Damage to Residual Trees in Thinning of Broadleaf Stand by Mechanised Harvesting System

Branko Ursić,Ivica Papa,Tomislav Poršinsky,Dinko Vusić,Željko Zečić,Andreja Đuka

doi:10.3390/f13010051

Abstract

This research was conducted to determine the cause, intensity and location of damage (stem, butt end, root collar, root) and the extent of damage to standing trees during felling and processing by an harvester and timber extraction by a forwarder (cut-to-length system). The research was conducted in the central part of the Republic of Croatia in the Management Unit (MU) “Bjelovarska Bilogora” during the thinning of Subcompartment 14b, area of 18.28 ha, in the stand of hornbeam (Carpino betuli—Quercetum roboris fagetosum Rauš 1975), age 70, and of Subcompartment 14c, area of 9.07 ha, in a stand of common beech (Carici pilosae—Fagetum Oberdorfer 1957) aged 79 years. The thinning intensity was 12.13% in Subcompartment 14b and 13.72% in Subcompartment 14c. Field measurements were carried out on sample plots—the first time in 2017 to determine the intensity and characteristics of the damage to standing trees with regard to the cause of the damage (harvester or forwarder), and the second time in 2018 to determine the overall intensity and features of the damage to standing trees after finishing harvesting operations. For all trees remaining in the stand after the harvesting operations, the following were determined: tree species, diameter at breast height (DBH), the position of the tree in the stand depending on the forest traffic infrastructure, and—if damaged—cause of damage, type of damage, the position of damage on the tree, and dimensions of damage. The intensity of the damage was expressed by the ratio of damaged and undamaged trees, with a detailed analysis of bark damage (squeezed-bark damage and peeled-bark injuries). The results of the research indicate the highest prevalence of peeled-bark injuries. In relation to the total number of standing trees, trees with peeled-bark injuries were more represented in Subcompartment 14c (39%) than in Subcompartment 14b (33%). In Subcompartment 14b, the harvester and the forwarder damaged an equal number of trees, while in Subcompartment 14c, the harvester damaged 59% of the damaged trees. In both subcompartments, an average of 83% of (peeled bark) injuries were up to 1.3 m above the ground. In both subcompartments, the most common (67%) were injuries up to 100 cm2 in size, for which many authors claim the tree can heal by itself. Given the increasing use of harvester-forwarder systems in deciduous stands and research results that indicate possible damage to standing trees, it is necessary to pay attention to all phases of planning and execution of timber harvesting operations, thus minimising negative effects.

Highlights

IntroductionThinning as a treatment is a procedure that, with the help of positive selection, systematically directs the growth and development of selected trees, shapes the optimal structure of the stand following management goals, increases the quality, stability, and vitality of the stand, and prepares stands for natural regeneration [1]
14c was higher by approximately 18% (37 trees were damaged by the harvester and 26 trees by the forwarder)
In Subcompartment 14c, 70 individual peeled-bark injuries were recorded following the work of the harvester, which primarily occurred on the butt end (56%), root collar

Summary

Introduction

Thinning as a treatment is a procedure that, with the help of positive selection, systematically directs the growth and development of selected trees, shapes the optimal structure of the stand following management goals, increases the quality, stability, and vitality of the stand, and prepares stands for natural regeneration [1]. Each stand, managed according to even-aged principles, is exposed to thinning several times during its rotation period. In addition to the principles of thinning, it is to be expected that the future quality of timber be affected by the quality of performed harvesting operations. Silvicultural operations (such as thinning) are performed to achieve positive management goals, timber harvesting operations can negatively affect forest stands, which is primarily reflected in the damage of forest soil and the remaining trees [3]

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Conclusion