Abstract
Key messageRut depth in fine-grained boreal soils induced by an 8-wheeled forwarder is best predicted with soil moisture content, cumulative mass of machine passes, bulk density and thickness of the humus layer.ContextForest machines are today very heavy and will cause serious damage to soil and prevent future growth if forest operations are carried out at the wrong time of the year. Forest operations performed during the wettest season should therefore be directed at coarse-grained soils that are not as prone to soil damage.AimsThe study aimed at investigating the significance of the most important soil characteristics on rutting and developing models that can be utilized in predicting rutting prior to forest operations.MethodsA set of wheeling tests on two fine-grained mineral soil stands in Southern Finland were performed. The wheeling experiments were conducted in three different periods of autumn in order to get the largest possible variation in moisture content. The test drives were carried out with an 8-wheeled forwarder.ResultsSoil moisture content is the most important factor affecting rut depth. Rut depth of an 8-wheeled forwarder in fine-grained boreal soil is best predicted with soil moisture content, cumulative mass of machine passes, bulk density and thickness of the humus layer.ConclusionThe results emphasize the importance of moisture content on the risk of rutting in fine-grained mineral soils, especially with high moisture content values when soil saturation reaches 80%. The results indicate that it is of high importance that soil type and soil wetness can be predicted prior to forest operations.
Highlights
Forest machines are today rather heavy, typically from 20 to 40 t, and may cause significant soil deformation if forest operations are not well planned
bulk density (BD), SOM and volumetric water content (VWC) are significantly correlated with each other
Penetration resistance is only correlated with VWC
Summary
Forest machines are today rather heavy, typically from 20 to 40 t, and may cause significant soil deformation if forest operations are not well planned. When the loading induced by the vehicle exceeds the bearing capacity of the soil, the soil begins to compact and deform. Exceeding the bearing capacity of soil leads to rutting and deformation, where soil particles. Data analyses and writing of the paper was conducted by the first author (Jori UUSITALO). All authors participated in finalizing the paper. Soil deformation occurring during timber harvesting includes both elements of compaction and rutting. The bottom of ruts is the most probably compacted and displacement of soil particles in the lateral direction creates bulges at the edges of the ruts (Haas et al 2016; Toivio et al 2017; Marra et al 2018)
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