Unfortunately, vegetation management is not as simple as removing undesirable plant species from a site. There are usually underlying problems that initially encouraged the growth of invasive or unwanted plant species. One of the biggest factors is erosion. Much of the severe erosion found in the southern United States is due to the cultivation of natural ecosystems, with crops, typically cotton. This cultivation entailed the use of such practices as clean tillage and planting rows vertically on slopes. Once the land could no longer grow profitable yields, it was abandoned and became “go-back land.” By then, erosion had removed the top several inches of soil containing most of the nutrients and organic matter needed for plant growth. The remaining soil had severely diminished productivity leading to reduced vigor of the grasses growing in it.

Water infiltration rate and holding capacity is also reduced by cultivation due to accelerated losses of organic matter and the creation of plow-pans and loss of soil structure. This results in a greater proportion of the infiltrated water being in the subsoil. Because woody species have deeper roots to obtain water and are good at sequestering plant nutrients, they are more competitive against grass in eroded areas than in the former non-eroded state. The loss of productivity potential of the soil limits expenditures that can be made for managing vegetation.

The second animal management factor that favors woody species is overgrazing. Overgrazing increases erosion, reduces water infiltration, and reduces the vigor of native grasses putting them at a competitive disadvantage to invading plant species. Another animal management factor leading to establishment of unwanted vegetation is grazing of an area by only one animal species, usually cattle. Cattle utilize predominantly grasses, a few forbs, and almost no browse. Grazed plants, especially overgrazed plants, are at a competitive disadvantage to ungrazed species (forbs and woody plant species) because of the loss of significant photosynthate. Another factor has been the suppression of periodic fires that would assist in reducing establishment of woody species. As a consequence of the above factors, permanent ecological changes have been created at many sites that give a competitive advantage to woody species. Thus, if there is a desire to maintain areas as savannahs or grazing lands, invasive woody and weedy plant species will have to be perpetually controlled.

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