Damage to eucalyptus stumps due to machinery and positioning of tree bundles during timber harvesting

The positioning of tree bundles within the forest stand can influence the movement of machinery during timber harvesting, causing damage to the stumps and reducing sprouting during stump management. This study aimed to assess the damage caused by timber harvesting machinery to the remaining stumps in planted eucalyptus forests based on the angle of tree bundle arrangement. The research was conducted at a forestry company in the southern region of São Paulo state, in a hybrid stand of 9-year-old Eucalyptus grandis × Eucalyptus urophylla, in the first rotation or cutting cycle, using a feller buncher and skidder. Damage to the stumps caused by machines based on tree bundle angles of 17º and 45º was assessed through measurements of the stumps after timber harvesting. The following quality parameters were evaluated: height, soil and/or forest residue coverage, tearing, peeling, and shearing. The data were analysed using a completely randomized design, with two treatments and eight repetitions composed of sub-plots with 20 stumps, compared using Student's t-test at a 5% probability level. Results showed that, at both tree bundle angles, the stump height was within the reference value of 10 to 15 cm. Similarities in physical damage to the stumps were observed with tree bundles arranged at both angles. The highest occurrence of damage was shearing, with 35.1% of stumps affected at the 17º angle and 19.2% at the 45º angle. The 45º angle of the bundled trees in the moment of timber harvesting at the flat terrain conditions facilitated the machines movements, reducing the stump damage and improving the shoot development and sprouting rates for the stand under the stump management regime.