1. Introduction
Analyzing forest stand structure is crucial for effective forest management, as it offers key insights for evaluating current conditions and developing future management strategies [
1]. Understanding forest structure is vital not only for restoration efforts and predicting the future forest states [
2] but also for maintaining ecosystem health and biodiversity [
2]. The structure of forest stands is crucial for maintaining forest health and species diversity, which significantly influences the biodiversity of forest ecosystems [
3]. Species diversity, an important element of forest structure, reflects changes within ecosystems and plays a vital role in overall biodiversity [
4].
One traditional forest management practice that exemplifies the importance of forest stand structure is the coppice system. This method utilizes the regenerative capacity of numerous broadleaved tree species, enabling them to sprout new shoots from stumps after harvesting (coppicing), thereby promoting natural regeneration and sustained forest structure. Coppice forests are typically harvested for local needs, with surrounding households often utilizing them for purposes such as shelter, cooking, and charcoal production. This system results in the development of multi-stemmed trees and diverse forest structures. The coppice system features relatively short rotation periods, typically between 15 and 20 years, extending up to 50–60 years depending on tree species and site conditions [
5]. Historically managed at the community level, coppice forests provide ecological and economic benefits such as rapid carbon sequestration, drought resilience, adaptability, and provision of diverse habitats and ecosystems [
6,
7]. Moreover, the structural diversity within coppice forests contributes to resilience against climate change and supports conservation efforts for threatened species, such as butterflies [
8] and moths [
9,
10], making them invaluable for conservation efforts.
In contrast, coppice-with-standard (CWS) forests maintain a certain density of standard trees, originating either from seeds or coppicing, within the coppice system. These well-regulated, non-coetaneous forests typically feature coetaneous coppices in the understory. CWS forests promote a diverse range of wood species and provide valuable resources such as grass forage for livestock in summer and foliage in winter. They also contribute to litter production and supply various cultural and economic ecosystems due to their diverse nature [
11,
12]. Light availability in CWS forests creates a mosaic of habitats that enhances biodiversity [
13,
14] by supporting both light-demanding and shade-tolerant plant species [
13,
15]. Furthermore, the retention of individual trees for timber production and the prevision of habitats for old-growth and dead-wood dwelling species significantly increase the ecological value of these forests [
10,
16]. Coppice forests play a crucial role in conserving biodiversity, supporting threatened butterflies, moths, and declining migratory birds of high conservation interest. Their biodiversity importance stems from the following: (i) a shifting mosaic of coupes with diverse ages and structures, creating high habitat diversity at the landscape scale, and (ii) the long-term continuity of open forest stages with warm microclimates. CWS further enhances biodiversity by retaining older trees, which provide habitats for old-growth and dead-wood species, including arthropods. Abandoning coppice management reduces plant species diversity. Beyond ecological value, coppiced forests are culturally significant, reflecting centuries of traditional management practices, tools, and customs [
17].
Numerous studies have examined the differences between coppice and coppice-with-standard (CWS) management systems concerning stand structure, woody species diversity, and dominant species. For instance, Kapm (2022) highlighted the significance of these systems in maintaining species diversity and stand structure in European forests [
17]. The study emphasized that the future of coppice management is closely tied to energy policies, as firewood remains a vital product [
17]. Similarly, research conducted in the Hyrcanian temperate forest of Golestan Province, Iran, focused on
Quercus macranthera across three habitats. The results suggest that particular stand structures enhance biodiversity and economic advantages in temperate forests [
2]. Vild et al. [
18] studied abandoned CWS oak forests in Central Europe, observing increased dominance of semi-light-demanding and shade-demanding tree species following stand structure restoration. This was particularly evident in heavily thinned plots, which saw an increase in light-demanding oligotrophic species, indicative of enhanced biodiversity. Meanwhile, native ruderal species also expanded significantly, though the presence of alien species remained relatively unchanged. Karamshahi et al. [
19] compared quantitative analysis and spatial structure models of Persian oak forests in a Mediterranean climate of Iran, finding greater Shannon (0.56 vs. 0.38) index in high forest compared to coppice systems. Aghabarati et al. [
20] investigated coppice forest stands in Fandughlou Forest (northwestern Iran), identifying
Fagus orientalis as the dominant species in one habitat and a combination of
Carpinus betulus and
Corylus avellana in another two habitats. The mean diameter at the breast height (DBH) of coppice forests was 14.3 cm, with a basal area averaging 23.5 m
2/ha. Researchers assessed the structure and diversity of coniferous forests with different management systems (coppice vs. CWS) in northwestern Iran, highlighting the importance of structural heterogeneity for biodiversity conservation. Their findings showed that the mean DBH of coppice forests was 10 cm, compared to 5 cm in CWS stands, with basal areas averaging 0.08 m
2/ha in coppice forests versus 0.52 m
2/ha in CWS forests. Bricca et al. [
21] examined how the structure of coppice forests affects understory plant diversity, emphasizing the importance of understanding the relationship between forest structure and understory diversity for sustainable forest management. In summary, understanding forest stand structure, particularly within coppice and CWS forests, is vital for successful forest management and biodiversity conservation. While coppice forests provide ecological and economic advantages, CWS forests provide a well-managed uneven-aged forest with high biodiversity value. In general, both forest systems contribute a wide range of ecosystem services. However, the differences between these systems have not been comprehensively studied in these forests. By analyzing the structure of forest stands, forest managers can make informed decisions to promote sustainable forest management and conservation efforts. However, it is crucial to recognize the impact of human activities on forest structure and other critical functions of these ecosystems, emphasizing the need for responsible management practices to protect and preserve biodiversity [
22].
The management of coppice and CWS forests in the Arasbaran region represents a significant intervention implemented in recent years. These mixed temperate forests have experienced significant changes due to traditional forest harvesting practices, which have altered forest stand structure and reduced resilience [
23]. Local uses of these forests include cutting trees for charcoal production, construction, cooking, and other necessities for nearby households. These activities have led to the formation of coppice forests over time, resulting in a high density of stems with small DBH, particularly at lower elevations. As a result, these forests often struggle to meet human needs sustainably. However, modern forest management practices, such as the transition to CWS forests, provide a balance between human needs and ecological benefits [
24]. Investigating the relationship between the forest structure and understory diversity in these forests provides valuable guides for sustainable forest management. The results of this research can inform management practices not only in the Arasbaran forests but also in similar forest ecosystems globally, promoting ecological health and human well-being. The principal objectives of this study were as follows: (i) to investigate the impact of coppice and CWS forest management approaches on species composition and stand structure; (ii) to gain a comprehensive understanding of the natural stand structure as a basis of strategies for optimal forest management and the conserving biological diversity, ecological dynamics, and overall stability; and (iii) to assess and compare biodiversity within these forest stands using various indices. According to the purpose of the research, this study assumes that the structural and quantitative characteristics of forest stands under coppice and CWS management are not significantly different and that the type of forest management does not significantly impact species diversity indicators. The uniqueness of this research lies in its focus on regional ecological development and the distinct ecological conditions of Iranian forests, characterized by their exceptionally high species diversity.
4. Discussion
4.1. Species Composition
The study findings reveal that
Q. macranthera was the dominant species across the study area. In the coppice forest,
C. orientalis and
A. campestre were the most abundant species, whereas in the CWS forest,
C. orientalis was the major species, along with
Q. macranthera and
A. campestre. These findings aligns with the observations made by Ghanbari et al. [
31], which found that
Q. macranthera dominated the oak coppice habitat, and
C. orientalis was the dominant species in the CWS habitat in Kalaleh and Vaygan sites in the Arasbaran forests.
Stand density is a critical structural parameter for assessing and predicting forest conditions [
32]. In this study, the coppice stand had a high density of 546 sprout clumps per hectare, indicating a dense stand structure. In contrast, the CWS habitat had a lower density of 421 sprout clumps per hectare, reflecting a semi-dense stand structure. Observations by Ghanbari et al. [
31] reported only 35 sprouts per hectare in the Kuran coppice habitat within the Arasbaran forests, highlighting the relatively lower density of that habitat compared to the present study area. Furthermore, these researchers reported woody species densities of approximately 318 and 569 individuals per hectare in two CWS stands located in the Vaygan and Kalaleh regions of the Arasbaran forests. The sprout clump density determined in the present study falls between these two habitat types, with fewer sprouts per sprout clump in the coppice forest than in the CWS stands. Notably, Rostamikia and Sagheb-Talebi [
33] reported an average of 3.86 sprouts per sprout clump in Hatem Meshgin-Shahr Reserve in Iran, a value comparable to the coppice stands in this study. The higher average height, DBH, and basal area observed in the CWS forest management system reflect a more mature and structurally diverse forest stand compared to the coppice system. This structural complexity holds ecological significance, as it provides a wider range of habitats for various species, particularly those reliant on vertical stratification and old-growth forest characteristics. Additionally, the increased DBH and basal area underscore the system’s enhanced carbon storage capacity, contributing to climate change mitigation efforts. From a practical standpoint, these findings illustrate how CWS systems can effectively balance biodiversity conservation with timber production, offering a flexible and sustainable approach to forest management. This balance is especially valuable in scenarios where ecological objectives must be harmonized with economic considerations, such as sustainable forestry or habitat restoration initiatives.
4.2. Diameter and Height Distribution
The average sprout diameter in the coppice (10.5 cm) and CWS (12.4 cm) stands suggests that these stands are relatively young in terms of diameter structure, indicating a uniform age class within the populations. This young diameter structure may result from traditional tree management practices, disturbances (e.g., human interventions and wildfire), and natural factors. The normal distribution of diameter dispersion curves in both the coppice and CWS stands further supports the similarity in age among sprout clumps. This contrasts with the findings from other studies that reported irregular diameter distributions in coppice stands; however, Ghanbari et al. [
25] observed a normal distribution pattern similar to that of the present study. Additionally, Danilović and Pantić [
34] emphasized the importance of diameter as a key characteristic in shaping the overall structure of forest stands. The absence of trees in the upper diameter classes, resulting from the lack of seed-based regeneration, presents structural challenges for these stands. The current study also showed that the average heights of trees in the coppice and CWS stands were 5.1 m and 6.4 m, respectively. These relatively low average heights likely reflect intense exploitation by local communities, which has altered the natural structure of these stands. The height distribution pattern indicates a concentration of sprouts within the central range, with fewer sprouts at both lower and upper extremes. By comparison, other researchers reported average stand heights of 4.3 m for the Kuran coppice habitat and 9.7 and 9.5 m for the Kalaleh and Vaygan CWS habitats in the Arasbaran forests [
32]. These researchers noted that the coppice habitat in their study had a shorter history of protection than the two CWS habitats.
4.3. Height Curves
The scatter plot of the point cloud in the coppice stands shows a distribution range of trees with low DBH and height, with a correlation coefficient of 0.27, indicating a weak relationship. In the CWS stands, the scatter plot suggests a more appropriate distribution range, with a higher correlation coefficient of 0.57. Previous studies have noted that a greater extension of the point cloud dispersion curve, extending to the right and upward, combined with a higher correlation coefficient, indicates a more favorable habitat [
2]. Accordingly, the CWS habitat appears more favorable than the coppice habitat. In both types of stands, the power model identified as the best non-linear regression model for estimating stand height, with coefficient of determination of 0.14 for coppice and 0.33 for CWS (
Supplementary Materials). Pourhashemi (2015) proposed the parabolic model as the best fit for height estimation, with a coefficient of determination of 0.62. The lower coefficient of determination observed in the present study suggests a weaker correlation between height and diameter variables of the sprouts, likely due to more extensive human exploitation and interference in the region [
35].
4.4. Stand Biodiversity
In this study, the average values of diversity, richness, and uniformity were higher in the coppice stands than in the CWS stands. These indices highlight the overall diversity of species within each management system, with mean diversity values notably greater for the coppice system than for the CWS system.
As Buckley and Mills [
36] noted, the higher diversity in coppice forests can be attributed to factors such as shorter cutting cycles, high spatial heterogeneity, a wider range of woody species, reduced windthrow risk, increased nutrient export, and limited fallen deadwood. Transitioning from the coppice and CWS management systems to standard forest management leads to a significant decrease in plant species diversity, shifts in species composition towards desirable forest species, and the decline or disappearance of light-demanding species. Vild et al. [
18] suggested that restoring CWS management could reverse these processes, supporting the survival of light-demanding species.
In recent decades, there has been increasing interest in reintroducing coppicing to protect endangered species and establish sustainable energy sources. Coppice forests are highly valued for their potential to support diverse biological communities. In regions where coppice forests have largely been converted to standard forests, reviving coppice management can enhance landscape diversity and maintain biodiversity, especially for species typically associated with coppice forests. Restoring these management systems contributes to environmental and biological stability. Numerous studies have shown that coppice and CWS management systems lead to greater species richness than in high forest with closed canopies. Consequently, these management practices facilitate high plant diversity, which, in turn, supports a variety of bird species, insects, and butterflies [
37].
The Arasbaran forests, with their extensive history of local exploitation, have experienced significant alterations in their natural structure, highlighting the need for further research to assess their current condition and guide restoration efforts. The scarcity of unaffected stands due to pervasive human intervention make this task especially urgent. Considering the potential transition from coppice stands to CWS and to standard stands, based on the unique attributes of each habitat, could be beneficial. Long-term management plans informed by research findings can enhance landscape diversity, protect endangered species, and enhance the environmental and biological stability of the region. These results highlight the importance of considering management systems’ impact on biodiversity, providing valuable insights for forest management and conservation. The significant differences in diversity indices emphasize the necessity for informed, data-driven decision-making to ensure the sustainable management of these ecosystems.
The PCA results demonstrated that species distribution is a key factor in distinguishing between the coppice and CWS management systems. Species such as F. excelsior, S. aucuparia, and C. sanguinea were closely associated with the coppice system, while L. caucasica, U. glabra, M. sieversii, and C. orientalis were more strongly linked to the CWS system. These patterns suggest that species distributions are significantly influenced by the type of forest management applied. Additionally, the CCA revealed that environmental factors also play a critical role in shaping species distributions within each management system. In the coppice system, elevation emerged as the most influential factor, with species such as R. canina and S. aucuparia showing sensitivity to changes in altitude. Conversely, in the CWS system, terrain aspect had the greatest influence, shaping the distribution of species like L. caucasica and U. glabra. Together, these findings highlight the intricate interplay between species traits and environmental factors in determining the distribution and success of species under different forest management practices. The PCA results emphasize that forest management strategies influence not only species presence and distribution but also structural attributes, diversity, and quantitative indices of tree species. Similarly, the CCA underscores that specific environmental factors drive species distributions differently in each management system, with elevation being pivotal in the coppice system and aspect being central to the CWS system. These insights suggest that optimizing forest management strategies requires integrating species–environment interactions into planning processes. By considering these dynamics, forest managers can make more informed decisions regarding forest regeneration, conservation, and species selection. Such an approach has the potential to enhance the sustainability and ecological integrity of forest ecosystems, aligning management practices with both biodiversity and productivity goals across different management regimes
Based on the CCA results presented in
Figure 7 and
Figure 8, the study highlights the critical role of environmental factors in shaping species distribution under different forest management systems. In the coppice system (
Figure 7), elevation emerged as the most influential environmental factor. Species such as
R. canina,
S. aucuparia,
S. graeca, and
Rubus sp. demonstrated a strong association with higher elevations. This finding underscores the sensitivity of these species to altitudinal gradients, which likely influences their ecological niches by affecting microclimatic conditions, soil properties, and water availability. In contrast, the CCA results for the CWS system (
Figure 8) revealed that aspect played a dominant role in determining species distribution. Species such as
L. caucasica,
U. glabra,
J. regia, and
Euonymus sp. showed a clear preference for specific terrain orientations. This suggests that aspect-related factors, such as sunlight exposure and wind patterns, significantly shape the ecological requirements and competitive dynamics of these species. The differentiation in key environmental drivers between the two management systems highlights the complexity of interactions between species and their habitats. Coppice systems, with their simpler structure, appear to rely heavily on elevation-related factors, whereas the structurally diverse CWS systems exhibit a more intricate relationship with terrain orientation. These findings align with previous studies emphasizing the role of environmental heterogeneity in promoting species diversity and forest resilience. From a management perspective, these results suggest that tailoring forest practices to the dominant environmental factors in each system could enhance ecological outcomes. For instance, prioritizing conservation efforts in higher elevation zones within coppice systems could help protect elevation-sensitive species, while managing slope and aspect in CWS systems could optimize habitat conditions for species dependent on specific terrain features. This nuanced understanding of species–environment relationships provides valuable guidance for developing adaptive forest management strategies that account for environmental variability and promote ecosystem sustainability.
4.5. Broader Implications for Forest Management in Other Regions
The findings from the Arasbaran forests provide valuable insights into the potential application and adaptability of CWS and coppice systems in other regions. The structural complexity observed in the Arasbaran CWS stands—characterized by higher basal area, greater DBH, and taller tree heights—mirrors the attributes desired for sustainable forest management in Mediterranean and temperate ecosystems. These systems are not only effective for timber production [
38] but also support essential ecological functions, such as carbon storage and soil stabilization. Similarly, the higher tree and shrub species diversity observed in the coppice system aligns with the conservation priorities of Mediterranean and temperate forests, where species-rich ecosystems are vital for resilience against climatic and anthropogenic pressures. The observed trade-offs between biodiversity and timber production in the Arasbaran study underscore the need for region-specific modifications to optimize these systems for both ecological and economic goals. By contextualizing the Arasbaran findings within global forest management practices, this study highlights the relevance of coppice and CWS systems in addressing diverse ecological and socio-economic needs. Future research should explore how these systems perform under varying climatic and management conditions in regions like the Mediterranean and European temperate zones. Such investigations will enhance understanding of their long-term ecological and economic benefits, supporting more informed and sustainable forestry practices globally.
5. Conclusions
This study underscores the significant impact of forest management systems on the structural characteristics and biodiversity of forest stands in the Arasbaran forests, Iran. The findings reveal that the CWS system is more effective in promoting forest growth and development, as evidenced by greater average height, DBH, and basal area. However, certain diversity indices were higher in coppice stands, highlighting trade-offs between structural complexity and species diversity under different management approaches. In the coppice system, the high stand density (546 sprout clumps per hectare) reflects a dense stand structure, while the CWS system exhibited a semi-dense structure with 421 sprout clumps per hectare. The average sprout diameters of 10.5 cm in the coppice system and 12.4 cm in the CWS system indicate relatively young and uniform stands across both systems. Statistical analyses confirmed significant differences between the systems in key parameters, including coppice shoot density, total height, DBH, and basal area. Furthermore, all species diversity indices, except Pielou’s evenness index, differed significantly between the two systems. These findings led to the rejection of the initial research hypothesis, emphasizing the distinct structural and biodiversity dynamics in coppice and CWS systems.
The results provide valuable insights for natural resource management and policymaking, particularly in balancing ecosystem services. Coppice forests, with higher tree and shrub species diversity, support essential ecosystem services such as water and soil protection, air purification, and water regulation. Conversely, CWS forests are better suited for wood production while maintaining conditions favorable for standard forest management. These differences highlight the need for management strategies tailored to specific ecological and economic goals.
Environmental factors, particularly elevation and aspect, emerged as critical determinants influencing species composition and habitat preferences within each management system. In the coppice system, elevation played a dominant role, shaping the distribution of species such as R. canina and S. aucuparia. In the CWS system, aspect significantly affected species like L. caucasica and U. glabra. These findings underscore the importance of incorporating species–environment interactions into forest management to enhance biodiversity, ecological sustainability, and regeneration practices.
The long-term effects of coppice and CWS management systems differ in terms of biodiversity, soil health, and carbon storage. Coppice systems, with periodic cutting and sprouting, enhance species diversity and regeneration but may lead to soil degradation and reduced organic matter over time if poorly managed [
39]. In contrast, CWS systems, characterized by continuous tree and shrub cover, create stable microclimatic conditions and improve soil structure, offering higher carbon sequestration potential. However, CWS systems can lead to the over-dominance of certain shrub species, suppressing tree regeneration and reducing long-term tree diversity. These dynamics emphasize the importance of adaptive management to balance ecosystem services and forest resilience.
Future research should explore the long-term impacts of these management systems on forest structure, diversity, and ecosystem services. Studies across different geographical regions and management histories can provide deeper insights into how coppice and CWS systems respond to varying conditions. Such research is crucial for designing sustainable forest management practices that optimize growth, diversity, and ecological integrity.