Pinus elliottii wood from different radial locations within trees was used to prepare two-layer preservative-treated wood joints with alkaline copper quaternary preservative and emulsion polymer isocyanates (EPI) or resorcinol-phenol-formaldehyde (RPF) adhesives. The radial variations in shear strength and wood failure percentage were analyzed. Radial variations in wood density and average penetration depth (AP) of adhesives were investigated to establish relationships between shear strengths and characteristics of bonded joints. The shear strengths of EPI- and RPF-bonded joints showed similar increasing trends from pith to bark, and they varied in ranges of 2.92 to 8.13 MPa and 2.03 to 7.12 MPa, respectively. The wood failure percentage of EPI joints (93% to 100%) had no significant differences in all the radial locations, but that of RPF joints (60% to 100%) showed a clear decreasing trend from pith to bark. High positive linear correlations were found between the shear strengths and wood density, and Pearson’s correlation coefficients for EPI and RPF were 0.934 (p < 0.01) and 0.931 (p < 0.01), respectively. Wood density is a very important factor influencing radial variations of bonding strengths. The correlation between the AP and shear strength was not significant at the 0.05 level.

The extraction of essential oil from pine needles was optimized by response surface methodology, and the following optimal conditions were obtained: a fresh pine needle of 100 g, an extraction time of 2 h, a water dosage of 850 mL, and a NaCl concentration of 2.50%. The extraction yield of essential oil was 0.611% under optimal conditions, which was extremely close to the predicted value. The extraction yields of essential oil from needles of 12 common pines in Guangxi were compared. The contents of essential oil in needles of Pinus massoniana, Pinus crassicorticea, and Pinus taeda were relatively higher than other pines. A total of 44 chemical components were identified by GC-MS, including 12 monoterpenes, 14 sesquiterpenes, and 12 alcohols. The chemical components of essential oil from different pines have their own features, and it is speculated that they have good and diversified application potential in the fields of medicine, food, spices, and so on. The chemical compositions of essential oil with high extraction yield have similar characteristics. This phenomenon can be used as the basis and means for the selection of pines with high content of essential oil in needles.