جستجوی مقالات مرتبط با کلیدواژه « Forest restoration » در نشریات گروه « جنگلداری »

Reproduction (regeneration) is a fundamental process that drives the dynamics of a forest, occurring continuously in a healthy and natural forest with a specific spatial and temporal pattern. Natural regeneration poses significant challenges in Zagros forests, Iran. This research was undertaken to examine and analyze the current state of reproduction of tree and shrub species in the monitoring sample plots of Zagros forests. This study, while scrutinizing the species composition, origin, distribution curves, and health of seedlings and saplings, explores the interrelationship between reproduction and nurse species. It will serve as the foundation for long-term studies that determine the temporal changes in reproduction and its characteristics in the Zagros forests.

This research was conducted in the permanent monitoring plots of Zagros, spanning from West Azerbaijan to Fars province. A total of 120 sample plots of 100 square meters were studied within these plots. Each province had 30 studied sites in the typical forests, with 10 of them located in the protected forests. The variables studied included reproduction density by species, origin and type of reproduction, nurse species, height of seedling, terminal bud, and health status of reproduction. A height of 0.5 meters was set as the criterion to distinguish reproduction. The t-test was used to compare parametric data in two groups, while the Kruskal Wallis and Mann-Whitney U tests were employed for non-parametric data.

In the studied area, the reproduction of 20 forest tree and shrub species was recorded, and the density of seedlings and saplings was calculated to be 366 plants per hectare. However, the reproduction was not uniformly distributed, with 37% of the sample plots lacking reproduction. The abundance distribution diagram in the height classes revealed a decrease in the number of oak (Quercus spp.) and hawthorn (Crataegus spp.) reproduction with a height of less than 5 cm. Of the total number of recorded reproduction, 72.5% originated from seeds and 25% were shoots. Overall, 66% of reproduction was dependent on nurses, with oak, hawthorn, stone, and rock playing the greatest roles as nurses. Stones and rocks played a more significant role in the revival of seedlings. Cerasus microcarpa (C.A.Mey.) Boiss., Q. infectoria Oliv., and Q. libani Oliv. had the highest dependence on the nurse, while Pyrus spp., Daphne mucronata Royle, and Crataegus spp. had the least dependence on nurse species. Reproduction sheltered by nurses was significantly healthier than those without nurses. Also, reproduction sheltered by stones and rocks had a higher health rate than reproduction sheltered by trees, although this difference was not significant. Lonicera nummulariifolia Jaub. & Spach, Fraxinus angustifolia Vahl, and Acer monspessulanum L. had the worst condition in terms of reproduction. Despite the presence of mature trees, they had no reproduction (L. nummulariifolia and F. angustifolia) or had very low reproduction (A. monspessulanum). The results showed that the number of reproduction in protected sites was higher than non-protected sites. Although this difference was not significant, the reproduction in the protected sites was significantly healthier.

The results indicated that the reproduction in the Zagros forests is not in a normal situation. However, given suitable spatial and temporal conditions, reproduction occurs and establishes. Although in conditions of disturbance and overgrazing, reproduction attempts to survive by taking shelter near stones, pits, or under thorny shrubs, the conservation of the forest stand by maintaining the tree canopy (oak, hawthorn, and other species) and the forest’s natural structure provides the best conditions for the establishment and survival of reproduction, thereby ensuring the sustainability of the ecosystem.

In this study, the effect of zinc oxide nano particle (ZnO) on 18 different growth, morphological and physiological characteristics of Persian oak (Quercus brantii L.) seedlings was investigated under drought stress. Before doing the experiment, initial characteristics of the two-year-old seedlings were measured after transferring them to Semnan and passing two months for stabilization in the greenhouse condition. Statistical analysis were performed with a completely randomized design under a factorial experiment using two factors of drought stress (field capacity 80%, 60%, 40% and 20%) and zinc nano oxide (concentrations 0, 30, 100, 300 and 1000 mg/l) with four replications. After twice spraying with zinc nano oxide with one-month interval and growing in greenhouse conditions for 6 months, all seedlings were measured and reassessed. The results showed that with increasing drought stress and nano oxide concentration, the number and longitudinal growth of leaves, height and diameter growth of seedlings and the number of seedling branches decreased, while the number of leaves and percentage of nano blight and the number of dried leaves increased. The best treatment in terms of growth and qualitative traits was related to the combination of irrigation with 40% of field capacity along with a concentration of 30 mg/l zinc nano oxide. The results also showed that only superoxide dismutase enzyme had a significant difference compared to the control with increasing drought stress at different concentrations of zinc nano oxide; however no significant difference was observed throughout other tested enzymes (catalase, ascorbate peroxidase and guaiacol peroxidase). Overall, due to the lack of prominent effect on seedling characteristics and creating the scorching spots on the leaf surface in some treatments, the use of zinc nano oxide is not recommended to improve the drought resistance, establishment and growth of oak seedlings.

The aim of this study was to investigate the woody and herbal frequency and species diversity in the mountain forests of northern Iran, Poudeh village of Roodsar, over time and as a result of traditional exclosure of these forests.

The study area is located in the forests of Poudeh village, Roodsar, Guilan province. According to the traditions of the region, people protected the spots of the destroyed forest areas near their hazelnut gardens for flood prevention and personal exploitation. They do this by using stones and placing shrubs on it, or using wooden stems and barbed wires. In this area, there are many of exclosure forest spots that have been protected and enclosed by the native people. Three exclosure forest spots were selected for this study. For this purpose, plots with different conservation history including low-term enclosed forest area (Less than 40 years), middle-term enclosed forest area (More than 40 years) and reference forest area were selected and the indicators of relative frequency, relative ecological importance value and species diversity were calculated.

The results showed that with increasing the duration of forest protection, the relative abundance of beech in both strata levels increased the relative abundance of hornbeam and the amount of species diversity also decreased. The highest and lowest differences in relative abundance of beech between the two strata were observed in reference forest area and low-term enclosed forest area respectively. The ratio between the abundance of beech in the upper story to the understory for low-term enclosed forest area and middle-term enclosed forest area was 1.18 and 1.24, respectively. In the control area where the highest relative abundance of beech species (80%) was recorded in the upper floor (tree), there is a moderate relationship between the two floors (r = 0.61, p <0.001) and in short-term protection, this relationship is significant (r = 0.72, p <0.001). In the middle-term enclosed forest area (more than 40 years) with increasing the relative abundance of beech in the upper story, its relative abundance in the understory also increased significantly (r = 0.88, p<0.001).

The process of species change is a complex and time-consuming process. The results show in the evolution of the stand structure in the affected areas, medium-term protection can facilitate the formation of understory. It is recommended that middle-term enclosed forest area along with silvicultural treatment be applied to formation of understory.

Sexual regeneration is amongst the most important factors that affect the survival and sustainability of forests. It is controlled by the total resources and conditions representing the role of microhabitats in the establishment of the regeneration. Thus, identifying the role of microhabitats on the establishment and diversity of regeneration is of great significance. Therefore, the present study was conducted in a central part of the Zagros region in Baba-Yadegar forests of Dalahoo County, Kermanshah province. A total of 372 5 × 5  plots were established with respect to the tree microhabitats, including Quercus brantii Lindl., Q. infectoria Oliv., Crataegus pontica C. Koch., mixed and open spaces (with no trees) along 7 transects. In each plot, the biological characteristics of the trees were measured together with sexual regeneration and soil litter depth. The results showed that the mean value of DBH was significantly higher for Q. infectoria microhabitat compared to other microhabitats. In addition, the number of sprouts was significantly higher for mixed microhabitat compared to others. The highest species diversity of regeneration was observed in Q. brantii microhabitat. Furthermore, the result of multivariate analysis showed that the species diversity and abundance of trees in the microhabitat were the most important factors in the discrimination among microhabitats with over 83 percent of accuracy. It was concluded that the microhabitats and their characteristics play a major role in the establishment of tree species regeneration, diversity and consequently on the future forest structure that can contribute to the success of the restoration plans in the Zagros forests.

Crataegus pontica, Cerasus microcarpa and Amigdalus orientalis are from important accompanying woody plant species in Zagros forests and their regeneration dynamic helps to improve the regeneration of tree species. This research was carried out with the aim of investigating and recognizing the regeneration establishment pattern of C. pontica, C. microcarpa and A. orientalis in three forest sites in Dalab , Ilam province with different site conditions and also studing the their seasonal changes during spring and summer 2016. In each site one basic transect was established perpendicular to the slope and regeneration establishment positions including "under tree canopy", "under shrubs", "under bushes", "next to rocks" and "without vegetation space" with three replications were selected. For each replicate a 15m2 circular permanent plot to investigate the seasonal changes was established and the number and height of seedlings for each species was measured. The results showed that the seasonal changes of C. microcarpa regeneration are associated with a significant decrease. The most density of C. microcarpa seedlings was in south aspect and altitude class of below 1500 m a.s.l., and for A. orientalis was in north aspect and altitude class of above 1500 m a s l. The most density of C. microcarpa seedlings was found under the crown of oak trees, and for C. pontica was under the crown of shrubs and for A. orientalisat was next to the rocks. The most density of seedlings for C. microcarpa, C.pontica and A. orientalis was found in north side of tree crowns and also at the first third of tree crown radius. The most percentage of tall seedlings for C. microcarpa was at a first third of tree crown radius and for C. pontica and A. orientalis was at the third of tree crown radius. It was concluded that the crown of trees and shrubs has the most important role in seedlings establishment and protecting them against cold and heat. However, the role of rocks in soil preserving and seedlings establishment is considerable.