فصلنامه تحقیقات جنگل و صنوبر ایران
سال سی و یکم شماره 1 (پیاپی 91، بهار 1402)

One of the most important challenges of climate studies in Iran is the lack of access to long-term climate data. Tree climatology, by examining the effects of climate on the annual rings of trees, provides the possibility of reconstructing the temperature and precipitation of past periods. The main goal of this study is to reconstruct precipitation from the width of annual circles of juniper trees (Juniperus polycarpus K.Koch) in the Garkhod region, located in the northwest of Khorasan province in Iran. The samples were prepared from the juniper trees with a chronometer drill and after initial preparation, they were read by LINTAB device and their time agreement was checked with TSAPWIN software. The final chronology was prepared using ARSTAN software and based on reconstructing the precipitation in the period 1850-2020. The results showed that the widths of juniper annual circles were not affected by temperature fluctuations. Still, the total precipitation of January-May showed the maximum positive and significant correlation coefficient with the growth of these trees. Between the months of the year, February, March, April, and May had the most positive and significant correlation with the width of the annual circles. In general, during the period of 1850-2020, 8 years except for positive symbolic years and 9 years were reconstructed as negative years. The highest precipitation occurred in 1864 and the lowest in 1917. It can be said that the precipitation influences the growth of juniper trees in the region. In this way, suitable conditions for the activity of cambiums are provided with the increase in precipitation.

Forest destruction causes soil destruction as the basis of terrestrial ecosystem life. Therefore, monitoring the soil and evaluating the process of changes over time can prevent the destruction of the soil and consequently the ecosystems with scientific data. In this study, the chemical and biological properties of soil were investigated in two Brant's oak (Quercus brantii Lindl.) sites, Chari and Mavarz, as a part of Zagros Forests in Chaharmahal and Bakhtiari province, Iran. Soil samples were collected from a depth of 0-10 cm and chemical and biological characteristics were measured in two years 2019 and 2021. The results in Chari site showed that the values of organic carbon, organic matter, substrate induced respiration, and nitrification potential increased significantly in the second year compared to the first year. This finding can be attributed to the more species diversity, higher canopy percentage, and relative protection of the Chari site. While in Mavarz site, only electrical conductivity and dry weight of soil showed significant changes in the second year compared to the first year which could be caused by livestock grazing and decrease in rainfall. The trend of changes in the Chari site has been positive which made improvement of some soil characteristics. Generally, management based on protecting the Zagros habitats as well as its positive effect on the biological and chemical characteristics of the soil can have a significant role in the health of oak trees which are encountering the oak decline.

Identifying the most suitable Brant`s oak (Quercus brantii Lindl.) seed origins (provenances) due to the increase in the intensity of summer drought in the Zagros forests is very important for the reforestation issue. In this research, the physiological and biochemical responses of Brant`s oak seedlings from eight provenances located in different altitudes and latitudes of Southern Zagros were investigated under drought stress (with the stopping of irrigation for one month). The data were analyzed in the factorial (2 levels of drought stress treatment and 8 levels of provenance), randomized complete design experiment by examining the simple and interaction effects of them. Also, drought resistance indexes of provenances were calculated and compared with each other by applying the photosystem II value before and after the stress. Results showed that severe drought stress significantly increased electrolyte leakage, osmolyte, Na, and proline contents in seedling leaves for all provenances. Although, the response of different provenances in terms of photosystem II was not similar. The provenances were located in lower altitudes (Basht site in Kohgiluyeh and Boyer-Ahmad province and Ghaemiyeh site in Fars province) and had higher resistance and resilience values due to adaptation to high temperature and or low precipitation. Also, Chitab provenance (a cold site with less dryness in Kohgiluyeh and Boyer-Ahmad province) became drought tolerant by closing its stomata during the day and thus reducing the photosystem II and improving it in the dark. Consequently, the drought resistance of Brant`s oak seedlings is partly influenced by the seed provenances and climatic conditions. The use of these results can be recommended to managers in the reforestation of the Zagros forests.

Since dead trees contain significant amounts of organic matter, they play an essential role in forest dynamics. In the present study, the changes in soil carbon stock were studied in relation to the dead tree features and its soil beneath in mixed broadleaf stands of Loveh forest in Golestan province, Iran using the Principal Component Analysis (PCA) and random forest model. For this purpose, the characteristics of 15 dead trees consisting of hornbeam, oak, Cappadocian maple, and ironwood were recorded in three decay classes 3 to 5, and the soil beneath them was collected from a depth of 0 to 15. The random forest model was implemented based on the relationship between the dependent variable (carbon stock) and the independent variables (effective factors) using the randomForest package in R software. The results showed that using the studied parameters, the random forest model justifies about 54% of the changes in soil carbon stock. According to the final model, the carbon stock of the soil beneath of dead tree is most affected by the three parameters of C/N ratio, nitrogen (%), and soil pH, so in a general trend with the increase of C/N ratio and nitrogen (%) and the decrease of pH, the amount of soil carbon stock around the dead tree has been increased. The present study's findings indicate that dead trees provide great potential for soil carbon storage, especially when faced with an old-growth forest ecosystem.

Managing Hyrcanian Forests in Iran requires a well-designed and constructed network of roads that are appropriately distributed and aligned with the silviculture method. These roads enable access to protection, support, and tourism activities, as well as facilitate the execution of all necessary measures. Around 10,000 kilometers of roads have been built in Iranian forestry projects. Constructing roads in forests has both positive and negative consequences on nature and its natural functioning, including impacts on biodiversity, grass and plant cover, and physical and chemical soil properties. The design and construction of these structures should adhere to the principles and technical-engineering standards of forestry to minimize adverse reactions. To ensure compliance with road construction technical instructions (Publications 131 and 148 of the technical deputy in the Management and Planning Organization of Iran), it is recommended that the Natural Resources and Watershed Management Organization of Iran supervise their implementation in all forest areas, alongside forestry plans. Furthermore, the organization should increase its direct supervision of the country's entire natural resource field to improve project outcomes.

This article delves into the management process of the Extra-Hyrcanian Forests, situated outside the Hyrcanian eco-region, starting from the first forestry organization. The sources used to compile this information include reports, implemented forestry plans, identification and semi-detailed studies, field observations, and over 30 years of experience in the Extra-Hyrcanian Forests. In the article, the report of the management process during several significant time periods is examined. Firstly, from the initial organization to the establishment of the Forestry Company in 1949, where there was a lack of attention or little attention given. Secondly, from the establishment of the Forestry Company to the beginning of the decade 1960, when there was an apparent beginning of attention and creation of the first organizations. Thirdly, from 1960 until 1972, scientific management began by preparing forestry plans. Fourthly, from 1961 until 1978, saw forestry restoration and the development of green space. Fifthly, the period from 1973 to 1978 focused on the protection and reclamation of forestry plans. A summary of the multi-year activities of the Extra-Hyrcanian Forests reveals that despite an increase in government and organizational presence since the 1960s, there was no clear policy with a definite goal and perspective for those involved. Consequently, all types of activities were repeated trials and errors. In contrast, during the same period, the Hyrkan forests were managed with a single and specific policy, even a single service description and manual (with a few case changes). Unfortunately, in the Extra-Hyrcanian Forests, plans and programs with a short life were implemented in the form of trial and error without defining and establishing a particular policy for forest management. Of course, it must be acknowledged that this management history was inevitable in dry and semi-arid forests, which, like the Hyrcanian humid forests, did not have the support of solid data, i.e., several-year history of European temperate humid forest management.