Pine stands occupy about 60 % of forest area in Zhytomyr Polissya zone. The great part of the stands reaches the age of maturity. Correspondingly, the proportion of the area needed to be reforested is increasing. However, despite scientific knowledge and practice, the issue of pine plantation density for getting high productive stands remains unresolved.
The aim of our research was to determine the influence of the density on some mensuration indices of 40-year-old planted pine stands in Zhytomyr Polissya zone and to identify the trends in their changing.
Materials and Methods
The research has been conducted at the stationary experiment No 1 in Krimokske forestry in Radomyshl Forestry and Hunting Enterprise. The stationary experiment was established in production pine plantations, which were created in 1972. In the stationary experiment, the planted pine stands were divided into 3 sections with four subsections in each according to the density as follows: the section with subsections No 1–4 – 4,000 stems per ha, the section with subsections No 5–8 – 2,000 stems per ha and the section with subsections No 9–12 – 1,000 stems per ha. In subsections 1, 5 and 9, herbicides were used; herbicides with mineral fertilizers were applied in subsections 2, 6 and 10; mineral fertilization were used in subsections 3, 7 and 11, and power-driven tending was used in subsections 4, 8 and 12. The research has been carried out using the standard methods of forestry and forest inventory.
The data analysis showed that the lower average tree diameter values were observed in more dense pine stands. One-way ANOVA test revealed the significant difference between the diameters in the subsection with herbicides with stand density 4,000, 2,000 and 1,000 stems per ha. In this subsection, the difference between mean diameters was 14 % at the densities of 4,000 stems per ha and 2,000 stems per ha and 19 % at the stand densities of 2,000 stems per ha and 1000 stems per ha. Between sections with a density of 4,000 stems per ha and 1,000 stems per ha it was 31 %. The difference of the mean diameters was also significant in other subsections: with simultaneous using herbicides and mineral fertilizers, with mineral fertilization and with power-driven tending. In the subsection with mineral fertilization, the difference in mean diameters was 13-34 % between sections with stand density of 4,000, 2,000 and 1,000 stems per ha. In subsection with herbicides and mineral fertilization the difference was 14–34 % and for power-driven tending, 10–23 %.
A simple comparison of mean heights showed the height dependence on the density of pine plantations, specified in young age. One-way ANOVA test revealed a significant mean height difference in the subsection with use of herbicides and in the subsection with mineral fertilization. The difference was noticed among sections with a density of 4,000 and 1,000 stems per ha and amounted to 7 %. In subsection with joint use of herbicides and mineral fertilization and in power-driven tending subsection, a significant difference in mean values of height was not found.
The mean stand volume per hectare is the main inventory index characterizing the productivity of stands. The difference in stand volume was 2–8 % in the subsection with use of herbicides, between sections with the density of 4,000, 2,000 and 1,000 stems per ha. It was 2–4 % in the subsection with joint use of herbicides and mineral fertilization and 2–9 % in the subsection with power-driven tending.
The principal mensuration indices of pine stands, grown in fresh fairly infertile sites in Zhytomyr Polissya zone, depend on the density of the stands to a greater (mean diameter) or a lesser (mean height and stand volume) extent. The average diameter increased by 15–21 % with increasing density from 1,000 to 2,000 stems per ha and by 23–34 % with increasing density from 1000 to 4000 stems per ha depending on variants of the study. The general trend of the influence of the pine plantations’ density, specified in young age, on the stock volume and the average height could not be identified.
1 Fig., 4 Tables, 17 Refs.