A review of the effect of fertilization on the wood properties of Pinus trees

The use of intensive silviculture to increase forest productivity in commercial plantations will undoubtedly persist into the future. This review synthesizes and analyses studies that have investigated the influence of fertilization on density, microfibril angle (MFA), and modulus of elasticity (MOE) of different Pinus species under intensive management. It was found that in general, ring width or growth rate demonstrated a negative correlation with density, and a positive relationship with MFA. Also, the relationship between growth rate and density and MFA were age specific and often non-significant at the whole stem level. Earlywood and latewood were influenced differently by fertilization: Earlywood width and density increased while in latewood, width stayed constant but density decreased. This resulted in a decrease in within-ring heterogeneity of density and density-related properties. Since latewood generally contributed more to whole-ring density, the net effect was that whole-ring wood density of pines mostly decreased with fertilization. Given that fertilization often resulted in a decrease in wood density and an increase in MFA, MOE decreased with fertilization. Most fertilization-wood-property studies on Pinus involved nitrogen and phosphorus fertilizers with differing quantity and ratios. Results suggest that nitrogen may cause the greatest change in wood growth and properties. An important question that was often unanswered in research, was whether the effect of specific fertilization treatments on wood properties were purely based on the influence of increased growth or whether there were direct influences not explained by growth. Also, despite potassium being an important elemental component of many fertilizers, relatively little work has been done to determine its effect on wood properties.