1- Semnan University
Abstract: (107 Views)
Background: The complexity of the vegetation structure is an important feature of natural ecosystems, often associated with higher ecological performance. Studies have shown that plant communities that are structurally more diverse are also more complex. However, the shape and overall nature of this relationship, as well as the mechanisms involved, are not well known. On the other hand, the assets and services of forest ecosystems have significantly declined due to destruction and deforestation in some parts of the country, particularly in mountainous landscapes. This study aims to evaluate the structural changes in forest stands affected by varying degrees of degradation in a mountainous ecosystem. The research focuses on analyzing structural indicators such as abundance, species composition, density, diameter at breast height (DBH), tree height, and the regeneration status of woody species. The primary goal is to achieve a better understanding of the human disturbance process and its effects on forest structure. Additionally, the study emphasizes providing recommendations and strategies for the sustainable management and restoration of degraded forest stands based on the findings.
Methods: This study was conducted in three stands with different composition, structure, and degrees of degradation in the Abr Forest of Shahroud, Semnan Province. In each stand, three square plots (100m×100m) were arranged along a transect of eight hundred meters. The regular equidistance between the plots was 150m to ensure the representativeness of the inventory area. The transects were parallel to each other and perpendicular to the general orientation of slope hillside. In each sample plot, the characteristics; species, diameter at breast height (D.B.H≥7.5 cm) of all trees was measured and recorded. For seedlings and saplings, the sub-plots with 2m ×2m established, within the main sampling plot. The regeneration characteristics of woody species were measured in three groups with height less than 0.3, 30-1.30m and more than 1.30 meter. Species diversity, composition, distribution of number and basal area in diameter classes and regeneration status were compared using one-way ANOVA test and Tukey's multiple comparisons at the 5% level according to the type of stand disturbance.
Results: The results of the research showed that 2838 individuals belonging to 11 woody species were observed in the study area. The distribution of species abundance varied among the forest stands. The structure of the stands exhibited a wide range of young and small-diameter individuals (D.B.H <30 cm) and a decrease in small and large individuals (D.B.H >55 cm) in all three stands. The moderate degradation stand had the most diversity and abundant regeneration of woody species. The distribution pattern of the number in the diameter classes of the studied stands shows a decreasing or semi-hyperbolic trend, as well as Uneven-aged natural stands, so that their population distribution curve follows an inverted J shape. Carpinus orientalis and Quercus macranthera were the most prevalent in the three stands. In intact and severe degradation stands, these two species constitute 60.5% (667 and 440 individuals) and 22.7% (250 and 165 individuals) of the total individuals under investigation, respectively. Also, The regeneration frequency of the studied stands was obtained with 335±89 (mean± standard deviation) seedlings and 132±35 (mean± standard deviation) sapling (in 4 m2).
Conclusion: The intensity of exploitation and harvesting in the environment with moderate disturbance and degradation was higher, while in the highly degraded stand, it was lower. However, the results indicate that the harvesting and exploitation of trees by local communities and even recreational users do not seem to have adverse effects on the abundance, structure, and regeneration of the studied stands. Instead, other factors such as illegal logging and trafficking, road construction, gas and electricity transmission routes, land-use changes, and possibly climate change may play a significant role in the degradation of these valuable stands. Based on the research results, improving the status of natural regeneration of native tree species through various afforestation methods is recommended. There is an urgent need for protection to ensure sustainable exploitation and management of the forest.
Methods: This study was conducted in three stands with different composition, structure, and degrees of degradation in the Abr Forest of Shahroud, Semnan Province. In each stand, three square plots (100m×100m) were arranged along a transect of eight hundred meters. The regular equidistance between the plots was 150m to ensure the representativeness of the inventory area. The transects were parallel to each other and perpendicular to the general orientation of slope hillside. In each sample plot, the characteristics; species, diameter at breast height (D.B.H≥7.5 cm) of all trees was measured and recorded. For seedlings and saplings, the sub-plots with 2m ×2m established, within the main sampling plot. The regeneration characteristics of woody species were measured in three groups with height less than 0.3, 30-1.30m and more than 1.30 meter. Species diversity, composition, distribution of number and basal area in diameter classes and regeneration status were compared using one-way ANOVA test and Tukey's multiple comparisons at the 5% level according to the type of stand disturbance.
Results: The results of the research showed that 2838 individuals belonging to 11 woody species were observed in the study area. The distribution of species abundance varied among the forest stands. The structure of the stands exhibited a wide range of young and small-diameter individuals (D.B.H <30 cm) and a decrease in small and large individuals (D.B.H >55 cm) in all three stands. The moderate degradation stand had the most diversity and abundant regeneration of woody species. The distribution pattern of the number in the diameter classes of the studied stands shows a decreasing or semi-hyperbolic trend, as well as Uneven-aged natural stands, so that their population distribution curve follows an inverted J shape. Carpinus orientalis and Quercus macranthera were the most prevalent in the three stands. In intact and severe degradation stands, these two species constitute 60.5% (667 and 440 individuals) and 22.7% (250 and 165 individuals) of the total individuals under investigation, respectively. Also, The regeneration frequency of the studied stands was obtained with 335±89 (mean± standard deviation) seedlings and 132±35 (mean± standard deviation) sapling (in 4 m2).
Conclusion: The intensity of exploitation and harvesting in the environment with moderate disturbance and degradation was higher, while in the highly degraded stand, it was lower. However, the results indicate that the harvesting and exploitation of trees by local communities and even recreational users do not seem to have adverse effects on the abundance, structure, and regeneration of the studied stands. Instead, other factors such as illegal logging and trafficking, road construction, gas and electricity transmission routes, land-use changes, and possibly climate change may play a significant role in the degradation of these valuable stands. Based on the research results, improving the status of natural regeneration of native tree species through various afforestation methods is recommended. There is an urgent need for protection to ensure sustainable exploitation and management of the forest.
Send email to the article author
| Rights and permissions | |
 |
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. |
