فصلنامه تحقیقات جنگل و صنوبر ایران
سال سی و یکم شماره 2 (پیاپی 92، تابستان 1402)

The single tree selection method was applied in the Hyrcanian forests of northern Iran to imitate nature and enhance the ecosystem characteristics and functions such as biodiversity, flexibility, and adaptability. However, the effectiveness of this imitation and the changes in the forest stand characteristics were unclear. This research compared the regeneration characteristics of tree species in canopy gaps larger than 100 m2 in a beech (Fagus orientalis Lipsky) stand in the Hyrcanian forests that underwent single tree selection in 2013 with an unmanaged beech forest as a reference. The abundance of seedlings and saplings of all tree species was recorded in each microplot (with an area of 4 m2) in the center and four edges of each gap. The height, collar diameter, crown width, health, stem form, and mode of branching of beech saplings were also measured in each sample microplot and compared. The results indicated that the mean collar diameter (26.6±2.2 mm), height (270.4±23.6 cm), and frequency of orthotropic beech saplings (0.3±0.06) in the managed compartment were significantly higher than the unmanaged compartment (p < 0.05). The average frequency of regeneration in the managed and unmanaged compartments was 7.9 and 6.3 per microplot, respectively. The frequency of beech regeneration in the managed compartment was higher in large gaps, while it was higher in medium gaps in the unmanaged compartment. Although the low harvesting in the studied forest improved the growth conditions for beech seedlings, the abundance of dead trees should be considered. Moreover, the presence of Hedera pastuchovii Woron. exGrossh. in these forests should be examined and managed accordingly.

Mangrove forests are coastal ecosystems that provide various benefits for ecology, economy and society. To manage these forests sustainably, accurate mapping of their distribution using modern techniques is crucial. This study aimed to map the mangrove forests along the southern coast of Iran from Khuzestan province to Sistan and Baluchestan province and identify new sites using remote sensing. The Mangrove vegetation index (MVI) was applied to Sentinel-2 images on the Google Earth Engine (GEE) cloud computing platform. The MVI images were classified by the random forest algorithm. The final maps were evaluated by accuracy, F1-score and other common indices. The results indicated that the total area of mangrove forests in southern Iran was about 12471.8 ha (accuracy 0.98, F1-score 0.97) in October 2021 in 40 sites across four provinces: Khuzestan (286.7 ha), Bushehr (296.9 ha), Hormozgan (11281.9 ha) and Sistan and Baluchestan (606.3 ha). Moreover, some new sites, such as the mangroves of Mahshahr Harbor with an area of around 290 ha in Khuzestan province, were discovered in this study.

Drought is a major threat to vegetation and can cause its decline. Due to natural and human factors, droughts are becoming more frequent and intense around the world. This research examines the trend and severity of droughts in the past and future using the standardized precipitation evapotranspiration index (SPEI) for a Juniper forest reserve in Keygooran, Lorestan Province, Iran. The SPEI index was calculated using daily precipitation and temperature data from the Aligudarz synoptic station for a 33-year period (1987-2019). The frequency and severity of droughts were assessed for the recent past (1987-2019) and the future (2030-2060) using the NorESM2-LM model under the SSP126, SSP370 and SSP585 scenarios. The results showed that the longest droughts occurred in 1990-1991, 1998-2000 and 2010-2012. Moreover, 2003, 2013, 2017 and 2018 were the years with the most severe droughts. In the future (2030-2060), drought periods will be projected to decrease under the SSP126 and SSP585 scenarios (6, 9 and 12 months) and increase under the SSP370 scenario (3, 9 and 12 months). The intensity and duration of extremely severe droughts will be projected to increase in the future despite the decrease in drought frequency based on SPEI. Therefore, the Juniper forest reserve will face more severe droughts in the future, which will affect the reproduction of juniper trees significantly.

The aim of this study was to evaluate the effect of white rot fungus (Trametes versicolor (L.) Lloyd) on physical and mechanical properties of treated and untreated poplar wood (Populus deltoides Marshall and P. nigra L.). Heat treatment was used as wood modification. Heat-treated and untreated poplar wood specimens were evaluated after exposing to the white rot fungus for 16 weeks. The evaluated properties was included: laccase activity, mass loss, density changes, impact strength and compression strength parallel to grain due to thermal modification and also fungus efficiency. Evaluation of lacase activity showed more efficiency of this enzyme in controls in compared to modified specimens in which also caused more mass loss. In both two poplar wood species, thermal modification reduced the density and the impact strength of the specimens, but improved the compression strength parallel to grain. Evaluation of physical and mechanical properties of the specimens exposed to white rot fungus also showed that thermal modification limits efficiency of this fungus on both poplar wood species. As a result, the reductions in the studied physical and mechanical properties, including mass loss, density, compression strength parallel to grain, and impact strength, were significantly more pronounced in the control group than the modified specimens.

An analysis was conducted to determine the number and influence of stakeholders involved in managing and protecting mangrove forests in Bushehr province. Field and library research was performed to select beneficiaries, and an institutional analysis questionnaire was administered to each organization. Data analysis was carried out using UCINET6.528 software. The results can be interpreted in two ways: 1) an overall assessment of the actors in the sample and 2) the significance of network analysis in highlighting the organizational coherence of institutions involved in mangrove forest protection in Bushehr province (such as conservation efforts, optimal habitat utilization, information exchange and experience sharing, participation in seedling production and planting, and community involvement). The Department of Education and Department of Natural Resources in Dayyer, and the Village Management, Council of Akhand, and Environment Department in Assaluyeh had the highest betweenness centrality. An important finding of this study is the limited power of the environmental department, particularly in Dayyer county, despite being the main authority responsible for conserving these coastal vegetation areas. The research results can be categorized into two areas: first, the lack of cooperation among executive institutions has resulted in conflicts, lack of coordination, and decreased trust among local communities; second, social indicators on both micro and macro levels have the potential to demonstrate the role of institutions in conflict reduction.

After implementing a logging ban in the northern forests of Iran and increasing protection forces in recent years, the current performance needed to be evaluated. The purpose of the research was to compare two approaches - sustainable exploitation and exploitation cessation - from the perspective of local stakeholders and experts, considering the physical and technical challenges in forest protection. The validity and reliability of the questionnaire were confirmed using acceptable content validity (above 0.7) and incongruity rate (below 0.1) in pairwise comparisons based on AHP. Two groups, consisting of 20 local stakeholders and 21 forest experts in the Chafroud 10 and Malakroud 24 basins, conducted a hierarchical analysis to compare the physical and technical challenges in forest protection. The results indicated that physical protection challenges were three times more important than technical challenges. Among the technical challenges, the establishment of protection belts, fence weaknesses, and issues with silvicultural operations were prioritized. In terms of physical protection, trespassing, constructions, illegal wood cutting and smuggling, livestock grazing, traditional exploitations, and fires were ranked from first to fourth. Therefore, the sustainable exploitation approach was favored over exploitation cessation. The Mann-Whitney U test revealed no significant difference between the opinions of local stakeholders and forest experts in the study area. Thus, it can be concluded that simply halting wood exploitation and forest management plans is not the solution to the physical and technical protection challenges faced by the Hyrcanian forests. To address these challenges, it is recommended that past forestry plans be revised and implemented in accordance with the criteria and principles of sustainable management for all forest units.