مجله جنگل ایران
سال پانزدهم شماره 2 (تابستان 1402)

Forest ecosystems are one of the principal sources of carbon storage. The Lirehsar forest in Tonekabon was studied to assess the carbon sequestration capacity of underground biomass, soil, and roots of beech and hornbeam mixed stands. Thirty samples of uprooted beech and hornbeam trees were unintentionally selected. Soil sampling was carried out at three depths (0-10, 10-30, 30-50 cm), and root diameter sampling was conducted in six classes (50 mm) from distinct parts of the root. Soil samples were passed through a 2 mm sieve, and root samples were dried and pulverized with a grinder. The carbon storage value in beech and hornbeam roots was 8404 kg.ha-1 and 6235 kg.ha-1, respectively. The total amount of carbon deposited in soil mineral layers from 0-10 cm to 30-50 cm depth on beech and hornbeam was calculated 121 and 161 t.ha, respectively. Furthermore, the study results on soil carbon sequestration in beech and hornbeam revealed that the amount of soil carbon sequestration in all layers was 56.9, 72.5, and 62.3 t.ha for hornbeam, while its value for beech in all layers was 42, 43.6, and 35.7 t.ha. The independent t-test results showed no significant difference between carbon stored in diverse root diameters in beech and hornbeam. Findings showed that the amount of soil carbon sequestration on hornbeam was higher than on beech in all layers, revealing the influence of species diversity on soil carbon sequestration. It is expected that a variety of different tree species can be employed for reforestation in suitable areas as a result of the species diversity effect on carbon storage and carbon sequestration compared to pure beech species. It is supposed that hornbeam is a mitigated species for decomposition of soil elements and carbon sequestration in forest soil due to the developed distribution of the studied species in Hyrcanian forests.

Understanding the structure of a forest is crucial for detecting forest dynamics, describing ecosystem stability, and designing effective management plans and protection and restoration measures. This study primarily aims to investigate the spatial pattern and structural characteristics of beech forests in the optimal developmental stage using variable area sample plots. In compartment 327 of the Grozban district of Kheyrood forest, eleven variable area sample plots with geometric shapes, exhibiting characteristics of the optimal developmental stage, were selected. The location, diameter, and height of all trees larger than 7.5 cm were measured in each sample plot. The results revealed that the largest contribution of trees among the investigated sample plots was related to mid-diameter and low-diameter classes. The Clark and Evans index and uniform angle results indicated a regular distribution of trees in all studied sample plots. The mingling index averaged 0.19 across all sample plots, suggesting low mixing and a minimal tendency of beech trees to blend with other species. The average diameter and height differentiation index were calculated as 0.31 and 0.30, respectively, indicating an average difference between neighboring trees. Overall, the use of indices based on the nearest neighbor with variable area sample plots and geometric shapes demonstrated that these indices effectively quantify the structural characteristics of forest stands in the optimal developmental stage. Consequently, it is recommended to conduct similar research in other developmental stages.

Spatial patterns of tree species can provide valuable insights into forest dynamics, including processes such as forest establishment, tree growth, species competition, and mortality. This study aimed to investigate the structure, spatial pattern, and interactions of beech trees during the volume accumulation stage of forest evolution in the climax stage of succession. Three one-hectare sample plots with characteristics representative of this stage were selected, and tree characteristics, including species type, DBH, and location, were measured and recorded for all living trees. The results of the uniform angle index indicated a regular pattern among neighboring trees. The average mingling index was 0.08, suggesting intense intra-species competition and a low tendency for beech trees to be located near other species. The mean diameter and height differentiation indices were 0.36 and 0.28, respectively, indicating an average difference between neighboring trees. According to the results of the univariate L11 function, in sample plots one, two, and three, trees exhibited a regular pattern up to distances of 7, 4, and 6 meters between trees, respectively. At greater distances, trees were located within the Monte Carlo range. Based on the results of the L12 bivariate function, in all three sample plots, small diameter trees had a negative interaction with medium and large diameter trees up to a distance of at least 5 meters. Any intervention based on silvicultural programs should take into account the preservation of the structural features of stands at this stage of beech evolution.

Wild Pistachio (Pistacia atlantica var. mutica Rech. f.) is an important tree species in the forests of Iran that has faced many challenges in its natural restoration. This study investigated the interaction effects of Funneliformis mosseae, MycoRoot biofertilizer, and Pseudomonas fluorescens on Pistacia atlantica seedlings under two water treatments: 100% field capacity as a non-stress treatment and 50% field capacity as a drought stress treatment. Decreased soil moisture reduced the growth (root collar diameter, shoot and root fresh weight, shoot dry weight) of Pistacia atlantica seedlings. The interaction of mycorrhizal fungi and phosphate-solubilizing bacteria on seedling growth, as well as chlorophyll, carotenoid, and leaf proline content, was significant at the 5% level. The highest stem height was observed in the combined treatment of Funneliformis mosseae and Pseudomonas fluorescens (24.54 cm) under non-stress conditions, while the shortest belonged to the control treatment (8.8 cm) under drought stress conditions. Proline content in seedlings inoculated with Funneliformis mosseae in the presence of Pseudomonas fluorescens was higher (8.87 μmol/g) than other treatments, and this treatment was more effective in reducing drought stress symptoms than other treatments. Under non-stress conditions, the presence of Pseudomonas fluorescens alone did not play a significant role in improving seedling growth, but its positive effects on growth appeared when interacting with mycorrhizal fungi and during drought. Although this research observed that mycorrhizal and bacterial seedlings had better growth than control seedlings and that microorganisms had the same effect as irrigation on some growth characteristics, it is necessary to conduct similar additional experiments in nurseries and natural habitats on P. atlantica seedlings using different irrigation levels to confirm these results.

In order to plan and make managerial decisions for the development of wood farming in Guilan province, parameters such as area, distribution, and biometric variables of poplar trees were measured separately for each county. To conduct this research, the field of poplar plantations was located using the Global Positioning System (GPS) and measured with 100% inventory method. In each poplar plantation section, for every 2000 square meters, nine middle trees were measured for the biometric variables. The correlation between the characteristics of area and increment of trees with climatic indicators and soil was also plotted. According to the findings of this project, the total area of poplar plantations in Guilan province was 12,179 ha in 2018, with the highest belonging to Sowme`eh Sara county with 6,944 ha, comprising 11.8% of the county area. This county ranked first in poplar tree cultivation with the highest number and volume of trees. The area of poplar plantation was the lowest in Astara, Amlash, and Fouman counties. The highest mean age of trees was obtained in Rudbar and Tavalesh, while the lowest mean age and number of trees were obtained in Fouman county. The characteristics of the total number of trees, volume, and area of poplar plantation showed the highest correlation coefficient with climatic indicators and total nitrogen. The findings of this research can provide valuable basic information for monitoring the area of poplar plantations, planning and management decisions, and identifying areas suitable to poplar plantations for wood farming in Guilan province and the country.

The slow growth of hazelnut seedlings, particularly during the initial years of afforestation, hampers the rehabilitation and development programs of hazelnut forests. In this context, biological fertilizers, especially plant growth-promoting bacteria, can be an effective strategy to enhance the growth and physiological traits of hazelnut seedlings. In May 2017, new hazelnut potted seedlings from two seed sources - Fandoglou (Ardabil Fandoglou forest) and Makesh (Aghvalar Guilan forest) - were propagated in an Ardabil hazelnut nursery. These seedlings were inoculated separately and in combination with Pseudomonas putida DSM291, Bacillus subtilis FzB24, and Enterobacter cloacae E1. In November 2017, the one-year-old hazelnut seedlings were transferred to agricultural lands bordering the Fandoglou forest. The seedlings were planted in rain-fed conditions following a randomized complete block design with three replications of 12 based on two factors: fertilization and seed origin. After four years, it was observed that inoculated seedlings from both origins outperformed non-inoculated ones in all investigated traits. The largest parameters of the studied variables were attributed to the Fandoglou-origin seedlings inoculated with a combination of three bacteria. These seedlings showed a survival rate of 49.7%, collar diameter growth of 51.1%, height growth of 60.4%, and dry mass increases in roots (85.6%), stems (75.1%), and leaves (68.2%). Additionally, photosynthesis increased by 49.9%, stomatal conductance by 58.04%, water consumption efficiency by 121.7%, and chlorophyll content by 46% compared to non-fertilized Fandoglou-origin seedlings. In conclusion, considering the role of the studied growth-promoting bacteria (especially the combined treatment) in enhancing the growth characteristics and physiology of hazelnut provenances, inoculating hazelnut seedlings with bacteria in nurseries can be a beneficial strategy for successful field transplantation.

Oak gallwasps (Family: Cynipidae) are among the most important insects associated with oak trees. To identify the parasitoid communities of gall wasps on Quercus infectoria Oliv., galls were sampled in October 2018 due to the collection of asexual generations of oak gall wasps. Sampling was carried out at two altitudes (1300-1500 and 1500-1700 m) in the Pidaranan and Mirabad areas in 2018. Parasitoid species were identified, and their abundance, species diversity, and richness indices were calculated using Ecological Methodology ver. 3.0 software. The means of the treatments were compared between altitude slopes using an independent student t-test with SPSS ver. 21 software. Results showed that 20 species of gall wasps and 10 species of parasitoid wasps belonging to five families of the order Hymenoptera were collected and identified. Of the 20 species of oak galls, 15 had parasitoids. The two species Andricus coriarius Hartig and Andricus coriariformis Melika et al. had the highest number of parasitoid wasps. Among the parasitoid wasps, the most frequent species was Aulogymnus gallarum L., which was introduced as the main parasitoid in at least 10 gall wasp species with high population density. The mean values of parasitoid species diversity and evenness indices for gall wasp species on Q. infectoria in different regions and altitude slopes were not significantly different from each other.

Drought is predicted to increase drastically in the coming decades, making it crucial to understand the adaptive responses of tree species to such conditions. This study evaluates the effect of drought stress on the morphological, physiological, and biochemical parameters of Fraxinus excelsior, a native species from the Hyrcanian forest. The experiment was conducted using a completely randomized design, where one-year-old seedlings were subjected to four water stress conditions: 25% (severe stress), 50% (moderate stress), 75% (mild stress), and 100% field capacity (no stress). Results showed that drought reduced the growth rate and biomass of seedlings. Compared to the control treatment, the rate of decline in seedling height, biomass, leaf area, and specific leaf area index was 47.6%, 43.2%, 77.1%, and 38.1%, respectively, in the severe stress treatment. The root-to-shoot ratio increased by 44.8%. As water stress increased, the content of chlorophyll, chlorophyll a, chlorophyll b, and carotenoids showed a slight and insignificant decrease. The relative water content of seedlings decreased by 34.20% and 23.18% in severe and moderate stress treatments compared to the control treatment. Proline and malondialdehyde increased by 93.8% and 165.06%, respectively, in the severe stress treatment. Superoxide dismutase enzyme activity increased by 5%, while peroxidase enzyme activity increased by 273% and 240% in mild and moderate stress treatments, respectively. The data from this study suggests that F. excelsior seedlings cope with drought through avoidance and tolerance strategies such as reducing growth and biomass, increasing root-to-shoot ratio, retaining photosynthetic pigments and osmotic potential, and increasing enzymatic activities up to 50% FC. This species is recommended for afforestation and reforestation in drought-prone areas.