Conversion of Norway spruce (Picea abies (L.) H. Karst.) tree stem volume to volumes of produced logging residues and wood chips

Abstract As a renewable fuel, logging residues, as well as other dendromass, are in high demand. On the other hand, they can serve as a natural fertilizer and stabilize biodiversity in forest ecosystems. Therefore, they need to be used rationally, with due care for the volumes extracted from a particular stand. The volume of logging residues is difficult to measure; thus, foresters need a tool to estimate it, ideally via a simple method based on easily measurable parameters. Conversion factors, based on tree stem volume can serve this purpose. In this study, we develop such conversion factors for thinnings of Norway spruce (Picea abies (L.) H. Karst.) stands. First, we analyzed the relationship between the tree stem volume (ranging between 0.03 and 0.44 m3 stem−1) and the volumes of related logging residues or wood chips via linear regression and correlation analysis. Then, we assessed the significance of differences between volumes of logging residues or wood chips for trees in the five relevant stem volume classes and determined appropriate conversion factors. The conversion factors for wood chips ranged between 1.37 loose cubic meters of logging residue per cubic meter of timber in the largest stem volume class to 2.17 for the smallest stem volume class. The model, on which the conversion factors were based had a coefficient of determination of 0.88. Conversion to logging residue volume yielded factors ranging from 2.2 stacked cubic meters per cubic meter of timber for the largest stem volume class to 10.2 in the smallest stem volume class. The coefficient of determination of the underlying model was 0.69. The conversion factors are based on sufficiently accurate models and can be used in practical forestry for planning purposes, recordkeeping, and remuneration of loggers.