Photogrammetry estimation of wheel ruts dimension and soil compaction caused by a forwarder.

Soil compaction and rutting are consequences of forest logging and is usually investigated by means of time-consuming methods, not able to represent the whole longitudinal profiles of forest trails. New methods based on photogrammetry have been developed. The overall objective of this study was to compare photogrammetry and traditional methods (cone penetrometer, manual rut depth measurements, soil bulk density and porosity) for evaluating rutting (depth and rut volume) and its relation with traditional measurements after repetitive passes of a loaded forwarder and two different levels of tire pressure. The comparison of photogrammetric vs manually-measured profiles resulted in R 2 of 0.934. The results showed the effect of tire inflation pressure and number of passes on soil disturbance. The estimation of the rut volume caused by the forwarder on 100 m long trails after 60 passes were 8.48 m 3 and 5.74 m3 for tire pressure of 300 kPa and 150 kPa, respectively. The results showed a relation between soil compaction, rut volume and soil porosity. Increased rut volume correlated positively with increased soil compaction and decreased soil porosity. Structure For Motion photogrammetry can be an accurate instrument for high-resolution Digital Evolution Model creation and for morphology description of forest soil disturbance after forest logging.