Growth and competition response in intensively established loblolly pine plantations at crown closure

Abstract

Chemical and mechanical applications to improve pine growth, decrease time to canopy closure, and increase yields are applied to much of the 18 million hectares of pine plantations in the southeastern United States. Although these treatments are known to increase pine productivity, it is not clear whether treatment effects will persist to canopy closure. Therefore, we examined the response of loblolly pine (Pinus taeda L.) growth and competing vegetation with various levels of plantation establishment intensity in southern Mississippi to evaluate the effectiveness of establishment regimes at crown closure. Although differences in dbh were reduced compared with those reported for years 3-5, the most intensive treatment combination of chemical and mechanical site preparation plus 2 years of broadcast herbaceous weed control maintained a height advantage through year 8. Chemical site preparation provided greater long-term control of woody competition than mechanical site preparation. However, hardwood competitors present at canopy closure probably will not pose a threat to future pine growth in any treatment. Pine height growth to crown closure appeared to benefit mainly from an additional herbaceous weed control application. Combined chemical and mechanical site preparation appeared to be unrelated to faster growth at this period, and managers may wish to limit costs by using a single method only. © 2013 Society of American Foresters.