In order to compare
different methods for estimating forest biomass, the dry mass of needles,
branches, stem and roots at tree to stand levels was investigated in a mixed
Norway spruce ( Picea abies )–Scots pine ( Pinus sylvestris ) stand in
southern Finland by means of direct weighing to allometric functions. The
results revealed a substantial difference among estimations made with various
methods. For instance, at the stand level, with the above-ground tree biomass
(170.8 Mg ha^–1) estimated using partial harvesting methodas a
baseline, tree biomass had a higher estimate (+10%) based on the dry mass of
selected understorey, medium and dominant trees as the sample trees, but a lower
estimate (–18%) by means of the allometric functions established based on the
data gathered from nearby trees. At the individual tree level, the allometric
functions overestimated dry weight of needles and branches by 20%–207% and
38%–263% for dominant pine and understorey spruce, respectively, but
underestimated the stem weight. These results imply the utmost importance of
considering the estimate error when calculating the tree biomass in a forest
stand with an indirect approach.