why do soils differ from one place to the other
Why do Soils Differ? There are numerous reasons why soils differ regionally. The most
influential factors include the parent material (the rocks from which the soil has come), the climate and terrain of the region, as well as the type of plant life and vegetation present, and, of course, human influence. Parent material - this refers to the original underlying rock upon which the soil formation takes place. Essentially, the nature of parent rock in a particular region will affect the type of soil that eventually develops. For example, in an area of mainly sandstone, the soil formed due to the weathering of the rock is likely to be well-drained, course and sandy. Climate The world consists of a broad range of climatic regions, each with its own specific types of soil. A common example of this is tundra soil, which tends to occur mainly in northern-hemisphere areas such as the Arctic and Scandinavia, where the climate is often cold and hence the organic materials do not break down very easily and peat tends to form. In contrast, red and grey desert soils which are found only in hot, arid regions, such as Africa and the Middle-East, contain very small amounts of organic material because it is rapidly oxidised under the warm conditions.
These soils but are less leached than the tundra soils. Terrain this is another important factor in soil development. Areas with many slopes in the land tend to have more freely drained soils, as water can run off or percolate more rapidly. In contrast, regions with mostly flat areas of land can often be waterlogged, because of the lack of gradient to promote lateral or sideways flow. Plants The type of plant life and vegetation obviously varies according to a region s climate and other factors. Plants also have a strong influence on soil development they take up nutrients from the ground, whilst adding organic material to the soil surface. Humans We should not forget the influence of man who has managed the land over the last few thousand years. Agriculture, in particular, has had a big influence on developing the soils we see today. What makes one soil different from another? Each soil tells a different story of its origins and management practices.
On, Eric Brevik at Dickson State University, North Dakota, points out that these differences are the result of five factors. He refers to them as ClORPT: climate, organisms, relief, parent materials and time. Temperature and precipitation are the main factors making soils different from one another. Precipitation dissolves minerals and salts in the soil. These move with the water down through the soil profile. Climate and temperature also influences which plants and other organisms live in the soil. Animals and microorganisms living in soil decompose plant and animal tissues, and wastes. Eventually these become humus which influences soil color. Organisms and humus also affect and the size and shape of the clumps of soil particles, called peds. Peds are important because that is what makes a soil's structure. Where a soil is found in the landscape relief or topography affects its characteristics. Soils on slopes, for example, often experience more erosion and thus are shallower than soils on the top of a hill. Soils at the bottom of the slope are often much deeper due to the deposition of the eroded soil from the slope above.
A soil's position in the landscape can also indicate its inherent drainage (well, imperfect or poorly drained). Soils develop from parent materials including minerals and rocks. Some soils form directly over bedrock but others develop from the materials transported and deposited by glaciers, gravity, wind, rivers, lakes, or oceans. These materials give soils their properties including particle size and minerals. The minerals contribute color and influence chemical factors that affect pH and nutrient availability. All soil-forming processes take time. Younger soils are typically shallower and often more fertile than older soils. It takes less time for a soil to form in sediments deposited by wind than from bedrock because plants can readily grow in sediments. Bedrock has to weather first into soil-sized particles. As you look at different soils in a pit or a trench, think about how ClORPT factors gave them their character. For other interesting posts about why soils matter visit:
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