This research was carried within an area of tropical forest of “terra-firme”, in Breu Branco,
Pará, in order to estimate the volume of trees, considering only the diameter of the trunks
leftovers, which is necessary for the overseers to precisely estimate the volume of trees that
were either illegally took away or were inappropriately cut off, even if respected the forest
management plan. The area belongs to the company IBL (Izabel Madeiras do Brasil Ltda),
which forest management plan was inspected and authorized by IBAMA. A total of 113 trees
with DBH 51 cm, of different species and diameter classes were selected to determine the
real cubic volume of commercial trunk. The selection of the species and trees was done
according to the company’s forest management plan set. The trees were cubed by the method
of Hohenadl considering the division of the commercial trunk in ten sections of equals lengths
and the volume of each section of the trunk was determined by the Smalian formula.
Equations were adjusted to estimate the commercial volume of the trees in function of trunks
leftovers (d0). Equations of commercial volume in function of DBH and DBH and height were
adjusted too, to comparisons. Due to the presence of trees with irregular shape and non-
cylindrical trunks leftovers by the buttresses, different methodologies were tested to estimate
the trunks leftovers diameter (d0), which is often measured 30 cm above the meeting with the
buttresses. The results showed that d0 has a high correlation with the commercial volume of
trees within an area of forest of “terra firme” and it can be used in the adjustment of
mathematical models in order to estimate the commercial volume of trees. No significant
difference between the real and the estimated volume of trees – generated through an adjusted
linear equation in function of d0 was found. Therefore it is possible to precisely obtain the
volume of trees from their d0. The precision of volume equations generated from the d0
compares to those generated from the DBH, within a significance level of 5% by the t test.
The results also showed that it is possible to estimate d0 of non-cylindrical trunks by measuring
the diameter either on the soil level ( Dcs ) or on the cut level ( Dcc ). Factors of estimation of d0
obtained by the ratio between either d0 and Dcs or by the ratio between d0 and Dcc , can be
used to estimate d0. The estimations of d0 were precise (5%) when obtained either from an
average estimation factor, generated from Dcs , for the sampled population or from
mathematical equations that estimates the estimation factor as a function of Dcs and Dcc .
Therefore, whenever one uses a volume equation as a function of an unknown d0 to estimate
the volume of a tree with a non-cylindrical trunk and an irregular shape, it is possible to obtain
d0 either by the estimation factor of the tree (equation) or the average estimation factor of the
area of the study, obtained from Dcs . Hence, the results leads to conclude that it is possible to
estimate the volume of trees within an illegally deforested area of land, where there is no data
about the harvested volume of wood, by measuring the diameter of the trunk leftovers
remained after the exploitation.
