Strip Clear-Cutting Application and Logging Typologies for Renaturalization of Pine Afforestation—A Case Study

Application of the strip clear-cutting system in a running bamboo (Phyllostachys glauca McClure) forest: feasibility and sustainability assessments

Introduction

As a renewable forest resource, bamboo plays a role in sustainable forest development. However, traditional cutting systems, selection cutting (SeC) and clear-cutting (ClC), result in an unsustainable production of bamboo forests due to labor-consuming or bamboo degradation. Recently, a strip clear-cutting (StC) was theoretically proposed to promote the sustainability of bamboo production, while little is known about its application consequence.

Methods

Based on a 6-year experiment, we applied the strip clear-cutting system in a typical running bamboo (Phyllostachys glauca McClure) forest to assess its feasibility and sustainability. Using SeC and ClC as controls, we set three treatments with different strip widths (5 m, 10 m, and 20 m) for strip clear-cutting, simplified as StC-5, StC-10, and StC-20, respectively. Then, we investigated leaf physiological traits, bamboo size and productivity, population features, and economic benefits for all treatments.

Results

The stands managed by StC had high eco-physiological activities, such as net photosynthetic rate (P n), photosynthetic nitrogen use efficiency (PNUE), and photosynthetic phosphorus use efficiency (PPUE), and thus grew well, achieved a large diameter at breast height (DBH), and were tall. The stand biomass of StC (8.78 t hm-2 year-1) was 1.19-fold and 1.49-fold greater than that of SeC and ClC, respectively, and StC-10 and StC-20 were significantly higher than SeC or ClC (p< 0.05). The income and profit increased with the increase in stand density and biomass, and StC-20 and StC-10 were significantly higher than SeC or ClC (p< 0.05). Using principal components analysis and subordinate function analysis, we constructed a composite index to indicate the sustainability of bamboo forests. For the sustainability assessment, StC-10 had the highest productive sustainability (0.59 ± 0.06) and the second highest economic sustainability (0.59 ± 0.11) in all cutting treatments. StC-10 had the maximum overall sustainability, with a value of 0.53 ± 0.02, which was significantly higher than that of ClC (p< 0.05).

Conclusion

The results verified that StC for Phyllostachys glauca forests is feasible and sustainable as its sustainability index outweighs those of traditional cutting systems (SeC and ClC), and 10 m is the optimum distance for the strip width of StC. Our findings provide a new cutting system for managing other running bamboo forests sustainably.

Carbon Storage in Biomass and Soil after Mountain Landscape Restoration: Pinus nigra and Picea abies Plantations in the Hyrcanian Region

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.

Variations of Soil Physico-Chemical and Biological Features after Logging Using Two Different Ground-Based Extraction Methods in a Beech High Forest—A Case Study

Considering that forests are crucial in the ecosystem of our planet and that forests provide timber products as well as several ecosystem services, it is evident that the application of sustainable forest operations (SFOs) is of substantial importance to achieve sustainable forest management (SFM). One of the most important issues to be evaluated when dealing with SFOs is limiting the disturbance and impacts related to logging. Harvesting activities can indeed alter the conditions of soil through compaction and litter removal which can also lead to modifications from the biological point of view, for example, diminishing the presence of soil microarthropods. While keeping these objectives in focus, the aim of the present study was to evaluate physico-chemical and biological impacts on forest soil in Mediterranean beech forests after forest logging with two different extraction systems, which are forestry-fitted farm tractors equipped with winch and forwarder. Specifically, authors aimed to investigate: (i) soil disturbance levels of ground-based extraction methods; (ii) soil disturbance levels of the applied forestry intervention; (iii) soil disturbance levels between winching-skidding and forwarding. Findings showed that the physical, chemical, and biological soil features were slightly disturbed by the forestry itself. In addition, forest operations and machine traffic showed clear soil disturbance, resulting in a substantial alteration of the characteristics. Between the two extraction techniques tested, winching caused less disturbance while forwarding had stronger impacts. However, it should be noted that these impact levels are found only on approximately 28% of the surface where operations were carried out. From the evidence gathered in this study, winching seems a less impactful extraction method in the studied context. On the other hand, to decrease the impact of forwarding, some technical adjustments such as bogie-tracks, as well as improved operator training, should be applied.

Addressing Gender Inequities in Forest Science and Research

Forest research and professional workforces continue to be dominated by men, particularly at senior and management levels. In this review, we identify some of the historical and ongoing barriers to improved gender inclusion and suggest some solutions. We showcase a selection of women in forestry from different disciplines and parts of the globe to highlight a range of research being conducted by women in forests. Boosting gender equity in forest disciplines requires a variety of approaches across local, regional and global scales. It is also important to include intersectional analyses when identifying barriers for women in forestry, but enhanced equity, diversity and inclusion will improve outcomes for forest ecosystems and social values of forests, with potential additional economic benefits.

Soil Compaction after Increasing the Number of Wheeled Tractors Passes on Forest Soils in West Carpathians

Soil disturbance and compaction are inherent in ground-based harvesting operations. These changes are affected by numerous factors, related mainly to the technical parameters of the machines, soil conditions, and the technology used. This study aimed to analyze the changes of surface layers of soil caused by skidder traffic without loads on the Cambisols of Western Carpathians. We observed changes in the soil bulk density and penetration resistance. The results showed that only machine traffic caused a 0.32 to 0.35 (g cm−3) increase in soil bulk density. Besides machine traffic, bulk density was affected by soil moisture content. Penetration resistance of soil increased by 0.15 to 1.04 (MPa) after traffic of 40 machines. Penetration resistance showed a lower increase after traffic, and regression and correlation analysis proved a relationship between penetration resistance, skeleton content, and penetration depth, besides the number of machine passes (r = 0.33–0.55). Observing the changes in the physical properties of soils caused by machine traffic allows for a more detailed view of the effects of forest harvesting machinery on forest soils.

Evaluation of Leaf Litter Mulching and Incorporation on Skid Trails for the Recovery of Soil Physico-Chemical and Biological Properties of Mixed Broadleaved Forests

Engineering applications can be used to mitigate the adverse effects of soil compaction and amend compacted soils. Previous literature has highlighted the beneficial effects of interventions such as litter mulching and incorporation on skid trails. However, little is known about the effectiveness of these alternatives in restoring forest soil quality after forest logging. The objective of this study was to properly elucidate the effects of the above mentioned soil protection methods, litter incorporation before skidding (LI) and litter mulching after skidding (LM), on the recovery of compacted soil’s physico-chemical and biological properties on skid trails over a 2-year period in the Hyrcanian forests of Iran to identify the best option for restoration intervention. The litter used in both methods consisted of dried leaves of the hornbeam and maple tree in three intensities of 3, 6, and 9 Mg ha−1. The results showed that the application of both methods (LI and LM) significantly improved the soil properties when compared to the untreated skid trail. Results showed that the recovery values of soil properties in the LI treatments were significantly higher than those of the LM. The recovery values of soil properties by 6 and 9 Mg ha−1 were significantly higher than those of 3 Mg ha−1, while the differences were not significant between 6 and 9 Mg ha−1. Our findings showed that soil properties were partially recovered (70–80%) over a 2-year period from treatment, compared to untreated, but the full recovery of soil properties required more time to return to the pre-harvest value. Overall, the results of this study demonstrated that the application of soil protection methods accelerates the process of recovering soil properties much faster than natural soil recovery, which can take more than 20 years in these forests.

Soil Natural Recovery Process and Fagus orientalis Lipsky Seedling Growth after Timber Extraction by Wheeled Skidder

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

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.

Earthworms as an Ecological Indicator of Soil Recovery after Mechanized Logging Operations in Mixed Beech Forests

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.

Soil Disturbance and Recovery after Coppicing a Mediterranean Oak Stand: The Effects of Silviculture and Technology

Traditional coppice management system is one of the most debated topics in the Mediterranean area, as it is a forest management system that accounts for over 23 million hectares. Coppicing is considered the oldest form of sustainable forest management. Its past and current widespread popularity is mainly due to its capacity to positively contribute to the rural economy and ecosystem services. This research aimed at assessing the effect of coppicing on soil characteristics, understanding a possible treatment return time, and evaluating the implementation of proper sustainable forest operations (SFOs) in order to have a better understanding of the disturbance caused by silvicultural treatment and forest operations with two different harvesting techniques. The results demonstrated that physical, chemical, and biological soil features were partially disturbed by the coppicing. Both silvicultural treatment and forest operations influenced soil disturbance. The least impactful technique was extraction by winch, while forwarding resulted in heavier alterations of soil characteristics. It took about five years for the soil to recover its original pre-harvest conditions when the disturbance was caused by the silvicultural treatment alone (non-trafficked areas) and about eight to nine years when the disturbance was the cumulated effect of silvicultural treatment and logging activity (trafficked areas).

Soil Recovery Assessment after Timber Harvesting Based on the Sustainable Forest Operation (SFO) Perspective in Iranian Temperate Forests

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.

Assessing the impacts of log extraction by typical small shovel logging system on soil physical and hydrological properties in the Republic of Korea

Typical small shovel logging system, using manual felling and extraction by small crawler excavator with grapple and crawler carriers, is the predominant logging method in the Republic of Korea, due to the associated high productivity. The trails with ground pressure and one more passes of the shovel and carriers may lead to soil compaction. However, impacts of these bunching-extraction technologies on physical and hydrological properties of soils are not well known. The main objectives of this study were to: (1) determine the bulk density, porosity, and saturated hydraulic conductivity of soils in logging operation areas with three different disturbance types (i.e., undisturbed areas [UAs], bladed trails [BTs], and skid trails [STs]), and (2) compare soil compaction between these disturbance types. The most intense compaction occurred within BTs and STs, with increased bulk density and reduced porosity and hydraulic conductivity. Soil bulk density increased by 27–53% at all depths in BTs and STs compared to UAs, while porosity decreased by 23–49%. On average, saturated hydraulic conductivity at depths of 0–20 cm decreased from 337.5 mm h⁻¹ to 30.5 mm h⁻¹ in the most compacted sections of BTs and STs. Skid trails, which are characterized by trail construction and frequent vehicle movement, also caused greater impacts on soil compaction than BTs. This study provides useful insights to aid forest consultants and field managers in planning more environmentally sound mechanized logging operations.

Post-Harvest Evaluation of Soil Physical Properties and Natural Regeneration Growth in Steep-Slope Terrains

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.

Morphology, Growth and Architecture Response of Beech (Fagus orientalis Lipsky) and Maple Tree (Acer velutinum Boiss.) Seedlings to Soil Compaction Stress Caused by Mechanized Logging Operations

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.

Sustainability Assessment of Alternative Strip Clear Cutting Operations for Wood Chip Production in Renaturalization Management of Pine Stands

In Mediterranean regions, afforested areas were planted to ensure the permanence of land cover, and to protect against erosion and to initiate the vegetation processes. For those purposes, pine species were mainly used; however, many of these stands, without silvicultural treatments for over fifty-sixty years, were in a poor state from physical and biological perspective, and therefore, clear-cutting on strips was conducted as silvicultural operation with the aim to eliminate 50% of the pine trees and to favor the affirmation of indigenous broadleaves seedlings. At the same time, the high and increasing demand of the forest based sector for wood biomass related to energy production, needs to be supplied. In a modern and multifunctional forestry, in which society is asking for sustainable forestry and naturalistic forest management, forestry operations should ideally be carried out in a sustainable manner, thus support the concept of sustainable forest management. All these aspects are also related to the innovation in forestry sector for an effective energetic sustainability. Three different forest wood chains were applied in pine plantations, all differing in the extraction system (animal, forestry-fitted farm tractor with winch, and double drum cable yarder). The method of the sustainability impact assessment was used in order to assess potential impacts of these alternative management options, and a set of 12 indicators covering economic, environmental, and social dimensions was analyzed. Further, to support decision makers in taking informed decisions, multi-criteria decision analysis was conducted. Decision makers gave weight towards the indicators natural tree regeneration and soil biological quality to support the achievement of the forest management goal. Results showed that first ranked alternative was case 2, in which extraction was conducted by a tractor with a winch. The main reason for that lies in the fact that this alternative had best performance for 80% of the analyzed criteria.