Damage Caused to the Remaining Trees of a Pinus Stand Submitted to Two Mechanized Thinning Models

Abstract

The objective of this study was to evaluate the damage to remaining trees of pine stand submitted to two models of mechanized thinning. Data were collected in the wood harvesting areas of a forest company in Southern Brazil during the first commercial thinning with 10-year-old trees. The thinning was executed by a harvester in cutting the trees and a forwarder in extracting the logs, which was defined by thinning in the 5th planting line (treatment T1); and by a chainsaw in felling the central trees, by a harvester in cutting the other lines, and by a forwarder in extracting the logs in the experimental area defined by thinning in the 7th planting line (treatment T2). The damage to remaining trees in the stand in relation to the dimensions and location of the machinery operating trail was evaluated, and data were analyzed through descriptive statistics. The results showed that treatment T2 caused greater damage in the remaining trees due to greater handling of felled and processed trees and a higher concentration of wood piles in the operating trail of the machines. In addition, there was greater contact of the harvester with the remaining trees when searching for the trees felled by the chainsaw was conducted to perform the final processing. Treatment T1 proved to be more suitable for thinning pine stands.

Damage Caused by a Wheeled Harvester to the Residual Trees of a Pinus Stand in the First Mechanized Mixed Thinning

“…The percentage of remaining trees with injuries was considered high in this study when compared to the results obtained by Lineros et al (2003), which presented 12.3% of damage in the first thinning of Pinus radiata at 10 years old, performed in the cut to lenght system with systematic removal of the 5 th row. Having studied the first combined thinning of pine trees at 10 years of age in 3 × 2 m spacing in southern Brazil, with systematic cutting in the 5 th and 7 th lines, Cabral et al (2018) found 13% and 17% of damage to the remaining trees, being lower than in this research. However, in another stand with a similar regime but with 12 years of age and systematic cutting in the 5 th line, Lopes et al (2018) found higher percentages with 36.1% and 29.1% in the slopes from 0 to 10º and 10 to 20º, respectively.…”

“…According to Vasiliauskas (2001), it is important to mention that the trunk sections of trees with a larger diameter are the most sensitive when affected by damage from thinning, with the possibility of not being able to close the lesion and it being attacked by fungi and insects; therefore, it can cause significant losses in the final product. Cabral et al (2018) warned that minor damage found in pine trees is usually still amenable to closure (healing), preventing the occurrence of future phytosanitary problems in the trees.…”

“…In addition to the intrinsic operational aspects of each situation, it is recommended to carry out studies in relation to other factors which may affect damage occurring, as their intensity may be related to the time of year, the location and the physiological conditions of the stand (for example). Cabral et al (2018) observed that it is difficult to avoid damage occurring to the remaining trees of a stand submitted to thinning caused by the movement of wood and machinery; however, Sirén et al (2015) described the need to plan thinning and develop better working techniques in order to reduce damage occurrence to trees in forest stands.…”

“…The damaged area in the trees was obtained by measuring using a 1 cm² grid, being classified as light (≤ 100 cm²), moderate (> 100 cm² ≤ 200 cm²) and intense (> 200 cm²). An individual count was carried out within each sampled plot regarding the number of damaged trees and the location of the damage, and classified in three different heights: base damage (≤ 1.3 m), trunk/shaft damage (> 1.3 m ≤ 6 m) and crown damage (> 6 m), according to guidelines by Lineros et al (2003) and Cabral et al (2018).…”

“…When carrying out a study on the impacts caused by these two machines on the commercial thinning of pine in Chile, Lineros et al (2003) observed that 12.3% of the remaining trees in the stand were damaged and suffered injuries to the crown and the lower section. Likewise, when studying two pine thinning models in southern Brazil, one with the systematic removal of the 5 th row and the other of the 7 th , Cabral et al (2018) found a high intensity of damaged trees in the plots in both thinning models, indicating the need to improve operational procedures.…”