Abstract
The use of fully-mechanized operations, normally targeted at coniferous species, has also been on the rise in mixed-species and continuous-cover forests comprised of a strong share of deciduous species. With special form characteristics (complex crowns, large-diameter branches, forks and sweeps, high wood density, etc.), deciduous trees can lead to wide-ranging harvesting productivities, often divergent from those originally derived from coniferous species. Due to the importance and growing interest in mechanizing operations in close-to-nature mixedwood and deciduous stands, obtaining insight on harvesting productivity in large-diameter deciduous trees was of interest. This study located in Bavaria, Germany, monitored four harvesters (two wheeled and two tracked machines) operated in four distinct harvest blocks (case studies), all of which had a high percentage of large-diameter European beech and oak trees. Harvesting productivity and volume recovery was assessed and quantified. Based on the field inventory of European beech and oak trees and continuous time-and-motion study, average harvesting productivity ranged from 29 to 43 m3/PMH0 (productive machine hours without delay), whereas volume recovery fluctuated between 73% and 85% for trees that were completely felled and processed by machines. Because of the rather limited sample size and the variable conditions between case studies, results should only be used as general orientation on the performance of the tested machines and additional research is suggested to further understand the influence of tree form characteristics on impediments to mechanized processing.
Highlights
The use of machines in forest operations has been on the rise in many countries
Four independent case studies were performed during regularly scheduled forest operations at four sites in Bavaria, Germany: Bad Brückenau (BB), Hammelburg (HA), Heigenbrücken (HG), and Rothenbuch (RO)
With increasing shares of deciduous trees being managed under mixed-species stands and close-to-nature forestry, the interest in using fully-mechanized to perform forest operations is
Summary
The use of machines in forest operations has been on the rise in many countries. In German public forests, approximately half the wood volume harvested is with fully-mechanized systems, commonly comprised of (single-grip) harvesters and forwarders [1]. From the time of their development in the Nordic countries, single-grip harvesters and especially harvesting heads have been adapted to the characteristics of coniferous trees, for which they normally reach their highest productivity. With the higher shares of deciduous species being both naturally or artificially regenerated and managed under a close-to-nature forestry, the level of interest in expanding the use of mechanized cut-to-length (CTL) systems into mixedwood and deciduous stands is increasing. The advantages seem noteworthy; increased worker safety and improved ergonomics, but most of all, higher productivity compared to motor-manual operations. Labelle et al [2] reported
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