Relationship between relative wood density of Picea abies logs and simple classification systems of decayed coarse woody debris

The relationship between relative density and simple classification systems of decayed coarse woody debris was assessed for 384 cross-sections of deca yed Norway spruce [Picea abies (L.) Karst.] logs collected at five differen t study sites in south-eastern Norway. The relative density was computed as the ratio of actual density to the density of fresh wood. Three different classification systems were tested. One consisted of five classes and the o ther two consisted of eight classes each. All of the systems classified the samples according to variables related to bark. wood and trunk shape. The Spearman rank correlation coefficient between relative density and decay cl ass ranged from - 0.77 to - 0.80. The correlation coefficients of the three classifications did not differ significantly from each other. The mean rel ative density within each decay class also decreased successively from one decay class to the next for all classification systems. For the five-class system the mean relative density decreased from 0.97 in the least decayed c lass to 0.28 in the most decayed class. For the two eight-class systems the mean relative density decreased from 0.94 to 0.39 and from 0.97 to 0.24, r espectively.