and Oklahoma are grazed. In both areas mentioned here there are some native species of grass that decrease in cover, biomass and abundance the first year because of grazing pressure.
Conversely, some species increase in cover, biomass and abundance, and the two are referred to as decreasers and increasers. Generally speaking the decreasers are selectively grazed by cattle or sheep, whereas the increasers which tend to be less palatable or nutritious are not grazed as easily even when they resprout and their new buds may have been considered susceptible to damage by grazing by cattle or sheep. However, even increasers do begin to diminish if grazing pressure is constant for several years. At this point the former grassland may become non-productive because of the lack of forested vegetation.
It was noted by Dyer, Coleman and Hilbert in 1982 that the removal of herbage by grazing animals and the return of nutrients to the soil is similar to the effect of burning.
- Explain how soil type contributes to the maintenance of Tallgrass Prairie at the expense of the forested vegetation
In 2000 Sims and Risser told us that the soils of the prairie are heavy, fine-textured, fertile, and rich in humus, dark and deep, because of the growth and decay of grass roots.
The soil itself however is in turn a factor that assists with the limitation of the invasion of prairie and plains by woody vegetation. This is because trees find it harder to grow in the type of environment that these particular. In this way the soil assists with the maintenance of the Tallgrass Prairie, in that it protects and maintains the environment that it grows in, and works towards the detriment of forested vegetation – it does not provide a suitable area for the growth of that type of vegetation.
Often, a determining factor in whether a site will support grassland or an oak hickory forest is the soil, as trees occupy sandy soils and grasslands are on clay.
Because of this grasslands are often productive croplands.
Dyer, Coleman and Hilbert (1982)
Sims and Rissher (2000)