Introduction and Objective: Given the high volume of broken and fallen trees in the forests of northern Iran and the ban on timber extraction due to environmental laws, the decline in the quality of the wood of these trees can be examined in the long term in the forest environment. Therefore, this study aimed to investigate changes in wood quality decline over a one-year period to answer the question of what types of damage are observed in broken and fallen trees depending on the tree species around forest roads.

Material and Methods: In order to examine the quality of wood of tree species (cracks in the trunk and fungus), at least 30 fallen trees for each species were selected around forest roads up to a maximum distance of 200 meters from both sides of the road. The depth and length of the cracks and gaps in the trunk were measured with calipers. Also, each macroscopic wood-decaying fungus sample was taken for identification based on morphological features and cap color, shape, size, and surface ornamentation.

Results: The results showed that the highest abundance was recorded for the Auricularia mesenterica, which was mostly found on the trunk of the Pterocarya fraxinifolia. The Ganoderma applanatum recorded the highest abundance (34%) on the maple species. But the abundance of Auricularia mesenterica is almost the same in the three species of hornbeam, alder and maple.  The length of the cracks in the alder species is significantly more than in the other species. In this study, the maximum depth of cracks was recorded 25 centimeters for distances of 5 to 20 meters, which is significantly different from other distances. Also, based on the results, the average crack depth was recorded higher for beech and maple. An examination of the apparent decline in wood quality shows that after a one-year period, on average, hornbeam wood, beech wood, and alder wood had a decline in quality of 48 percent, 17 percent, and 30 percent, respectively. The results of Pearson correlation analysis show that there is a positive and significant correlation between crack length and crack depth. There is also a negative and significant correlation between crack depth and wood quality. There is also a negative and significant correlation between the abundance of fungi and wood quality decline.

Conclusion: This study showed that leaving wood on the side of the road compared to inside, rainfall and direct sunlight causes reduces the quality of the wood and reduces its value and provides conditions for decay agents, including wood-decaying fungi, which are among the most important of them, so that they may decompose after a while. Given the importance of this issue and the country's need for wood, it is better to remove the wood by the roadside and not expose it to decay by wood decay fungi.