Response of Loblolly Pine Plantations to Woody and Herbaceous Control--Eigth-Year Results of the Region-wide Study-The COMProject
Eight-year response of planted loblolly pine to woody and herbaceous control following site preparation, studied at 13 locations, differed by pine response variable and hardwood level grouping. Treatments affected average pine height the same at both low hardwood (<6ft2/ac basal area at age 8) and high hardwood (>13ft2/ac) levels, and ranked: total control (woody + herb control) > herb control only > woody control only > no control. The same ranking held for pine dbh, basal area/ac, and volume index/ac at teh low hardwood level. However, at the high hardwood level, dbh response from woody control only exceeded that for herb control only, while basal area/ac and volume index/ac response were equal for the two treatments. Volume index increases over no control on the low and high hardwood levels averaged 127% and 336% greater with total control; 32% and 57% greater with woody control only; and 92% and 73% with herb control only, respectively. Treatment effects on all pine response variables were additive at the low hardwood level, and more than additive at the high hardwood level.