جستجوی مقالات مرتبط با کلیدواژه « Radial growth » در نشریات گروه « جنگلداری »

This study was carried out in the oriental beech communities in order to investigate the natural regeneration and assessment of radial growth trend from 1960 to 2016. In each area, 50 1000-m2 circular plots were established based on a random-systematic method. Regeneration was sampled on two concentric circles with an area of 20 and 10 m2 of the sample plot center (for seedling and sapling, respectively). Then, 160 core samples were taken from selective trees by increment. The results of harvested stand indicated that natural and human disturbances regimes lead to change in the diameter distribution, age distribution, radial growth pattern and establishment of tree's regeneration. In the unharvestedarea, sapling of F.orientalis and seedling of Carpinus betulus and Acer velutinum had the highest density. Whereas, the seedlings of F.orientalis and C.betulus were dominate in the harvested stand. During the studied period, 324 tree species were established in the unharvested area and the highest frequency of tree recruitment was belonged to 1970-1980 decades. However, in the harvested stand, 262 tree species were established and the greatest frequency was recoreded from 1960 to 1970 years. The radial growth of trees in the harvested area showed the higher variations during the studied period and the highest frequency of release events was belonged to moderate releases. Therefore, this stand should be managed in order to return their historical composition and structure, maintaining natural regeneration and the optimal development of stand for future.

Due to variances in response of different tree species in different habitats to climate changes, further studies in this field is clearly required. On the other hand, the lack of studies on chronology to evaluate the effect of solar radiation on radial growth of tree species due to lack of long term data of an important climatic variable, new approaches to determine the effect of this parameter on growth diameter is inevitable. The main objective of this study was to evaluate the effect of temperature and irradiance climatic parameters on growth of diagonal oak (Quercus castaneifolia) as one of the main tree species of forests in Iran. For this purpose, 17 harvested Quercus castaneifolia disks from trees in Astara forest were used and chronology of the species and the response of radial growth to temperature and radiation climatic variables were studied. The findings revealed that although the chronology obtained from two perpendicular directions of each disk for 15 disks had the desired result but the chronology obtained from the 15 selected disks with each other reflected the fact that only 10 disks had acceptable results for chronology of Quercus castaneifolia in Astara forest. Results also revealed that both temperature and solar radiation parameters had negativly significant effect on growth of Quercus castaneifolia. The correlation coefficient (R) between the radial growth and these two variables was -0.52 and -0.45, respectively. Therefore, it can be concluded that although both solar radiation and temperature have a negative effects on growth of Quercus castaneifolia, the temperature is more important than radiation. This fact can be related to cloudy condition of weather in the north part of Iran.

The beginning and the ending of radial growth in trees depend on genetics and climatic factors and its intensity varies during a growing season. Studying wood formation dynamics in a growing season will increase our knowledge about xylogenesis of important species and the influencing parameters. For this reason and in order to have a better understanding of a radial growth in oak, four Quercus castaneifolia individual treeswere selected in the research forest of University of Tehran located in the Hyrcanian forest. In 2012, micro-core samples were extracted from trees by Tropher in monthly intervals. Cambial cell divisions and radial growth started approximately on mid-April and terminated at the end of September. The highest number of cambium cell (15-17) and the maximum daily growth rates of all trees were achieved around Mid-June. The results of this research showed that the majority of radial growth in oak occurs from May to mid- July and this fact should be considered in dendroclimatological studies.