فصلنامه جنگل و فرآورده های چوب
سال هفتاد و ششم شماره 3 (پاییز 1402)

In this study, the impact of boxwood moth pest defoliation on the dynamics of leaf litter and soil nutrients in the Cheshmebolbel boxwood (Buxus hyrcana) reserve was evaluated. A random sampling technique was employed to collect litter layer samples (using a 400 cm2 frame) and soil samples (using a metal cylinder with an 8 cm diameter and a 10 cm depth) from 32 sites in unpolluted and polluted boxwood stands. The results revealed that only soil moisture percentage differed significantly among the soil physical variables, whereas all chemical soil variables showed significant differences between the two polluted and unpolluted boxwood sites. Furthermore, basal respiration (0.14, 0.12), metabolic rate, microbial ratio, and carbon availability index were significantly higher in the polluted sites compared to the unpolluted site, while no significant difference was observed based on the microbial-carbon respiration index. The principal component analysis (PCA) results demonstrated a distinct separation of the two sites, both polluted and unpolluted, along the first axis, based on both litter and soil variables. In this context, nitrogen, metabolic rate, moisture, nitrate, ammonium, and stimulated respiration (0.30, 0.39) exhibited a positive correlation with the first axis, representing the concentration of the unpolluted stand. On the other hand, C/N ratio, potassium, magnesium, calcium, and microbial biomass carbon displayed a negative correlation with the first axis, representing the concentration of unpolluted sites. In general, the findings of this research underscore the substantial influence of defoliation induced by pest outbreaks on an important aspect of forest ecosystem health, performance, and nutrient cycling.

Swelling soils, characterized by fine particles, undergo volume changes due to water absorption and loss, posing challenges in road construction. Hence, enhancing the mechanical properties of such soils is crucial. Considering lime as a cost-effective, readily available, and easily applicable water-repellent material, this study investigates its influence on the swelling characteristics of high-plasticity clay soil (CH). Atterberg limit tests, including liquid limit (LL), plastic limit (PL), shrinkage limit (SL), plasticity index (PI), Proctor compaction, free swell, and swelling pressure tests were conducted based on standard procedures on control soil samples and soil samples mixed with different percentages of lime (3, 5, and 7%). Furthermore, mechanical test assessments were performed on specimens cured for 7, 14, and 28 days. The results indicated that the addition of lime decreased LL and PI while increasing PL and SL. Moreover, lime addition led to a reduction in the dry unit weight of the soil, an increase in the optimal moisture content, and a decrease in free swell and swelling pressure, with the most significant reduction observed in samples containing 5% lime. Additionally, the findings revealed that with increased curing time, free swell and swelling pressure reduced notably in samples mixed with 3% lime. In conclusion, the study demonstrates that lime can effectively improve the mechanical properties of swelling clay soils, especially crucial for road construction and soil classification purposes. Therefore, it can be concluded that lime is effective in reducing the swelling of forest soils.

Given the importance of measuring tree volume and the potential for selling standing trees, as well as the time-consuming and costly nature of measuring the actual volume of trees, this study aimed to find an alternative method that is more economical in terms of time and cost for predicting the standing volume of poplars (Populus deltoids) using an artificial neural network (ANN) method for harvesting and sales management. In this study, the diameters and heights of 416 randomly selected trees were measured. The tree diameters ranged from 10 to 15, 15 to 20, 20 to 25, 25 to 30, 30 to 35, 35 to 40, 40 to 45, and 45 to 50 centimeters. Their standing volumes were then predicted using both simple and multiple ANN models. In this study, diameter at breast height and height were considered predictor indices for the input data, while the standing volume of the tree was the output data. The number of input, hidden, and output layers was kept uniform at one layer. The number of hidden layer neurons was determined to be 10 using trial and error. The results showed that the simple ANN model using the diameter index yielded MAPE and R-squared values of 10.22 and 0.9785, respectively, while the model using the height index produced MAPE and R-squared values of 35.43 and 0.8004, respectively. Due to the simple model's ability to predict volume with an error of approximately 10% using the diameter predictor, the simple model with the diameter index was suggested as the best model overall, considering its ease of implementation and superior accuracy.

As a sustainable forest indicator, biodiversity plays a crucial role in understanding the effects of climate change on forest ecosystems. Measuring the diversity of trees and shrubs in forests is essential for monitoring and evaluating changes in biodiversity. Remote sensing (RS) is an effective tool for collecting such data. To estimate tree and shrub species diversity, we used Sentinel-2 data from August 10 and October 13, 2021. We measured 75 field plots with dimensions of 20 m × 20 m in the Patom, Namkhaneh, and Gorazban districts. In each field plot, the tree species and diameter at breast height of all trees with a diameter greater than 7.5 cm were recorded. We used the Jaccard and Sorensen indices in R software to calculate the beta diversity indices for each sample plot. Preprocessing steps were applied to the Sentinel2 data, and we then performed several spectral transformation approaches, that is, vegetation indices (VIs), principal component analysis (PCA), and Tasseled Cap, and generated texture variables. A vector map was used to extract the spectral and textural values corresponding to each field plot. Correlation analysis between the measured species diversity and spectral and textural variables was conducted at a 95% probability level. Multiple Linear Regression (MLR) analysis was performed using stepwise and Random Forest (RF) methods for modeling. Our regression analysis revealed that texture variables with a window size of 5×5 and spatial resolution of 10 m in Sentinel-2 summer images had the best performance in estimating the Sorensen diversity index( R2= 0.383 and RMSE%= 36.57). However, based on our results, we can conclude that the Sentinel-2 data has a moderate performance in estimating diversity in the Patom, Namkhaneh, and Gorazbon districts.

Plant leaves react to environmental changes with high adaptability. This study investigated the morphological characteristics of Persian oak (Quercus brantii) and wild pistachio (Pistacia atlantica) leaves from 15 forest sites in Ilam province at an elevation range of 1000 m (from 1111 to 2048 m a.s.l.). At each site and for each tree species, five healthy individuals and five healthy and mature leaves were collected from the outside and middle of the crown. The leaf area index, petiole length, main vein length, leaf circumference, blade length, blade width, and the number of leaf margin dentations were measured. The data were analyzed based on the nested research design, and the means of the studied traits were compared using the LSD test. In the Persian oak trees, the results showed that the petiole length (1.72 cm), leaf circumference (20.23 cm), leaf length (8.17 cm), leaf width (4.43 cm), and leaf area (28.16 cm2) at higher elevations had higher averages than at lower elevations. However, the number of leaf left and right dentations were 12.26 and 12.47, respectively, indicating higher average weight at lower altitudes. In pistachio, all measured characteristics like petiole length (0.46 cm), leaf circumference (13.98 cm), leaf length (5.53 cm) and leaf width (3.29 cm), and leaf area (12.31 cm2) at higher elevations had higher averages than the lower elevations as 0.24 cm, 12.26 cm, 5.18 cm, 3.0 cm, and 10.85 cm2. The significant intra-population changes strengthen the idea of intra-population morphological diversity for oak species at the regional level and even in Zagros to some extent. Among the studied features, those that are less sensitive to environmental changes can be used as distinguishing features for species separation.

One of the environmental problems of Zagros forests is oak decline, which is less intense in northern Zagros than in middle and southern Zagros. The purpose of this study was to investigate the oak decline in Baneh County (Kurdistan Province) in 2019, 2020, 2021, and 2022. In order to carry out this research, two plots (with 100 trees) were considered in Belveh (tree dieback–southern slope) and Saraki (tree dieback–northern slope) sites in Baneh County in the northwest of Kurdistan Province. In 2019, oak trees were numbered at the desired sites, and in October 2019, 2020, 2021, and 2022, oak decline classes (five classes) were recorded for each tree. The results showed that the number of healthy trees in the Saraki and Belveh sites decreased by 25 and 28 trees, respectively, from 2019 to 2022; in contrast, the number of dieback trees increased by 14 and 19 trees, respectively, and the intensity of oak decline was greater in the Belveh site (southern dieback stands) than in Saraki (northern dieback stands). In general, the decline rate in the southern stands was higher than that in the northern stands, and the highest oak decline was observed in the southern slope. To optimally manage these forests, it is necessary to manage the factors that exacerbate oak decline and to control human interference and forest destruction so that the current situation is fixed and the seeds of healthy stands on the northern slopes are used for the regeneration and development of the forest.

The emission of volatile organic compounds, including formaldehyde, is one of the important and well-known disadvantages of wooden products. The aim of this study is to measure the amount of formaldehyde gas released from medium density fiber board and reduce its emission by adding a mixture of fibers and stabilizers. For this purpose, medium density fiber boards were made from the extracted residue of licorice root and two types of stabilizers. Then, using the desiccator method, the amount of formaldehyde gas released from each sample was calculated in micrograms of formaldehyde per milliliter of solution. The obtained results show that in the treatment where the mixing ratio of industrial fibers to licorice root residue fibers is 70 to 30 and urea formaldehyde glue is modified with traditional stabilizers (alum, tragacanth gum and walnut leaf extract), the lowest formaldehyde emission is measured. Also, the control treatment (100% industrial fibers and pure urea-formaldehyde glue) has the highest formaldehyde emissions. Therefore, if the waste fibers of the licorice root are combined with factory fibers and the urea formaldehyde glue is modified with traditional stabilizers of the first type (oak fruit extract, Copper sulfate, zedo gum) and the second type (walnut leaf extract, alum, tragacanth gum), the amount Formaldehyde gas emissions are reduced by more than 50%. As a result, modified treatment with traditional stabilizers is considered the most optimal type of treatment to reduce formaldehyde emission.

One of the most important concerns of policymakers is to achieve policy goals, which can be measured through evaluation. Evaluation and monitoring of policy implementation play a significant role in enhancing public awareness, promoting learning about the policies, and ensuring accountability of bureaucrats. By strengthening the evaluation and monitoring process, policymakers can improve the policymaking process and implementation, as well as enhance shared knowledge of policymaking among the involved organizations. This paper focused on the evaluation stage of implementing the Comprehensive Forest Safeguarding Policy (CFSP) in the Hyrcanian forests, Guilan province, Iran. The research employed a qualitative approach and field research methods. Semi-structured interviews were conducted with 20 experts from the General Administration of Natural Resources and Watershed Management (GANRWM), the General Administration of Environment (GAE), and the Management and Planning Organization (MPO) of Guilan Province using chain sampling. Thematic analysis was employed to analyze the interviews, and 26 themes related to monitoring and evaluation were identified. The findings indicate that there was no third-party evaluation in assessing the implementation of CFSP in Guilan province. Weak capacity for evaluation and monitoring, the merger of the country's MPO with other presidential organizations in the last decade, and the deficiency of intersectoral cooperation and coordination, particularly between the GANRWM and GAE of Guilan province, have been among the reasons for the failure in a comprehensive evaluation of this program. The evaluation of forest policy implementation should be conducted based on scientific methodology by a third group independent of the executive and policymaking bodies.