The effect of thinning on loblolly pine specific gravity as measured by the gamma densitometry technique

Author

Deborah D. McRae

Date of Award

6-1981

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

Ronald L. Hay

Committee Members

John Rennie, Robert Little

Abstract

Study objectives were to correlate the gamma densitometry technique with conventional methods of measuring specific gravity and to use the gamma densitometer to analyze a thinned loblolly pine (Pinus taeda L.) stand for earlywood specific gravity, latewood specific gravity, average specific gravity, percent latewood and radial growth. In 1980 a 12 mm increment core was extracted from each of 160 sample trees in a 40 year old planted loblolly pine plantation which had been thinned in 1963 to residual basal area of 60 ft²/acre, 100 ft²/acre, and 140 ft²/acre; the control plot was unthinned and had a basal area of 158 ft²/acre. Two conventional specific gravity estimates were obtained for each core: (1) ovendry weight divided by green volume measured physically; (2) ovendry weight divided by green volume measured by water displacement. Average specific gravity values were also obtained by the gamma densitometer. The correlation of specific gravities between the gamma densitometer and the first conventional method was high: R² = .76. The specific gravity correlation between the gamma densitometer and the second conventional method was not as high: R² = .56. The specific gravity correlation between the two conventional methods was high: R² = .73. The gamma densitometry technique also provided estimates of earlywood specific gravity, latewood specific gravity, as well as average specific gravity, percent latewood and radial growth. Significant differences were not found among basal area treatments for average specific gravity or percent latewood. However, earlywood specific gravity decreased significantly after thinning to 60 ft²/acre and 100 ft² /acre. Latewood specific gravity increased significantly after thinning to a basal area 60 ft²/acre and 100 ft²/acre. Radial growth of trees in plots thinned to 60 ft²/acre and 100 ft²/acre was significantly greater after thinning than that of trees in the 140 ft²/acre and control plots.

Recommended Citation

McRae, Deborah D., "The effect of thinning on loblolly pine specific gravity as measured by the gamma densitometry technique. " Master's Thesis, University of Tennessee, 1981.
https://trace.tennessee.edu/utk_gradthes/7692