Effect of Long-Term Soil Application of Major Nutrients on Pinus sylvestris (Pinaceae) Wood Microstructure

This paper investigates the effect of long-term annual fertilization with major mineral nutrients (N, K, P) on microstructural parameters of wood in artificial pine stands on fire-affected sandy soils. Fertilization has resulted in augmentation of the annual layer and, hence, a decrease in latewood percentage and density, but the differences in these parameters were below the confidence level. All qualitative characteristics showed the highest values under treatment with nitrogen. Within the observation period, the width of annual rings increased, while the wood density remained as in the control. Under N treatment, the thin-walled early- and latewood tracheids were formed, and their total number in radial rows was the smallest; it was counter-balanced by the formation of a greater number of rows of thick-walled larger-size latewood tracheids in the aftereffect period. Evaluating the set of the parameters in question it was found that wood quality does not deteriorate under nitrogen fertilization. Phosphorus had a minor effect on the wood quality. While the share of latewood and density decreased slightly during the period of observations, annual ring width increased. The greater increment was due to rows of thicker-walled larger-diameter latewood tracheids. Tracheids in earlywood have thinner walls. Fertilization with potassium resulted in a reliable decline in basic density due to lower latewood content compared to the control plot, and to the formation of thin-walled earlywood tracheids. Pine trees on burnt heather cutovers regenerating in lingonberry pine communities consume high amounts of nitrogen. Pine wood from the sites annually fertilized with major nutrients on a long-term basis can be recommended as high-quality sawtimber fulfilling the state standard (GOST 968-68) and the criteria of the Institute of Pulp and Paper Industry Raw Material Laboratory.