Identifier

etd-07052017-145224

Degree

Doctor of Philosophy (PhD)

Department

Renewable Natural Resources

Document Type

Dissertation

Abstract

Leaf area and crown dynamics control how trees grow through their supply of carbohydrates and growth regulators, and their influence on tree mechanical stability. The influence of leaf area and crown dynamics to tree growth was investigated by testing the interdependence between leaf area, branch, and stem growth on young loblolly pine trees. The objectives were to (1) determine the influence of current and previous year’s leaf area on elongation of branches; (2) describe and test a unique way of quantitatively measuring the effect of neighbor branches on net growth of a target branch; (3) quantify the growth impact of reduced leaf area on selected branch whorls on stem diameter growth; and (4) describe the changes in the stem profile of young loblolly pine trees in response to different combinations of artificial defoliation and shade stress treatments. A series of shade and defoliation treatments were applied on branches on the fourth (target) whorl from the top of selected trees, considering the positional effect of branches in the crown. Ten trees were randomly assigned one of nine treatments designed to effect the carbohydrate production and growth factors on branch growth. Three levels of treatments unaltered control, foliage removed, or foliage shaded, were applied on the target branches or its upper and lower neighbors. Treatments were replicated twice in each of the five blocks in the field. Growth responses were measured from elongation of terminal leaders, diameter of branches on the target whorl, and the diameter of internodes adjacent to treated branches. Results show that elongation of terminal buds and growth of new leaves were affected by removal or shading of leaf area and the initial base diameter of the branch. The number of new fascicles, representing stem units carried on a bud, could be predicted with the length of the fully elongated bud using the power law. Growth in tree diameter was sensitive to minor changes in the leaf area of the tree crown. Stem profiles varied with reduction in leaf area of selected branches, and the effect of treatments was localized to internodes immediately above or below the branch whorls that were treated.

Date

2017

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Dean, Thomas J.

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