First research results on the use of the Pfanzelt Moritz FR75 at the Weihenstephan University of Applied Sciences.
Compact tracked skidders in practice – opportunities and challenges
Compact tracked skidders are becoming increasingly important for flexible use in forestry. Thanks to their compact design, versatile applications and comparatively low acquisition costs, they represent an attractive alternative to classic forestry machines. The German Council for Forestry Work and Technology (Kuratorium für Waldarbeit und Forsttechnik e. V., KWF) describes these compact implement carriers as easy-to-transport and easy-to-operate machines with high practical benefits, whether for harvesting wood, reforestation or cultivation.
In practice, however, the use of these machines requires careful planning. While they are well-suited for moving timber from the skid trail to within reach of a harvester, it is generally not permitted under PEFC and FSC requirements to drive them off roads and trails in wood harvesting. This is in contrast to forestry requirements, such as for soil preparation, where work in strips or across areas off roads and trails may be appropriate and permissible.
Test series on soil preservation – Weihenstephan University of Applied Sciences investigates tracked skidders
The investigations showed that there were hardly any detectable changes in the ground structure as a result of low-intensity traffic (two passes) compared to the reference surface. More pronounced compaction, on the other hand, occurred after four and eight passes, especially regarding the air pore volume, which decreased significantly in these cases.
Air pore volume
In undisturbed soils as well as in ground with two passes, the values were around 10–15% of the soil volume. Here, the values in undisturbed forest soils remained at a similar level to the measurements after two passes. However, there were significant reductions in cases with four or eight passes.
Total pore volume
On average, the values were around 50%. Here, too, the unaffected area performed best. Interestingly, however, there were no significant differences between the variants subject to different intensities of tracked skidder traffic, although there were in comparison to the skid trails.
Summary and outlook
The results so far prove that under certain conditions, a low traffic intensity with compact tracked skidders is compatible with soil preservation. However, compaction effects become measurable as soon as the volume of passes increases. It should be noted that in the first test run, only a simple pass was examined without additional load from attachments such as cable winches or mulchers. Potential shear effects caused by turning manoeuvres were also not taken into account.
We do not currently see any need to leave skid trails for work with a cable winch in wood harvesting.
Further investigations already started
Turning manoeuvres (shear load) and the use of a cable winch outside the skid trails were examined. In addition, mulching strips were created. The soil samples from these scenarios will be evaluated in the coming months. Resampling after twelve months should reveal potential long-term effects.
We are very much looking forward to receiving the results of these further tests...
The authors
Lecturers at Weihenstephan-Triesdorf University of Applied Sciences, Faculty of Forests and Forestry
Florian Rauschmayr – specialist in forestry and wood harvesting technology
Dr Michael Jeschke – specialist in soil science, geology and land evaluation
The full study can be found in “Allgemeine Forst- und Jagdzeitung”, 193rd year, issue 9–12, title: “Analyse der Bodenverdichtungen von kleinen Forstraupen (MFC) bei verschiedenen Befahrungsszenarien auf unbefahrenen Waldböden und herkömmlich befahrenen Rückegassen”