A study was conducted to investigate the effects of skid trail slope and traffic levels on soil disturbances at two soil depths （0--10 and 10-20 cm）. The treatments were set at four traffic levels （2, 7, 12 and 20...A study was conducted to investigate the effects of skid trail slope and traffic levels on soil disturbances at two soil depths （0--10 and 10-20 cm）. The treatments were set at four traffic levels （2, 7, 12 and 20） two slope classes （〈20% and 〉20%） and two soil depths （0-10 and 10-20 cm）. Results show that skidder traffic, longitudinal slope and soil depth have significant effect on soil bulk density in skid trail. Compari- son of average soil bulk density in different traffic levels shows that there are significant differences in average bulk density between different traffic levels and control （p〈0.05）. The average bulk densities in different slopes and soil depths are significantly increased with increase in traffic levels, maximized at 12 passes （p〈0.05）, but there are no significant differences between 12 and 20 passes. The interaction effects between traffic and soil depth are significant （F005,3=0.109, p〈0.001）. For all traffic treatments, there are significant differences in soil moisture con- tent between the two slope classes and the two depths （p〈0.001）. However, the interaction effects between traffic levels and slope classes are not significant （p 〉0.05）, although skidder traffic and slope affected soil moisture content.展开更多
Short-term recovery of soil physical properties on skid trails was investigated upon cessation of skidding operations and 1 year later. Bulk density and porosity were assessed at three levels of traffic intensity and ...Short-term recovery of soil physical properties on skid trails was investigated upon cessation of skidding operations and 1 year later. Bulk density and porosity were assessed at three levels of traffic intensity and two slope gradients. Compared to undisturbed areas, bulk density increased, total porosity and macroporosity decreased, and microporosity increased in the compacted areas immediately after skidding. In all cases, changes were significantly greater when traffic intensity was higher and when slopes were steeper. Surface soil compaction did not show any recovery over the 1-year period, illustrating the persistent effects of compaction on soil structure. In fact, surficial compaction further increased and macroporosity further decreased after 1 year of recovery, compared to immediately after skidding. While these changes may reflect inherent small-scale site variability or differences in soil moisture content at times of sampling, direct negative physical impacts on newly exposed soil（such as by raindrops）, in addition to the loss of organic matter after canopy removal and skidding, likely delayed any physical recovery, particularly on heavily trafficked trails on steeper slopes. These results raise serious concerns about longterm resilience to traffic on forest soils and indicate the necessity to properly retire skid trails to avoid further soil degradation as trails age.展开更多
Wood extraction by heavy machinery has always been associated with soil disturbance in mountain forests,and the degree of soil degradation is influenced by several factors,including site and soil characteristics,soil ...Wood extraction by heavy machinery has always been associated with soil disturbance in mountain forests,and the degree of soil degradation is influenced by several factors,including site and soil characteristics,soil moisture,type of equipment used,and number of machine passes.The effects of ground-based skidding operations on the physical properties of soils with different texture were evaluated at different levels of traffic frequency and trail gradient at two sites in an Iranian temperate forest.The treatments included combinations of three different traffic frequencies(3,8,and 14 passes of a rubber-tired cable skidder),three levels of trail gradient(<10%,10%–20%,and>20%) and two soil texture classes,clay loam(Site 1) and sandy loam(Site 2).The average gravimetric soil moisture at the time of skidding was 23%(Site 1) and 20%(Site 2).The average dry bulk density and total porosity of the undisturbed soil(control) were0.71 g cm-3 and 73.3% at Site 1(clay loam) and 0.86 g cm-3and 59.1% at Site 2(sandy loam),respectively.At site 1(fine-textured soil),rutting began after three passes of the skidder,whereas at site 2(coarse-textured soil),rutting occurred only after eight passes.Independent of the traffic frequency and trail gradient,machine impact on the fine-textured soil caused greater increases in bulk density and rut depth compared to that on the coarse-textured soil.After three skidder passes and independent from trail gradients,dry bulk density at Site 1 increased by 54.8% compared to that of the undisturbed control,and the increase was 45.5% at Site 2.Therefore,medium to fine-textured soils are more susceptible to compaction than coarse-textured soils.Such soils,especially when moist,should be protected using brush mats created from harvesting residues during the forest processing phase.展开更多
文摘A study was conducted to investigate the effects of skid trail slope and traffic levels on soil disturbances at two soil depths （0--10 and 10-20 cm）. The treatments were set at four traffic levels （2, 7, 12 and 20） two slope classes （〈20% and 〉20%） and two soil depths （0-10 and 10-20 cm）. Results show that skidder traffic, longitudinal slope and soil depth have significant effect on soil bulk density in skid trail. Compari- son of average soil bulk density in different traffic levels shows that there are significant differences in average bulk density between different traffic levels and control （p〈0.05）. The average bulk densities in different slopes and soil depths are significantly increased with increase in traffic levels, maximized at 12 passes （p〈0.05）, but there are no significant differences between 12 and 20 passes. The interaction effects between traffic and soil depth are significant （F005,3=0.109, p〈0.001）. For all traffic treatments, there are significant differences in soil moisture con- tent between the two slope classes and the two depths （p〈0.001）. However, the interaction effects between traffic levels and slope classes are not significant （p 〉0.05）, although skidder traffic and slope affected soil moisture content.
文摘Short-term recovery of soil physical properties on skid trails was investigated upon cessation of skidding operations and 1 year later. Bulk density and porosity were assessed at three levels of traffic intensity and two slope gradients. Compared to undisturbed areas, bulk density increased, total porosity and macroporosity decreased, and microporosity increased in the compacted areas immediately after skidding. In all cases, changes were significantly greater when traffic intensity was higher and when slopes were steeper. Surface soil compaction did not show any recovery over the 1-year period, illustrating the persistent effects of compaction on soil structure. In fact, surficial compaction further increased and macroporosity further decreased after 1 year of recovery, compared to immediately after skidding. While these changes may reflect inherent small-scale site variability or differences in soil moisture content at times of sampling, direct negative physical impacts on newly exposed soil（such as by raindrops）, in addition to the loss of organic matter after canopy removal and skidding, likely delayed any physical recovery, particularly on heavily trafficked trails on steeper slopes. These results raise serious concerns about longterm resilience to traffic on forest soils and indicate the necessity to properly retire skid trails to avoid further soil degradation as trails age.
基金financially supported by University of Guilan, Iran
文摘Wood extraction by heavy machinery has always been associated with soil disturbance in mountain forests,and the degree of soil degradation is influenced by several factors,including site and soil characteristics,soil moisture,type of equipment used,and number of machine passes.The effects of ground-based skidding operations on the physical properties of soils with different texture were evaluated at different levels of traffic frequency and trail gradient at two sites in an Iranian temperate forest.The treatments included combinations of three different traffic frequencies(3,8,and 14 passes of a rubber-tired cable skidder),three levels of trail gradient(<10%,10%–20%,and>20%) and two soil texture classes,clay loam(Site 1) and sandy loam(Site 2).The average gravimetric soil moisture at the time of skidding was 23%(Site 1) and 20%(Site 2).The average dry bulk density and total porosity of the undisturbed soil(control) were0.71 g cm-3 and 73.3% at Site 1(clay loam) and 0.86 g cm-3and 59.1% at Site 2(sandy loam),respectively.At site 1(fine-textured soil),rutting began after three passes of the skidder,whereas at site 2(coarse-textured soil),rutting occurred only after eight passes.Independent of the traffic frequency and trail gradient,machine impact on the fine-textured soil caused greater increases in bulk density and rut depth compared to that on the coarse-textured soil.After three skidder passes and independent from trail gradients,dry bulk density at Site 1 increased by 54.8% compared to that of the undisturbed control,and the increase was 45.5% at Site 2.Therefore,medium to fine-textured soils are more susceptible to compaction than coarse-textured soils.Such soils,especially when moist,should be protected using brush mats created from harvesting residues during the forest processing phase.
