Ecology of Iranian Forest

Extended Abstract
Background: In the northern forests of Iran, wind throw and uprooting of trees are frequently observed in many areas due to the occurrence of storms and strong winds. Considering the large number of broken and fallen trees in these forests — especially due to the forest resting plan — conditions have arisen that allow for assessing the degree of wood quality deterioration in these trees. Among the damaging agents, macroscopic wood-decaying fungi are particularly important. These macroscopic fungi are a group of species that, through specific biochemical mechanisms and enzymatic activities, are capable of degrading various chemical components of wood and eventually cause decay. The extent and spread of wood decay are among the key factors in grading timber. This study aims to examine the types of changes associated with wood quality loss and to answer the question of what kinds of damage, depending on tree species, occur in fallen and broken trees along forest roads over a one-year period.
Methods: This research was carried out in Series No. 1 of Watershed 72, approximately 40 km from Neka County, within the working area of the Estakhrposht forest district. To assess the apparent wood quality of tree species (cracks, splits, fungal infection, and decay), at least 30 fallen and broken trees (logs and cut pieces) of each species were selected along forest roads up to a maximum distance of 200 m on both sides. The depth and length of cracks and splits on the trunk were measured precisely using a caliper. For collecting samples of macroscopic wood-decaying fungi, each observed fruiting body was collected and identified based on morphological characteristics, such as color, shape, size, and surface ornamentation of the cap, stipe, and gills. To measure microscopic structures, 20 elements of each organ were measured using a microscope equipped with a graded eyepiece. Ultimately, fungal taxa were identified using both macroscopic and microscopic features in combination with relevant identification references. All analyses were performed using SPSS version 22, and graphical illustrations were prepared using Excel and SigmaPlot software. Prior to analysis, data normality and homogeneity were verified using the Kolmogorov–Smirnov and Levene’s tests, respectively.
Results: Auricularia mesenterica had the highest frequency, mostly observed on Alnus subcordata, and Ganoderma applanatum showed the greatest abundance (34%) on Acer velutinum (Maple). All five fungal species were identified in beech (Fagus orientalis), alder (Alnus subcordata), and hornbeam (Carpinus betulus). Three fungal species were observed on Acer velutinum and only two on Alnus subcordata; however, the frequency of A. mesenterica was nearly similar among C. betulus, A. subcordata, and A. velutinum. The mean crack length decreased from the road toward the forest interior, and the mean crack length in A. subcordata was significantly higher than in A. subcordata, F. orientalis, A. velutinum, and C. betulus. The highest crack depth (25 cm) was recorded for trees located 5–20 m from the road, showing a significant difference compared to the other distances. Furthermore, the mean crack depth in F. orientalis and A. velutinum was greater than in the other species. After one year, the average visible quality loss of wood was 48% in C. betulus, 17% in F. orientalis, and 30% in A. subcordata. Pearson’s correlation analysis showed a positive and significant relationship between crack length and depth, and a negative and significant correlation between crack depth and wood quality grade. There was also a negative and significant correlation between the abundance of wood-decaying fungi and the degree of wood quality loss. Evaluation of decay grades among the studied species (A. subcordata, F. orientalis, A. velutinum, A. subcordata, and C. betulus) within 200 m of the Hezarjerib forest road in Neka indicated that decay grades 3 and 4 were predominant, with A. velutinum exhibiting the highest rate of decay. Moreover, decay grade 3 occurred more frequently than the other grades.
Conclusion: Many of the broken and fallen trees along forest roads are still suitable for conversion and utilization and have considerable economic value. These trees can be efficiently harvested with proper management, and the resulting profits can be allocated to protective measures, such as forest road restoration. The findings revealed that wood pieces remaining in open areas beside roads, due to exposure to rainfall and direct sunlight, experienced a more severe decline in quality than those within the forest interior. This exposure facilitates the activity of wood-decaying fungi — one of the main agents of wood degradation — and may eventually lead to complete decomposition. Given the importance of this issue, it is recommended to remove only the wood located beside roads from the forest to prevent fungal decay and quality loss.