Growth and Yield Relative to Competition for Loblolly Pine Plantations to Midrotation- A Southeastern United States Regional Study

Lohlollypine (Pinus taeda LJplantations were studied across 13 southeastern sites grown for 1.5 yr with near-complete control o f woody, herbaceous, and woody plus herbaceous components during the f irst 3-5 yr . This mult iple object ive experiment ( the COMProject) documents stand dynamics at the extreme corners o f the response surface that encompasses most compet i t ion condi t ions common to pine plantat ions . This is the second of two companion reports. Merchantable pine volume after 15 yr with ear&, near complete competition controlreached2,35&4,415f~/ac by site compared to I, 132-2,965f$/ac on the no controls. With control o f both woody and herbaceous competi t ion, 15 yr volumes were increased by 23-121% and gains increasedas hardwoods andshrubs increased on the no controls . Early woody control increased merchantable pine volume on 1 I s i tes by 14-1 I8%, while herbaceous control yielded somewhat less on average, a I7-50% increase on ten sites. Nogains andsome volume losses occurred when control ofone component releasedsevere competi t ion from an enhanced remaining component , otherwise gains were generally addi t ive for control o f both components. Pine volume was decreased by about 1% for each 1 f?/ac of hardwood basal area (BA) present at age 1.5. Annual measurements detemzined that culmination of current annual increment (CAI) with control of both competition components occurred in.yr 8-I I at 250-4 7Of$/ac/yr. CAIsforpine height, BA, and volume were decreased by about 5-27% when growing Season rainfall (March-October9 was less than 36 in, Mean annual increment had not culminatedfor any treatment at any locat ion by yr 15 and rangedfrom 195250 f$/ac/yr with both woody and herbaceous control . Fusiform rus t mainstem ga l l s [Cronart ium quercuum (Berk.) Miyabe ex Sh ira i f. sp. fusiforme (Hedge. & Hunt) Burdsall & Snow] in high severi ty areas increased additively with control of both components, more so with herb control. Contrary to the widespread assumption that hardwood out-competepine, the hardwoodproport ion qfstand BA decreasedfrom yr 5-15 on s i tes where hardwood BA in yr 5 exceeded 10 f$. South. J. Appl. For. 27(4):00-00.