Productivity and Quality Issues In Young Stand Mechanized Tending In Latvia: A Case Study

Young stand tending is common practice in Latvia, where every year around 60,000 hectares are tended. The purpose of the tending is to create the desired composition of the tree species with a specified number of trees to provide them with sufficient growth space. Tending, where biomass is not collected is highly manual work, done with brush-cutters. Due to the lack of labor, which is a common problem in forestry, mechanized young stand tending is a solution to keep tending at the same intensity shortly. To compare mechanized young stand thinning productivity and quality, the study was done in 11 sites, where in 5 sites job was done when trees had leaves and in 6 sites in leafless state. In 5 sites trees were regenerated naturally and in 6 sites were planted. Work was done in 9-16 year old birch, spruce, and pine stands, where tree height was 5 – 8 meters. The tending was done without biomass collection and all felled trees were left on the ground. From the LIDAR data cloud, different sample plots regardless of tree density (high, average, and low) were installed in sites, where working productivity and tending quality were measured. As base machine was Malva 560.H4 and the cutting head was Risutec RII. The time spent during thinning was analyzed using the GPS tracker, which recorded base machine coordinates every second. Tending productivity was measured in 450m2 plots and tending quality in 100m2 plots. This study aimed to evaluate mechanized young stand tending without biomass collection productivity in different tree species, densities, leaf conditions (in autumn when trees and bushes have leaves, and winter time, when they are without leaves), and quality. Average mechanized tree tending in all sites was 10.7 hours ha-1, whereas, in areas with low tree density, it was 8.1 hours ha-1, with medium 10.3 hours ha-1, and with high tree density 13.6 hours ha-1. The average tending time in sites where the work was carried out in the leaf period (early autumn when the tree has leaves and heavy grass overgrown, which obstructed visibility and made the base machine move slower) was 13.1 hours ha-1, while in the leafless period (early winter) it was 8.7 hours ha-1. Average tending productivity in spruce sites was 12,6 hours ha-1, in birch sites 11,8 hours ha-1, and in pine sites 8,9 hours ha-1. In almost all sites, the number of trees left is less than optimally required, except for one site where it was significantly higher. Despite limited visibility from the machine cab, mechanized tending can ensure, that quality requirements are met by cutting trees with double tops, crookedness, and animal damage. Despite the swinging and free movement of the cutting head, the bark abrasions and notches on the left tree bark are mostly small (4 x 5 cm) and will not affect the future growth of the trees. The growing conditions and stand density in the site usually are different, which must be considered when tending productivity is predicted in the site.