مجله پژوهش و توسعه جنگل
سال هشتم شماره 1 (بهار 1401)

The rate of litter decomposition is influenced by various factors such as climatic conditions, litter quality and population of decomposers. Changes in precipitation patterns and increasing temperatures are the most important consequences of the climate change may change the decomposition rate of leaf litter. Hence, the present study aimed to simulate the effect of throughfall exclusion and increasing temperature on the process of hornbeam and oak leaf litter decomposition in the oak-hornbeam stand. For this purpose, four treatments were considered including two combined treatments consist of 25 and 50% throughfall exclusion and increasing temperature, warming and the control treatment (natural conditions). The hornbeam and oak leaf litter decomposition rate were studied using litter bags for 200 days. The average soil temperature of the treatments during the study period was 0.2-0.3 °C more than the control treatment, which resulted in a decrease in soil moisture content 13%. The combine effect of increasing temperature and decreasing soil water content cause a significant increase in the leaf litter decomposition rate of hornbeam, especially in the treatments of 25 and 50% compared to the control. The decomposition rate of the control treatment was decreased over time; while the decomposition rate of oak increased in the treatment of 25%. The results showed that changing in the climate conditions (i.e., increasing the temperature and decreasing the precipitation) will significantly change the rate of litter decomposition of thermophilic species (oak). It will lead to increase the rate of nutrient exchange in the forest soil ecosystem. Therefore, in forests with fertile soil, it is possible to shorten the exploitation period‎.

The first and basic step in identification, conservation, protection of gene resources, genetic research, and breeding programs is determination of genetic diversity in plant material. Using of molecular markers is one of the most important tools in this field. Therefore, the conservation and evaluation of genetic diversity of native plants is necessary. In order to evaluate the genetic diversity of 140 Iranian walnut seedlings, 20 SSR primer pairs were used. The used SSR loci generated 138 alleles. The minimum and maximum number of alleles were for SSR loci WGA69, WGA71, JRHR211298 (five alleles) and WGA202 (nine alleles), respectively. Loci JRHR211298 and loci JRHR217037 produced the minimum and maximum number of effective alleles, respectively. The most value of observed heterozygosity (Ho) generated by loci WGA69. All used SSR loci, showed deviation (P≤0.001) from Hardy–Weinberg. Neigbour-joining dendrogram divided 140 walnut seedlings into five main groups. The study of population structure, with Structure 2.3.1 software, identified two possible groups (k=2). The results of both were largely consistent. The data based on the individual membership share matrix and the Fst rate showed that there was no significant difference between two possible groups.

In this research, the effect of different forms of nursing on establishment of natural regeneration in the forests of Vezg region in Boyer-Ahmad basin was investigated. For this purpose, an area of six hectares was selected and the type of nurse species and forms, the type of target species (regeneration) were measured. Overall, 14 woody species of nurse plants with a total of 423 individuals were recorded in the research area, among them, two thorny species include Amygdalus lycioides and Pyrus glabra with 195 and 77, respectively, have the highest number. Also, out of 912 regeneration individuals (target species) under the canopy of nurse plants and rocks, the highest number belonged to Daphne mucronata, Amygdalus lycioides, Prunus sp and Lonicera nummulariifolia. RDA analysis also showed that the regeneration of target species is affected by A.lycioides and P.glabra nursing plants. The results of this study showed that the regeneration of woody species in this area, with the exception of A. lycioides, depends on conservation and nursing. This indicates the role of nurse species in establishing regeneration in semi-arid forests of Zagros, which can be used as a model in forest restoration programs in other parts of the Zagros forests‎.

The aim of this study was to investigate the trend of changes in basic density and green moisture content of hornbeam trees in the vertical and radial direction of trunk wood. Therefore, a complete disk was prepared from 10 fallen trees in 20-40, 40-60 and 60-80 diameter classes and different decay degrees (grades 1, 2 and 3). The disks were prepared at intervals of 5, 35 and 65% of the vertical sections of the trunk. Then, the sample pieces with a fixed volume of 2× 2× 2 cm3 were fragmented at a ratio of 10, 50 and 90% of the radial sections of the disks and were obtained their basic density and green moisture content. The results showed that the green moisture content and trunk basic density of hornbeam trees in different diameter classes with the degree of decay had a significant difference with a probability of 99% (P <0.001). The highest mean basic density values were observed in the distance of 5% in the vertical direction and 90% in the radial direction of the trunk wood with 0.59 and 0.60 g / cm3, respectively. The highest mean values of green moisture content were observed in 90% in the radial direction of 0.65 and the distance of 5% in the vertical direction of 0.66. Of course, green moisture content in vertical sections showed a significant difference with changing the degree of decay (P> 0.05), but no significant difference was observed in radial sections. The results of correlation showed that basic density has the highest significance correlation with diameter equal to the breast and the lowest significance correlation with the coefficient of moisture.

Paulownia is a fast-growing, industrial and ornamental tree with medicinal properties. The present study was performed to investigate the osmotic potential of MS basal culture medium under the effect of macronutrients and micronutrients. Also, the effect of osmotic potential on callus induction, somatic embryo, regeneration, antioxidant activity and somaclonal variation were investigated. The present experiment was carried out factorial in a completely randomized design with two factors, explants (leaves and petioles) and eight types of culture media containing different combinations of culture medium elements with different combinations of plant growth regulators (PGR). The results showed that the highest level of callus induction, somatic embryogenesis and regeneration were observed in media with one-half and one-quarter times the macronutrients of MS culture medium. Anthocyanin activity, chlorophyll content, embryo number and osmotic potential increased with decreasing macronutrients, especially nitrate sources in culture medium. However, callus growth rate and somaclonal variation decreased. In culture medium, calluses and embryogenic calluses without burns, transparent, regenerated seedlings were more vibrant and the most pigments were observed in the leaves of seedlings. In complete MS media, callus induction, somatic embryo, osmotic potential, anthocyanin, chlorophyll decreased. While callus growth rate and somaclonal variation increased.

This research investigated some physical and chemical characteristics of soil as well as quantitative and qualitative characteristics of trees in three stands of pure beech, pure hornbeam and beech-hornbeam mixture. In each stand, 25 plots of 400 m2 were selected by systematic-random method. In each plot, quantitative and qualitative characteristics were recorded. Also, litter and soil samples (up to 10 cm depth) were collected from each stand. According to the results, maximum DBH (54.47 cm), total height (22.31 m), basal area per hectare (82.03 m2) and volume per hectare (991.43 m3) were observed in pure beech while having the lowest number per hectare (314 tree per hectare). The highest C and C/N ratio of litter in pure beech were 33.16% and 13.52, respectively. Also, the highest quantity of N in litter was determined in two species of pure hornbeam (3.22%) and mixed beech-hornbeam (3.06%). In terms of soil characteristics, pure hornbeam stand showed the highest amounts of soil reaction (7.09), N (0.33%) and soil N sequestration (5.49 tons per hectare) compared to the other stands. However, the highest amounts of C (2.63%), C/N ratio (10.27) and soil C sequestration (77.16 t / ha) were observed in pure beech. The results showed that pure beech stand in terms of quantitative and qualitative characteristics and pure hornbeam stand in terms of soil fertility are in a more favorable condition.

In this research, morphological, physiological and biochemical of 6 tree species in industrial Foolad Mobarakeh of Isfahan region at different irrigation intervals (seven, 14, 21 and 28 days) were studied in a completely randomized design and factorial in 2019. Survival, height, diameter, crown characteristics, photosynthesis, transpiration, stomatal conductance, water use efficiency, proline, and whole leaf chlorophyll were evaluated. The results of comparing the means showed that with the prolongation of irrigation cycles from once every seven days to once every 28 days, the survival rate of species and morphological traits such as height, diameter, and crown of the species decreased. Physiological and biochemical characteristics under the influence of species did not differ statistically significantly, while increasing the irrigation period from seven days to 28 days showed dramatic changes in these characteristics. Photosynthesis, stomatal conductance, transpiration, water use efficiency and total leaf chlorophyll were highest in irrigation cycle once every seven days and minimum once every 28 days, while leaf proline content had the opposite trend so that the lowest amount in the irrigation cycle once every seven days and its maximum amount was observed in the irrigation cycle once in 28 days. There was no difference between species in terms of physiological parameters. Generally, the results showed that the species Caucasian nettle tree, chinaberry and black locust have good performance in irrigation periods. Although it has been determined that the best irrigation treatment is once every 7 days, but 14 and 21 days also have high survival rate and can be used to reduce water consumption‎.