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Abstract
Intensive silvicultural management in the southeastern United States has significantly accelerated loblolly pine productivity, enabling stands to reach merchantable size in substantially shorter rotations. Timber harvested from plantations generally contains a higher proportion of corewood (juvenile wood), which has reduced stiffness, strength, and dimensional stability compared with outerwood (mature wood). This study reports whole-disk properties from 4,219 disks and ring-by-ring properties from 3,629 disks collected from 487 loblolly pine trees in 45 stands located across the southeastern United States. The stands are grouped into two groups: Coastal and Inland. This dissertation systematically investigates wood and bark properties in these two groups in the following four chapters: Chapter 2 compares disk and whole-tree wood and bark properties between the Coastal and Inland groups. Trees from the Coastal areas had significantly higher wood specific gravity (SG) than trees from Inland areas. The data was also compared with a legacy dataset from conventionally managed pine plantations and the intensively managed trees had significantly higher wood SG than the conventionally managed trees. Predictive models were developed to estimate wood and bark SG and MC% for each region group.
Chapter 3 develops region-specific parametric models to predict ring SG, earlywood SG, latewood SG, and latewood percentage as functions of cambial age and relative tree height. This chapter also includes tree maps illustrating radial and longitudinal variations in ring SG within the tree.
Chapter 4 creates region-specific parametric models to predict ring ultrasonic velocity (USV) and dynamic modulus of elasticity (MOEdyn) as functions of cambial age and tree height. Tree profile maps demonstrate within-tree variation in USV and MOEdyn.
Chapter 5 utilizes models developed in Chapters 2 and 3 to simulate loblolly pine wood properties across a 30-year rotation. The objective was to predict the delivered cost of the dry mass of the wood and bark, and to quantify the dry mass of carbon contained within the wood and bark. Five timber products were considered throughout the rotation including pulpwood (whole tree), pulpwood top, chip-n-saw, chip-n-saw log, and sawtimber.
This dissertation represents the most intensive field and laboratory sampling effort to measure and model wood properties of loblolly pine in the southeastern U.S. in the last 20 years. The parametric equations presented here can be used in many ways including to predict the amount of wood to water present in roundwood, predict the quality of structural products produced from loblolly pine, and estimate the amount of carbon stored in the wood and bark.