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

Effects of Logging Wounds on Caucasian Alder Trees (Alnus subcordata C.A. Mey.) in Iranian Caspian Forests

Caucasian alder is a large tree and one of the commercial species in the Caspian forests. We investigated the wound healing rate (WHR) and compared the diameter growth (DG) of 66 wounded and 66 unwounded alder trees 15 years after selected logging in these forests. The conditions of the wounds after 15 years were as follows: 56.1% had closed, 25.7% were open, and 18.2% had decayed. The mean WHR was 4.95 cm2/yr, ranging between 0 and 17.3 cm2/yr, and DG of wounded trees was 13.3% lower than in unwounded trees. The WHR and DG were related to the size, intensity and location of the wound, stem diameter (diameter at breast height; DBH), and ratio of wound size to stem basal area. The WHR in middle-aged trees was more than in young and older trees. The reduction in DG of wounded alder trees was only observed in the DBH range below 58 cm. Wounds that were larger than 100 cm2 in area significantly reduced diameter growth of alder trees. Height of wound from ground level had significant negative effects on WHR and DG. Closed wounds had no significant effect on DG, but open or decayed wounds reduced DG by 13.8% and 34.3%, respectively. 72.7% of total logging wounds were caused by skidding operations where 20.8% of them were decayed, and reduced DG by 12.2%. Selective logging needs more careful planning of roads, skid trails, and winching corridors

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

Long-Term Effects of Timber Extraction by a Crawler Tractor on Soil Condition Recovery in a Mixed Forest

In this study, the physical, chemical and biological characteristics of compacted soil due to tracked skidding (LTT-100A) after 35 years (from 1986 to 2021) of clear cutting operation were investigated in an even aged mixed deciduous stand in Masal forests, Guilan province, northern Iran. Three levels of machine traffic intensity (TI) (low, LT; medium, MT; and high, HT), two levels of skid trail slope (SC) (Gentle, <10%, GS; and steep, ≥10%, SS), two sample locations(SL) (Between track, BT; and On tracks, OT), and two soil depths (SD) (0-5 cm, and 5-10 cm) were considered as independent variables affecting the process of soil profile recovery. The values measured from the abandoned skid trails were compared with those of undisturbed areas to estimate the soil profile recovery rates. Results showed that TI had significant effects on all soil physicochemical (except for soil moisture) and biological properties (i.e., leaf litter, above-and below-ground biomass); all physicochemical and biological properties (except for soil moisture and leaf litter) were affected by SC; the effect of SL on soil texture, density and moisture was significant; and soil texture and density were the only characteristics affected by SD. The values of soil bulk density and penetration resistance on the skid trails were 35% and 49% higher than those of the control area, respectively, while total porosity value was 17.5% lower than that of the control area. Furthermore, soil organic carbon on the skid trails was 20% less than that of the control area. The amount of soil biomass on the skid trails was not recovered after 35 years, so the above and below ground biomass on skid trails were 42% and 46% less than the control area, respectively. The value of leaf litter on the skid trails was 31% less than that of the control area. Overall, the results of this research revealed that the soil of the studied forest is sensitive to the activity of timber harvesting machines. Thus, sustainable forest management needs to reduce the impact of logging within the context of best management practices (BMPs)

Detailed Analysis of Residual Stand Damage Due to Winching on Steep Terrains

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Study of Forest Road Effect on Tree Community and Stand Structure in Three Italian and Iranian Temperate Forests

Roads are built in forests for two main reasons, but always in function of management of forest ecosystems, and these reasons are to provide access to the forest area for transportation mobility and wood extraction. This creates a relatively even network in the forest. This topic has received much attention in recent years due to its function and effect on forested rural landscapes and the related environment. Forest road network is important for various types of functional use, such as the interface between forested lands and roads. The aim of this study is to assess the effects of road existence and use on the occurrence of tree dieback and on the composition of the tree community in three forest areas (two in Italy and one in Iran). The effort to determine the dynamics of the effects caused by road use was done by examining the changes in stand structure and abundance of species. As demonstrated by the results, the edges (20 m) of the forest road network are a fine mosaic composed of different trees (qualitative and quantitative), coupled with the moderate presence of dead trees. In the three areas, from the road edges to the interior forest, a similar taxonomic composition of forest community was found. The first main difference was related to the abundance of less shadow tolerant species along the road. The second main difference was related to the tree biodiversity indices that are higher along the road. The main similarities are in the structure of live and dead trees

Effect of location and diameter of different tree species on bole decay due to logging wounds in Nav-e Asalem forests, Iran

Logging secondary damages on remained trees are one of the challenges in management of uneven-aged stands which have been less studied in the northern forests of Iran. In this research decay frequency and volume of bole trees after 15 years from wound occurrence were studied through systematic-random sample plots with 1000m2 plots in the Nav-e Asalem forests, Iran. The conditions of trees were registered in two types: safe and wounded, the wounds were registered in two types: open and decayed; and volume of decayed bole was calculated by Smalian formula. Results indicated that 16.1% of wounds were led to bole decay. Decay frequency and volume were estimated to 5.5 trees ha-1 and 1.7 m3ha-1, respectively, that includes 1.96% of total trees and 0.72% of total stand volume. Coefficients of decay frequency and volume on the base of frequency of logging primary damage (12.2%) were calculated 0.16 and 0.06, respectively. Decay frequency of wounded trees bole were related with tree species, wound location, diameter at breast height (DBH), situation of wounded tree in stand, and slope aspect. Decay frequency and volume in the trees of lime and oak were more than other tree species. Decay frequency was increased by decreasing wounds distance from ground. Decay frequency and volume in the high diameter wounded trees were more than low diameter wounded trees. The wounds on the trees in edge of skid trails were more decayed than the other wounds. Decay frequency of wounded trees on the northern aspect slopes were more than the southern aspect slopes. In general, minimizing of primary logging damages, reducing harvest intensity, increasing logging period, and harvesting bole-decayed trees in the next logging periods are suggested

Effect of ground slope on extent and intensity of soil disturbance from skidder logging (Case study: Nav-e Asalem forest, Gilan province)

Protection of forest soil is one of key factors in having sustainable productive forests. In this research extent and intensity of soil disturbance due to extraction of logs of felled trees (20.5 m3/ha) were studied in Nav-e Asalem forest in Gilan province. After finishing the skidder logging operations, soil disturbance were studied by point-transect sampling method and visual assessing. Results indicated that about 19 ± 6.2 percent of surface soils were disturbed due to winching of logs that 11.3 percent of them disturbed with shallow intensity and 7.7 percent disturbed with deep intensity. The extent and intensity of soil disturbance were decreased by increasing distance from skid trail. The extent and intensity of soil disturbance were increased by increasing of ground slope. Soil bulk density in the shallow disturbed soils (1.29 g/cm3) and deep disturbed soils (1.44 g/cm3) were increased 2.4 and 14.3 percent, respectively, than control soils. Soil bulk density of disturbed areas were increased by increasing ground slope, so in slopes greater than 50 percent soil bulk density was increased 20.8 percent more than control soils. Including ways to reducing soil disturbance during skidder logging in the study area are reduction in harvest intensity, implementation of felling direction and skidder logging limitation to slopes less than 50 percent