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Showing 4 results for Oak

Hengameh Shiravand, Shahriar Khaledi, Saeed Behzadi, Hojjat Allah Sanjabi,
Volume 20, Issue 57 (6-2020)
Abstract

   Decline phenomenon is one of the most important reasons for the destruction and mortality of oak trees in Zagros forests due to the wide variety and diversity of the topography of its determination through track and field operations is not readily possible. Changes in an ecosystem are often gradual changes, but sometimes changes occur in an ecosystem in a short time. This change can cause a catastrophe in the ecosystem, which is difficult to identify. A proposed method for identifying a general change in time series is use the BFAST model, which, by analyzing the time series in the process, season, and residual components, identifies the changes in the time series and also repeatedly estimates the time and amount of the changes, and The path and amount of variation in this study, using this model and satellite images to monitor and evaluate the changes in coverage and decline of oak forests in Lorestan province during the statistical period (2000-2017). The results showed that more than 42804 hectares (1.5%) of the oak forests of the province were lost due to the decline phenomenon during the studied period. Also, according to the BFAST method, the trend diagram is a failover and their frequency variations are irregular. Comparison and study of different forest coverings also showed a decrease in NDVI, which indicates that the process of decreasing forest cover is inclusive. The study of autocorrelation and Kendal coefficient showed that there were significant changes and severity of failure (-0.7) in the area Study. The seasonal chart also has uneven and irregular variations due to changes in oak forests in the region. The results of this research can be used to study the changes in the coverage of oak forests in the area and management and the way to think about this phenomenon.

Mr Mohammad Safaei, Dr Hani Rezayan, Dr Parviz Zeaiean Firouzabadi, Dr Ali Asghar Torahi,
Volume 22, Issue 65 (6-2022)
Abstract

Examining the effects of climate change on the oak spatial distribution, as the main species of Zagros forests and its ecological and economic values is of significant importance. Here, we used species distribution models for simulating current climatic suitability of oak and its potential changes in 2050 and 2070. For this purpose, five regression-based and machine learning approaches, four climatic variables related to temperature and precipitation and two optimistic (RCP 2.6) and pessimistic (RCP 8.5)  greenhouse-gas scenarios were used. The results of measuring the accuracy of models by AUC indicated the good performance of all algorithms and Random Forest achieved the highest accuracy (AUC = 0.95) among other methods. The results showed that in both time periods and under both scenarios, changes will occur in oak spatial distribution and the most severe one would be a 42.9 percent loss in the oak climatic suitability in 2070 under pessimistic scenario (RCP 8.5).
 
- Ahmad Hosseini, - Mostafa Khoshnevis, - Mohammad Reza Jafari,
Volume 24, Issue 73 (6-2024)
Abstract


Old trees as the most important genetic reserves of the country have great importance and value in various aspects of ecology, forest restoration management, ecotourism and even history. In this research, after identification of the old trees in the forests of Ilam province, their morphological characteristics including DBH, trunk height, total height, crown length, min & max crown diameter, crown health, crown firmness, crown symmetry, Trunk health and trunk shape were examined. The selection of old trees was based on DBH criterion. After the forest survey, 43 old trees including 5 Petrocarya fraxinifolia, 5 Ulmus glabra, 11 Fraxinus rotundifolia, 3 Celtis caucasica, 4 Platanus orientalis, 4 Ficus carica, 7 Olea europea and 4 Cupressus sempervirens were identified. The results showed that among single-stranded trees, P. orientalis had the highest mean DBH (171 cm), total height (15.8 m) and trunk height (6 m), and among multi-stranded trees O. europea had the highest mean DBH (260 cm). P. fraxinifolia and U. glabra had the highest mean of crown length (11 m) and F. rotundifolia had the highest crown area (195 m2). The highest percentage of single-trunks belonged to the P. fraxinifolia (80%) and C. caucasica (67%). The highest percentage of healthy trunks belonged to C. sempervirens (50%) and O. europea (50%) and the highest percentage of healthy crowns belonged to P. fraxinifolia (100%), C. caucasica (100%), P. orientalis (100%), O. europea (100%) and F. carica (100%). The highest percentage of crown symmetry was belonged to C. caucasica (100%) and the highest percentage of crown freshness was belonged to P. fraxinifolia (100%), F. rotundifolia (100%), C. caucasica (100%), P. orientalis (100%), O. europea (100%) and F. carica (100%). Based on the desirable morphological characteristics of old trees, it is possible to help the strengthen and restoration of Zagros forests by producing resistant seedlings from their seeds.
Key words: Old trees, Morphology, Oak forests, Ilam.

Shamsallah Asgari, Tayeb Razi, Mohamadreza Jafari, Ali Akbar Noroozi,
Volume 25, Issue 76 (3-2025)
Abstract

Due to the significance of forests in both the natural and human environment, this study aims to investigate the impact of meteorological drought on oak forest dieback in Ilam province. Specifically, the study seeks to determine the relationship between Zagros Forest drought and droughts in this particular region. The analysis utilizes the Standard Precipitation Index (SPI) to identify the frequency of droughts during different time periods. The results indicate that the years 2007, 2008, 2011, 2015, and 2016 experienced the highest occurrence of droughts. Additionally, remote sensing data from MODIS images were employed to examine the trend in tree greenness (NDVI) from 2000 to 2016. The analysis reveals a significant correlation (R2 = 0.9999) between the greenness trend and the drought index (SPI). Moreover, a land survey of oak drying points and simulation using Landsat satellite images, with a 15×15 pixel output from GIS software, indicate that approximately 17,894 hectares of forests in the region experienced drying and destruction between 2000 and 2016. By combining the oak forest drying layer with the output layers derived from drought zoning, visual indicators were created, and statistical analysis was conducted for three 5-year time series. The results demonstrate a correlation coefficient of 96.6% and an explanation coefficient of R2 = 0.985 for the 2002-2006 time series, a correlation coefficient of 95.4% and an explanation coefficient of R2 = 0.980 for the 2007-2011 time series, and a correlation coefficient of 98.8% and an explanation coefficient of R2 = 0.995 for the 2012-2016 time series. These findings illustrate the influence of drought and its variations in terms of intensity and duration on oak forests in the Zagros region of Ilam. Based on the study results, it is predicted that if the drought persists with the same trend, approximately 1,118.4 hectares of oak forests in Ilam province will dry up and be destroyed annually.


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