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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]

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]

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]

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]