مجله جنگل ایران
سال پانزدهم شماره 1 (بهار 1402)

Iran’s Hyrcanian forests are part of the temperate forests and have survived since Tertiary. These forests have experienced severe damages in recent decades because of socio-economic issues such as overgrazing. This study aimed at investigating the Nurse-protégé interaction and the impact of understory shrub species on the regeneration of the Hyrcanian main tree species in Kheyrud Forests. Filed sampling was carried out using the random-systematic method. Regeneration and their features under and outside of the canopy of shrub species, as well as some environmental variables were recorded in strip plots. According to the results, the canopy cover percentage of 25-50% provides the best regeneration protection efficiency for the six nurse shrub species. Overall, regeneration density was found to be higher outside the canopy area of the shrub species than beneath their canopy area; however, regeneration under the shrub species caused higher mean height and age. Moreover, the mean cover and the depth of the litter under the shrub canopy were significantly higher than that of outside the canopy area. Although the shrub species allow more durable and complete development of seedlings by providing protection against grazing, suitable conditions for seed germination and seedling growth may not be provided because of high litter depth and insufficient sunlight due to the massive canopy of trees as well as nurse shrubs’ dense foliage (especially, evergreen understory species).

Environmental factors have a major impact on the distribution and yield of plant species. For this purpose, considering the importance of Astragalus ovinus (L.) Boiss. in forage production and the possibility of using it in improvement and reclamation of forest ecosystem. In the present study, the responses of A. ovinus were evaluated to some environmental factors in one of its habitats of southwest of IRAN (Kohgiluyeh and Boyer-Ahmad province) in 2018- 2020. Redundancy Analysis (RDA) and Generalized Additive Models (GAM) were used to determine the ecological factors affecting vegetation changes and to evaluate the response of A. ovinus along the gradients of  ecological factors, respectively. Data analysis was performed using SPSS17 and CANOC4.5 software. According to the results, the response pattern of A. ovinus along the gradient of soil surface litter, percentage of bare soil, percentage of land slope, and altitude, followed the unimodal model and the optimum growth levels for these factors were 20%, 20%, 30%, and 2220 m, respectively. Also, the response of this species to aspects has followed the unimodal model, so that in the eastern and western slopes, the presence of the species increased and the northern, southern slopes of the species decreased. The reaction of this species to changes in soil sand content followed the bimodal model indicatinga competitive constraint along the environmental gradient. The results of the A. ovinus phenology study showed that the best time for livestock to use of this species is mid-May and the best time to collect seeds of this species is late June to the first half of July. Percentage of canopy cover in forest it has not affected the performance and frequency of this species. Regarding the response of this plant to the gradient of studied environmental factors, it is recommended to pay attention to its habitat characteristics and ecological requirements in improvement programs on oak forests understorey vegetation.

Given the pressure of population growth, economic difficulties, and climate change, the mangrove forests of Iran need a management plan based on forest protection, reforestation, and afforestation. In this study, the sustainability of mangrove forests in coastal areas of the Bushehr Province in the north of the Persian Gulf was evaluated using two criteria including “extent of forest resources” and “forest health and vitality” from 1993 to 2009. Indicators of area changes, density changes or survival rate, natural regeneration establishment, and height growth were measured as part of the assessment method. Google Earth images were visually interpreted, and a random sample technique was used. A total of 70 circular samples of 100 m2 were chosen. The results showed that Avicennia marina was planted in 7 sites in Kangan and Dayyer townships on the coasts of the Bushehr Province. Out of 370 ha of the plantation, only 42.4 ha remained, showing an area reduction of 88.5% and an average survival rate of 48.5%. Forest planted density averaged 6635 seedlings per hectare which has decreased by 69.5% (i.e. 4611 seedlings/ha). The decreased area in the Khan site was 91% and in the Basatin site was 52.5%. It is necessary to take into account management measures to improve the status of forest sustainability indicators on the coasts of the Bushehr Province, especially in the process of site selection, to improve the success rate of reforestation and afforestation plans.

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).

Micro-morphological characteristics of leaves such as stomata and trichomes are reliable indicators of plant response to environmental conditions. The aim of this study was to determine the adaptation strategies of 10 woody species growing in semi-arid Zagros forests in western Iran based on leaf microstructures, focusing on trichomes and stomata using light and scanning electron microscopy. Different types of trichomes and stomata were recognized. Stomata were generally more visible on the abaxial sides of leaves, a feature that helps reduce water loss from leaf surfaces exposed to direct airflow and radiation. Trichomes were classified into two different types: glandular trichomes and non-glandular trichomes with subgroups such as solitary, two-armed T-shaped unicellular, crypt, hooked hairs with cystoliths, fasciculate, stellate, long coiled, tufted stellate, long multiradiate, short bristles with cystoliths, peltate scales, and dendritic hairs. The abundance of trichomes on the leaves indicates their role as biological control parameters. Eucalyptus camaldulensis was the only introduced species studied that lacked trichomes on both sides of the leaf. The most frequently observed types of stomata were "Anomocytic" and "Paracytic". The striking differences between the micro-morphological characteristics of the leaves of different species are an expression of the plants adaptations to the environmental ecological conditions.