Ecology of Iranian Forest

Extended Abstract
Background: To effectively mitigate the sensitivity of forest stands to environmental hazards, it is essential to have a comprehensive understanding of how these factors impact trees. One important metric in this regard is the tree height-diameter ratio, which serves as a key index of tree resistance and overall stand stability. The present study aims to evaluate the height-diameter ratio in a mixed-species natural forest stand located in a protected area of Arasbaran. By doing so, we seek to gather fundamental information regarding the stability of the stand and its resilience to environmental challenges.
Methods: In this research, a total of 500 sample trees with a diameter at breast height (DBH) of 7.5 cm or greater were randomly selected from the most abundant species present in the region. This selection was designed to encompass a wide range of diameter classes, from the smallest to the largest trees within the stand. Each individual tree was treated as a separate sample for the analysis. To calculate the height-diameter ratio, measurements of both the diameter at breast height and the total height of each tree were taken. The height-diameter ratio for the entire stand, as well as for each species, was computed by dividing the height of each tree by its diameter. This method allowed for a detailed assessment of how tree size correlates with stability across different species and diameter classes.
Results: The findings from this research indicated that the overall height-diameter ratio at the stand level was 54.31. When analyzed at the species level, the ratios were found to be 54.93 for maple, 55.04 for hornbeam, 54.63 for ash, and 52.64 for oak. These results suggest that the trees within this forest stand fall into a stable category regarding their height-diameter ratios. Further analysis revealed that the height-diameter ratio varied across different diameter classes, showing a consistent trend: the ratio decreased as the diameter classes increased. This trend implies that larger trees may be more susceptible to instability, which could have implications for forest management practices. Correlation analysis conducted during the study demonstrated a high, positive, and statistically significant correlation between tree height and the height-diameter ratio. Specifically, the oak and hornbeam species exhibited the strongest significant correlations, with values of 0.718 and 0.729, respectively. This strong correlation underscores the importance of tree height in determining the stability of the species within the forest stand.
Conclusion: The computation of the height-diameter ratio is vital for quantifying tree resistance to adverse environmental factors, such as snow, storms, and wind. Understanding this ratio is not merely an academic exercise; it has practical implications for forest management. By estimating the value of the height-diameter ratio, we can identify specific diameter classes where instability may occur for various tree species. This information is invaluable for future silvicultural planning and protection strategies. Effective management of forest stands requires attention to the spatial arrangement of trees within diameter classes, as well as the density of the stand. By regulating the critical values of height-diameter coefficients, we can enhance the stability of the stand and ensure that it remains resilient to environmental threats. The insights gained from this study can help inform conservation practices aimed at maintaining healthy and stable forest ecosystems. In summary, the relationship between tree height and diameter is a significant factor in understanding forest dynamics. This research highlights the importance of monitoring the height-diameter ratio as a tool for assessing tree stability and resilience. By integrating these findings into forest management practices, we can better prepare for and mitigate the impacts of environmental hazards on forest stands, ultimately contributing to the sustainability of these vital ecosystems.