Recovery of Forest Soil Chemical Properties Following Soil Rehabilitation Treatments: an Assessment Six Years after Machine Impact

Several rehabilitation treatments have been applied to mitigate runoff and sediment in machine trafficked areas following logging operations, while the knowledge on the consequence of these remediation techniques on the recovery of soil properties remains scarce. The objective of the study was to determine the effect of different rehabilitation treatments including sawdust mulch (SM), water diversion structure (WDS), untreated/bare trail (U), and undisturbed or control area (UND) on the recovery of soil chemical properties over a six-year period after machine-induced compaction occurred on three longitudinal trail gradients (10, 20, and 30%). In each treatment, the following soil properties were measured: litter thickness, pH, EC, soil organic C, total N, and available P, K, Ca, and Mg. Five sampling plots (with 10 m length and 4 m width) were positioned in each trail gradient classes and three of these plots were randomly considered for soil sampling. The results demonstrate that litter thickness differed among the three treatments, with the highest amount present on the UND area and lowest on the U treatment. Meanwhile, the highest pH (6.75), EC (0.21 Ds m−1), N (0.27%), available P (14.61 mg kg−1), available K (123.5 mg kg−1), available Ca (135.1 mg kg−1), and available Mg (42.1 mg kg−1) and the lowest C (1.21%) and C/N ratio (7.83%) were found on the SM with gradient of 10% compared to other gradient classes on SM, WDS and, U treatments. The recovery value of litter depth, pH, EC, C, N, C/N ratio, and available nutrients (P, K, Ca, and Mg) were higher on the SM than the WDS at the gradient of 10%, while significantly higher levels of these variables were measured under WDS installed on trail gradients of 30% and 20% when compared with the same gradients on SM. Results of the study revealed that soil chemical properties showed some evidence of recovery following SM and WDS rehabilitation treatments compared to U, although these properties did not fully recover within 6 years as compared to UND area

Effects of Rubber-Tired Cable Skidder on Soil Compaction in Hyrcanian Forest

The use of skidders equipped with rubber tires is a well accepted practice for the extraction of timber from the forest, but the application also causes considerable environmental problems. The aim of the study was to evaluate the effects of different slope gradient, number of machine passes on skid trails and soil depth on soil compaction. The study was designed as an experiment with the factors including slope gradient, soil moisture, and soil depth on various skid trails and with different number of machine passes. The effects of four slope classes (flat, 10%, -10% and -20%), three soil depth classes (5, 15 and 25 cm), and different compaction levels based on various number of machine passes (0, 1, 5, 8, 10, 15, 20, 25 and 30) were evaluated. A Timberjack cable skidder was used and the study location was in the Kheyrud Educational and Research Forest located in the Hyrcanian forest in northern Iran. The increased number of machine passes increased soil bulk density, but the highest rate of compaction occurred after the initial few passes. Uphill skidding increases soil compaction more than downhill skidding. The increases in bulk density were still significant at the maximum sampling depth of 20–30 cm. Soil bulk densities at 5, 15 and 25 cm depth averaged 35, 22 and 17% higher than densities of undisturbed soil

Effectiveness of Three Post-Harvest Rehabilitation Treatments for Runoff and Sediment Reduction on Skid Trails in the Hyrcanian Forests

Ground-based skidding operations can lead to soil compaction and displacement, which could cause negative effects on forest soil. Hence, some efforts such as forestry best management practices (BMPs) must be implemented in the prone area to mitigate these possible impacts. Several materials and treatments have been adopted to suppress these adverse effects by increasing the ground cover. However, the effects of mulch treatments on runoff and sediment yield are inconclusive with a diverse range of effectiveness. For these reasons, in this research mulch treatments were tested as to determine how the application of organic mulch amendments such as straw and leaf litter and contour-felled logs would alleviate the runoff and sediment yield on machine operating trails and ensure successful hillslope stabilization. The aims of the study were to analyse and compare the effectiveness of leaf litter (LM) and straw mulch (SM) rate and different distances of contour-felled logs (CFL) to mitigate the runoff and sediment yield, and examine the impact of rainfall intensity on effectiveness of litter mulch, straw mulch, and contour-felled logs. Totally, 30 bounded runoff plots in the machine operating trails and four treatments including litter mulch (LMR1: 0.62, LMR2: 1.24, and LMR3: 1.86 kg m-2), straw mulch (SMR1: 0.45, SMR2: 0.92, and SMR3: 1.34 kg m-2), contour-felled logs (CFL10: 10, CFL20: 20, and CFL30: 30 m), and untreated area were established in triplicate with 4 m width and 100 m length. During the study period, the runoff and sediment yield in the untreated trails (U) were 2.36 mm and 11.84 g m-2. Straw (from 41.5 to 60.6%) and litter mulch (from 38.1 to 55.1%), and contour-felled logs treatments (from 70.8 to 88.1%) significantly decreased the runoff, compared to U treatment. Results show that mulch treatments with three different levels of Litter Mulch Rate, LMR1, LMR2, and LMR3 decreased mean sediment by 46.6, 64.0 and 71.8%, in the treatments with three different levels of Straw Mulch Rate, SMR1, SMR2, and SMR3 decreased mean sediment by 42.9, 62.1, and 69.9%, and in the treatments with three different distances of Contour-Felled Logs, CFL10, CFL20, and CFL30 decreased mean sediment by 90.6, 94.7 and 88.3% comparing to U, respectively. The relationships of the runoff and sediment responses to increasing mulching rate of litter and straw followed as negative logarithmic curves, but the decreasing-increasing trends were observed in runoff and sediment yield as the distance between contour-felled logs increased from 10 to 30 m. Polynomial regression equations were developed for predicting the runoff and sediment yield as a function of the application rate of litter and straw mulch and the distance between contour-felled logs, and rainfall intensity. We concluded that contour-felled logs treatment was more effective than both litter and straw mulch to mitigate the runoff, runoff coefficient, and sediment yield on machine operating trails. As a management measure, it could be possible to propose that the contour-felled logs with a distance of 20 m be prescribed to protect the machine operating trails from the negative effects of surface waterflow

Performance, Capability and Costs of Motor-Manual Tree Felling in Hyrcanian Hardwood Forest

Motor-manual tree felling is the most labor-intensive component of all harvesting operations and frequently represents a bottleneck in wood production. The study of motor-manual tree felling was carried out in two compartments in the Namkhaneh district of Kheyrud Forest. The objects of this study were as follows: time study of tree felling operations, estimate of chainsaw productivity and costs, development of a regression model in uneven-aged stand using single-tree selection methods. The factors affecting total felling time regression model (increasing order of importance) were DBH of harvested trees, direction of felling regarding the lay and inter-tree distance. The hourly production of chainsaw felling with and without delay time was 56.4 cubic meters per hour (13 tree/hour) and 80.7 cubic meters per hour (19 tree/hour), respectively. Productivity of chainsaw felling increased in relation to tree DBH as power relation. The cost of chainsaw felling with and without delay time was 0.55 and 0.39 USD/m3, respectively. The cost of felling increased as simple exponential equation when DBH of harvested trees decreased. However, the unit felling cost for chainsaw operation decreased as the tree size increased. Total felling cycle time without delay averaged 3.14 minutes and with delay time it averaged 4.5 minutes. Productivity was more sensitive to DBH than felling direction and inter-tree distance

Strategies to Mitigate the Effects of Soil Physical Disturbances Caused by Forest Machinery: a Comprehensive Review

Purpose of Review Ground-based mechanized forest operations can cause severe soil disturbances that are often long lasting and detrimental to the health of forested ecosystems. To reduce these soil disturbances, focus is being increasingly directed at identifying and using appropriate mitigation techniques. This systematic review considered 104 scientific articles and reported the main findings according to four core themes: terrain-related factors, operational planning, machine modifications, and types of amendments used to mitigate machine-induced soil impacts. Recent Findings For terrain-related factors, most severe disturbances occur on machine operating trails exceeding 20% slope and that soil bulk density and rut depth show greater increases in fine-textured soils. When considering operational planning, trafficability maps proved to be helpful in reducing the frequency and magnitude of soil damages as well as the length of trails needed within harvest sites, especially if they are regularly updated with weather information. Machine modifications, through high flotation tires, use of extra bogie axle, lower inflation pressure, and use of steel flexibles tracks, are highly researched topics because of the considerable upside in terms of machine ground pressure distribution and increased traction. Two main types of amendments emerged to mitigate soil disturbances: brush mats and mulch cover. Brush mats created from harvesting debris can spread the load of a machine to a greater area thereby lowering peak loads transferred to the soil. Brush mats of 15-20 kg m(-2) are being recommended for adequate soil protection from harvesting operations. To conclude, we outline recommendations and strategies on the use of soil mitigation techniques within cut-to-length forest operations. New research opportunities are also identified and discussed. Considering single factors causing machine-induced soil disturbances remains important but there is a pressing need for having a multi-disciplinary approach to tackle the complex problems associated with machine/soil/plant interactions

Effectiveness of Water Diversion Structure to Mitigate Runoff, Sediment Yield, Nitrate and Phosphate Concentrations in Skid Trail of Mountainous Forest Ecosystem

It is well-known that soil and water conservation actions (e.g., installing water diversion structures) are necessary to restore skid trails after logging operations. However, there are some points that have yet to be determined concerning the efficacy of rehabilitation on sediment yield and nutrient export to the aquatic environment. The objectives of this study were to determine the optimal distance among the water diversion structures (WDSs) to suppress runoff, sediment yield, and measure nitrate and phosphate concentrations on the skid trails of a mountainous ecosystem. The study was conducted on a total of 18 bounded runoff plots, each with a width of 4 m and a length of 120 m, divided into six treatment compartments done in triplicate. Beech logs were placed at a distance of 5, 10, 20, 30, and 40 meters. An untreated area (U) was set up during the recording period from 18 September 2015 to 17 September 2016. In all the WDS treatments and untreated trails (U), the observed peaks of runoff, sediment yield, as well as nitrate and phosphate concentrations was found to be significantly correlated with the amount of rainfall events. Results show that there was a decrease in surface runoff and runoff coefficient, sediment yield, and nitrate and phosphate concentrations by installing of WDS at different distances. The runoff and runoff coefficients (2.67 mm and 0.101, respectively) were at the lowest level in the WDS20 (WDS at a distance of 20 m). The sediment yield was significantly higher on the U, 13.52 g m-2 followed by WDS40, whereas the lowest values were detected at the WDS10. Significantly higher values of nitrate were found in the U (3.63 mg l-1), while the lowest amounts of nitrate were determined at WDS5 followed by the WDS20 treatment. The highest values of phosphate were found on the U treatment (0.278 mg l-1) followed by the WDS40 treatment, whereas the lowest phosphate values were measured in the WDS20 treated area. Therefore, it can be deduced that the recommended water diversion structure should be placed at a distance of 20 m to mitigate runoff, sediment yield, nitrate and phosphate exports on the skid trails

Environmental Impacts to Residual Stand Damage due to Logging Operations in Hyrcanian Forest

The development of harvesting systems aims to provide physically feasible, economically viable, and environmentally sound solutions. Residual stand-damage data have been collected from a mixed broadleaved stand in Kheyrud area in Hyrcanian forest in the northern of Iran. After the harvesting operations, for all trees, damage to the bole, roots, extent of the damage, wounding patterns, size and distribution was assessed using stratified systematic sampling with a random start and fixed area plots. Results show that wounding occurred on 16.4% of the remaining trees, but the severity of wounding varied significantly by species. Forty-six percent of wounding for all species combined was considered as small size. The greatest average amount of damage, to a bole, occurred along the first 1m up from the ground and also within 3m of the skid trail centerline (86.4%). Gouges were present on 79% of all scars. The stratification of the study unit would effectively improve accuracy of stand damage surveys. Selection of the appropriate method for damage reduction to trees adjacent skid trails was crucial. According to the results, skidding damage cannot be completely avoided in practice. We suggest that the education and the entertainment of the foresters and workers in forest would be enhanced and the injuries could be explained before the harvesting to the workers. In such a way the damages would be less in the future

Effects of protection treatments on prevent log checking (Case study: Kheyrud forest)

The remaining the logs in the stump area and especially along the forest roadside, can increase the check in the caused by growth stress in the both sides of log. All of these factors led to a decline in the quality of the logs, which can be lined up in the ends of log with suitable coating materials such as end coating and anti-checking iron treatments to prevent log checking. A field-based study was performed to study the effects of end coating and anti-checking iron treatments on prevent log checking in beech and hornbeam logs in Gorazbon district in Kheyrud forest northern Iran. In this study, 180 logs were randomly selected from two spices; beech and hornbeam and for any spices, 30 logs were selected for anti-checking iron treatments, 30 logs for paraffin treatments and 30 logs for control. Duncan’s test showed that in the hornbeam logs anti-checking iron treatments was the lowest checking increase comparing the paraffin and control treatments and this difference was statistically significant. Duncan’s test showed that in the beech logs anti-checking iron treatments was the lowest checking increase comparing the paraffin and control treatments. It can be concluded that the lowest check has been shown in the anti-checking iron treatments in two beech and hornbeam logs and this treatment has the greatest role in preventing ends check in compare with the paraffin treatment

Effects of Slope Gradient on Runoff and Sediment Yield on Machine-Induced Compacted Soil in Temperate Forests

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

Productivity of timber extraction using farm tractor equipped with trailer (Case study: in Kheiroud Forest in northern Iran)

In the Hyrcanian forest of Iran, farm tractors equipped with 2-wheels trailer are mostly used to perform forwarding operations of pulpwood and fuelwood in small-scale timber harvesting. This study was carried out in Gorazbon district in Kheiroud experimental forest to evaluate time regression models and estimate the forwarding costs. A continuous time study was conducted to explore farm tractor for forwarding pulpwood and fuelwood, to assess farm tractor productivity and costs and to identify those variables which are most likely influential. The model indicates that the most influential important on forwarding productivity were the forwarding distance and the number of logs per turn. The average productivity of forwarding with farm tractor was 2.66 and 3.83 m3 for pulpwood and fuelwood, respectively. When the forwarding distance increased, the total time of a cycle increased as well. In addition, productivity of farm tractor was decreased by increasing the forwarding distance in a logarithmic manner. The cost of the farm tractor logging system was 508635 Rial per productive machine hours. Furthermore, hourly costs of pulpwood and fuelwood forwarding were 132730 and 190960 Rial/m3, respectively. The cost of farm forwarding was increased as simple power equation when extraction distance was increased. The element time consumption showed that the loading phase was the highest time consumption phase per turn, mainly due to labor-intensive manual loading and physical handling of logs. The forwarding operation is, however, concluded to bear advantages such as larger payload, less soil disturbance, and transportation of the logs from stump to the logging truck off-ground. It is therefore a good alternative for extraction of pulpwood and fuelwood in gentle slope in the Hyrcanian forests