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Determining Harvester Productivity Curves of Thinning Operations in Birch Stands of Central Europe
Silver birch (Betula pendula Roth) is a popular tree species forming stands in nearly the whole of Europe. In Poland, birch is one of the most representative broadleaved species growing on rather poor soils, very often as a mix species with Scots pine (Pinus sylvestris L.). In Central Europe, birch forms trunk often with sweeps, and at the older age with thick branches. Due to that, a harvester thinning operation in birch stands can be challengeable when trying to process logs from the top part of trees, which can finally impact on productivity. The objective of this research was to determine harvester productivity for birch with particular attention to production of logs from the top part of a tree. The research was carried out in stands of North and North-West Poland. All together 21 tests were completed in 16 stands, in which 9 harvesters were used (8 different models). The mean diameter of harvested trees was 23.7 cm with the mean height of 21.7 m. Obtained productivity without delays was on average 21.98 m3 h-1 and varied from as low as 5.14 to maximum 44.66 m3 h-1, and depended mainly on harvested tree size. It was also confirmed that top diameter of the last log depended on diameter at breast height (DBH). The model developed based on that relationship can be used for prediction of biomass volume from birch stands when harvesters are used for thinning.
Technodiversity - glossary of forest operations terms
The Technodiversity project addresses technological diversity by gathering a common basis of technological knowledge and increasing the sensitivity for diversity in forest engineering. It aims to bring together and make generally available the existing knowledge in forest operations that is scattered across various European countries. It will serve as a bridge between different regions of Europe and generations of students, practitioners, scientists and academics. In this article, a small part of the e-learning module (https://technodiversity-moodle.ibe.cnr.it/) is presented in a glossary of some of the terms of forest operations.
Mechanised Harvesting of Broadleaved Tree Species in Europe
Abstract Purpose of the Review The application of cut-to-length (CTL) technology for harvesting and processing timber from broadleaved tree species is a challenging process, due to thick branches, stem sweep, forks and high wood density. The objective of this review was to describe the current state of harvester use and characterise the effectiveness of mechanised forest operations for broadleaved and mixed forest stands in Europe, paying particular attention to productivity and product quality aspects. An additional aim was to identify the greatest difficulties associated with harvesting broadleaved tree species today and to indicate future challenges and areas for improvement. Recent Findings An interest in wider harvester use for broadleaved tree species started after the storm Lothar in France in 1999. Early experiences demonstrated that lower productivity is common when harvesting broadleaved tree species, due to limitations in delimbing and the high frequency of sweep. Initially, modifications were made to harvester heads, while a newly designed head (CTL 40 HW) was later developed within a European project in 2005–2007. Using various heads, very high productivity was achieved in some cases, but log recovery was unsatisfactory, with large tree tops left without delimbing. The delimbing was of lower quality and log length inaccuracy was observed, as well as economic losses due to damage to plywood caused by feed rollers. These issues resulted in a change in harvester head construction, including work on a patent for a head designed specifically for harvesting broadleaved tree species. Summary The harvester heads that have been developed to date for broadleaved tree species have mainly been used within Central Europe, where the high incidence of broadleaved tree species and their particular morphological features (thick branches and sweep) are a major challenge for CTL technology. There have been many research projects related to this issue: in the last 15 years, there were a few larger initiatives leading to the design and development of harvester heads for broadleaved tree species, with participation from institutions and universities in France, Germany and Poland. There are currently no ongoing initiatives, but the formation of new ones is strongly recommended because today’s forests have a growing share of broadleaved tree species and are being managed to an increasing extent with CTL technology.