m. zarafshar

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.

Nowadays, the oak decline phenom in the Zagros region of Iran has converted into a serious crisis that needs more attention and research to provide forest managers with solutions. The aim of the study was to understand the soil quality and leaf nutrients of declined oak stands (Quercus btantii) in the Kohmareh Sorkhi region. To do so, soil samples were taken from the under of the healthy and declined trees’ crowns and then soil characteristics including moisture content, pH, electrical conductivity (EC), organic carbon, nitrogen, phosphorus, potassium, gypsum, calcium carbonate, calcium, and magnesium contents were measured and compared. Morover, NPK content was measured on taken leaves from each trees. The results indicated that soil moisture, EC, gypsum, lime, P, K, Ca, and Mg contents had significant differences. Although gypsum and lime contents were higher in the declined stands compared to the healthy ones, moisture content, EC, P, K, total Ca, and Mg content were higher in the healthy stands. The leaf nutrient statistical analysis demonstrated that the dieback individuals suffer phosphorus shortage, but N and K content were the same as the healthy ones. Given that some shortages were observed in the nutrient elements such as P, K, Ca, and Mg in soils under the crown of declined trees and P in their leaves, it seems that the nutrient shortage has an important role in the oak decline since the greatest shifts were recorded for which.

Oak decline has occurred along the Zagros forest from 10 year ago. In the current study, situation of tree decline of Brant`s oak (Quercus brantii Lindl.( of Kohmareh Sorkhi, Fars was assessed. The two affected stands by dieback in north and south aspects were identified and then two plots with variable areas were set so that 100 individual trees can be found in each plot. Moreover, two unaffected stands in the same geographical aspects were found and the same plots set as controls. Then, tree dieback severity was classified into four groups including fully health trees, sign of dieback just in upper parts of branch, dieback into the crown but less than 50% and finally dieback into the crown but more than 50%. All the oak trees within the sample plots were classified according to the four groups. Also, some tree characteristics such as origin (seed or root), coppice number, DBH, height and leaf area and dry biomass were recorded for all the trees. Also, we measured soil moisture content in all the plots. According to the results, around 11% of the trees in each affected plot belonged to the severe tree dieback group. Most of the moderate and severe dried trees were occurred in medium classes of diameter and height and their distribution follow a bell-shaped. Furthermore, soil moisture content in control plots were higher than dieback plots. Mean of leaf area and biomass of control plots were greater than those affected plots by tree dieback. Totally, there was no any significant difference in tree dieback rate between north and south aspects but it seems that moisture level is one of the key factors in tree dieback prevalence.

Wild pistachio seeds have a hard coat and deep physiological dormancy, which declines their germination success. In this study, the effect of seed priming with carbon nanotubes was studied on two species of wild pistachio (Pistacia atlantica and P. Khinjuk) and was then compared with common treatments. For this purpose, seeds of each species were primed for four hours in solutions containing 0, 10, 25, 50, 75 and 100 mg / L of carbon nanotubes. In addition, some of the seeds were also treated by the common acid concentrations (65%, 5 and 10 min) and cold treatments (4 °C for one month), followed by an analysis of their germination characteristics. According to the results, carbon nanotubes affected the germination characteristics of the both species. The highest germination rate of P. khinjuk occurred under 75 mg/l and for P. atlantica at 10 mg / l. for P. atlantica, whereas the lowest germination was observed in acid (5%) and control treatments. Although cold treatment showed higher germination (18.33%) compared to control and acid-treated seeds, it was less than carbon nanotube treatments. For P. khinjuk, the lowest germination was also observed for acid treatment (11.67%). The seed germination rate and percentage of both species at concentrations of 100 mg/L were lower than those at concentrations of 10 and 75 mg/l, thus the use of lower concentrations of the nanomaterial economically is recommended.