Herbicide effects on ground-layer vegetation in southern pinelands, USA: Areview

Despite the fact that herbicides are widely used across the southeastern Un ited States, their effects on ground-layer vegetation (woody and herbaceous species <1.4 m tall) are not well understood. We conducted a literature re view to examine published studies and compile available data. More than 125 studies were examined, based on several criteria (e.g., a sound experiment al design, quantitative data, study conducted in southern pinelands). Only 21 studies were retained for our review, and the majority of studies were c onducted in pine plantations. Few clear, consistent results were revealed, probably due in large part, to the wide array of herbicides and diverse res ponse variables examined in the studies. Woody plant cover generally declin ed with herbicide application, an expected result from use of hardwood-spec ific herbicides in most studies, but results for herbaceous plant cover wer e mixed. Most studies showed a decrease in total (woody and herbaceous plan t) species richness. We also examined the response of plant species of spec ial concern to herbicide application. Most species declined, while wiregras s (Aristida beyrichiana Trinius and Ruprecht [syn. A. stricta Michx. s.i.]) showed mixed responses across studies. Because our findings show that few studies have been conducted under natural conditions, experimental design s hortfalls have been common, and study conclusions have been widely divergen t, we suggest that research precede extensive herbicide use in pinelands.