Hardwood competition reduces loblolly pine plantation productivity

Abstract

A hardwood suppression treatment applied in a 7-year-old loblolly pine (Pinustaeda L.) plantation enhanced productivity through a 27-year rotation that included two commercial thinnings. By age 27, the suppression treatment reduced the hardwood overstory but did not alter the species diversity of the understory vegetation. Pine diameter at breast height, basal area, and merchantable volume for suppressed and check treatments averaged 29.4 and 26.6 cm, 27.1 and 21.6 m2/ha, and 182 and 141 m3/ha, respectively. Harvest volumes for the respective treatments were 27.8 and 12.8 m3/ha with treatment mean total volume growth being 201.3 and 145.1 m3/ha. Besides reducing total volume yields by 27%, hardwood competition had a significant effect on product volume distribution. Check treatment sawtimber volume was 52.5 m3/ha less than the suppressed treatment. Lower sawtimber yields reduced check treatment revenue potential at age 27 by $1442.32/ha. If the revenue losses based on age 27 stumpage value were discounted at 8%, then the cost of an age 7 hardwood suppression treatment could not exceed $305.58/ha for a 27-year rotation. After 20 years, an early hardwood suppression treatment improved the multiple use potential of a loblolly pine plantation.