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Skid trails are a major management‐induced disturbance in temperate forest ecosystems with considerable impact on soil ecological processes that are so far poorly understood. In German forests, skid trails comprise 10%–20% of the forest area that is potentially affected by soil compaction through heavy machinery. We systematically investigated the influence of skid trails on physical, chemical and microbiological soil parameters at 84 paired plots across four Central European forest types.In low mountain forests with steeper topography, skid trails had more drastic effects than in lowland forests. Skid trails in low mountain areas showed a decrease in the C to N ratio of microbial biomass (MBC/MBN), as well as increased microbial (MBC/SOC) and enzyme activities leading to faster carbon turnover (lower C/N, EOC/EN) and increased CO2 losses (CO2/SOC) from the soil.The overall effects of the skid trails in lowland forests were small. On base‐poor soils, we found an increase in the MBC/MBN ratio, while skid trails in base‐rich lowland soils showed a reduction in CO2/SOC, suggesting a proportional increase in soil carbon storage.Regardless of region‐specific effects, the relative increase in the bulk density of the fine soil was identified as a 'golden trait' that determined the effects of skid trails on many soil parameters, as shown by negative correlations with SOC, N, MBC, MBN, MBP, MBC/SOC and CO2/SOC and positive ones with the activities of certain hydrolytic enzymes.Synthesis and applications: Our data clearly showed that carbon conversion processes and soil respiration leading to significant carbon and nutrient losses increased significantly on skid trails in low mountain regions with relatively steep slopes, which was in sharp contrast to lowland sites. The strong context dependence of our findings suggests that the mapping of soil conditions in terms of slope, substrate and moisture with high spatial resolution is mandatory to assess the vulnerability of sites to soil compaction by heavy machinery. Based on such vulnerability analysis, negative impacts can be minimised through the designation of permanently fixed skid trails, technical adaptation of vehicles (e.g. wide base tyres) as well as careful planning and timing of management operations that should be restricted to dry weather and soil moisture conditions or periods of frost. [ABSTRACT FROM AUTHOR]

Featured Application: Penetration resistance is a descriptor of soil compaction. In this study, we have exercised control over the weight of the payload of three timber extraction options, therefore the results may be used to estimate the contribution to soil compaction of each pass, as well as for comparison and for planning of operations, given the trends and the magnitude of penetration resistance between the passes. Local effects of ground-based timber harvesting, such as soil compaction, are often important for forest management and resilience of forests. One way to evaluate the compaction of the forest soils is by the penetration resistance. Most often, however, the control over the weight of the means used to extract the wood is difficult to maintain, influencing therefore the outcomes of the comparison studies. In this study, a controlled experiment was set up to see how the penetration resistance is affected by the number of passes of three wood extraction methods. A first objective of the study was to characterize the undisturbed soils by the mean values of penetration resistance along the profile. The second objective of the study was to compare the changes in penetration resistance induced by the number of passes along the soil profile. The extraction means were selected based on their typical use in flat-land operations, namely horse logging, skidding and forwarding, and the weight of their loads was determined before the experiment; then, each one was tested in a different area by operating in a closed loop on flat land, with 15 passes over the respective testing area. Penetration resistance was sampled up to 80 cm in depth in 10 control points, as well as in 10 sampling points over the wheels' footprints. Ten samples were taken on the latter after the first, second, third, fourth, fifth, tenth and fifteenth passes, and comparisons were set up based on natural changing points in penetration resistance found in the control areas. The comparisons found significant differences by an increase in penetration resistance for all three extraction means, and there was a difference by an order of magnitude and depth; horse logging affected it the least and forwarding the most in magnitude, while skidding seemed to produce more significant changes in depth. However, the magnitude and depth of these changes may have depended on the characteristics of the soils from the test areas, and it cannot be concluded that the found levels of penetration resistance will affect the trees located nearby the experimental trails. The problem of soil compaction should be further examined by dedicated studies, given the variability in soil characteristics and diversity in means used to extract timber. [ABSTRACT FROM AUTHOR]

he mechanized tillage systems of agricultural soils for the cultivation of quinoa in the central Ecuadorian highlands are influenced by several factors, among them: the skidding that occurs in soil tillage, with different implements used both in conventional tillage and in minimum or reduced tillage, in plowing, harrowing, furrowing, which are executed for the cultivation of quinoa, without considering the slope, humidity, soil compaction and the increase in cost and time. The objective of the study was to determine the percentage of skidding in sandy textured soils for quinoa cultivation, with slope ranges from 5 to 12% with moisture contents from 13 to 18% under conventional and minimum or reduced tillage systems in plowing, harrowing, furrowing, using disk plow, chisel plow, disk harrow, furrower coupled to an agricultural tractor of 95 KW of power with assisted traction. [ABSTRACT FROM AUTHOR]

Fine roots are an important component of forest soil as they play a key role in fundamental processes like plant nutrition and water supply. As with all the features of forest soil, the compaction related to the forest operations and, in particular, to the wood extraction via ground‐based technologies could lead to a significant impact on the presence of fine roots in the soil affected by the passage of the machines. Considering the lack of a review, we used a meta‐analytic approach to synthesise effect sizes of ground‐based extraction technologies affecting the presence of fine roots in the soil, using a multivariate mixed‐effects meta‐analytic model. The obtained results revealed that the presence of fine roots in the soil affected by the passage of the machines was significantly reduced by both skidding (g = −1.23, 95%CI ‐1.87, −0.60) and forwarding (g = −1.37, 95%CI ‐2.01, −0.74). Due to the higher soil compaction caused by forwarding, this method had a marginally but statistically significant greater impact than skidding. We further confirmed the hypothesis that soil compaction and the presence of fine roots were strongly correlated, with the latter being greatly reduced in compacted soils characterised by higher bulk density. What is more, even more than 20 years after a harvesting intervention, the presence of fine roots was significantly lower in both strip roads (forwarding) and skid trails (skidding) as compared to areas which were not impacted by the machine passage. This shows that fine roots are particularly vulnerable to forest operations. On the other hand, the majority of the trails in the database used for the meta‐analysis were created in countries that favour the creation of a small number of widely used trails. Therefore, it would be scientifically valuable to do a comparative evaluation in various forestry contexts, such as in the Mediterranean area, where the development of the forest trails network is oriented on creating a large number of trails with low traffic volumes. Because machinery‐induced soil compaction is the major driver of the decrease in fine roots in skid trails and strip roads, both the application of best management practices as well as of a smarter planning of the trail network to limit soil compaction are strongly recommended. Both applications are highly recommended to be used in the planning phase and in the practical implementation of logging activities. [ABSTRACT FROM AUTHOR]

Forest soils are complex ecosystems including a huge biodiversity including different microbial communities that are responsible for soil nutrient cycling and organic matter decomposition. One of the main threats to forest soil health is soil compaction caused by forest exploitation activities and, in particular, by wood extraction operations. These latter may change the physical, chemical and, in turn, biological properties of soil, eventually impacting tree growth and regeneration. However, there is a significant lack of knowledge in understanding the response of soil microbial communities to soil compaction. Furthermore, most of previous studies did not properly frame the short-term response of soil microbiota to compaction, which could serve as an early indicator of soil health. This study aims to investigate and monitor the short-term response of forest soil to severe compaction stress integrating soil physico-chemical analysis with biological and biochemical analysis. To investigate the early response of soil microbial communities to compaction over time, forest soil was analyzed 8 and 12 months after the repeated passage of a tractor pulling some logs simulating skidding operations in a heavily trafficked area for wood extraction. Despite the initial strong increase in bulk density (up to 42 %), the soil almost recovered from compaction after just one year. Most of the soil chemical parameters (i.e. pH, C, and N content) were not affected by soil compaction, while the analysis of enzymatic activity showed a change of some functions upon soil compaction in the first 8 months, followed by a substantial recovery after one year. The microbial communities showed different responses to compaction, highlighting a greater bacterial community resilience in the short term compared to the fungal community, which showed persistent and significant shifts between compacted and not-compacted soil. We also identified some indicator species that may be useful for monitoring early changes in microbial communities and activities following soil compaction. • Machinery induced soil compaction was intense but transient. • Most of the physico-(bio)chemical soil properties already recover after 12 months. • Higher bacterial community resilience in the short term than fungal one. • Species possibly useful as early indicators of soil degradation were identified. [ABSTRACT FROM AUTHOR]

• The present work seeks to construct a mathematical model of soil compaction. • The high demand for forest products stimulate the logging activity. • The primary impact of machinery is soil compaction. Soil compaction from wheeled vehicles poses a huge challenge for the forest ecosystems. Modeling the impact of skidding machines on the soil could help solve the problem. The present work seeks to construct a mathematical model of soil compaction under the cyclic dynamic loading of wheeled skidding machines using the vibration analysis method for elastic dynamic systems. The study found that 4 × 4, 6 × 6 and 8 × 8 forestry vehicles have similar amplitude-frequency characteristics regardless of driving speed and load. The analysis of soil compaction from dynamic loading revealed that loaded and unloaded skidder passes cause the least damage (21–31%) to forest roads compared to skid trails. As regards skid trails, 4 × 4 and 6 × 6 tractors were found to compact the soil by 23–50% in the first four passes. The subsequent passes will lead to 60–66% of compaction. Finally, 8 × 8 trucks cause 98–99% of soil compaction. The difference between the experimental and theoretical values of soil density does not exceed 12%. The unevenness coefficient of the soil compaction and the confidence interval fall within the acceptable range. The mathematical models are in good agreement with the experimental data and can be used to calculate the operating modes of wheeled forestry equipment. [ABSTRACT FROM AUTHOR]

Animal logging is one of the most ancient wood extraction methods and it is still applied in different parts of the world, including industrialised countries. Animal logging is often imagined as a low-impact method and sometimes, or rather often, it is recommended as a best-management practice. However, the literature findings depict a more complex scenario, and the goal of the present review is to shed light on the topic of environmental sustainability of logging operations performed by animals. Usually, animal logging causes less pollutant emissions and less damage to the residual stand in comparison to ground-based mechanised extraction methods. However, when applied in commercial forestry interventions such as coppicing, animal logging showed levels of soil compaction in line with those of ground-based machinery like tractors, skidders and forwarders. Specifically developed trials revealed that in the animal skid trails a strong disturbance to the soil microarthropod community occurred. Furthermore, the soil features in the animal trails seemed to get worse over time after logging, thus suggesting the possible presence of strong localised erosion along these trails. Despite the strong need to further investigate this topic, concerning the ecological aspects of forest soil which were generally neglected by the literature, the use of animal logging can be recommended in the case of small-scale forestry with wooden material sparsely located throughout the logging site. In the case of commercial logging on steep slopes instead it is recommended to replace animal logging with cable-based extraction systems. • Logging operations by the use of animals are still very common. • Animal logging causes lower emission and less damage to the residual trees than machinery. • Animal logging can cause disturbance to soil physicochemical and biological features. • Animal logging is recommended for isolated pockets of timber to be harvested. • Cable systems should be preferred to animal logging on steep slopes. [ABSTRACT FROM AUTHOR]

Poplar plantations have been widely practiced in the coastal area of the Caspian Sea in northern Iran. In this research, soil compaction following logging operations carried out by wheeled cable skidder was investigated in two poplar plantations with different characteristics including moist soil and dry soil. The soil gravimetric moisture content (MC) in the dry site ranged from 13% to 14.4%, while in the moist site it ranged from 30.5% to 34.6%. The mineral soil samples were collected from the skid trails in both sites. The impact of skidding operations on soil layers (soil depth, SD) was examined by measuring rut depth (RD), penetration resistance (PR), bulk density (BD), and total porosity (TP) at five traffic intensities (TI). Results indicated that MC and TI had a significant effect on RD, PR, BD, and TP; however, SD had a significant effect on PR and BD. The values of BD were significantly higher in the moist site than in the dry site, while the values of PR and TP were significantly higher in the dry site than in the moist site. The RD in the moist site (11.7 cm) was 1.65 times more than RD in the dry site (7.1 cm) after one pass where a pass was defined as one empty and one loaded trip over a spot. The differences between BD after 10 and 15 passes were not significant on the dry site, but significant in the moist site. We concluded that skidding operations should be conducted when soil conditions are dry. [ABSTRACT FROM AUTHOR]

The purpose of this work was to develop a model of the interaction process between the wheeled forwarder and the soil of the cutting area, which allows evaluating the influence of soil conditions, the parameters of the wheeled forwarder, as well as load and number of cycles of its application, on the indicators of resistance and adhesion of the forwarder to the traction surface. Modeling results for 3- and 4-axle forest machines with different load levels showed that for different soil categories, types of bodies, and tire sizes. The results of the approximation analysis enabled the derive of calculation formulas for estimating the propulsive coefficient and rut depth after the first passage depending on the values of load-bearing capacity, body load coefficient, wheel width, and soil deformation module. The proposed model can be used at laying down the skidding roads and its optimization not only in economic terms but also with respect to the environment as intensive harvesting operations lead to extensive soil destructions. The practical application of the results is expressed in increased performance capacities of wood skidding operations and minimization of costs for restoring the productivity of forest area. [ABSTRACT FROM AUTHOR]

The growth and quality of natural seedlings are important goals of forest management in uneven-aged high stands. In this study, the recovery process of the physical and chemical properties of soil, as well as growth variables of beech seedlings on the skid trails after skidding operations in three time periods (10, 20, and 30 years) were investigated in the Hyrcanian forests of Iran. Results revealed that the soil chemical properties (organic C, total N, and pH) were fully recovered after 20 years, while soil physical properties (bulk density, porosity, and penetration resistance) were not yet fully recovered even after 30 years. The values of growth characteristics (stem and root system) and the quality index of beech seedlings were not statistically different from those of the control area ones after 20 years. According to our findings, the process of recovering soil characteristics after forest operations is long and takes more than 30 years. Considering the effect that soil compaction can have on seedling establishment and growth, proper planning of the forest operation is needed to limit the negative effects of forest operations, which meets the requirements of sustainable forest management. We suggest designing skid trails with a minimum distance of 140 m from each other and with a longitudinal slope of less than 15%, in compliance with the principles of best management practice (BMP).

The effects of traffic frequency and skid trail slope on dry bulk density, litter mass and rutting are examined. Treatments included a combination of four different traffic frequencies (3, 7, 14, and 20 passes of a rubber skidder) and three levels of slope ( 20%.) The results showed that dry bulk density, rut depth and soil displacement increased with the increase of traffic frequency and slope, but floor coverage decreased. Within each traffic treatment soil compaction raised with the increase of skid trail slope, so that significant differences in dry bulk density were observed between slope of < 20% and those one >20% . Bulk density has become quite close to the critical value after 14 cycles. With increase of the skidder cycles from 14 to 20, bulk density remained approximately constant. We observed soil displacement on the treatments with 7 cycles: rutting on the treatments started with 7 cycles and slope of >20%. Soil disturbance increased significantly on slopes with > 20 % inclination with a dry bulk density of 1100 kg m-3 after 3 cycles compared to 830 kg m-3 on slopes < 10 %. In addition the forest floor mass on the treatments with 7 cycles and slopes of >20% (437.6 kg/ha) was significantly (p20% may be associated with increasing load on the rear axle combined with slipping on steep slope trail.

Increased soil compaction following harvest traffic is an inroad for adverse changes in soil biological properties and processes, soil microbial activity, bacterial communities, and growth and development of plant roots. This study investigated the impacts of three levels of traffic intensity (3-6, 7-14, and 15+ passes) of a Timberjack 450C skidder on changes in several chemical soil properties at two levels of skid trail slope gradients (gentle =<20% and steep >20% inclination) in the Hyrcanian forest. Skidding increased soil bulk density between 19% and 39% and, averaged over both slope gradients, reduced amounts of soil organic carbon (33-67%), concentrations of nitrogen (51-80%), phosphorous (0-17%), potassium (11-36%), and hydrogen ions (78-98%) compared to undisturbed areas. Most soil damage occurred after a few skidder passes, particularly on steep slopes that generally experienced the highest level of soil deterioration. The primary mechanism that induced immediate chemical soil changes was an uplift and exposure of deeper soil layers in response to compression and displacement of the former soil surface. Skidding can jeopardize the sustainability of forest ecosystems by creating unfavorable changes in soil characteristics and nutrient status. [ABSTRACT FROM AUTHOR]

Abstract: This study intended to determine the plant species on a skid road subjected to soil compaction due to timber skidding in a pure sessile oak (Quercus petrea L.) forest. Our previous studies show that ground based skidding destroyed the soil and ecosystem. The timber skidding limits recovery and growth of plant cover on skid roads. However, some herbaceous plant species show healthy habitat, and they can revegetate and survive after the extreme degradation in study area. The composition and cover-abundance scales of these plant species investigated in a 100m×3m transect. Twelve plant species belongs to 10 plant family were determined. Compositae and Liliaceae were the most abundant families. Daphne pontica L., Smilax aspera L., Trachystemon orientalis (L.) G. Don, Carex distachya Desf. var. distachya Desf. have the highest cover-abundance scale among all of determined species on compacted skid road. [Copyright &y& Elsevier]

• The restoration of soil properties after applying leaf litter has been characterized. • The highest soil physio-chemical and biological were measured on the undisturbed area. • The litter mulch adding enhanced soil microbial properties and enzyme activity. • Four years was not long enough to return the soil properties to undisturbed levels. • The leaf litter with level of 1.31 kg m−2 could be applicable as an optimal level. Various engineering measures, such as mulching, have been applied on decommissioned skid trails to suppress the adverse effects of overland flow and flood hazards. However, very little research has been done on the effects of such treatments on soil recovery. The aim of this study is to determine the effectiveness of different leaf litter levels on the restoration of soil properties and enzyme activity, when spread on decommissioned skid trails over a four-year period after soil compaction. In total, 90 soil samples in 18 runoff plots were measured under six treatments, including undisturbed (control) treatment, UND; untreated skid trail, U; and four levels of leaf litter, LML1, LML2, LML3, and LML4, with levels of 0.42, 0.81, 1.31, and 1.69 kg m−2, respectively. Soil bulk density and penetration resistance under the litter mulch treatments were lower than that under the U treatment, and at the lowest in the UND treatment. The total porosity, macroporosity, and aggregate stability were at the highest level in UND, followed by LML4 ≈ LML3 > LML2 ≈ LML1. Soil organic C, total N, C/N ratio, C and N sequestration, available nutrients (i.e., P, K, Ca, and Mg), and fulvic and humic acids were at the highest level in UND followed by LML4, and at the lowest level in U followed by LML1 ≈ LML2. The highest earthworm density and dry mass, fine root biomass, soil microbial respiration, microbial biomass carbon, NH 4 +, NO 3 −, nitrogen mineralization, and microbial biomass nitrogen were measured in UND, followed by LML4. Compared with U, all litter mulch treatments enhanced enzyme activity. Four years after mulch application, the values of soil biological and microbial properties and enzyme activity were significantly higher in LML4 ≈ LML3 followed by LML2 ≈ LML1, compared to U, but were still lower than the values of the UND treatment. We can conclude that the increased levels of leaf litter mulch moderately improved soil physio-chemical, biological, and microbial properties, as well as enzyme activity, after mechanized operations over a four year period, compared to the U treatment. However, the values of soil properties and enzyme activity were still lower than those in the UND treatment, indicating that four years is not long enough to restore the soil properties to pre-harvest levels in the study area. In conclusion, leaf litter level of LML3 with 1.31 kg m−2 can be applied as an optimal level for spreading leaf litter on skid trails to modify and enhance soil quality. [ABSTRACT FROM AUTHOR]