A double-entry tree volume table for beech (Fagus sylvatica L.) coppices in Piedmont

The aim of the present work is to fill a gap in the collection of available algorithms for the estimation of standing tree volume. The deficiency of such tools is especially marked when their object is represented by stands undergoing strong or rapid changes in forest structure. Such is the case of beech (Fagus sylvatica L.) coppices in Piedmont, once managed mainly for firewood, i.e., with fast rotations and a mean tree size much smaller than what observed in current stands. In addition, the structure of most of these stands was heavily impacted by selection cuttings in the early '90s, aimed at the conversion of coppices to high forests in the long run. A single tree volume table (inclusive of branches and bark volumes) has been prepared according to the following steps: (1) selection of relevant stands, representative in their extent, density and merchantability (13 alpine valleys in 6 provinces); (2) computation of sample size according to the observed variability in the selected study areas (1085 model trees for height and volume); (3) tree measurement and data mining (statistical detection of outliers and selection of the most suitable model form for a double-entry tree volume table). The main output of the study is the volume table itself. The paramount importance of such tool for forest management is confirmed by the abundance of beech forests (136000 hectares, i.e., the second most represented forest cover type in the study region), 90% of which is still managed as coppice stands