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Although the United States has many sites with contaminated soils, it has been a leader in defining and implementing standards for cleanup. [4] Each year, thousands of sites complete soil contamination cleanup, some by using microbes that “eat up” toxic chemicals in soil, [5] many others by simple excavation and others by soil vapor extraction, air stripping, or solvent extraction, with ...
When heavy machinery is used to clear forests or develop land, the soil becomes compacted. When the soil is compacted, the soil particles are packed tightly together. Soil compaction results in water supply not being absorbed by tree roots and can be deadly to the growth of trees. Soil compaction also can create flooding.
A relatively small amount of rainfall coupled with the slow decomposition of organic material allows the acidic plant debris to sit and saturate the top horizons of the soil profile. As a result of the infertile soil, only a few plant species can really thrive in the taiga. The common plant species in the taiga are coniferous trees.
The project called for large-scale planting of trees across the Great Plains, stretching in a 100-mile wide zone from Canada to northern Texas, to protect the land from wind erosion. Native trees, such as red cedar and green ash, were planted along fence rows separating properties, and farmers were paid to plant and cultivate them. The project ...
For the 300 years following the arrival of Europeans, land was cleared, mostly for agriculture, at a rate that matched that of population growth. [7] During the 19th century, while the U.S. population tripled, the total area of cropland increased by over four times, from seventy-six million to three hundred nineteen million acres.
Notable early examples of live plant harbored pests—such as beech scale, chestnut blight, and white pine blister rust—led to the Plant Quarantine Act of 1912 and regulations from the US Department of Agriculture in 1919. Despite these and subsequent regulations, insects and pathogens have continued to be introduced through live plants. [1]
The rows formed slow surface water run-off during rainstorms to prevent soil erosion and allow the water time to infiltrate into the soil. Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination
With habitats ranging from tropical to Arctic, U.S. plant life is very diverse. The country has more than 17,000 identified native species of flora, including 5,000 in California (home to the tallest, the most massive, and the oldest trees in the world). [4] Three quarters of the United States species consist of flowering plants.