Assessment of the impact of ground-based skidding on soil physical properties: initial effect and medium-term recovery (original) (raw)
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Silva Fennica, 2012
Ground-based skidding can have detrimental effects on soil properties trough soil profile disturbance and compaction that can persist for decades. We investigated the recovery of physical properties of disturbed brown soils on four abandoned downhill skid trails in a deciduous mountain forest in northern Iran. The most recent skidding operations had taken place 1â5Â yrs, 6â10 yrs, 11â15 yrs, and 16â20 yrs ago, providing a 20-year chronosequence with four 5-year recovery periods. For each recovery period, mean values for soil bulk density (BD), total porosity (TP), macroporosity (MP), soil moisture content (SM), and rut depth (RD) were assessed for three levels of traffic intensity (Primary (PS), Secondary (SS) and Tertiary (TS) skid trails) and two levels of slope gradients (Gentle (G) and Steep (S)) and compared to those in undisturbed (control) areas. Over the 20-year recovery period, PS trails on gentle slopes exhibited mean values that were 35â42% (BD), 3â7% (SM), an...
2017
Harvest traffic with heavy equipment causes damage to forest soils. Whereas increased soil damage has been reported with increasing harvest equipment traffic and on increasing slope gradients, it is unclear how much soil damage is caused by different directions of skidding. We examined the effects of traffic frequency, skid trail slope and skidding direction on the dry bulk density and total porosity of skidding trail soil in an Iranian temperate forest. The studied treatments included combinations of three different traffic frequencies (3, 7, and 12 passes of a rubber-tired skidder), three levels of slope (<10%, 10–20% and >20%) and two skidding directions (uphill and downhill). The impact on soil properties was greatest during the skidder initial passes. On steep slopes, only three skidder passes were required to cause substantial increases in soil bulk density relative to control plots, regardless of skidding direction. Independently of the traffic frequency and trail slope...
International Journal of Forest Engineering, 2023
Skidding operations affect soil physical properties, which may impact soil sustainability and forest productivity. While the relationship among harvest machine traffic, slope gradients, and increased soil damage has been well-investigated, it is still unclear how soil damage due to repeated passes of different skidder types is interacting with soil moisture and slope conditions. We examined dry bulk density (BD), total porosity (TP), and rutting depth (RD) of skid trail soil in an Iranian temperate forest. The study took into consideration a combination of five different traffic intensities (TI) (1, 4, 8, 12, and 15 passes), two levels of slope gradients (SGs) (≤20% and > 20%), two rubber-tired skidder types (STs) (Timberjack 450C and TAF E655), and two soil moisture contents (SMC) (18% and 31%). Results showed that changes in BD and TP were mainly related to TI regardless of the ST and the skid trail slope. Regardless of TI, SG, and SMC, the TAF E655 skidder caused a higher dry BD increase and soil porosity reduction than the Timberjack 450C. Furthermore, the higher the SMC, the deeper the ruts at all combinations of TI, SG, and ST. Our findings highlighted that ST, SMC, TI, and SG strongly affect rutting and physical properties of soil.
Soil disturbance caused by different skidding methods in mountainous forests of Northern Iran
Harvest traffic with heavy equipment causes damage to forest soils. Whereas increased soil damage has been reported with increasing harvest equipment traffic and on increasing slope gradients, it is unclear how much soil damage is caused by different types of harvesting equipment. We visually assessed 16 categories of soil surface disturbances and measured soil bulk density, porosity, and rut depth on skid trails following increasing harvest traffic intensities by two rubber-tired skidders, a crawler skidder, and a mule. Regardless of the skidding type, the most severe soil disturbances were observed where equipment traffic was most frequent and on steeper slope gradients. The different skidding equipment resulted in different proportions of disturbed soil areas that ranged from 61.5% of harvested area for mule hauling to 70.3% for skidding with a crawler skidder, 76.6% for skidding with a Timberjack 450C skidder, and 87.1% for skidding with a TAF E655. Shallow disturbances, slash cover, and apparent compaction (i.e. a deep soil disturbance) were the most common types of machine-induced soil disturbance. Mule hauling did not cause any deep soil disturbance. Results showed that bulk density increased with traffic intensity regardless of the skidding method used and the slope of the skid and mule trails. Porosity decreased in the surface layer (0–10 cm) with increasing number of passes and the impact increased with increasing slope. Rutting was not observed when skidding with a crawler skidder or hauling with a mule. The results indicated that equipment type, traffic intensity, and slope gradient had strong effects on the physical properties of the soil.
Soil physical properties degrade further on skid trails in the year following operations
Journal of Forestry Research, 2017
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.
Journal of Forestry Research, 2010
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. Comparison 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 (F0.05,3=0.109, p<0.001). For all traffic treatments, there are significant differences in soil moisture content 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.
Journal of Forest Science, 2013
With increasing mechanization of forest harvesting operations the impacts on soil have increased quite dramatically. The objective of this paper was to examine the relationship of slope and soil loss. This research was carried out in parcels 14 and 26 of the third district of Nav-Asalem forest in the north of Iran. Erosion plots were 75, 150 and 225 m<sup>2</sup> with two slope classes. After each rainfall event the amount of runoff was measured; then, a sample was taken to determine the weight of soil loss. The results of correlation analysis by Pearson’s test between soil loss and slope classes, soil loss and slope length showed that there was a significant (P < 0.05) and positive correlation between the mentioned factors. Also, linear regression between soil loss, slope length and slope gradient was significant. It could be concluded that studying and underlying factors that increase soil loss such as soil type, rainfall intensity, should also be taken into c...
This study evaluates the effects of ground-skidding operations on the physical and chemical properties of soil at different levels of slope gradient and traffic frequency. Three levels of traffic (four, eight and 16 passes of a rubber-tired skidder Timberjack 450 C), and two levels of slope gradients (gentle b20%, and steep ≥20%) were applied in three replicates consequently, 18 plots with 10 m long by 4 m wide were utilized in the study. In each sampling plot, three lines were set up perpendicular to the skidding direction. At three different points on each line (left track, between track and right track) one sample was taken from forest floor and the 0–10 cm soil layer. Soil bulk density, forest floor biomass, organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K) and soil acidity (pH) were affected by traffic frequency and slope gradient. The soil class of our study area in soil classification according to WRB was Combisols. Soil texture was analyzed using the Bouyoucos hydrometer method and was determined to be clay loam along the trails. Soil bulk density was 60% higher in samples taken from skid trails compared with samples taken from an undisturbed area. The average forest floor biomass ranged from 2185 kg ha −1 to 243 kg ha −1 on the skid trails, while the respective value was 3335 kg ha −1 for the undisturbed area. Skidding caused a decrease in the amount of soil OC (by 38%) and the concentrations of N (57%), P (25%), K (31%) and hydrogen ions (33%) compared with undisturbed areas. Increased soil disturbance occurred more markedly with fewer passes on the steeper trail. The dramatic increase in soil disturbance on the skid trail with a slope N20% is presumably associated with the difficulties of skidding on steep terrain. To minimize soil disturbance , skidding should be confined to areas with more gentle slopes and alternative harvesting methods should be used where slope gradients exceed 20%. We hypothesized that skidding can jeopardize the sustainability of forest ecosystems by creating unfavorable changes in soil characteristics and nutrient status.
Skidding operations induce considerable and wide spread soil disturbance. It is unclear how much additional damage is caused by increased soil moisture content at the time of skidding. We visually assessed 16 categories of soil surface disturbances, measured surface layer bulk density, porosity, and rutting in two oriental beech sites in northern Iran following five frequencies of traffic on two slope gradients with 19% and 33% soil moisture content. At both moisture contents, the most severe soil disturbances occurred with more frequent equipment traffic and on steeper slopes. Soil disturbances were detected on 65% of the harvested area at lower and 87% at higher moisture content. Bulk density, porosity, and rut depth were significantly affected by traffic frequency, trail slope and moisture content. Bulk density nearly reached critical values of 1.4-1.55 g cm–3 after 7 passes at higher and 12 passes at lower moisture content. Adverse effects on porosity caused by increased traffic and trail slope increased with increasing soil moisture content. Rutting was observed after one and seven passes at high and low moisture content, respectively, and was deeper on steeper slopes. To minimize disturbance, groundbased skidding should be limited to times when soil moisture content is low.