Pine forest regeneration across the southeastern coastal plain has relied upon intensive mechanical site preparation methods for stand establishment following clearcut harvest. These methods often result in long-term degradation of the site, characterized by lowered productivity; reductions in wildlife food plant populations, with associated decreases in wildlife diversity; and overall negative ecosystem impacts (Swindel et al. 1986). The use of forest herbicides has been developed as an alternative site preparation method that is more economical and causes less soil disturbance and nutrient displacement than do most mechanical methods. Consequently, chemical site preparation is replacing mechanical preparation in many southeastern forests (Walstad and Kuch 1987).

Maintaining biodiversity has become a focus of land managers worldwide because of the rapid loss of plant and animal species and consequent ecosystem degradation. The National Forest Management Act (1976) requires that silvicultural practices maintain the diversity of publicly owned forest ecosystems. However, a primary goal of forest vegetation management is to concentrate site productivity on a preferred tree species. This conflicts with the mandate of the legislation described above. Therefore, site preparation treatment methods must be evaluated to assess their impact on plant species diversity, which could, in turn, influence wildlife species diversity.

The need to maintain natural biodiversity as well as to restore and manage critical wildlife habitats has led to various management strategies in forest lands. In a few studies, forest herbicides have been shown to be effective in managing wildlife food plant populations and in restoring certain habitat types. However, questions concerning the impacts of herbicides on the forest ecosystem remain largely unanswered.

Hexazinone, 3-cylohexyl-6(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione is a forest herbicide that has received widespread use in the southeastern United States as a preplanting site preparation tool. This chemical is used where competition from hardwood species is most prevalent. One of nine compounds used for chemical preparation of southeastern forest lands, hexazinone is a selective herbicide registered for site preparation, release, and herbaceous weed control in pine production. Commercially, hexazinone is known as Velpar (ULW and L) and Pronone 10G.

Hexazinone is highly soluble in water and is potentially mobile in subsurface solution. According to previous research, its persistence in forest soils is relatively short-lived; however, long-term studies have not yet been conducted. Hexazinone is absorbed from soil solution by plant roots and distributed to the site of action in the plants' chloroplasts (Ashton and Crafts 1973). The compound binds to a specific protein that inhibits other reactions and causes the affected plant to die from oxidative stress.

A Case Study

Overall Plant Responses

References

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