Assessing specific gravity of young Eucalyptus plantation trees using a resistance drilling technique

Abstract

The resistance drilling technique has been in focus for assessing the specific gravity (SG) of young Eucalyptus trees from plantations for pulpwood production. Namely, the data of 50 34-month-old and 50 62-monthold trees from Eucalyptus grandis × Eucalyptus urophylla clonal plantations was evaluated, while the relative resistance profiles were collected with the amplitude in a scale from 0 to 100% of each tree at the breast height. For laboratory determination of SG and moisture content (MC), 3-cm-thick disks were taken at breast height. The average resistance amplitude of a full drill penetration or a halfdiameter penetration showed weak correlations with SG for both 34-month-old and 62-month-old trees. However, when the two age classes were combined, the strength of the relationship was improved significantly, with a correlation coefficient ranging from 0.71 to 0.77 with respect to SG determined from strip samples and from 0.59 to 0.72 with respect to SG determined from wedge samples. The drill penetration depth had a significant effect on the relationship between average amplitude and SG. A clear trend of weakening correlation was observed with increasing drill penetration. As a result, the average resistance amplitude of a half-diameter drilling (from bark-to-pith) is more advantageous for assessing the SG of young Eucalyptus trees than a whole-diameter drilling.

Citation

Oliveira, José Tarcísio da Silva; Wang, Xiping; Vidaurre, Graziela Baptista. 2017. Assessing specific gravity of young Eucalyptus plantation trees using a resistance drilling technique. Holzforschung. 71(2): 137–145.