Grassland Types

It is estimated that prior to the European settlement of North America, the largest continuous grasslands in the United States stretched across the Great Plains from the Rocky Mountains and deserts of the Southwestern states to the Mississippi river. Other extensive grasslands are, or were, found in Europe, South America, Asia, and Africa (Figure 2). Grasslands can be broadly categorized as temperate or tropical. Temperate grasslands have cold winters and warm to hot summers and often have deep fertile soils. Surprisingly, plant growth in temperate grasslands is often nutrient limited because much of the soil nitrogen is stored in forms unavailable for plant uptake. These nutrients, however, are made available to plants when plowing disrupts the structure of the soil. The combination of high soil fertility and relatively gentle topography made grasslands ideal candidates for conversion to crop production and thus have led to the demise of much of the grasslands across the world.

Grasslands in the Midwestern United States that receive the most rainfall (75-90 cm) are the most productive and are termed tallgrass prairies. Historically, these were most abundant in Iowa, Illinois, Minnesota, Missouri, and Kansas. The driest grasslands (25-35 cm of rainfall) and least productive are termed shortgrass prairie or steppe. These grasslands are

Figure 2 Map of the grasslands of the world. World Resources Institute - PAGE, 2000. Sources: GLCCD, 1998. Loveland TR, Reed BC, Brown JF, etal. (1998) Development of a Global Land Cover Characteristics Database and IGBP DISCover from 1 km AVHRR Data. International Journal of Remote Sensing 21(6-7): 1303-1330. Available online at http://edcaac.usgs.gov/glcc/glcc.html. Global Land Cover Characteristics Database, Version 1. Olson JS (1994) Global Ecosystem Framework - Definitions, 39pp. Sioux Falls, SD: USGS EDC.

Figure 2 Map of the grasslands of the world. World Resources Institute - PAGE, 2000. Sources: GLCCD, 1998. Loveland TR, Reed BC, Brown JF, etal. (1998) Development of a Global Land Cover Characteristics Database and IGBP DISCover from 1 km AVHRR Data. International Journal of Remote Sensing 21(6-7): 1303-1330. Available online at http://edcaac.usgs.gov/glcc/glcc.html. Global Land Cover Characteristics Database, Version 1. Olson JS (1994) Global Ecosystem Framework - Definitions, 39pp. Sioux Falls, SD: USGS EDC.

common in Texas, Colorado, Wyoming, and New Mexico. Grasslands intermediate between these extremes are termed mid- or mixed grass prairies. In tallgrass prairie, the grasses may grow to 3 m tall in wet years. In shortgrass prairie, grasses seldom grow beyond 25 cm in height. In all temperate grasslands, production of root biomass belowground exceeds foliage production aboveground. Worldwide, other names for temperate grasslands include steppes throughout most of Europe and Asia, veld in Africa, puszta in Hungary, and the pampas in South America.

Tropical grasslands are warm throughout the year but have pronounced wet and dry seasons. Tropical grassland soils are often less fertile than temperate grassland soils, perhaps due to the high amount of rainfall (50-130 cm) that occurs during the wet season and washes (or leaches) nutrients out of the soil. Most tropical grasslands have a greater density of woody shrubs and trees than temperate grasslands. Some tropical grasslands can be more productive than temperate grasslands. However, other tropical grasslands grow on soils that are quite infertile or these grasslands are periodically stressed by seasonal flooding. As a result, their productivity is reduced and may be similar to that of temperate grasslands. As noted for temperate grasslands, root production belowground far exceeds foliage production in all tropical grasslands. Other names for tropical grasslands include velds in Africa, and the compos and llanos in South America.

Although temperate and tropical grasslands encompass the most extensive grass dominated ecosystems, grasses are present in most types of vegetation and regions of the world. Where grasses are locally dominant they may form desert (see Deserts) grassland, Mediterranean (see Mediterranean) grassland, subalpine and alpine grasslands (sometimes referred to as meadows or parks), and even coastal grassland. Most grasslands are dominated by perennial (long-lived) plants, but there are some annual grasslands in which the dominant species must reestablish each year by seed. Intensively managed, human-planted, and maintained grasslands (e.g., pastures, lawns) occur worldwide as well.

Was this article helpful?

0 0
Caring For Your Lawn

Caring For Your Lawn

The Secret of A Great Lawn Without Needing a Professional You Can Do It And I Can Show You How. A Great Looking Lawn Doesn't Have To Cost Hundreds Of Dollars Or Require The Use Of A Professional Lawn Care Service. All You Need Is This Incredible Book.

Get My Free Ebook


Post a comment