فصلنامه تحقیقات جنگل و صنوبر ایران
سال سی و دوم شماره 4 (پیاپی 98، زمستان 1403)

The production, cultivation, and exploitation of fast-growing species, such as poplar, can serve as a successful starting point for extensive research in crop breeding and production, as well as plant pest and disease control. The goal is to enhance production per unit area in terms of both quantity and quality to supply raw materials for various industries. This study aimed to monitor pests of poplar (Populus nigra L.) in North Khorasan Province, Iran, with the objective of detecting key pests and identifying new emerging damage factors. Access to these findings can significantly aid in the timely prevention of outbreaks and reduction of control costs.

Five index stations (Rooieen, Ordeghan, Gerivan, Kohnehkand, and Chenaran) with different poplar plantation stands, locally known as Sepidar, were selected in North Khorasan Province. To study the level of infestation and pest damage, sampling was conducted from May 2019 to September 2022 at each station once a month during the growing seasons. At each sampling, 10 trees were randomly selected, and pests were sampled using direct observation methods, including hand collection, forceps, brush, aspirator, and Steiner trap. Sampling of wood-boring pests was also conducted in the trunks and crowns of suspected trees. The degree of pest damage and infestation was estimated as a percentage per tree unit. The damage degree was determined using a scoring method. Collected samples were labeled (including sampling date, distribution range, and damage degree) and placed in freezer bags before being transferred to the plant protection laboratory at the North Khorasan Agricultural and Natural Resources Research and Education Center for further study. Larvae and pupae of unknown pests were reared in plastic containers in the laboratory to complete their life cycle until adult insects emerged.

Field observations in this study identified seven important and key pests: Monosteira unicostata (Mulsant & Rey), Chrysomela populi Linnaeus, Melanophila picta Pall, Phyllonorycter populifoliella (Treitschke), Nycteola asiatica (Krulikovsky), Pemphigus spyrothecae Passerini, and Pemphigus vesicarius Passerini. The results from monitoring poplar pests showed that the emergence of some pests was observed as outbreaks in certain monitoring years but not in others. M. unicostata in 2019 at the Rooieen station (61-80%) and P. populifoliella in 2020 at the Gerivan station (81-100%) appeared as outbreaks. Wood-boring beetles were observed in most stations, but significant damage was noted at the Rooieen station (Esfarayen city). C. populi in 2020 and N. asiatica in 2019 had moderate infestations at the Kohnehkand station (41-60%). P. spyrothecae and P. vesicarius had moderate infestations (41-60%) in Gerivan and Ordeghan stations in both 2021 and at the Rooieen station during 2019 and 2022.

This observational research revealed that among the identified pests, four (i.e., P. populifoliella, P. spyrothecae, P. vesicarius, and N. asiatica) were reported for the first time from North Khorasan Province. The amount of pest damage and infestation degree varied and fluctuated at each station according to the management method, growth grade, and age of the poplar trees

To better understand forest types and implement management strategies that align with natural processes, studying their structure and spatial patterns is essential for addressing various ecological issues. Research on natural forests, particularly their spatial structure, provides pathways for developing forest management strategies to achieve desirable structures. The spatial pattern of trees and their mutual relationships offer valuable insights into forest structure. These patterns are qualitative characteristics that need to be quantified for more detailed analysis. This research aims to determine the spatial distribution pattern of trees in the dominant types of Hyrcanian forests in Iran to investigate forest dynamics.

This research was conducted in the educational and research forest of Kheiroud Nowshahr. After identifying the primary forest types based on habitat potential and forest community characteristics—such as species appearance, predominance, mixture, diversity (overall abundance of all species), physiographic conditions (elevation, aspect, and slope), and species expansion area—four one-hectare sample plots of dominant types were studied. These included hornbeam-ironwood, hornbeam-beech with oak, mixed beech, and pure beech. In each plot, a 100% inventory was applied, and the diameter at breast height of all trees with a diameter over 7.5 cm was measured. The coordinates of the southwest corner of each plot were recorded using GPS. The distance and azimuth of the first tree were measured with a Vertex device and inclinometer, and its coordinates were calculated using trigonometric relations. The coordinates of other trees were obtained similarly relative to the previous tree. Ripley's K function was used to analyze the spatial pattern.

The results showed that tree density in the studied types varied between 158 and 314 trees per hectare. For hornbeam (Carpinus betulus L.) in the hornbeam-ironwood type, the L function value was higher than the Monte Carlo interval up to a distance of 32 meters, indicating a cumulative spatial pattern. Between 32 and 45 meters, the pattern was random due to being within the Monte Carlo interval. In this forest type, ironwood (Parrotia persica C.A.Mey.) exhibited a completely cumulative distribution pattern. In the hornbeam-beech with oak type, the L function for hornbeam and beech (Fagus orientalis Lipsky) was significantly above the Monte Carlo interval, showing a cumulative pattern. Due to the low number of oak (Quercus castaneifolia C.A.Mey.) individuals, its spatial pattern could not be determined. In the mixed beech type, the L function was entirely within the Monte Carlo interval, indicating a random spatial pattern for beech. In the pure beech type, the distribution was random up to 4 meters, cumulative from 4 to 30 meters, and random again beyond 30 meters.

The results of such studies can serve as models for implementing sustainable management in other forest types and as patterns for conducting breeding interventions to adjust tree locations and species mixtures. Additionally, for afforestation with different species, it is possible to use the natural structure of forests as a model.

The assessment of forest stands' exposure to multiple environmental hazards constitutes a pivotal dimension in vulnerability assessments, serving as the initial stage in comprehensively evaluating the resilience of these ecosystems. Such evaluations, through the quantification and mapping of various environmental hazards, furnish indispensable insights for strategic planning aimed at mitigating forest degradation. Consequently, this study sought to evaluate the exposure of forest stands within the Kooh-e-Dil protected area in Kohgiluyeh and Boyer-Ahmad province of Iran to a suit of environmental hazards.

For modeling and assessing the intensity of multiple hazards, initially, risk maps related to 11 environmental hazards including drought, dust storms, evapotranspiration, wildfires, maximum temperatures, floods, storms, landslides, human presence intensity, soil erosion intensity, and road impact ratio were prepared. Subsequently, employing the Delphi method in conjunction with expert opinion analysis, the relative weight of each environmental hazard was determined. These risk maps were then classified into four classes: low, moderate, high, and very high, and multiplied by the respective relative weights derived from the Delphi method. Consequently, an exposure map for the protected area was generated by averaging the weighted environmental risk maps, subsequently classified into the aforementioned categories. Furthermore, the intensity of exposure for each of the five forest density categories of 1-5%, 5-10%, 10-25%, 25-50% and 50%< to multiple hazards was delineated.

The Delphi method implementation and determination of relative hazard weights indicated that drought (0.151) and wildfires (0.145) carried the highest relative weights, whereas floods (0.043) and landslides (0.036) were of comparatively lower priority. Analysis of the weighted maps and subsequent calculation of exposure intensity maps revealed a range in the index value from 0.116 to 0.276, indicative of spatial variability. Classification of exposure intensity maps highlighted that regions with low intensity were predominantly concentrated in the eastern portion, while those with very high intensity were clustered in the northern and southern segments of the protected area. Notably, forest density class of 1-5% exhibited minimal extent in categories with high and very high intensity (25.1%), yet the highest extent in categories with low and moderate intensity (74.9%) of multiple environmental hazards. Conversely, forest density class of 10-25% demonstrated the highest extent in categories with high and very high intensity (53.7%) and the lowest extent in categories with low and moderate intensity (46.3%) of multiple environmental hazards. Among the total extent of two density classes of 50%< and 25-50%, accounting for more than one-third of the protected area's forests, 49.4% lay within categories with high and very high intensity, while 50.7% fell within categories with low and moderate intensity of multiple environmental hazards.

The escalation of human activities and the ramifications of climate change pose a potential threat, potentially elevating the proportion of high-density forest extent within categories with high and very high intensity of multiple environmental hazards, thereby augmenting the vulnerability of the protected area. The outcomes of this research furnish detailed spatial insights into the exposure intensity of various forest density classes to multiple environmental hazards, thereby facilitating the formulation of targeted protective and supportive measures.

The oak moth, Porthesia melania Stgr. (Lepidoptera: Lymantriidae), is a destructive pest of oak trees in Iran. The first and second instar larvae feed on the upper surface of leaves, while most damage is caused by the fourth and fifth instar larvae, which consume entire leaves. Chemical control methods have several disadvantages, including environmental harm. Biological control using entomopathogens offers an environmentally friendly alternative to chemical pesticides. Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin are two of the most important fungi used in pest control. This study investigates the efficacy of indigenous isolates of B. bassiana and M. anisopliae against P. melania.

In May 2022, leaves of Iranian oak (Quercus brantii Lindl.) infected with P. melania eggs were collected from an oak forest in Markazi Province, Iran, and transferred to plastic containers (17×25×6 cm³) with net-covered lids for aeration. They were kept in an incubator at 25±2°C and 60±5% relative humidity with a 16 h L:8 h D photoperiod. Before conducting bioassay tests, conidial viability was determined. The susceptibility of second instar P. melania larvae to three isolates of entomopathogenic fungi, B. bassiana (BG and B2) and M. anisopliae (M1), was assessed using five concentrations (10⁴, 10⁵, 10⁶, 10⁷, and 10⁸ conidia/mL) and a control treatment via immersion and spraying methods under laboratory conditions. Three replicates were used for each treatment, and the entire experiment was repeated four times. Statistical analysis was performed using Analysis of Variance (SAS Institute, Version 9.4). LC₅₀, LC₉₀, LT₅₀, and LT₉₀ values were compared using the LDR (Likelihood Difference Ratio) method.

The mean viability of conidia for all B. bassiana and M. anisopliae isolates ranged from 95% to 99%. Mortality in the control group was very low, with no fungal growth observed. The three strains (BG and B2 of B. bassiana and M1 of M. anisopliae) differed significantly in virulence but caused high mortality (over 78%) at the highest dose in both bioassay methods. Applying 10⁸ conidia/mL of BG resulted in the highest mortality (100%), while M1 caused the lowest (78%). Notably, BG's mortality was significantly higher than that of other isolates in both methods. The mean lethal concentration values (LC₅₀) for BG, B2, and M1 were 6.74×10³, 7.37×10³, and 2.62×10⁴ conidia/mL (immersion method) and 1.33×10⁴, 3.45×10⁴, and 5.59×10⁶ conidia/mL (spraying method) 96 hours post-treatment, respectively. The calculated LT₅₀ values using 10⁸ conidia/mL for each isolate (BG, B2, and M1) on second instar larvae were 24.94, 32.12, and 36.54 hours (immersion method) and 30.73, 31.67, and 45.57 hours (spraying method), respectively.

This research demonstrates that indigenous isolates of B. bassiana, particularly BG, are effective in controlling the oak moth (P. melania). BG exhibited significant virulence, causing 100% mortality at the highest concentration in both immersion and spraying methods. The larval immersion method was the most effective treatment. The environmentally friendly nature of entomopathogenic fungi makes them a promising alternative to chemical pesticides for managing P. melania populations. Fungal activities play a crucial role in stabilizing insect population dynamics in natural ecosystems. This study provides valuable insights into sustainable pest control strategies, highlighting the potential of the BG isolate from B. bassiana in biological control programs against oak moth infestations.

Zagros forests, as one of Iran's most important carbon sinks, play a crucial role in maintaining ecosystem balance and the carbon cycle. Given the increasing threats to these forests, accurately identifying and assessing carbon stocks in various forest components, such as deadwood, litter, and soil, is particularly important. This study aims to investigate how the stand form (high forest and coppice) of Persian oak (Quercus brantii Lindl.) affects biomass and carbon stock in deadwood, litter, and soil in the Atashgah forest area of Lordegan County in Chaharmahal and Bakhtiari Province, Iran. The goal is to provide more accurate data to support better and more sustainable management of these vital ecosystems.

This study evaluated the aboveground biomass and carbon stocks of deadwood, litter, and soil in high forest and coppice of Persian oak trees in the Lordegan forest zone. The study area, covering 90 hectares, is located in the central Zagros plateau and is predominantly characterized by Persian oak vegetation. Thirty random sample plots of 1000 square meters each were established to select sample trees. Within each plot, the nearest tree to the center that fell within the desired diameter class was chosen, ensuring samples were collected across different diameter at breast height (DBH) classes for single-stem trees and different crown diameter classes for coppice shoots. Following this procedure, 16 single-stem and 14 coppice trees were randomly selected and marked for measurement. The selection aimed to quantify the amount of standing deadwood in the form of dried branches present in the investigated trees. Litter and soil samples were collected from a depth of 0 to 30 centimeters beneath each tree. A computational formula based on carbon concentration, bulk density of the soil, sampling depth, and the percentage of coarse fragments was used to measure soil organic carbon. The collected samples were transferred to the laboratory for determination of dry weight and carbon content, following standard methods for measuring the percentage of organic carbon in plant and soil samples.

The findings showed that standing deadwood in high forest trees had significant statistical differences among various diameter classes, while fallen deadwood did not exhibit such differences. The highest values of standing deadwood biomass were observed in the 30-40 cm diameter class. In contrast, in coppice shoots, fallen deadwood biomass showed significant statistical differences among different crown diameter classes. However, the difference in standing deadwood biomass between different crown diameter classes of coppice shoots was insignificant. A comparison between high forest and coppice revealed that standing deadwood biomass in high forest trees exceeded that in coppice. Additionally, the average carbon sequestration of deadwood in the study area was calculated as 0.171 tons per hectare. No significant statistical differences were observed in soil carbon, nitrogen, and phosphorus content between high forest and coppice bases. A high correlation coefficient of 0.94 was observed between soil carbon and nitrogen, while no significant correlation was found between soil carbon and phosphorus. The carbon content of litter did not show significant statistical differences between high forest and coppice in the study area. Overall, the average carbon sequestration of litter in the study area was estimated as 0.327 tons per hectare.

Despite considerable attention to aboveground and belowground carbon stocks in forest ecosystems, carbon stored in deadwood has received less emphasis. However, deadwood can represent a significant portion of forest carbon reserves. Dominant tree species and structural characteristics of the forest, such as population density, diameter at breast height, and tree height, are important factors in determining aboveground biomass and carbon storage. This study identified the average quantitative differences between high forest and coppice trees as the main reasons for differences in aboveground biomass and carbon storage in standing and fallen deadwood. Furthermore, the impact of disturbances and human interventions on the reduction of soil carbon stocks was examined. The study found that soil carbon stocks were similar in both growth forms, which was related to the similarity in litter volume in the two habitats. This research highlights the importance of carbon storage in deadwood, litter, and soil and its impact on forest ecosystems, contributing to improved forest management and biodiversity preservation.

In underdeveloped countries, one measure to ensure food security involves exploiting natural resources, often leading to their destruction. Forests serve as a direct source of food and fuel and provide income, while ecosystem services enhance families' capacity to cope with food insecurity. Food insecurity refers to limited or uncertain access to nutritionally adequate food or the inability to obtain food in socially acceptable ways. There is a close relationship between villagers' food security and their willingness to change forest land use, yet few studies have explored these issues and their interconnection. This research aimed to understand the food security situation of rural households living in forest edge areas and their desire to change forest land use in Golestan Province, Iran.

This descriptive survey research was conducted in 2023 in villages with the highest rates of forest land destruction and use change in Golestan Province. The statistical population consisted of 350 household heads living in five forest-edge villages, and 183 individuals were selected as the research sample using the Krejcie and Morgan table and proportionate stratified sampling method. Data collection was done via a questionnaire, whose content and appearance validity were confirmed by extension specialists and experts from the General Department of Natural Resources and Watershed Management of Golestan Province. The questionnaire's validity was determined using Cronbach's alpha method, with coefficients of 0.934 and 0.775 for different parts. Data analysis was performed using SPSS 19 software.

The research findings showed that over 80% of households faced various levels of food insecurity, and more than half of the respondents (55.7%) had a strong or very strong desire to change forest land use. Correlation tests revealed a negative and significant relationship between respondents' age, village residency history, and distance from their residence to the city with their desire to change forest land use. Conversely, there was a positive and significant relationship between total family income and respondents' willingness to change forest land use. Regression analysis indicated that age, total monthly household income, village residency history, and distance from the city influenced the willingness to change forest land use. Age had the most negative effect, while income had the most positive effect.

The results showed no significant relationship between food security and respondents' willingness to change forest land use. However, increasing income was a variable influencing this willingness. To reduce this desire, it is suggested that, in addition to educating villagers about the importance of forests and their protection, livelihood improvement programs be implemented to shift their income reliance from natural resources to alternative sources.