Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Rousseau, Randall J.

Committee Member

Roberts, Scott D.

Committee Member

Renninger, Heidi

Committee Member

DuBien, Janice

Committee Member

Schmulsky, Rubin

Date of Degree

5-3-2019

Document Type

Dissertation - Open Access

Major

Forestry

Degree Name

Doctor of Philosophy

College

College of Forest Resources

Department

Department of Forestry

Abstract

The justification for development of elite loblolly pine (Pinus taeda L.) genotypes includes potential increases in stand uniformity and reduction in planting densities and corresponding establishment costs. However, some genotypes produce less desirable characteristics than others. The ability to realize full potential genetic gains is dependent on selecting appropriate combinations of genetic material and silvicultural management. In 2008, a study was established in the upper coastal plain of Mississippi to examine the performance of two varietal loblolly pine genotypes, a “crop tree” ideotype (CROP) and a “competitor” ideotype (COMP), at two levels of management intensity and three different initial tree spacings. After nine growing seasons, differences in crown morphology, top dieback frequency, and growth and yield variables are apparent between genetics and silvicultural intensity. The COMP ideotype had, on average, greater crown volume, less acute branch angles, and LAI than the CROP ideotype. Increasing management intensity had greater impact on crown characteristics than genotype. Current annual increment growth of stem wood was statistically higher in the COMP ideotype under intensive management and lowest stocking level. The interaction of ideotype, management intensity and spacing level significantly impacted growth and yield. The COMP ideotype is projected to produce greater volume than the CROP ideotype on this site. There was no significant difference between ideotypes with respect to specific gravity for any combination of cultural treatments. Instances of top dieback were significantly higher in the CROP ideotype across management and spacing levels. Nutrient sufficiency levels for fast growing loblolly pine and foliar levels in the current study were statistically significant. Differences due to management intensity were related to reduced competition and lower incidence of damage. The results of this study provide a reference point for elite loblolly pine under different silvicultural regimes for landowners interested in performance potential in Mississippi’s upper coastal plain.

URI

https://hdl.handle.net/11668/21065

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