فصلنامه جنگل و فرآورده های چوب
سال هفتاد و ششم شماره 2 (تابستان 1402)

In the present study, the crown dieback of Persian oak trees was monitored over a period of four years (2019 to 2022) in order to determine the characteristics of oak trees that are sensitive to crown dieback in the Mele-Siah forests of Ilam. Two plots, with varying areas in order to include 100 oak trees, were selected on the northern and southern slopes. The characteristics of each tree, including the diameter at breast height, tree height, and the large and small diameters of the crown, were measured and recorded. The crown dieback of each tree was evaluated based on the percentage of crown dieback over the course of four years at the end of the summer season, and the trees were divided into four classes of crown dieback. The results showed that there is variation within the species in terms of the extent of crown dieback. On the northern slope, the majority of trees were in the declining and less than 50% crown dieback classes, while on the southern slope, the majority of trees were in the healthy and more than 50% crown dieback classes. The healthy class had the lowest average diameter at breast height, height, and crown area, while the higher crown dieback classes had higher averages for these characteristics. Additionally, the results showed that there is variation within the species in terms of the annual variability of crown dieback intensity. In the northern site, 17 trees and in the southern site, 14 trees were moved from the healthy and low crown dieback classes to the higher crown dieback classes. The results indicated that the transplanted trees had larger diameters at breast height, heights, and crown areas compared to the trees in the same class that were not transplanted. It was concluded that trees with larger dimensions in terms of diameter at breast height, height, and crown area, which are also older, are more sensitive to dieback. Conversely, trees with less crown variability or greater crown health have greater adaptability or tolerance to drought conditions, which can be used to produce resilient seedlings for the restoration of dieback-affected forests. The findings of this study can be utilized in the identification and protective management of forest trees that have not yet experienced decline or are situated near affected trees and stands.

The duration of vegetation restoration in the skid trails after logging operations is crucial and fundamental for preserving forests. The purpose of this research is to evaluate the long-term vegetation restoration of the skid trails in Kheyrud forest after logging operations. Therefore, 54 sample plots (1×1 m) were randomly positioned. This included 27 plots on the skid trails with ages of 5, 10, and 15 years at three traffic intensities (low, medium, and high). Additionally, 27 sample plots served as controls with a distance of 10 m from the skid trails parallel to these trails. All the plants in the plots were identified, their abundance was counted, and their species and families were identified. The results of the current research showed that among the three investigated treatments, traffic intensity alone had a significant effect on the recovery of vegetation along the skid trails. However, the age after harvesting and the interaction of traffic intensity and age after harvesting did not have a significant effect. The results also showed that traffic intensity significantly affected the abundance of species. Furthermore, in all three factors (traffic intensity, age after harvesting, and the interaction of traffic intensity × age after harvesting), tree species were more affected by soil changes compared to herbaceous species. Therefore, traffic intensity can significantly affect the variety of species and number of plants in the skid trails, with a greater effect on tree species than herbaceous species.

In recent years, there has been a great demand to replace fossil materials with environmentally friendly and sustainable ones. One of these materials is the adhesives that are usually produced from fossil sources and are commonly used in wood products. Formaldehyde-based resins are the most common commercial crosslinker used in the wood industry, which is considered one of the biggest sources of environmental pollution in cases based on wood products and endangers human health. Therefore, research on natural adhesives based on lignin and tannin is currently increasing, and today many efforts are underway to replace natural adhesives with synthetic adhesives. In this research, an adhesive was prepared from tannin and lignosulfonate as an environmentally friendly raw material. Furfural and polyethyleneimine, siricin, and glutaraldehyde were used as crosslinkers. Initially, the raw materials were mixed with furfural crosslinker, and then other binders were added in different proportions and mixed at 80°C for half an hour. By mixing these materials, 12 types of different adhesive compounds were prepared. These compounds were subjected to FT-IR spectroscopy to identify the functional groups and to check the thermal properties of different adhesive treatments such as TGA and DSC analysis. The results showed that compounds containing polyethyleneimine had good resistance to thermal degradation, and furfural also improved the characteristics of the adhesives. The combination of raw materials, furfural, polyethyleneimine, and sericin showed the most stability in the TGA test. In fact, the presence of more crosslinkers led to an increase in the thermal stability of the adhesives due to the presence of functional groups and the increase in the density of resin joints.

This study investigates the production of flooring from oriented strand board (OSB) made with urban and garden tree pruning waste, with the aim of reducing urban management costs and creating stable income. Two types of directional chipboard flooring were produced: "B," using 45% garden tree pruning and 55% urban tree pruning, and "T," using 100% garden tree pruning and urea formaldehyde resin. The study varied the percentage of resin in two levels (10% and 12%) and the percentage of cake moisture in two levels (12% and 14%). Several tests were conducted based on international flooring standards, including surface wettability, free fall impact resistance, surface hardness, concentrated loading, and abrasion resistance. The results showed that OSB type T flooring had less moisture absorption and shrinkage in the surface wettability test, while T-type OSB flooring had better surface hardness, wear resistance, and resistance to force in the concentrated load test at point 2 compared to other types. The study concludes that producing flooring with 100% garden tree pruning chips, 12% urea formaldehyde resin, and 14% cake moisture can yield the best results. Based on the results, it is possible to use all four types of finished flooring in humid climates and high-traffic environments such as industrial buildings, companies, and residences. It is suggested that the biodegraded pruning of trees be used in the production of other engineered boards to preserve forests as the source of oxygen and habitat for animal species.

Melamine-formaldehyde (MF) resin is commonly used in coating and casting mold production because of its favorable physical and thermal characteristics. However, its use is restricted due to formaldehyde release, short shelf life, and high fragility. A variety of substances like lactams and alcohols have been employed to enhance MF resin properties. This study attempts to improve MF resin's characteristics by including ethylene glycol and caprolactam as plasticizers in resin formulation to reduce free formaldehyde content and prolong its shelf life. Two different molar ratios of melamine to formaldehyde (1.6 and 1.5 mol) were used in the synthesis of the MF resin, with the inclusion of plasticizers: caprolactam and ethylene glycol. The physical characteristics such as viscosity, density, and gelling time, chemical attributes (Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR)), and thermal properties (thermogravimetric analysis (TGA)) of MF resins were examined. The results showed that the addition of ethylene glycol and caprolactam increased curing time, density, solids content, and shelf life while reducing free formaldehyde content. While the individual application of either plasticizer had no significant effect on gelation time, their simultaneous use increased it. FTIR and 1H-NMR confirmed the presence of the plasticizers in the MF resin's chemical structure, while TGA demonstrated that the addition of plasticizers leads to an increase in its thermal stability. However, the amount of resin residue after TGA analysis was different according to the type of plasticizer.

In the current study, the quantity, quality, and bole form of trees were investigated in three parcels of selectively logged, protected, and recreational areas in the mixed beech (Fagus orientalis) stands in Nav-e Asalem forests. The quality and bole form of trees were measured and evaluated through systematic plot sampling. The results of the research showed that the abundance of live trees in the selectively logged parcel (268 trees ha-1) and recreational parcel (210 trees ha-1) was lower than that in the protected parcel (389 trees ha-1). The abundance of beech, maple (Acer cappadocicum), and alder (Alnus glutinosa) species in the selectively logged parcel, and the abundance of beech and alder species in the recreational parcel were significantly higher than their abundances in the protected parcel. The abundance of snags in the protected, selectively logged, and recreational parcels was 18, 9, and 8.4 stems ha-1, respectively. The average abundance of stem deformity in the protected, selectively logged, and recreational parcels was 18.3, 9.4, and 8.4 stems ha-1, respectively. Logging operations, although increased the frequency of leaning and bending stems, decreased the frequency of conical and decaying stems. In general, the abundance of high-quality trees and boles in the selectively logged and recreational parcels was higher than in the protected parcel. Regular and long-term monitoring of the quantity, quality, and form of tree trunks may be a good approach to align ecological and economic goals in forest management.

The use of starch in the future will face limitations due to food competition in the paper industry. Therefore, in this research, soda lignin was chemically modified using the amination method to extend its reactivity and improve water solubility. Sizing solutions were prepared using both unmodified and aminated lignin, as well as a combination of starch and lignin in a 25:75 ratio. The surface, barrier, and mechanical properties of the sized testliner papers were measured using the aforementioned sizing solutions. SEM images show that both unmodified and aminated lignin almost completely fill the voids and spaces between the fibers, creating a relatively uniform and homogenous sizing layer on the paper surface. The roughness values increased for the sized papers using both unmodified and aminated lignin. Applying a sizing layer with unmodified lignin reduced the air resistance of the paper, while papers treated with aminated lignin showed a slight increase in air resistance, though not as high as those sized with pure starch. Contact angle evaluation confirmed the positive effect of chemical modification through amination on the hydrophobicity rate of the paper. Surface sizing with aminated soda lignin, even without starch combination, resulted in increased stiffness, burst index, and Ring Crush Test (RCT) compared to the control papers.

The production of seedlings with no stress is the first step in the nursery. Hence, the effects of pericarp removal, irrigation treatments, light, and their interaction on the physiological characteristics of grey mangrove seedlings were investigated in the nursery (Hormozgan province- Sirik Port). The aim of this study was to investigate the content of chlorophyll (a and b) and carotenoids in the leaves of grey mangrove seedlings using pericarp removal treatments (manual, fresh water, 50% seawater, 100% seawater), regular irrigations (twice a day, once a day, every other day, and every two days), and light intensities (100, 75, 50, 25, and zero percent). The analysis was performed using the GLM test. Based on the results, applying different treatments of pericarp removal, irrigation, and light treatments led to significant changes in physiological parameters (chlorophyll a, chlorophyll b, and carotenoids) (p<0.01). Removing the pericarp using fresh water and 50% seawater, irrigation regimes (twice a day and once a day), and light intensities (50 and 75%) caused the highest amount of chlorophyll content in seedlings. Furthermore, the highest amounts of carotenoids were observed in the 100% seawater treatment for pericarp removal, absence of light (0% light), and every two days irrigation treatment. In addition, the interaction effects (light × pericarp) indicated that carotenoids had the highest amount in the absence of light and pericarp removal using 100% seawater. Additionally, grey mangrove seedlings under moderate light, pericarp removal using 50% seawater, and once or twice a day irrigation treatments provide appropriate conditions for their activities. Therefore, it is recommended to use the above results in the production of grey mangrove seedlings in the nursery.