Diversity

Diversity is defined as the state of being diverse, having a variety. Diversity is apparent in many aspects of soil. Two examples of soil diversity are the different soil orders and the soil biodiversity.

Soil Orders in the United States

The United States exhibits a vast array of soil orders, as shown in the image above. The soil orders included in this map are: Alfisols, Andisols, Aridsols, Entisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, and Vertisols. 

Alfisols have a base saturation over 35 percent and have subsoil horizons enriched with clay. This type of soil is typically found under forest and savanna vegetation. Alfisoils are generally fertile, with production levels similar to that of Mollisols and Ultisols. They are typically abundant in nutrient cations of Ca, Mg, K, and Na. They make up about 10 percent of the world's ice free land areas.

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Andisols form in or near areas of recent volcanism and are made from volcanic parent materials unique chemical properties. They have limited geographic distribution, but have potentially high productivity due to their tendency to accumulate organic material, and are easily cultivated. They lack development of soil horizons and are not typically extensively weathered. They make up about 1 percent of the worlds ice-free land areas.

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Aridsols are soils in arid climates that have visible chemical/weathering alteration. They often have accumulation of CaCo3(lime) and NaCl(salt), but normally have low amounts of organic matter content. Aridsols normally are water deficient, and do not allow for the growth of crops without irrigation. Without irrigation and fertilization, the productivity of Aridsols are generally low. They make up 12 percent of the world's ice free land areas.

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Entisols lack development of Soil Horizons.

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Histosols are soils that are mainly composed of organic materials.

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Inceptisols are freely draining soils soils that exhibit minimal development of horizons.

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Mollisols have a base saturation over 50 percent and have significant accumulation of organic C.

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Oxisols are located in the tropics and are highly chemically altered.

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Spodosols are coarse-textured soils located in northern latitude forests. The Fe and Al compounds in this soil have a strong geochemical separation.

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Ultisols occur in warm, humid climates and have clay-enriched B horizons.

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Vertisols exhibit a shrink-swell behavior and have a high concentration of silicate clay.

Soil Biodiversity

Soil biodiversity refers to the diversity of living organisms in the soil. The most biologically diverse part of the earth is the soil. The soil has a vast biological web of interactions between organisms, plants, and small animals. Bacteria, fungi, worms, spiders, springtails, ants, and countless other organisms make up the diversity of the soil. These organisms are important to the flow of nutrients through the soil. Below is a picture of a

Citations

1 - Amundson, R., Guo, Y. & Gong, P. Ecosystems (2003) 6: 470.

2 - Bailey, Robert G. Description of the ecoregions of the United States. U.S. Dept. of Agriculture, Forest Service, 1995

3 - Guo, Yinyan, et al. “Pedodiversity in the United States of America.” Geoderma, vol. 117, no. 1-2, 2003, pp. 99–115.