Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

Abstract The study analysed four volume increment indexes in terms of basic statistical characteristics. Empirical material consisted of 314 pine trees, growing in a 35-year old pine stand. Stem analysis was conducted on cut trees and 4 volume increment indexes C₁, C₂, C₃ and C₄ were calculated in successive 5-year growing periods. The lowest variation was found for two increment indexes, C₂ and C₄. A slightly higher variation was observed for index C₃, while the highest for C₁. The highest coefficients of variation of indexes C₁, C₂ and C₃ were recorded in the growing period of 6-10 years, while the lowest for the period of 11-15 years. In case of index C4 it was the period of 31-35 years and 16-20 years, respectively. No distinct trend or relationship was found between the arithmetic mean of increment index C₃ and the age of trees. The mean of index C₁ increased with the age of trees, similarly as it was the case with index C₂, with only one difference that in the last growing period this mean decreased. Index C₄ decreased with the age of trees. In most cases the highest variation of indexes was recorded for trees of Karft’s classes IVb and Va. In those tree stands in which tending operations were conducted, the variation of all volume increment indexes should be lower.