Short-term effects of hexazinone applications on woody species diversity in young loblolly pine (Pinus taeda) plantations

Data from four studies determining the susceptibility of woody plant species to foliar applications of several rates of liquid hexazinone (Velpar L®) were used to examine the short-term effects of the herbicide on woody species diversity in young loblolly pine plantations. Woody species diversity, as measured by four similarity measures between pretreatment and post-treatment species importance or diversity, decreased significantly with increasing hexazinone rate. Woody species shown to be among the most susceptible (sumacs (Rhus spp.) and oaks (Quercus spp.)), and least susceptible (loblolly and other pines, and Vaccinium spp.) to hexazinone in previous herbicide screening trials decreased and increased in importance, respectively. Differences in similarity measures between the no-hexazinone treatment and the 1.0 × hexazinone rate (1.2 to 1.5 kg a.i./ha depending on the study location) 2 years after herbicide application were small.