فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال سی‌ام شماره 3 (پاییز 1402)

Natural disturbances caused by the canopy gap an important role in forest dynamics. Analyzing the dynamics of the canopy gap provides an accurate understanding of the process of forest stands dynamics as well as natural disturbances that play an important role in the future management of the forest ecosystem. The present study examines the dynamics of the canopy gap in the Arab Dagh forestry in Golestan province.

The identification and preparation of the gaps map was done by the basic object classification method. The classification of the basic object can be done in three general stages, which include segmentation, classification and evaluation of classification accuracy.In the next step, the 1345 canopy gap in 2011 and the 1058 canopy gap in 2019 were extracted from the method that had the best performance compared to other methods of preparing gap maps. The characteristics of the gaps were obtained at each time period. Also, with the intersection of these two maps, the dynamics of the gaps was analyzed by calculating the characteristics Gap formation rate, Gap closure rate, Gap expansion rate, Gap reduction rate, and Gap number increase rate.

The results of the canopy gap dynamics during the 9 years showed that the number and density of the canopy gap decreased. But the average area canopy gap and the share of the area of the canopy gap in the total area increased.In both periods, 65% of the canopy gap have an area of less than 150 m2, and a large canopy gap (larger than 300 m2) covered the lowest frequency and share of the total area of the canopy gap. The highest rate of changes in the canopy gap source was related to the Gap expansion rate (1.09% per year). The Gap closure rate is almost equal to the Gap reduction rate. The lowest rate of changes in the light is the Gap formation rate (0.77% per year). The logarithmic Gap number increase rate (GNIR) was negative (-2.6) that in all canopy gap classes, the number of closed canopy gaps per year is more than It is the number of new canopy gap that is created.

With the passage of 9 years, the density of gaps and the number of gaps have decreased and the total surface of gaps has increased. This increase in the total level of gap can be attributed to the increase in the Gap expansion during the period. Because the Gap expansion rate is higher than the Gap formation rate, the Gap closure rate and Gap reduction rate.In both periods of time, the most abundant size was related to small holes. which indicates the predominance of small lights in the studied area. which shows the predominance of small gaps in the studied area, small gaps make up most of the dynamics of gaps and close faster than big gaps.Keywords: Gap, UAV, dynamic indicators, coniferous forestry, remote sensingps.

Many competitive models have been developed from simple to multidimensional in order to estimate the competition of trees in forest stands. All of them are measured to show the interaction between trees, and the purpose of these indices is to evaluate the competitive tension according to the interactions between trees. These indices are generally based on the morphological characteristics of trees or a function of the distance of the neighborhood of trees. The individual competition of trees evaluate using competition indices is based on mathematical techniques, which indicate the degree of competition that the tree is affected by its neighbors. This result is often assumed to be the negative effects of the neighborhood on the growth of trees to absorb limiting resources.

Distance-independent competition indices are usually considered as tree size ratios (such as dbh, height, basal area, or canopy cover) to show the competitiveness of that species. In distance-dependent indices, the dimensions of neighboring trees and their distance from each other are used. In order to calculate the competitive indices including distance-independent competition index (IDI), distance-dependent competition index by diameter (DDIdbh), and distance-dependent competition index by height (DDIh), the parameters of diameter and the total height of all trees were measured in sample plots (one-hectare area) in four stands of poplar plantation in Gilan province. The distance of the trees was also measured. Then, in order to calculate the wood density and use its value in the distance-independent competition index, 15 trees were randomly selected in different diameter classes in each plot and were cut to perform the wood density analysis, and the process of calculating the density was carried out.

The results showed that the stands had significant competitive conditions in terms of both types of indices. All stands had a significant difference (p ≥ 0.05) in terms of the independent distance index. However, the comparison of the distance-dependent index for tree diameter showed that stand 3 has a significant difference from other stands, and 1, 3, and 4 stands also had significant differences (p ≥ 0.05). The comparison of the distance competition index for tree height also showed that stands 1 and 2 had no difference but showed a significant difference with stands 3 and 4 (p ≥ 0.05).

Calculating all types of competition indices can be useful in silvicultural programs such as thinning. The results of such studies can provide a clear understanding of the spatial structure of trees.

In the south of the country, due to the harsh habitat conditions and the lack of natural forests compared to other regions of the country, the issue of forest plantation is of particular importance. Considering the severe decrease in soil moisture due to the decrease of rain in recent years, the outflow of runoff during the growing season and the inappropriate distribution of rainfall in the southern and dry regions of Iran, the use of catchment systems can be an important factor in the establishment and vegetative growth of seedlings in the dry areas of southern Iran. The purpose of this research is to investigate the effect of different drainage systems along with natural mulch on the vegetative characteristics of P. aphylla seedlings.

For this purpose, P. aphylla seedling in two levels of mulch (with organic mulch and no mulch) and water harvesting system in four levels (crescent, pitting, negarim system and control), in block randomized design as split plots were designed in the field (120 seedlings = (5 repetitions) number of seedlings × (2) mulch area × (4) number of systems × (3) repetition or number of blocks). Humidity was measured 24 hours after each rainfall over three years. Vegetative characteristics (viability, canopy length, canopy area, collar diameter growth and height growth) and vigority of all seedlings were also measured and analyzed using GLM test.

The results showed that the percentage of survival and canopy area of P. aphylla species was the highest with 100% and 1282.74 square centimeters respectively in pitting and crescent systems. The highest percentage of soil moisture with 22.14% was obtained in the negarim system. In general, regardless of the type of system, the percentage of soil moisture in the mulch treatment (21.66%) was higher than the no-mulch treatment (16.14%). The results of interaction effects showed that the canopy area and the growth height in the mulching system have the highest values of 1920.68 cm2 and 48.92 cm in the pitting system.

The results of the present research indicate the optimal performance of different methods of storing precipitation in collecting, storing and maintaining moisture in the Dehgin region, which gradually provides moisture to the plant gradually. After 3 years, results showed that the growth of P. aphylla seedling was better in water catchments especially in pitting system. Also seedling growth was better in water catchments that used organic mulch . Organic mulch is an effective factor which protects soil moisture in the root area. According to different performances of investigated factors, suggest that pitting system with organic mulch and native species should be used in Dehgin and habitats like that in the South of Iran.

The utilization of lignocellulosic crop residues, which remain after the final product in the agricultural sector, can be considered as a valuable resource for generating renewable energy. However, due to their dispersed distribution and the high cost associated with their collection, this task poses significant challenges. Currently, the application of spatial modeling to assess the sustainable potential of lignocellulosic residue biomass for renewable energy production in the agricultural sector is limited. Moreover, no such studies have been reported in the country to date. Therefore, the objective of this study is to assess the renewable energy production potential and identify suitable locations for bioenergy facilities that process lignocellulosic residues using cluster analysis within a geographic information system (GIS) environment.

To accomplish the objectives, descriptive-quantitative data regarding the production level and production area in the agricultural sector for the crop year 2020-21, as published by the Ministry of Agriculture, were collected and analyzed. Furthermore, spatial information pertaining to agricultural farms in Golestān province was gathered through satellite imagery, which was subsequently processed using cluster analysis and hotspot analysis within a geographic information system (GIS) framework. The biomass quantity in each field was estimated for four conventional crops: wheat, rapeseed, rice, and soybean, on a per-unit area basis. Subsequently, separate projection was conducted for each of these crops within the case study of Golestān province.

In the crop year of 2020-21, the total arable land area amounted to 12.9 million hectares, with a nationwide crop harvest of 91.8 million tons. Cereals accounted for the highest proportion (71%), while grain products had the lowest share. Golestān province, ranked 7th, possessed an agricultural area of 661 thousand hectares, contributing 4.27% of the country's total crop production, which amounted to 3.9 million hectares. Among the cereal production group, wheat had the highest production level at 63%, while grain corn had the lowest. Notably, Gonbad-e-Kavoos and Bandargaz counties exhibited the highest production levels and the largest areas for the cereal production group. Through the spatial analysis, the estimated amount of harvestable residue biomass was 840,000 Mg, derived from a total of 84,104 identified farms, with the largest proportion being wheat straw. The cluster analysis of the identified farms revealed that out of a total of 35,508 clusters, 15% belonged to the cold cluster category, while 18% fell into the hot cluster category. Furthermore, hotspot analysis identified four suitable sites for bioenergy sites within the study area. The available biomass can be transported to these potential sites at an average cost of $20.83 per kilometer per megagram.

The findings of this study highlight there is substantial biomass quantity within the agricultural sector of Golestān province, a significant portion of which is currently burned annually, resulting in the generation of large amounts of greenhouse gases and widespread environmental pollution. However, this biomass resource holds significant potential for the production of renewable energy if effectively harnessed with support from both the public and private sectors.

In the process of planning and developing nature tourism activities, ‎proper zoning and prioritization of recreational activities for establishment and location in ‎nature is of special importance. In this way, recreational activities that are suitable and can be ‎established in the selected areas are designed and then a sustainable management program is ‎provided, taking into account training, participation and monitoring of recreational activities. ‎In the present study, while identifying suitable areas for the development of ‎recreational activities that are in demand and can be developed in the mangrove forests of ‎Khamir and Qeshm, prioritizing each of these activities according to the potential and ‎capabilities of the natural areas of the region, as well as the proposed and effective criteria for ‎their development.‎

In this study, activities were zoning based on the linear relationship of ‎spatial indicators. Then the weighting and prioritization of these activities was carried out ‎according to a series of selected criteria based on the opinions of experts and specialists as well ‎as similar studies and documents. In the process of identifying the criteria, the environmental ‎conditions of the study area and other factors that can be effective on the development of ‎recreational activities in this area were taken into consideration. The studied criteria include road ‎access network, distance from the city, location of settlements, sea infrastructure and existing ‎patches, distance from protection spots and resident population. These criteria were first ‎standardized in the numerical range of 0 to 1 in a linear way, and then weight was assigned to ‎each of the criteria using the ANP model. Next, for each of the criteria, a location map was ‎prepared in Arc GIS software, and Topsis method was used in Topsis Solver software to ‎prioritize recreational activities.‎

Obtained results, the zoning of recreational activities in this area ‎includes 4 options of how to combine the recreational activities required in the mangrove ‎forests of Khmer and Qeshm, which option 1 includes zones with three recreational activities ‎‎(Walking in the Forest -Watching Marine ‎Wildlife -Visiting the Forest ‎‎with a Balloon), option 2 ‎includes areas with four recreational activities (Visiting ‎Villages near the Forest -Walking in the ‎Forest -Watching Marine ‎Wildlife -Visiting the Forest ‎‎with ‎a Balloon), option 3 includes areas ‎with five recreational activities (Photography ‎in ‎Mangrove ‎‎Forest‎ -Traditional ‎Fishing -Jet ‎Boating-Watching Marine ‎Wildlife -Visiting the ‎Forest ‎‎with a Balloon) and finally option 4 ‎including seven recreational activities (Sunbathing ‎on the Beach Atv's on the Beach -Camping in ‎‎‎Mangrove ‎‎Forest -Watching Muddy ‎Islands and ‎Forest -Walking in the Forest -Watching Marine ‎‎Wildlife -Visiting the Forest ‎‎with a Balloon). The results of the evaluation of the criteria also ‎revealed that the highest weight was assigned to the criterion of sea infrastructure and existing ‎ports, Finally, the ‎ranking of recreational activities indicates that the highest priority is related to option 2, and the ‎next priorities include options 3, 1, and 4, respectively. ‎

In general, according to the obtained results, one of the most important factors in ‎the development of sustainable nature tourism, as well as the possibility of utilizing the potential ‎and tourist attractions in natural ecosystems, is the zoning and prioritization of recreational ‎activities according to the environmental conditions of the area. Considering that the mangrove ‎forests of Khamir and Qeshm are among the valuable protected reserves of the southern coasts ‎of the country, prioritizing recreational activities in suitable areas and outside the protection ‎zones of the region can protect these natural habitats and sustainably use the capacity of natural ‎resources and the appropriate distribution of recreational activities in the area.‎

One of the ways to supply wood raw material is to plant fast-growing species, with regards to the lack of forest resources and the increase in demand for wood and its products. One of the fast-growing species cultivated in our country is Paulownia fortune, which has unique characteristics. Nowadays these valuable materials are modified in various ways, due to the importance of optimal use of wood in various applications.. Thermal modification, as an efficient and environmentally friendly method, is a suitable option for improving the characteristics of fast-growing wood species. Therefore, in this study, the effect of thermal treatment in air and oil on some physical and mechanical properties of Paulownia fortunei wood was investigated. The wood used in this research was three trunks of Paulownia tree (Paulownia fortune) from Shasat Kalate forest of Gorgan University of Agricultural Sciences and Natural Resources. The wood was dried in the open air after turning into boards. Then wooden samples with straight fibers and flawless appearance were prepared from them. The samples were modified by two thermal modification methods in air and oil. Thermal modification in air was done according to Thermo-D process (at 212 ± 3 ◦C and 2 hours). Also, thermal modification with rapeseed oil was used for the treatment of samples with the same temperature conditions as the method of thermal modification in air. Then colorimetric test, bending strength, hardness, impact resistance, water absorption and thickness shrinkage tests were performed on the samples. Results revealed that heat treatment with both methods had a significant effect on density, volumetric shrinkage and water absorption, colorimetry, impact resistance, hardness resistance, modulus of rupture and modulus of elasticity. In general, heat treatment with both methods caused a decrease in density, water absorption and elongation, brightness index, impact resistance, hardness, modulus of rupture and modulus of elasticity. The density, water absorption and volumetric shrinkage of the samples treated in oil were higher compared to the samples treated in air. The impact resistance, hardness resistance, modulus of rupture and modulus of elasticity of the samples treated in oil were significantly higher compared to the samples treated in air. In general, Paulownia fortune treated in oil showed relatively better physical and mechanical properties compared to the one treated in air. Therefore, heat treatment in oil is a more effective method to improve the physical and mechanical properties of Paulownia fortune wood compared to heat treatment in air.

Due to its many applications in other industries, nanocelluloses have attracted the attention of governments and investors. The recognition and potential of nanocellulose has encouraged countries to invest in this green product. However, in Iran, Production of nanocellulose is still in the laboratory Scale due to unidentified challenges and thus, it has not yet reached the huge production. Therefore, the purpose of this research is to identify the strengths, weaknesses, opportunities, and risks of the proposed situation and the use of nanocellulose in Iran using the SWOT method.

The indicators affecting the state of supply and demand of nanocellulose were presented and completed and identified by 10 experts consisting of academic professors and private manufacturing and technology companies and knowledge-based in three stages (or three rounds) by Delphi questionnaire. Then, using the studies and opinions of the scientific professors of the related field and several member manufacturing companies, the internal factors (strengths and weaknesses) and external factors (opportunities and threats) affecting the supply and demand situation of nanocellulose were identified in the separate tables of the SWOT analysis.

In the strengths of 8 indicators (creating high added value to the raw material and nanocellulose products - diversity and availability of the raw material - biocompatibility and biodegradability of the nanocellulose product - the ability to produce a new generation of efficient products with nanocellulose - creating sustainable development with the commercialization of nanocellulose - The share of manpower with high local technical knowledge - the need for less space for the production of nanocellulose - the variety of nanocellulose products) and in the weak points of 9 indicators (the size change of nanocellulose during drying - the high cost of energy, operation, land and machinery - the need for High investment - high cost of drying nanocellulose - lack of investment by the government and banks - low production efficiency - lack of efficiency of the equipment in companies for use in nanocellulose - production in the form of nanocellulose gel (with water) - expensiveness of nanocellulose production method compared to competitors ) and the opportunity points of 7 indicators (use of nanocellulose in various fields - high innovation and virginity of the field of nanocellulose applications - attracting foreign investors and the private sector - suitable export markets in the region - the possibility of accessing the technical knowledge of other countries' production - the need for high research and development - Government support for the nanocellulose production industry - high acceleration of transformation in nanocellulose products in the world) and opportunity points of 8 indicators (raw materials and alternative products - customization of nanocellulose - low price of raw materials and competing products - expensiveness of nanocellulose - lack of special production machines and equipment - Managers' lack of risk-taking in using hi-tech and new products-difficulty introducing and promoting new products in the market) were identified, each of which affects the supply and demand of nanocellulose.

The indicators affecting the supply and demand of nanocellulose were identified by experts through the Delphi and SWOT methods, and these factors have a significant effect on it, and by applying the presented solutions, mass production and commercialization of nanocellulose can be achieved in Iran.

Paper recycling currently is considered one of the most important solutions for the environmental and sustainable production of paper products. In addition to reducing the consumption of various resources such as water, energy, and virgin fibers using this process, the paper recycling rate is continuously increasing in different countries due to less pollution. Most of the recycled paper is usually used to produce packaging paper and board. Paper and paperboard should not only possess dry-strength, but also must be able to provide the required strength at wet condition for the packaging of products that need to be kept in the cold and freezer condition. For this purpose, different procedures such as refining and additives can be used. This research investigates the independent effect of each factor as well their interaction effect in order to improve the characteristics of office deinked pulp (DIP) for producing packaging paperboard.

DIP was obtained from Latif Paper Company. After refining the pulp to SR = 30, additives including cationic corn starch (at the levels of 1, 1.4, 2, and 3w%), wet strength resin (at the levels of 1, 2, and 3w%), and AKD (at the levels of 1, 2, and 3w%) were separately added to the pulp suspension based on the dry weight of pulp in order to manufacture handsheets with the basic weight of 120 g/m2. In order to compare and determine the effect of optimum treatment of the additives on the treated pulp, tests i.e. water absorption, tensile strength, burst and tear strength of the handsheets, as well as wet strength retention and absolute wet strength retention were measured. The relative retention strength was measured after determining the independent effect of each treatment on the tensile strength, burst, and tear strength of handsheets in both wet and dry conditions. The effect of optimal combination treatment on the characteristics of handsheets was investigated and compared, when the optimal values of each independent treatment were determined.

The independent effect of refining on the strength of handsheets made from DIP is statistically significant in the dry conditions. The results indicated that using 2w% cationic corn starch in the refined pulp could induce better performance in the term of increasing the strength of handsheets in dry conditions, specifically the tear strength, compared to the independent refining factor. Using wet strength resin and AKD also represented a significant increase in the strength of handsheets in the wet conditions and also a significant decrease in the water absorption compared to the control sample, respectively. Using of refining and optimal combination treatment of additives including 2w% cationic corn starch, 3w% wet strength resin, and 1w% AKD simultaneously caused a significant improvement in the wet and dry strength, and water absorption of handsheets.

All the properties of the handsheets were improved with the applying of optimal combination treatment including the refining of DIP and adding additives at the same time compared to the control sample, so it could be used for the packaging of products that should be stored in the refrigerator and freezer. The strengths of handsheets in the dry conditions are superior compared to the standard strength of bleached kraft paper according to the Iran national standard no. 2875 except for tear strength. The measurement of absolute relative retention wet strength demonstrated that the performance of the combination treatment is very suitable compared to other previous research reports. The combination treatment significantly has reduced the paper water absorption by 22 g/m2, which is suitable for paper storage in the freezer.