Biomass development for intensively managed loblolly pine plantations growing on Spodosols in the southeastern USA

Few published studies exist for intensively managed loblolly pine stands that document both above- and below-ground biomass accumulation over time. Site-specific biomass estimation equations (i.e., above-ground, above-ground + taproot, total tree including taproot, coarse roots and fine roots) for plantation-grown loblolly pine (Pinus taeda L.) were developed from 13 intensively managed stands (1-4 yr) established on a common soil type (Spodosols) on the lower Coastal Plain of southern Georgia, USA. Extensive areas of pine plantations have been established on seasonally wet Spodosols, a dominant soil type in this region. Covariance analyses indicated that a single regression equation could be used to predict either above-ground or total tree biomass for 1- and 2-yr-old or 3- and 4-yr-old stands across all locations. Variations in the allometric relationships among sites were perhaps reduced because of the intensive understory competition control and fertilizer treatments that were applied to enhance growth. Leaf area accretion rates for these developing stands were rapid and largely sigmoidal, reaching a high value of approximately 10.5 (all-sided) after three growing seasons. Total biomass increment ranged from about 2.0 Mg ha(-1) yr(-1) at age 1 yr to 10 Mg ha(-1) yr(-1) at ages 2 and 3 yr (total standing crop biomass at age 3 yr = 22.8 Mg ha(-1)). The largest increase in total biomass increment, approaching 25 Mg ha(-1) yr(-1), occurred during the fourth growing season (total standing crop biomass = 48.1 Mg ha(-1)). Roots (tap, coarse and fine) accounted for 32% of total biomass production at age 4 yr. Estimates of net annual biomass production documented in this study approach the upper limits of biological potential previously reported for this species within its native range. With the advent of advanced silvicultural systems that have combined genotype deployment, density control, and increased nutrient availability, differences between actual production and biological potential have become much narrower for loblolly pine over the last two decades. (C) 2002 Elsevier Science B.V. All rights reserved.