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The recovery of soil properties and the proper growth of natural tree regeneration are key elements for maintaining forest productivity after selective logging operations. This study was conducted on the soil properties and natural growth of two pioneer seedling species of alder and maple which were on skid trails in the mixed beech forests of northern Iran. To examine the long-term effects, we randomly selected six skid trails, with two replicates established for each of three time periods since last use (10, 20, and 30 years ago). Random plots 4 m × 10 m in size, three plots on each skid trail and six plots on areas without soil compaction (control), were selected. Measurements included the physical and chemical properties of the soil and the growth, and the architectural and qualitative characteristics of the seedlings. The results showed that all the soil properties of the 10- and 20-year-old skid trails were significantly different from the control area (except for the soil moisture in the 20-year-old skid trail). The 30-year-old skid trail showed values of other soil properties which were not significantly different from the control area, except for the amounts of organic matter and soil nitrogen, which was less than the control. The skid trails had a negative effect on all of the growth, qualitative, and architectural indices of seedlings. The characteristics of seedlings were related to soil characteristics and had the highest correlation with the soil penetration resistance (R-value from −0.41 to −0.63 for stem growth, p < 0.05; −0.57 to −0.90 for root growth, p < 0.01; and −0.76 to −0.86 for biomass, p < 0.01). The correlation coefficient between soil penetration resistance and the Dickson quality index of alder and maple seedlings was, respectively, −0.74 and −0.72, p < 0.01. The negative effect of soil compaction on root growth (−27.69% for alder seedlings and −28.08% for maple seedlings) was greater than on stem growth (−24.11% for alder seedlings and −16.27% for maple seedlings). The amount of growth, qualitative, and architectural indices of alder seedlings were higher than that of maple seedlings. Although alder is a better choice as compared to maple seedling in the initial year, the results of our study show that it is recommended to plant both alder and maple on skid trails after logging operations. [ABSTRACT FROM AUTHOR]

Logging operations change the forest environment by creating a heterogeneous canopy with a range of different microenvironments that differ mostly in light intensity and level of soil disturbance. In this study, the growth characteristics and architecture of beech (Fagus orientalis Lipsky) seedlings grown in three different microenvironments in terms of canopy and soil conditions were investigated. The experimental treatments (microenvironments) included skid trail (removal of canopy and compacted soil), winching corridor (natural canopy and compacted soil), felling gap (removal of canopy and natural soil), and comparison with the control area (canopy and soil in natural state). The results showed that the status of many growth and architectural indicators of seedlings is significantly less favorable than in the control area. These indicators include the length and biomass above and below ground, and the ratio of root length to stem length in the skid trails and winching corridors. The status of these indicators was, however, more favorable in felling gaps than in the control area. The seedling quality index decreased by −12.2% and −4.9% in skid trails and winching corridors, respectively, but increased by 2.4% in felling gaps compared to the control area. The growth characteristics and biomass of seedlings had a significant negative correlation (p < 0.01) with soil bulk density and penetration resistance and a significant positive correlation (p < 0.05) with soil porosity, moisture, and organic matter content. These results showed that the creation of a gap in the stand canopy due to the cutting of individual trees created a favorable micro-environment for the growth of seedlings, but the soil compaction caused by logging operations created an unfavorable micro-environment for these. Therefore, it is necessary to plan and execute the operation of extracting the cut trees in such a manner as to reduce the extent and severity of soil compaction with the goal of preserving and maintaining the stability of the forest ecosystem. [ABSTRACT FROM AUTHOR]

Among forest management methods, selection cutting puts into practice applications that follow the processes that naturally occur in the ecosystem. The purpose of this research was to investigate the effects of selection cutting on the stand structural characteristics and growth form of trees. The effect of selection cutting was evaluated in terms of the frequency and standing volume of trees and deadwood, diversity of tree species indices, stand structural complexity index (SCI), height-to-diameter ratio (HDR) or slenderness index, and live crown ratio of trees (LCR). These were measured and estimated through a systematic random plot sampling in two adjacent parcels with different management histories (parcel A, managed using the selection cutting method, and parcel B, managed using the protected method and without cutting trees) in mixed beech forests in Northern Iran. The results showed that the standing volume, Shannon index, deadwood volume, and SCI index in parcel A were lower than in parcel B. The selection cuttings had no effect on the HDR value of the upper-storey trees, while it decreased the HDR value of the middle-storey and light-demanding trees (maple and alder) and increased the HDR value of the lower-storey and beech trees. Also, the results showed that as a result of the implementation of selection cuttings, the total LCR of the lower-storey trees increased, but the total LCR of the upper-storey trees decreased compared to the protected forest. Furthermore, the results showed that tree growth form (HDR and LCR) are related to the SCI of the stands. These results showed that the implementation of the single-selection method had simplified the structure of the stands; also, with the changes made in the growth form of trees, the possibility of snow and wind damage was increased, especially in young trees. It is necessary to prioritize the ecological values of forest deadwood, thick trees, biological diversity, and the resistance of these stands against snow and wind damage in the next cutting operations. [ABSTRACT FROM AUTHOR]

The use of wheel skidders for timber extraction from tree stump to roadside landing has become more and more widespread. Although the use of wheel skidders has the advantages of high production and reduced extraction costs, it also damages the soil and impedes forest regeneration. The main purpose of this study was to investigate the effect of machine traffic using the Timberjack 450C (two, six and 15 passes) on two slope classes (SC) of skid trails. A low slope is considered to be <20% and a high slope is at >20%. The effects on soil physicochemical properties and seedling growth (alder, Alnus subcordata C.A. Mey. and maple, Acer velutinum Boiss.) in natural mixed beech stands in the Hyrcanian forests in Northern Iran were observed and studied. The results showed that the different factors of traffic intensity (TI) and SC had a significant impact on soil physicochemical properties and subsequent seedling growth. After two machine passes in a low TI on both low and high slopes, soil bulk density (BD) increased by 49.3% and 59.2% and penetration resistance increased by 30.5% and 38.5%, while total porosity decreased by 19.5% and 23.5%. The forest floor decreased by 30.9% and 42%, organic carbon decreased by 25.6% and 39.4%, nitrogen decreased by 18.5% and 26.3%, phosphorus decreased by 14.1% and 23%, and potassium decreased by 10.7% and 24.2%, respectively as compared with the control area. Our results indicated additional BD increments after two, six and 15 machine passes of 49.3%, 17.9% and 8.3% in the low slope, respectively, and 59.2%, 16.5% and 7.1% in the high slope, respectively. The mean of the germination rate (GR) of alder and maple seedlings in the control area was 58.3% and 46.1%, respectively, while after two, six and 15 passes, the GR of alder seedlings reduced to 50%, 46.4% and 37.5%, respectively, while that of maple seedlings reduced to 36.1%, 28.6% and 25.6%, respectively. Additionally, after two machine passes, stem length, main root length, and total dry biomass decreased by 28.7%, 34.9% and 34% in alder seedlings, respectively, and 27.9%, 27.6% and 33.3% in maple seedlings, respectively. Comparison of the response of the two seedling species to soil compaction showed that although alder had a higher GR than maple, the root growth of maple was higher than that of alder. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of road construction on plant species composition, and tree and shrub regeneration in relation to soil properties. Ten transects were established perpendicular to the main axis of the road that went up to 35 m inside the forest. The sampling was done at plots located at 5, 15, 25, and 35 m along each transect. The relevé method of Braun--Blanquet was used for vegetation sampling. A total of 40 relevés were established, with each relevé covering an area of 100 m² (10 m x 10 m), to count the number of woody species regeneration. To study the physical and chemical properties of soils, composite soil samples were collected from the depth of 0-10 cm from three cores taken near the center of each plot. Results showed that plant species were classified into two groups using two-way indicator species analysis. Multivariate analyses (principal component analysis and canonical correspondence analysis) were used to identify the most important soil variables and determine relationships between plant species composition and soil properties. Classification of vegetation into two recognizable groups indicated that species composition had been modified based on distance from the road. In plots near the road, moisture content, saturation, clay, porosity, and organic carbon decreased, while the amount of sand and silt, bulk density, and pH increased. Findings showed that roads could have significant influence on adjacent ecosystems, and therefore, it is essential to estimate the extent of the road-effect zone and to determine the environmental changes due to forest roads. [ABSTRACT FROM AUTHOR]

Damage to the residual stand caused by forest operations can have detrimental impacts on the biological processes of stand growth. This study shows the details from monitoring damages related to manual motor ground-based timber operations in a mountain mixed hardwood forest. The harvesting system was cut-to-length, and logs were extracted by wheeled cable-skidders. Data were collected from the remaining trees immediately after logging and 10 years after the logging session. The parameters assessed included stem injury, radial growth increment and wound healing rate for five hardwood species of commercial interest. The number of injured trees represented 15% of the residual stand, 23% of the wounds were related to the felling operation and 76% to extraction. Wound height, wound size and damage to bark, due to felling, were larger than those in extraction, while wound width and damages to cambium and wood caused by extraction were larger than those triggered by felling. Ten years after harvesting, average longitudinal and radial growth increments were reduced by 38% and 24%, respectively. Wound healing rates ranged from 12.90 mm yr−1 for extraction wounds to 19.70 mm yr−1 for felling ones within 10 years. On average 73% of all wounds were still unrecovered and 17% of these were decayed, while only 10% were fully healed within a 10-year recovery period. The analysis showed that the best recovering performance among damaged trees was mostly achieved in shade-intolerant species with a diameter less than 40 cm, located in the dominant canopy layer with a wound size smaller than 100 cm2. In addition to the significant effect on log quality, the ecological longevity of residual trees has major implications for pre-planning harvesting operations that can preserve the quality and value of residual trees. Understanding the damage inflicted upon residual trees is essential to reduce economic losses, improve planning of harvest operations and, ultimately, ensure a sustainable harvest of mixed hardwood stands in mountain regions. [ABSTRACT FROM AUTHOR]

Several factors are involved in the destruction of forest roads, and most of them are generated as a result of rainfall runoff which directly threatens the surface of forest roads. To minimize this damage, a well-designed drainage system in accordance with the situation in the region is needed, for which the optimal number and diameter of pipes must be calculated. Mixed broadleaf high-elevation forests in northern Iran. In this study, by employing hydrological models, geographic information systems (GIS), and field survey, we divided the area to 42 sub-areas. We then considered the factors such as hydrologic soil groups, hydrology situation, curve number (CN), and time of concentration, to calculate runoff and peak flow moments. The proper diameter and the number of transversal drainage pipes were then determined. The results showed that the existing cross-drains and their diameter are not sufficient, and are therefore not suitable for the high volume of water in this area. Our findings showed that all of the pipes that have been used in this region have a 60 cm diameter, although, while considering all the relevant factors, it should be at least 80 cm. The results showed that the changing land use and deforestation are the main causes of high rate of runoff in the study areas. Improper maintenance of roads has caused widespread destruction along the road, thereby affecting all the drainage channels and blocking all connections between them. [ABSTRACT FROM AUTHOR]

Forest plantations have significantly more potential for carbon storage than non-forested areas. In this study, the amount of carbon stored in the biomass (trees, shrubs, herb, litter, and deadwood) and soil of 25-year-old plantations with P. nigra and P. abies species was measured and compared with the non-planted adjacent area (control) in a mountainous region of northern Iran. The results show that the amount of carbon stored in the biomass of P. nigra and P. abies plantations was 4.4 and 3.3 times higher than the value of the control (4.59 C Mg ha−1), respectively. In addition, the amount of carbon stored in soil was 1.5 and 1.2 times higher than the value at the control site (47.91 C Mg ha−1), respectively. Of the total carbon stored in the biomass of plantations, the highest level was observed in trees (86.5–88.5%), followed by shrubs (4.6–6.5%), litter (2.7–2.8%), the herbaceous layer (1.8–2.5%), and deadwood (1.7–2.4%), while 45.5%, 34.6%, 10.8%, 5.8%, and 3.3% of the total carbon stored in the biomass of the control site were in shrubs, trees, the herbaceous layer, litter, and deadwood, respectively. The soil carbon sequestration rate (SCSR) in soil depths of 0–10 and 10–20 cm was 0.46 and 0.44 C Mg ha−1 yr−1 in the P. nigra plantation and 0.15 and 0.23 C Mg ha−1 yr−1 in the P. abies plantation, respectively. According to the results, we conclude that the restoration of the landscape by tree plantation has a substantially determining impact on the acceleration of carbon sequestration. [ABSTRACT FROM AUTHOR]

Mountainous hardwood mixed stands offer challenges to timber harvesting operations in practice, including a harsh climate, variable topography, steep terrain, and large-sized timbers. This paper aims to develop productivity and cost models for a mountain-ground-based harvesting operation across the terrain (e.g., slope conditions), stand (e.g., tree volume) environmental (e.g., weather), and yard (e.g., winching distance) variables and to assess GHG emissions related to the equipment in use. This development was implemented in a timber harvesting practice under single-tree selection in mountainous forests of Iran where a motor-manual chainsaw is used for felling and a rubber-tired cable skidder is used for log extraction. The average delay-free productivity was 4.55 m3 for felling and 14.73 m3 h−1 for skidding. Lower production costs and higher productivity rates were observed over the gentle slopes and in sunny conditions. The average production costs ranged between USD 4.27 m−3 for felling and USD 5.35 m−3 for skidding. The average emissions ranged between 0.96 kg m−3 for felling and 7.06 kg m−3 for skidding in snowy conditions over steep slopes. The study’s results confirm avoiding harvesting operations on steep slopes (greater than 35%) and in extreme weather conditions to obtain higher work efficiency and to minimize adverse effects of machinery on forest ecosystems. The results should be of use to harvest managers and forest planners considering the application of ground-based harvesting operations using a semi-mechanized system on a range of operating conditions in mountain hardwood stands. [ABSTRACT FROM AUTHOR]

In this study an attempt was made to assess how different mulches affect the soil environment. In particular, different organic mulches such as leaf litter, straw and sawdust were tested in order to assess their capacities to amend the soil conditions. These analyses were carried out in the Hyrcanian mixed broadleaved forest. Organic mulches can compensate the litter layer loss on compaction-induced soil and accelerate the restoration process of soil properties, which takes from a few years to several decades without mulching. However, comprehensive knowledge on the effects of organic mulch on soil quality in terms of compaction-induced soil in the scientific literature is still scarce and inadequate. The main aim of the study was to examine the effects of three organic mulches (leaf litter, straw and sawdust) on the restoration of forestry vehicle-induced soil properties in the skid trail over a 2-year period. The results showed as the values of soil physical and chemical properties in litter, straw and sawdust treatments were significantly restored as compared with the values in the untreated soil. In general, leaf litter supplies nutrients at higher rates than the straw and sawdust mulches. However, according to the current results, a 2-year period is not enough to return the soil physical and chemical properties to pre-traffic levels. Furthermore, the present study shows that organic mulch spread on the surface of mineral soil in the skid trails after machine traffic acts as a fertilizer to accelerate the decomposition of organic matter. [ABSTRACT FROM AUTHOR]

Natural treefall gaps have a substantial role in maintaining soil and plant diversity in old-growth forests. However, the amount of information on the effects of gaps on the recovery of physical and chemical properties of compacted soils is scarce. We tested the hypothesis that natural treefall gaps accelerate the restoration of compacted soil by enhancing biological and microbial activity in the topsoil after a period of five years. Five years after a ground-based skidding operation in the Hyrcanian forest, the recovery levels of soil properties were compared among different treatments including natural canopy gaps with an area of 200 m2 (NCG), clear-cuts with an area of 1600 m2 (CC), disturbed trails under a dense canopy (DDC), and an undisturbed area (UND) as control. The lowest soil bulk density (1.07 g cm-3), penetration resistance (1.11 MPa), and the highest macroporosity (36.3%), and sand content (14.4%) among treatments were recorded for the NCG followed by DDC and CC treatments. Significantly lower values of soil pH, and electric conductivity and the highest values of soil organic C, total N, available P, K, Ca, and Mg were detected under the NCG followed by the DDC and CC treatments, as compared to the UND area. The highest values of earthworm density and dry mass, and soil microbial respiration were found in the NCG followed by the DDC and CC treatments. Fine root biomass was significantly higher in the UND area (92.27 g m-2) followed by the DDC, NCG and CC treatments. We can conclude that the effects of gap size on the recovery values of compacted soil were significant in terms of greater nutrient availability and higher earthworm density and dry mass, suggesting that mimicking natural canopy gap was more effective than the clear-cut gap (CC) for the resilience of the forest stand in the restoration of soil quality. [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 aim of this study was to evaluate the long-term effect of selection cutting management on the stem quality of the trees remaining in the forest. For this purpose, three parcels managed for three decades by selection cutting were selected as managed stands (MP), and two protected parcels without tree felling as control stands (PP). First, the frequency of deformed stems in each parcel was determined for a circular 1000 m2 area of each plot by systematic sampling of 100 m × 100 m grid sections, and then a stem deformity index was estimated for each of the deformed stems. The results showed that the frequency of stem deformity in MP (6.5%) was significantly lower than in PP (20.7%) (p < 0.01). In addition, the frequency of all types of stem deformities in MP was significantly lower than in PP. Furthermore, selection cutting management reduced the indices of twisting, decay, conicity, forking, and ellipticity by 58.4%, 53.9%, 34.7%, 8.4% and 6.8%, respectively. The results for the correlation between frequency of stem deformity and tree diameter at breast height (dbh) showed that the curves followed a parabolic shape in both MP (r = 0.83) and PP (r = 0.80), where the frequency of deformed stems decreased with increasing dbh (up to 75 cm in MP, and up to 65 cm in PP), and then increased with larger dbh. Selection cutting management, regardless of tree species, improved the stem form. Decay accounted for a high proportion (24.1%) of the total deformity in MP, mainly due to logging damage. Overall, the results of this study show that selective management has been successful in improving the quality of tree boles in the studied mixed beech stands. Regular and long-term stand monitoring and statistical quality control (SQC) may be a good approach to aligning ecological and economic goals in forest management. [ABSTRACT FROM AUTHOR]

Thinning has a crucial role in retaining the future value of stands; hence, excessive soil disturbance and damage to residual trees can diminish thinning advantages. The research aims were to assess soil disturbance and the level of stand damage from thinning operations. Thinning intensity ranged from 8.3% to 19.1% of the standing volume. Soil disturbance and damage level to residual trees, were determined in five young even-aged hardwood stands, using ground-based extraction systems. Tree felling was done by chainsaw, and full trees were extracted by a skidder. Point-transect method and systematic sampling plots were used to characterize soil disturbance and residual trees damage, respectively. Surface of disturbed soil ranged from 14% to 27% and stand damage ranged from 5% to 18% of the residual trees and they were significantly increased by increasing thinning intensity. Soil resistance to penetration at a depth of 0–10 cm in the shallow disturbed (0.39 MPa), deep disturbed (0.52 MPa), and skid trails (0.79 MPa) were increased by 14%, 27%, and 54%, respectively, compared to the undisturbed soils (0.25 MPa). Winching was the main cause of soil disturbance and damage to residual trees. The highest frequency of damage was observed on trees with a dbh class of 20 cm (24.3%). Most of the stand damage occurred on the bole (55%) of trees, with wound sizes ranging from 50 to 350 cm2, and most of the wounds (53%) showed damage to the cambium and wood fibers, at heights of <1 m above the ground line (76%). [ABSTRACT FROM AUTHOR]

A study of work accidents in forests has shown that dangerous trees play an important role in forest accidents. Despite the importance of safe working environments for forestry operations, the definition of these areas in natural forests is still unclear. Dangerous trees are considered those snagged with broken branches and a canopy or ones with dead trunks and stumps that have a hazard potential to the forest workers. This study investigates the frequency of these trees in the managed and unmanaged forests in the Caspian forests of Iran. In order to do the study, 15 circular plots with a total area of 1,000 square metres in two studied parcels were selected and the trees, according to their dangerous characteristics, were evaluated. The final results indicated that 66 and 50 trees per hectare had signs of being dangerous trees in the managed and unmanaged stand, respectively. A comparison of the average number of dangerous trees in the two studied parcels using the Mann-Whitney test indicated a significant difference so that the average number of dangerous trees in the managed parcel was more than the ummanaged parcel. Trees with broken branches had the highest frequency in the managed stand, while trees with a dead trunk or stump, a broken branch and canopy in the unmanaged forest were more than the other classes. Considering the relative frequency of the dangerous trees in the two study areas, identifying them could be one of the main attempts in logging safety. The existence of hazardous trees with different risk classes in each of the forest stands requires the development of specific safety instructions to deal with the risks of each tree. [ABSTRACT FROM AUTHOR]

Beech is the most important commercial species in the Caspian forests of Iran. Selective cutting and harvesting methods may adversely impact the quality of the residual trees, as the injuries make the trees prone to future disease, insect infestations or timber defects. Although attempts to better understand how wounds affect the residual trees have been made in many different contexts, there are still few investigations on uneven-aged forests. In this study the key objectives were to determine and model the healing rate for different wound parameters (width, length, and area of wound); to analyse the relationship between wound healing rate (WHR), tree diameter growth and tree height growth; to analyse the WHR in relation to wound position on the stem; and to analyse the relationship between WHR, width and area of wound in DBH classes and social classes, with the aim of enabling the prognosis of logging wounds. Wounded beech trees were examined immediately after selective logging and after a 5-year period. The WHR was 31.2 ±7.7 cm² year-1. The wound width healing rate (18.4 ±3.4 mm·year-1) was significantly higher than the wound length healing rate (4.5 ±1.6 mm·year-1). Only 12% of wounds were completely closed after a 5-year period, and 15 years are necessary for the complete closure of 80% of total wounds. The ratio of wound area to stem area at wound height (RWS) showed a more pronounced effect on diameter than on height. Regression analysis showed that WHR was correlated negatively with wound area and width and positively with tree diameter growth, but no significant relationship was found between height growth and WHR parameters. The WHR was significantly higher at an upper position than at a lower one, and statistical tests showed that the tree vertical layering classes had a significant effect on WHR. Finally, it was shown that WHRs in upper-storey trees are significantly higher than in the middle and lower storeys. [ABSTRACT FROM AUTHOR]

We investigated the growth parameters of 20-year-old plantations of Pinus nigra J.F. Arnold and Picea abies (Linnaeus) H. Karsten and their impact on understory woody plants and we compared them with a natural stand in above-timberline mountain areas. 30 sample plots (each of 400 m2 in area) were systematically established on each site. Tree height, DBH, collar diameter, crown diameter and crown length of all trees were measured in each sample plot. The results of the diameter growth analysis of both species covered by this study showed higher numerical values in P. nigra than in P. abies. On the contrary, what was observed for data concerning height growth, showed higher numerical values in P. abies than in P. nigra. These conclusions showed that P. nigra has a lower slenderness ratio than the other species and is therefore more resistant to the adverse weather. Considering the effects on biodiversity, the planting of P. nigra showed a significant increase in density and species richness of woody plants while it decreased the diversity and evenness compared to the natural stands and plantations of P. abies. [ABSTRACT FROM AUTHOR]

Coarse woody debris (CWD) plays an important role in supporting biodiversity and assisting ecological processes. Sometimes local people intervene modifying the expected distribution of CWD components, harvested as fuel wood. The effect of the human accessibility (HA) on the volume and characteristics of CWD (snag, downed log and stump) was investigated in the natural uneven-age mixed hardwood stands of the Hyrcanian forests of Iran to quantify the impact on CWD. The HA was classified into three classes (easy, medium and difficult) on the basis of slope class, slope direction to the nearest road and road type. As expected, a negative relationship between the degree of accessibility was found with respect to the main qualitative and quantitative indices referring to CWD. The results showed that the volume of CWD decreased with an increase in human accessibility class (HAC), thus the mean volume of CWD in the difficult, medium and easy accessibility classes were 14.87 m³ ha-1, 8.84 m³3 ha-1 and 4.03 m³ ha-1, respectively. The decrease in CWD volume was more associated with the decreasing volume of small diameter of low decayed downed logs. The ratio of snag volume to standing volume, the ratio of downed log volume to the volume of trees and the ratio of CWD volume to standing volume increased with a decrease in HAC, while the ratio of downed log volume to snag volume decreased with a decrease in HAC. No selective behaviour on the botanical species of CWD was recorded. For ecological forest management, the effect of HAC on CWD should be considered. A constant supply of snags and downed logs must be preserved to assure a high level of biodiversity. To balance social needs and biodiversity requirements, an increased level of CWD retention might be needed in areas with easy accessibility. The obtained results may be useful when ecological and socio-economical needs have to be taken into consideration in future policy-making decisions. [ABSTRACT FROM AUTHOR]

The wound healing rate (WHR) was investigated in 234 wounded trees in Iranian forests and was found to range from 6.4 to 24.0 mm·yr-1. Tree species, slope aspect, elevation, wound age and wound type had significant effects on the WHR. The mean of the WHR in the Fraxinus excelsior (24 mm·yr-1), Alnus subcordata (18.9 mm·yr-1) and in the Fagus orientalis (17.9 mm·yr-1) were significantly higher than in the Acer insigne (15.7 mm·yr-1), Acer cappadocicum (14.6 mm·yr-1), Carpinus betulus (13.7 mm·yr-1) and Tilia begonifolia (6.4 mm·yr-1). In addition, the mean of the WHR on northern slopes (17.5 mm·yr-1) was significantly higher than on southern slopes. Moreover, the parameters that positively influenced tree growth showed a similar effect on the wound healing rate. The WHRs of 5-, 10- and 15-year-old wounds were 19.3, 16.9 and 10 mm·yr-1, respectively. The WHR increased the higher the wound from ground level. The WHR for horizontal wounds (18.4 mm·yr-1) was significantly higher than for vertical wounds. The highest WHR was estimated in a stand with a canopy closure of 60-80%. The WHR decreased according to increasing wound width. Wounds affect future income, lowering the number of trees that potentially provide a higher quality of saw and veneer logs. [ABSTRACT FROM AUTHOR]

Coarse woody debris (CWD) has a wide range of ecological and conservation values such as maintaining biodiversity in forest ecosystems. Each forest management method can have a detrimental effect on stand structure and CWD. We analyzed the volume and density of live trees and CWD (snags and downed logs) over a long-term (30 years) selection-logging managed compartment (harvested), and compared these with values obtained from an unlogged compartment (control) in the Iranian Caspian forests. Results showed that the volume and density of live trees and CWD in the harvested area was significantly lower than in the control area, especially large size trees and CWD, very decayed CWD, and rare tree species. The ratio of snags volume to total standing volume (RSS) was significantly higher in the control (7.9%) than in the harvested area (5.2%), and the ratio of downed logs volume to trees volume (RDT) in the control area (6.3%) was significantly higher than in the harvested area (4.6%), while the ratio of downed logs volume to snags volume (RDS) was significantly higher in the harvested area (83.6%) than in the control (74%). Based on the obtained results, we recommend selection cutting forests to be managed based on CWD management plans, including appropriate cutting cycles (15-30 years) and retention of large-diameter (DBH > 75 cm) and cavity trees as a suitable habitat for many wildlife species. [ABSTRACT FROM AUTHOR]

Although selection cutting has many advantages, its potential for damage to residual trees is a major challenge of forest management. The present study evaluated damage to residual trees during manual felling and cable-skidder logging operations in 18 instances of selection cutting in the Caspian forests of Iran. Data was collected from 100 m × 100 m systematic sample plots (0.1 ha) at each logging site. Harvest intensity ranged from 3.8 to 11 trees ha −1 and it averaged 7.3 trees ha −1 . Damage to residual trees was 10.5–23.6% with an average of 16.9%. There was a positive and significant correlation between amount of damage and harvest intensity ( R 2 = 0.65, P < 0.01). The multiple regression analyses also indicated that there were statistically significant relation ( R 2 = 0.77, P < 0.01) between amounts of trees damage and independent variables (harvest intensity, ground slope and stand density). Injury to the bottoms of tree boles 100–200 cm 2 in size was the most common types of damage. Damage was concentrated in small diameter trees (DBH < 40 cm). Most logging damage occurred during winching. Results suggest adherence to two silvicultural practices: (1) limit harvest intensity to 6 trees ha −1 , (2) limit selection cutting in slopes, less than 50%. Additional operational suggestions are implementation of felling direction and avoid log extraction through dense stands. [ABSTRACT FROM AUTHOR]

The deadwood (DW) of the forest is in the following two forms: standing (snag) and fallen (log). The DW categories and decay stage are important functional and structural components of forest ecosystems. We used a field-based assessment to quantify how the relative contribution of deadwood to total above-ground carbon stock changes across a silvicultural method and stand altitude gradient in mixed broadleaves stands. The characteristics of DW and carbon stock in selection-cutting managed stands (Sc), shelter-wood managed stands (Sh) and protected stands (Pr) were examined in three altitude ranges (low, <600; medium, 600–1200; and high, >1200 m a.s.l.) in a mixed broadleaves high forest. The results showed that with increasing altitude, the volume of DW increased. The volume of DW in Pr stands was about three times higher than Sh stands and twice higher than Sc stands. The volume of the standing DW was greater than that of the fallen DW in all stands. The highest volume ratio of fallen DW to standing DW was found in the medium altitude in the Sc stand. The amount of carbon stock by DW in the Sh, Sc, and Pr stands was 1.53–2.22, 2.29–3.19, and 5.03–6.80 t ha−1, respectively. The DW share of C-stock of above ground biomass was 4%–4.6% in Sh stand, 4.3%–4.8% in Sc stand, and 7.4%–7.9% in the Pr stand. Deadwood assessment and management, in terms of volume, type, species composition, diameter distribution, spatial allocation and decay stage, is one of the new challenges for a proper sustainable forest management. [ABSTRACT FROM AUTHOR]

Background: Poplar tree plantations for wood production are part of a worldwide growing trend, especially in moist soil sites. Harvesting operations in moist sites such as poplar plantations require more study for detailed and increased knowledge on environmental and economic aspects and issues. Methods: In this study, the effects of soil moisture content (dry vs. moist) on productivity, cost, and emissions of greenhouse gases (GHG) caused by operations of different harvesting systems (chainsaw-skidder and harvester-forwarder) were evaluated in three poplar plantations (two in Italy and one in Iran). Results: The productivity (m3 h−1) of both systems in the dry sites were significantly higher (20% to 30%) than those in the moist sites. Production costs (€ m−3) and GHG emissions (g m−3) of both systems in the dry sites were also significantly lower than those in the moist sites. The productivity of the harvester-forwarder system was about four times higher, and its production cost was 25% to 30% lower than that of the chainsaw-skidder system, but the calculated GHG emissions by harvester-forwarder system was 50–60% higher than by the chainsaw-skidder system. Conclusions: Logging operations are to be avoided where there are conditions of high soil moisture content (>20%). The result will be higher cost-effectiveness and a reduction in the emission of pollutants. [ABSTRACT FROM AUTHOR]

There has been a severely negative impact on soil water resources in temperate forests caused by the introduction of the type of heavy machinery in the forestry sector used for forest harvesting operations. These soil disturbances increase the raindrop impact on bare mineral soil, decrease infiltration rate, detach soil particles, and enhance surface flow. According to several studies, the role of slope gradient influence on runoff and soil loss continues to be an issue, and therefore more study is needed in both laboratory simulations and field experiments. It is important to define and understand what the impacts of slope gradient in harvesting practices are, so as to develop guidelines for forest managers. More knowledge on the key factors that cause surface runoff and soil loss is important in order to limit any negative results from timber harvesting operations performed on hilly terrains in mountainous forests. A field setting using a runoff plot 2 m2 in size was installed to individualize the effects of different levels of slope gradient (i.e., 5, 10, 15, 20, 25, 30, 35, and 40%) on the surface runoff, runoff coefficient, and sediment yield on the skid trails under natural rainfall conditions. Runoff and sediment yield were measured with 46 rainfall events which occurred during the first year after machine traffic from 17 July 2015 to 11 July 2016 under natural conditions. According to Pearson correlation, runoff (r = 0.51), runoff coefficient (r = 0.55), and sediment yield (r = 0.51) were significantly correlated with slope gradient. Results show that runoff increased from 2.45 to 6.43 mm as slope gradient increased from 5 to 25%, reaching to the critical point of 25% for slope. Also, further increasing the slope gradient from 25 to 40% led to a gradual decrease of the runoff from 6.43 to 4.62 mm. Runoff coefficient was significantly higher under the plot with a slope gradient of 25% by 0.265, whereas runoff coefficient was lowest under the plot with a slope gradient of 5%. Results show that sediment yield increased by increasing the slope gradient of plot ranging 5% to 30%, reaching to the critical point of 30%, and then decreased as the slope gradient increased from 35% to 40%. Runoff plot with a slope gradient of 30% (4.08 g m−2) ≈ plot length of 25% (3.91 g m−2) had a significantly higher sediment yield, whereas sediment yield was lowest under the plot with a slope gradient of 5% and 10%. A regression analysis of rainfall and runoff showed that runoff responses to rainfall for plots with different slope gradients were linearly and significantly increased. According to the current results, log skidding operations should be planned in the skid trails with a slope gradient lower than the 25 to 30% to suppress the negative effect of skidding operations on runoff and sediment yield. [ABSTRACT FROM AUTHOR]

Soil damage caused by logging operations conducted to obtain and maximize economic benefits has been established as having long-term effects on forest soil quality and productivity. However, a comprehensive study of the impact of logging operations on earthworms as a criterion for soil recovery has never been conducted in the Hyrcanian forests of Iran. The aim of this study was to determine the changes in soil biological properties (earthworm density and biomass) and its recovery process under the influence of traffic intensity, slope and soil depth in various intervals according to age after logging operations. Soil properties were compared among abandoned skid trails with different ages (i.e., 3, 10, 20, and 25 years) and an undisturbed area. The results showed that earthworm density and biomass in the high traffic intensity and slope class of 20–30% at the 10–20 cm depth of the soil had the lowest value compared to the other treatments. Twenty-five years after the logging operations, the earthworm density at soil depth of 0–10 and 10–20 cm was 28.4% (0.48 ind. m−2) and 38.6% (0.35 ind. m−2), which were less than those of the undisturbed area, respectively. Meanwhile, the earthworm biomass at a soil depth of 0–10 and 10–20 cm was 30.5% (2.05 mg m−2) and 40.5% (1.54 mg m−2) less than the values of the undisturbed area, respectively. The earthworm density and biomass were positively correlated with total porosity, organic carbon and nitrogen content, while negatively correlated with soil bulk density and C/N ratio. According to the results, 25 years after logging operations, the earthworm density and biomass on the skid trails were recovered, but they were significantly different with the undisturbed area. Therefore, full recovery of soil biological properties (i.e., earthworm density and biomass) takes more than 25 years. The conclusions of our study reveal that the effects of logging operations on soil properties are of great significance, and our understanding of the mechanism of soil change and recovery demand that harvesting operations be extensively and properly implemented. [ABSTRACT FROM AUTHOR]

In central Italy, there are extensive European black pine (Pinus nigra Arn.) plantations which range from 30 to 60 years of age and where no thinning operations have been made. The main purpose of this study was to provide a comparative analysis of two cable yarder technologies (Maxwald, mobile pulley carriage and Savall, semi-automatic carriage), in terms of fuelwood production and cost, from the first thinning of a 33 year old plantation in slope areas of these plantations. The results showed that fuelwood production was cost-effective in both systems (Savall by 15.1 and Maxwald by 14.8 € m−3), although the productivity of the Savall system was higher than the Maxwald system (6.1 vs. 5.7 m3 h−1). The respect amounts of productivity have the potential to increase by 27% for the Savall yarder and 25% for the Maxwald yarder upon condition that the delay times are reduced to minimum level by proper training of workers, by a better organization, and planning of operations. The total effective CO2 emission by the Savall yarder was lower than the Maxwald yarder (1735 vs. 1772 g m−3). A sustainable production of fuelwood that is economically advantageous and environmentally sound in these plantations can be realized through an appropriate mechanization level and constant interaction with the silvicultural planning. This must be completed with adequate and efficient worker training. [ABSTRACT FROM AUTHOR]

Loblolly pine (Pinus taeda L.) is one of the main exotic conifer species that has been widely planted for the past fifty years for timber production in the coastal areas of northern Iran. Heavy snowfall and strong winds can cause much damage to these forests over a short time span of only a few years. This study was conducted to estimate snow and wind damage and analyze the role of stand thinning in their resistance to snow and wind. Amount and type of snow and wind damage were examined through systematic (80 m × 80 m) sample plots (each plot area of 625 m2) in nine different stands (2–10 plots in each stand) in terms of age, structure, and silviculture history in three replications for each stand in April and May 2020. Results showed that the amount of snow and wind damage had a wide range from 1.3% to 30.7%. Snow damage was more than three times that of wind. Snow and wind damage in the young stands were significantly more serious (p < 0.01) than in the middle-aged and old stands, and damage was significantly higher (p < 0.01) in the unthinned stands than in the thinned ones. Slenderness coefficient (Height/Diameter ratio, HD ratio) of trees resulted to be a good indicator in young and middle-aged stands, while crown form indices (relative crown length and relative crown width) were acceptable indicators in old stands for risk of snow and wind damage. Our results showed that the normal thinning (15% of basal area) decreased snow and wind damage in all the stands, while the heavy thinning (35% of basal area) reduced the snow damage, but it increased the wind one. It is possible to recommend high intensity thinning in young stands, normal thinning in middle-aged stands, and light thinning (15% of basal area) in old ones. [ABSTRACT FROM AUTHOR]

In this study, damage to residual trees during thinning performed by motor-manual felling and whole tree skidding was studied in a loblolly pine (Pinus taeda L.) plantation. Forest intervention was carried out in 2016 and tree wounds were studied and examined over a period of three years. The results indicated that 8% of the residual trees suffered damage, of which 52% was caused by felling operations and 48% by extraction operations. Among the damaged trees, 13% had damage to the root system, 53% to the bole, and 34% to the crown area. The average wound size at the time of occurrence was 71.3 cm2. This was found to be reduced to 54.4 cm2 after a three year period. Wound intensity decreased with higher wound height and increased size. Three years after wound occurrence, only 6.6% were closed, 90.6% were still open, and 2.8% were decayed. The diameter growth in damaged trees was 1.7% lower than in undamaged trees (p > 0.05). Damage to the root system of residual trees reduced diameter growth by 3% (p < 0.05). Intensive wounds (damaged wood) caused a reduction of 22.7% in diameter growth (p < 0.01). In addition, the diameter growth in trees with decayed wounds was 27.4% lower than unwounded trees (p < 0.01). Pre-harvest planning, directional tree felling, marking of the extraction path before logging operations, employment of skilled logging workers, and post-harvest assessment of damaged residual trees are essential implementations in timber plantations. [ABSTRACT FROM AUTHOR]

Minimizing the impact of timber harvesting on forest stands and soils is one of the main goals of sustainable forest operation (SFO). Thus, it is necessary to make an accurate assessment of forest operations on soil that is based on the SFO perspective. The present study was conducted according to SFO principles to investigate the time required for the natural recovery of soil after disturbance by skidding operations in some Iranian forests. The physical, chemical, and biological properties of soil found in abandoned skid trails from different time periods were compared with undisturbed forest soils. The soil bulk density, the penetration resistance, and the microporosity of a 25-year-old skid trail were 8.4–27.4% and 50.4% greater, and the total porosity, macroporosity, and soil moisture were 1.9–17.1% and 4.6% lower than the undisturbed area. In a 25-year-old skid trail, the values of pH, Electrical conductivity (EC), C, N, available P, K, Ca, and Mg, earthworm density, and biomass were lower than in the undisturbed area, and the C/N ratio value was higher than in the undisturbed area. High traffic intensity and slope classes of 20–30% in a three-year-old skid trail had the greatest impact on soil properties. In order to have sustainable timber production, SFO should be developed and soil recovery time should be reduced through post-harvest management operation. [ABSTRACT FROM AUTHOR]

There are many data values describing deadwood in primary forests, however, there is much less information concerning managed forests, particularly in the Mediterranean area. Whole non-living woody biomass (deadwood) is the main component of forest types that plays a vital role in improving and maintaining biodiversity. The dynamics of deadwood and CO2 sequestration by deadwood were examined in three Mediterranean lowland forests: pine forest Pinus pinea L.), evergreen oak forest (Quercus ilex and Quercus suber L.), and deciduous oak forest (Quercus cerris L.). The aim of this study was to carry out a quantitative and qualitative evaluation of the deadwood to gather useful information for the Mediterranean forest management, and to provide some useful data that can be integrated into the methods of estimation for carbon stored in dead components of Mediterranean forest types. The investigations focused on the characterization of the deadwood, to determine which traits are dominant and their potentially functionality within the forest type. Results indicated the deciduous oak type had the highest amount of stand volume (379 m3/ha), deadwood volume (161.8 m3/ha), and C storage (31.43 t/ha). The major component of dead wood was the standing dead trees or snags. There was a higher volume of deadwood in the deciduous oak forest than in the pine and evergreen oak forests. In addition, the deciduous oak forest had a higher snag creation index, a higher fallen log creation index, and a higher past management index compared to pine and evergreen oak forest types. Deadwood volume increased as the decay class in the deciduous oak forest increased, while this trend decreased in the evergreen oak and pine forests. The amount of deadwood was affected by the forest type and forest management regime. Dynamic and past management of deadwood indices indicated that their structure was still in the initial phase of creation and decay in the pine and evergreen oak forests. A comparison with other studies on similar forest types brought out that the variation range of the main parameters for the management of deadwood fell within the variation of the parameters studied. However, the values of these parameters cover a broad range. The population of each forest type is extremely sensitive to the different evolutionary periods of the forest dynamics. [ABSTRACT FROM AUTHOR]

Protection of forest soils during harvesting operations is necessary to reduce damage and accelerate recovery time. The current study aims to evaluate soil physical properties, natural regeneration, and its recovery process in treatments including slope gradient, traffic intensity and skid trail after long periods of time, after ceasing the timber harvesting operations. The most recent skidding operations within each 5 years recovery period were studied for a chronosequence of 20 years. Soil samples were taken in abandoned skid trails and data were recorded on naturally regenerated species and density. The results revealed that most soil disturbances occurred on the slopes >20%, as well as the highest levels of traffic intensity. Bulk density and penetration resistance were still higher than the control area, with a significant difference between them, while total porosity was partially recovered. Twenty years after the skidding operation, soil bulk density and penetration resistance were 13.2% and 23.7% higher than the control area, while total porosity was 9.78% lower the than value of the control area. Seedlings of 50–150 cm and >150 cm in height on skid trails had significantly lower density than those in the control. The number of seedlings per m2 was less than the control area in all skid trails and for all height classes. The proportion of seedlings present in low traffic intensity was higher than in medium and high traffic intensities. The findings confirmed that full recovery rates are lengthy, and more time than 20 years is required to fully recover, especially with regards to penetration resistance. [ABSTRACT FROM AUTHOR]

The Caspian forests of Iran were monitored and evaluated for forest natural regeneration after logging activities for more than a decade. This large area has a substantial ecological, environmental and socio-economic importance. Ground based skidding is the most common logging method in these forests and soil compaction is the most critical consequence of this method. One of the current main topics and important emerging issue in forest research of the last decade are discussed in this study. Soil compaction has major influences on growth and/or mortality rates of forest seedlings. This study has lasted for over ten years so as to have a clear overview related to forest natural regeneration after logging activities. We monitored and evaluated physical soil properties (bulk density, penetration resistance and total porosity) and their effects on maple and beech seedlings on 10-year-old skid trails in the Iranian Caspian forests. Results obtained from evaluating the impact of skid trails within the aforementioned three soil physical parameters were significant; bulk density increased by 12.6% on log skidded routes (between two skidder tires on skid trail) and 36.1% on tire tracks, compared to non-skid trails (1.19 g/cm3), penetration resistance increased by 68% on log skidded routes and 220% on tire tracks, compared to non-skid trails (0.25 MPa), total porosity decreased by 12.8% on log skidded routes and 30.9% on tire tracks, compared to non-skid trails (54%). Among the morphological parameters, lateral root length (LRL) and root penetration depth (RPD) showed the highest decrease at soil compaction compared to the control (decrease in LRL: 60% in maple and 44% in beech; decrease in RPD: 56% in both maple and beech); the main response of growth parameters to soil compaction was found in roots (decrease in dry mass of 36% both in maple and beech); architectural parameters were also influenced by soil compaction, and the response of both seedling species was more evident in the ratio of main root to stem length (RRS) (reduction in RRS 42% in maple, 33% in beech); the ratio of RPD to main root length (RPL) also showed a great reduction (reduction in RPL 20% in maple 33% in beech). Physical soil properties, changes in other environmental properties of skid trails, created differences in beech and maple seedling growth between the skid trails and non-skid trails. This was closely related to the physiological characteristics of the two species studied. Beech seedlings reacted well to a moderate uncovering but they needed little disturbed soil, even if there was a very mixed bedding. Maple seedlings reacted better than beech seedlings to the uncovering and soil disturbance. The effects of the skid trail on morphology, growth and architecture of maple seedlings in the Hyrcanian beech forests showed that the maple, as a seedling, is a suitable species for maintaining the physical properties of skid trails after logging operations in the beech stands in the Caspian forests of Iran. [ABSTRACT FROM AUTHOR]

Working time studies, work productivity, and cost assessments of forest logging are of interest to forest managers and planners. These aspects are particularly important in salvage logging, because of difficulties due to irregularly positioned fallen trees in forest areas, and due to particular aspects related to the absence of work planning. In this research, system productivity and the cost of salvage logging are analyzed for two mountain forests managed with close-to nature-silviculture: the Hyrcanian forest, using extraction by a skidder, and the Camaldoli forest, using extraction by tractors. The system productivity of salvage logging by skidders and tractors was calculated as 1.54 and 0.81 m3·h−1, respectively. In contrast to common logging, system productivity was about 6- to 15-fold lower in salvage logging. The effective cost consumptions for the skidder and tractor were calculated as $72.57 and $118.62 USD·m−3, respectively. For both yards, winching time increased due to increasing winching distance and winching load volume. The same result was determined for skidding time in relation to load volume and distance. The possible cost decreases for the skidder and tractor were calculated as 2.6% and 4.3%, respectively. The results revealed that operational costs for extracting wind-fallen trees are higher than for traditional standing-trees extraction for both situations studied. In both cases, the harvesting costs were higher than the timber price by 10% to 30%. Therefore, extraction of wind-fallen trees has no economic justification in these forests. [ABSTRACT FROM AUTHOR]

• Three different leaf litters mulches were applied on compacted soils of skid trails. • The effect of mulches on runoff, sediment, and water holding capacity were studied. • The water holding capacity was higher in beech litter than hornbeam and maple. • Runoff and sediment yield significantly decreased as leaf litter rate increased. The surface of the mineral soil is covered by the forest floor forming water absorbent layers. This is how the forest floor plays an important role in soil and water conservation. The aim of this study was to individualize three leaf litters (beech, hornbeam, and maple) applied at three density rates (6, 12, and 18 Mg ha−1) to assess their soil protection capacities. A total of nine treatments were conducted (i.e., beech6, beech12, beech18, hornbeam6, hornbeam12, hornbeam18, maple6, maple12, maple18) on skid-compacted soils in the Hyrcanian forests of northern Iran to evaluate effects at reducing runoff and sediment yield, and to determine the oven-dry weights and water holding capacity of litters. A total of nine runoff plots with dimensions of 1 × 2 m were established on the skid trails during the study period from September to December 2017 in a field experiment under natural rainfall. At the study period, 29 events with a total of 752.2 mm rainfall were measured in the open space area, that 26% of the rainfall was intercepted by canopy cover. Regardless of leaf litter species, the runoff and sediment yield significantly decreased as the leaf litter rate increased. The average runoff in litter plots of beech, hornbeam, and maple was 102.71, 94.25, and 116.87 mm, whereas the average sediment yield was 27.07, 22.33, and 36.73 g m−2 for the study period, respectively. The mean water holding capacity of beech, hornbeam, and maple litter plots amounted to 84.1, 59.16, and 25.81 mm for the study period, respectively. Our study shows that the different species of leaf litter have a diverse range of hydrological functions and litter water holding capacities, which reduced runoff and sediment yield. [ABSTRACT FROM AUTHOR]

• 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]