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The mystery of soil diversity: How are America's 12 soils different?
The diversity of soils in the United States is amazing. With more than 19,000 soil series discovered, scientists are exploring the differences between these soils and why they form in different regions. This is not only a mystery of soil science, but also the key to resource management and environmental protection.
Classification and characteristics of soils in the United States
The soil classification system in the United States consists of many levels, including soil orders, suborders, major groups, subgroups, families, and series. Each series represents a unique soil type.
The 12 major U.S. soil orders include: Alfisols, Inceptisols, Andisols, Aridisols, Entisols, Gelisols, Histosols, Mollisols, Oxisols, Spodosols, Ultisols and Vertisols. Each soil has unique characteristics and the conditions under which it was formed.
For example, Alfisols are soils with a characteristic lower "B" horizon composed of clay deposits showing signs of migration from above, whereas Inceptisols have a less developed "B" horizon. layers, which are mainly caused by weathering or other processes.
Andisols are usually formed in areas after volcanic eruptions and are composed of materials such as volcanic ash. Aridisols, in contrast, occur in dry regions of the western United States and are unable to support the growth of mesophytes. Entisols are characterized by a poorly developed soil profile and are usually formed on recent river sediments.
Reasons for soil diversity
Soil formation is the result of the interaction of climate, biology and topography, which affect parent material (geological material) over time.
The diversity of geologic materials, topographic processes, climatic conditions, biomes, and ground ages in the United States all contribute to the great variation in mineral and organic soils. The diversity of these factors results in significant differences in the physical and chemical properties of the soil, affecting soil fertility and the distribution of vegetation.
For example, finer soil particles, such as clay, combined with climate-induced soil texture, allow for increased water retention, which aids plant growth. Conversely, sandy soils with larger particles drain well but have poor water retention capabilities.
Soil pollution and its countermeasures
While the United States has numerous sites of contaminated soil, it has been at the forefront of developing and enforcing cleanup standards.
Thousands of contaminated sites are cleaned up across the United States each year using a variety of methods, including the use of microorganisms that can "eat" toxic compounds in the soil, simple excavation, or soil vapor extraction and air dehydration.
In 1980, the U.S. Superfund Act (CERCLA) established strict regulations on legal liability related to soil contamination, driving the identification and cleanup of thousands of contaminated sites.
Land Management and Future Prospects in the United States
Soil protection, management and restoration are key to maintaining a healthy environment and require broad science and public engagement.
With the acceleration of urbanization and the increase in agricultural demand, soil management will face more complex challenges in the future. How to balance agricultural production, urban expansion and environmental protection has become an important issue at present.
The United States has rich soil resources, but each type of soil has its own unique formation conditions and ecological role, which suggests that we should continue to strengthen the research and protection of soil diversity. Good soil management is an indispensable foundation for food security, environmental protection and biodiversity. Can we better understand and value the uniqueness of each soil, laying the foundation for a sustainable future?
