نوع مقاله : علمی - پژوهشی
نویسندگان
1 دکترای جنگلداری، دانشکده منابع طبیعی، پردیس دانشگاهی دانشگاه گیلان، رشت، ایران
2 دانشیار، گروه محیط زیست و علوم جنگل، دانشکده منابع طبیعی و محیط زیست، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات، تهران، ایران
3 دانشیار پژوهش، مؤسسه تحقیقات جنگل‌ها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
4 استاد، گروه محیط زیست و علوم جنگل، دانشکده منابع طبیعی و محیط زیست، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات، تهران، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objective: Fires are among the most significant natural disturbances impacting plant ecosystems worldwide. Despite their destructive nature and considerable influence on forest ecosystem dynamics, forest fires are an inherent component of many ecosystems. Over millions of years, the interdependent relationship between fire and vegetation has led to their mutual adaptation, making fire an inevitable and inseparable part of these ecosystems. The bark of trees serves as a protective barrier for young trees and seedlings, shielding internal tissues from fire and preventing damage to all tree tissues below 60°C, which is the critical temperature for cambium death. This study aimed to assess the fire sensitivity of two tree species, beech (Fagus orientalis Lipsky) and hornbeam (Carpinus betulus L.), by examining bark thickness and determining cambium death times across trees with similar diameter classes.
Material and Methods: The study was conducted in the Lalis Forests of watershed No. 45, located in Mazandaran province, northern Iran. The area covers 2,127 hectares, and the climate is classified as very humid based on the De Martonne method. Random sampling of tree bark was conducted across diameter classes ranging from 5 to 120 cm for both beech and hornbeam species. A total of 192 trees (96 beech and 96 hornbeam) were sampled, with eight trees selected from each diameter class, resulting in 384 bark samples. At breast height, a 10×5 cm section of bark was removed using a knife, and the thickness was measured with a caliper to the nearest millimeter. The bark samples were then exposed to controlled burning at 60°C and 400°C. To compare species vulnerability to fire within the same diameter classes, a paired t-test was used. Bark thickness was entered into the formula to examine cambium death times.
Results: Significant differences were observed in bark thickness between the two species, with hornbeam exhibiting thinner bark compared to beech in the same diameter classes. A notable difference (P<0.05) was found in the time to ignition between beech and hornbeam bark at the fire environment temperature of 400°C. However, hornbeam bark demonstrated greater heat resistance. In both smaller and larger diameter classes, hornbeam exhibited higher survival rates than beech, despite beech having thicker bark in all diameter classes. One key factor contributing to the species' fire resistance is the physical and chemical structure of the bark, with light-demanding species typically exhibiting higher fire resistance. At 60°C, the cambium is destroyed, and hornbeam showed higher resistance, with its cambium changing color over a longer period. Beech cambium, despite having thicker bark, was destroyed more slowly than hornbeam cambium. This suggests that species with thicker bark tend to have longer cambium death times. Although the formula is linear, it does not account for all factors affecting tree resistance (such as the physical and chemical properties of the wood), limiting its accuracy in assessing tree mortality.
Conclusion: Bark thickness plays a crucial role in determining the time it takes for bark to burn and for the cambium to die, and this varies between species. When comparing burning times and cambium mortality within a species, bark thickness is a primary influencing factor. However, when comparing between species, factors such as species type, fire resistance, and the physical and chemical characteristics of the bark become more significant. Therefore, in the event of a fire, to protect the forest and minimize further damage, priority should be given to supporting younger, more vulnerable stands.
کلیدواژه‌ها [English]
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