Evaluation of impact of soil compaction in ditch-sides during forwarding of roundwood on groundwater level in neighbouring forest stand

Abstract

The aim of the study is to evaluate the impact of forest machines on soil compaction in ditch-sides and to describe the impact of soil compaction on water exchange between forest stands and drainage ditches. The study was carried out in Ceraukste parish. Three research objects have been selected nearby the newly constructed forest roads, where timber delivery has not yet been carried out. Each research object includes an experimental plot and a control area, each covering a 50-meter long area along the road, including a ditch tip and a 15-meter-wide forest strip. Field works include collection of data on soil penetration resistance, groundwater level monitoring, and collection of soil samples for determination of water permeability rate. The study concludes that, as a result of forwarding, the soil layer at the depth of 20-60 cm is substantially compacted during forwarding and soil compaction has a negative effect on changes of the groundwater level in the forest stand bordering with the test objects. The study concludes that the number of samples to be tested for water permeability should be significantly increased in order to characterize the water filtration rate. The results of the water permeability rate analyses in 2017 and 2018 are contradictory. It is possible that the difference in the results is due to the fact that the backing is overlapping during the construction process and then, after aligning the ditch-side after the transfer, is mixed. Water filtration properties tend to recover over time, so it is useful to repeat observations on the backwaters after several years to assess how long the impact of the timber delivery on the soil remains, as well as to increase the diversity and intensity of measurements by putting new sample plots in areas with different soil texture.