Stand Structure Research Articles

Effects of Stand Structure of Artificial Shelter Forest on Understory Herb Diversity in Desert-Oasis Ecotone

The relationship between the spatial structure of shelter forests and the diversity of understory herbaceous plants in desert–oasis ecotones is important for maintaining biodiversity indices and protecting the oasis ecosystem. In this paper, we explore the coupling relationship between tree layer structure (competition index, angle scale, neighborhood comparison, DBH, etc.) and understory herb diversity in the transition zone of shelter forest plots near oases and near deserts; in addition, we also aim to elucidate the dominant stand structure factors affecting herb biodiversity. The results indicated the following: A total of 13 herbaceous plant species were discovered in the transitional zone, with 11 species found near the oasis area and 4 species near the desert region. The Shannon, Simpson, and Pielou indices of understory herbaceous plants were significantly higher near the oasis area compared to the desert region. The Margalef index mean was higher in the oasis area compared to the desert region. Pearson and canonical correlation analyses revealed significant associations between specific stand structure indicators and diversity in the herbaceous layer. The results of the multiple linear regression analysis revealed that the competition index had a significant impact on the Shannon, Simpson, and Pielou diversity indices of the herbaceous layer in the understory of the shelterbelt forest near the oasis, with corresponding impact coefficients of 0.911, 0.936, and 0.831, respectively. The mingling degree was found to be the primary influencing factor for the Margalef index, with an impact coefficient of 0.825. However, in the understory of the shelterbelt forest near the desert, the neighborhood comparison ratio negatively affected the Shannon and Margalef indices, with impact coefficients of −0.634 and −0.736, respectively. Additionally, tree height negatively impacted the Simpson and Pielou indices, with impact coefficients of −0.645 and −0.677, respectively. In order to enhance the diversity of understory herbaceous species in the transitional zone and preserve the ecological system of the oasis, specific modifications to the forest structure and arrangement are essential. Pruning and thinning are necessary for shelterbelt forests located near desert regions, while shelterbelt forests near oases should use a suitable mix of tree species. These measures can help preserve or enhance the diversity of understory herbaceous plants.

The Relationship between Stand Structure and Tree Growth Form—Investigating the Effects of Selection Cuttings in Mountainous Mixed Beech Forests

Among forest management methods, selection cutting puts into practice applications that follow the processes that naturally occur in the ecosystem. The purpose of this research was to investigate the effects of selection cutting on the stand structural characteristics and growth form of trees. The effect of selection cutting was evaluated in terms of the frequency and standing volume of trees and deadwood, diversity of tree species indices, stand structural complexity index (SCI), height-to-diameter ratio (HDR) or slenderness index, and live crown ratio of trees (LCR). These were measured and estimated through a systematic random plot sampling in two adjacent parcels with different management histories (parcel A, managed using the selection cutting method, and parcel B, managed using the protected method and without cutting trees) in mixed beech forests in Northern Iran. The results showed that the standing volume, Shannon index, deadwood volume, and SCI index in parcel A were lower than in parcel B. The selection cuttings had no effect on the HDR value of the upper-storey trees, while it decreased the HDR value of the middle-storey and light-demanding trees (maple and alder) and increased the HDR value of the lower-storey and beech trees. Also, the results showed that as a result of the implementation of selection cuttings, the total LCR of the lower-storey trees increased, but the total LCR of the upper-storey trees decreased compared to the protected forest. Furthermore, the results showed that tree growth form (HDR and LCR) are related to the SCI of the stands. These results showed that the implementation of the single-selection method had simplified the structure of the stands; also, with the changes made in the growth form of trees, the possibility of snow and wind damage was increased, especially in young trees. It is necessary to prioritize the ecological values of forest deadwood, thick trees, biological diversity, and the resistance of these stands against snow and wind damage in the next cutting operations.

Vitality Structure of the Middle-Aged Northern Taiga Pine Forest Stands

On the example of the northern taiga pine (Pinus sylvestris L.) forests of the western Kola peninsula (67°30′–68°10′ N, 33°57′–34°21′ W) the vitality structure of the middle-aged forest stands was studied in the communities within the lichen, lichen-green moss and green moss groups of forest types (12 permanent sample plots). It has been established that the studied forest stands are characterized by a numerical predominance of moderately and severely weakened trees (total share of 55–70%), and of moderately weakened and healthy trees in terms of trunk volume (total share of 50–75%). The significant factors found to contribute into the formation of the middle-aged pine forest stands’ vitality structure are their density, the sum of the basal areas and the forest type. The density of the forest stand is the main contributor to the nature of the trees’ vitality differentiation. Three main types of pine vitality spectra were identified, differing in the value of the stand vitality index.

Scots pine stands in the Left-Bank Forest-Steppe of Ukraine

Abstract The article presents the results of the research on the features of Pinus sylvestris L. condition and productivity in forest stands of the Left-Bank Forest-Steppe of Ukraine (in Kharkiv and Sumy regions) for 2006–2021. The study was carried out using the ‘Forests of Ukraine’ Database as of 01.01.2017, and the results of field research at 30 temporary sample plots (TSP), 3 permanent sample plots (PSP) (in 2006–2018), and 13 monitoring plots (2009–2021). Generally accepted methods and new standards were used. The dynamics of forestry and evaluation indicators of Scots pine stands at sample plots were analyzed and compared with high-productive Scots pine stands. The characteristics of natural regeneration are given. It was revealed that the age structure of pine stands is not optimal: there is an excess of middle-aged stand areas. Changes in the structure and development of managed Scots pine stands with respect to changing environmental conditions were observed for 2009–2021. Studied forest stands showed a tendency for negative changes in stand structural characteristics related to regeneration and growth. Drought mainly in combination with even medium anthropogenic impact can further worsen the health status of Scots pine stands in lowland areas of the Left-Bank Forest-Steppe of Ukraine. Thus, the formulation of forest management measures to mitigate the impact of these stress factors is needed.

Komposisi Jenis dan Struktur Hutan di Taman Hutan Raya Dr. Moh. Hatta, Padang, Sumatera Barat

According to Law of Republic of Indonesia No. 5 of 1990, the Forest Park is a nature conservation area which collects natural and unnatural plants and animals. The composition and structure of stands can be used to estimate the density of trees in various diameter classes. This study aims to determine the composition and structure of the vegetation contained in the block protection, utilization, and collection. The research was conducted from January to February 2021 at Bung Hatta Forest Park Conservation Area Padang, West Sumatera. The research result show that dominant type found in the protection block for the tree’s level was Glochidion obscurum. In the utilization block, the dominant type called Pinus merkusii, then in the collection block dominated by Swietenia macrophylla. The diversity index value (H') on the three blocks is classified as the moderate with H' value between 1-2. Meanwhile, the wealth index is classified as the low with a value of R1 <3.5. The result also found that the pattern of species distribution is clumped. The stratification of Bung Hatta Forest Park Conservation Area’s crown is in the B and C stratum.
 Keywords: diversity index (H'), dominant type, composition, richness index (R1), vegetation structure

A novel model to evaluate spatial structure in thinned conifer-broadleaved mixed natural forests

In order to ensure the effective analysis and reconstruction of forests, it is key to ensure the quantitative description of their spatial structure. In this paper, a distance model for the optimal stand spatial structure based on weighted Voronoi diagrams is proposed. In particular, we provide a novel methodological model for the comprehensive evaluation of the spatial structure of forest stands in natural mixed conifer-broadleaved forests and the formulation of management decision plans. The applicability of the rank evaluation and the optimal solution distance model are compared and assessed for different standard sample plots of natural mixed conifer-broadleaved forests. The effect of crown width on the spatial structure unit of the trees is observed to be higher than that of the diameter at breast height. Moreover, the influence of crown length is greater than that of tree height. There are nine possible spatial structure units determined by the weighted Voronoi diagram for the number of neighboring trees in the central tree, with an average intersection of neighboring crowns reaching 80%. The rank rating of natural forest sample plots is correlated with the optimal solution distance model, and their results are generally consistent for natural forests. However, the rank rating is not able to provide a quantitative assessment. The optimal solution distance model is observed to be more comprehensive than traditional methods for the evaluation of the spatial structure of forest stands. It can effectively reflect the trends in realistic stand spatial structure factors close to or far from the ideal structure point, and accurately assesses the forest spatial structure. The proposed optimal solution distance model improves the integrated evaluation of the spatial structure of forest stands and provides solid theoretical and technical support for sustainable forest management.

Canopy structure and understorey light availability in Nothofagus and podocarp-broadleaf stands in a New Zealand forest

ABSTRACT The ability of some ectomycorrhizal fungi to access organic sources of nitrogen is known to influence decomposition, nitrogen mineralisation and soil carbon storage. The consequences for aboveground ecosystem structure and processes are less well-documented. We used the LAI-2200C Plant Canopy Analyzer to compare leaf area index and understorey light availability of ectomycorrhizal Nothofagus stands and arbuscular mycorrhizal podocarp-broadleaf stands growing on similar soils at a dry forest site in the Wairarapa district of New Zealand’s North Island. N. solandri was the sole overstorey tree in the three Nothofagus stands, and the ericaceous shrub Leucopogon fasciculatus was prominent in the understorey. The three podocarp-broadleaf stands were more diverse and more varied, the major contributors to basal area being Elaeocarpus dentatus, Hedycarya arborea, Cyathea dealbata, Carpodetus serratus and Dacrydium cupressinum. Leaf area index of Nothofagus stands averaged one unit lower (4.04) than that of neighbouring podocarp-broadleaf stands (5.11). Average light availability under Nothofagus stands (3.6–4.9%) was twice that beneath podocarp-broadleaf stands (1.6–2.1%). The lower leaf area index, greater light transmittance, and monodominance of Nothofagus stands probably reflects suppression of arbuscular mycorrhizal species by ectomycorrhizal short-circuiting of the nitrogen cycle. This study expands the evidence of positive feedback mechanisms stabilising ectomycorrhizal dominance in some forests.

Біотопи існування та живлення зубра в Національному природному парку Цуманська Пуща (Україна)

The conservation and restoration of the bison (Bison bonasus L.) is one of the fundamental issues of international importance in the Tsumanska Pushcha National Nature Park, Ukraine. The distribution of bison in the territory of the park and adjacent areas is associated with the specific requirements of the species regarding food and protective properties of the terrain. In spring, with the beginning of the growing season, the grass cover is thin and the amount of food is insufficient, so bison prefer swampy biotopes. In March–April, birch–alder and aspen–birch–alder stands provide optimal feeding conditions for the animals. Within the territory of spring distribution of bison, the biotopes they inhabit are represented by wet and fairly fertile sites (types C3 and C4,), as well as moist and fairly infertile pine site (type B3). Biotopes these animals inhabit during the spring–summer period (March–August) cover an area of about 1640 hectares, of which 350 hectares are within the national park, and the rest are part of the territory of the Muravyschensky and Sokyrychivsk forests of the Kivertsi Forestry State Enterprise. The territory of the forest districts is characterised by a mosaic structure of stands, alternating areas of broad-leaved and coniferous species, wetlands and grass glades with good feeding conditions for the animals. The animals have adapted to almost all types of forest biotopes. During the entire growing season, the trophic activity of bison is particulary high in pastures, forest clearings, and swampy meadows adjacent to woodlands. The main bison biotopes are located at a large distance from human settlements and characterised by poorly developed road network, low level of disturbance, and favourable living conditions. The current size of the bison population in the national park is 21 individuals, and the presence of calves and young animals is a sign of favourable conditions and positive population dynamics that may lead to further increase in the future. In order to minimise the impact of negative factors, relevant measures should be implemented to maintain the stability of the subpopulation, to protect the habitats of the animals, and to conduct active educational and informational activities in the park. The technologies of forest felling, harvesting of minor forestry products, and other forestry works must include elements aimed at preventing negative effects on bison.

The Effect of Urbanization on The Stand Structure of A Mangrove Forest in Likas Bay, Sabah Malaysia

The aims of this study were to determine the effect of urbanization on species composition, change to stand structure and tree species on the mangrove stand between the housing development and the river. Two (2) plots were established, with five (5) subplots each measuring 10m x 10m. Simpson’s Index, Shannon-Weiner Index, Shannon evenness and Important Value Index (IVI) were used to determine the diversity and abundance of tree species. There are 4 species found in both plots which are Avicennia alba, Avicennia marina, Rhizophora mucronata and Rhizophora apiculata. The most abundant species is the R. apiculata with an IVI of 86.99 percent (%). The Simpson’s Index value calculated for the forest was 0.75, while the value for the Shannon-Weiner (H’) was 1.38. This indicates the area has low diversity in mangrove trees. The Shannon evenness (E) was 0.99. This means the area is completely covered in standing trees. In this study, the stand structure was measured using tree Diameter at Breast Height (DBH), height and crown size. The data indicates that mangrove trees approaching the housing developments experienced a steady decrease in DBH, height, and crown size. Trees in the middle of the forest had the largest DBH and height. The DBH and height of trees approaching the river steadily decreased but had larger crowns compared to the other subplots. Whereas, water quality and the presence of sediments were two other additional aspects used to measure the impact of housing developments on mangrove forests. Urbanization projects do not leave any noticeable impact on the clearness of water in mangrove forests, but does for sediments. As a conclusion, urbanization project such as housing development do leave an impact on mangrove forests in the Likas bay, Malaysia. More future studies will shed more light on how housing developments impact mangrove forests

Влияние реконструктивной рубки в лиственно-еловом древостое на корневую конкуренцию пород

The predominance of mixed forest stands in a productive forest fund, which is located in the middle taiga subzone of Northwest Russia, determines the relevance of an investigation of the growth and development characteristics of the trees. In secondary stands, created by an extensive human consumption of primary spruce stands, spruce trees are generally presented in a minor quantity. The recovery of their dominance is an urgent economic and ecological issue. Despite the unity of approaches concerning the maintenance of deciduous-spruce forests, the research characteristics on the structure of the root systems differ considerably along with age and geographical position. This article investigates a root system competition between spruce and deciduous species in a 70-year-old blueberry-type forest that was 100 thinning by a reconstructive cutting 35 years ago. The mass of fine roots and their distribution in the upper solid layers were examined by the method of soil monoliths in the mixed stands with different proportions of spruce. The numerical characteristics of the stands were determined by the results of a regular complete enumeration on the trail plots. Besides, the tree diameters were measured around the circular plots, which were made for the collection of the monoliths. The records were made on the dynamics of changes in forest floor thickness and vegetation. The relationship between the underground and elevated parts of the stands was explored. It was shown that the roots of spruce can occupy the same ecological niche as the roots of deciduous species. A correlation analysis revealed a statistically significant relationship between the mass of fine spruce roots and the competitive influence of deciduous species, the proportion of spruce in the stand, and its current volume increment. There was a significant difference in spruce root mass under joint growth with birch and aspen. Therefore, it was concluded that this phenomenon has a complex nature. Namely, the mass of the spruce roots has a direct dependency on their closeness to the maternal trees in combination with the spatial heterogeneity of the organic soil layers. The gained findings are important for the regulation of the composition and structure of the mixed deciduous-spruce stands for growing sustainable stands with a high economic value. For citation: Karpechko A.Yu., Sinkevich S.M. Influence of Reconstructive Cutting in Deciduous-Spruce Stands on Root Competition of Species. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 99–112. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-99-112

Select or Not? Comparing the Impact of Selective and Schematic Thinning on Scots Pine Tree Growth and Stand Structure

The first commercial thinning usually entails a high cost in harvest operations and a low resulting income. From a practical forestry perspective, a schematic spatial selection might be more efficient than a selective approach. Therefore, this study aimed to compare basal area, total and standing volumes, and periodic annual increment (PAI), as well as stand structure, between different thinning designs (selective and schematic thinning) and strategies (thinning once or more than once) over a long-term monitoring period of Scots pine (Pinus sylvestris) plantations in Sweden. We also evaluated the relevancy of distance-dependent competition indices (CIs) in individual tree growth models by comparing growth model predictions with the use of distance-dependent and distance-independent CIs. Despite higher heterogeneity in schematically thinned stands, there were no significant differences in standing and total volumes (m3·ha−1) among treatments in the short or long term. Although the inclusion of a distance-dependent CI improved the model slightly, distance-independent models predicted diameter growth just as effectively. Schematic thinning could be a viable option for a first commercial thinning or one-time thinning if, at least, one more thinning is included in the management plan, or if the motivating interest is mainly volume.

Towards Intricate Stand Structure: A Novel Individual Tree Segmentation Method for ALS Point Cloud Based on Extreme Offset Deep Learning

Due to the complex structure of high-canopy-density forests, the traditional individual tree segmentation (ITS) algorithms based on ALS point cloud, which set segmentation threshold manually, is difficult to adequately cover a variety of complex situations, so the ITS accuracy is unsatisfactory. In this paper, a top-down segmentation strategy is adopted to propose an adaptive segmentation method based on extreme offset deep learning, and the ITS set aggregation strategy based on gradient change criterion is designed for the over-segmentation generated by random offset, and the precise ITS is realized. Firstly, the segmentation sub-plot is set as 25 m × 25 m, the regional point cloud and its treetop are marked, and the offset network is trained. Secondly, the extreme offset network is designed to carry out spatial transformation of the original point cloud, and each point is offset to the position near the treetop to obtain the offset point cloud with a high density at the treetop, which enhances the discrimination among individual trees. Thirdly, the self-adaptive mean shift algorithm based on average neighboring distance is designed to divide and mark the offset point cloud. Fourthly, the offset point cloud, after clustering, is mapped back to the original space to complete the preliminary segmentation. Finally, according to the gradient change among different canopies, the ITS aggregation method is designed to aggregate adjacent canopies with a gentle gradient change. In order to investigate the universality of the proposed method on different stand structures, two coniferous forest plots (U1, U2) in the Blue Ridge area of Washington, USA, and two mixed forest plots (G1, G2) in Bretten, Germany, are selected in the experiment. The learning rate of the deep network is set as 0.001, the sampled point number of the sub-plot is 900, the transformer dimension is 512 × 512, the neighboring search number of points is 16, and the number of up-sampling blocks is 3. Experimental results show that in mixed forests (G1, G2) with complex structures, the F-score of the proposed method reaches 0.89, which is about 4% and 7% higher than the classical SHDR and improved DK, respectively. In high-canopy-density areas (U2, G2), the F-score of the proposed method reaches 0.89, which is about 3% and 4% higher than the SHDR and improved DK, respectively. The results show that the proposed method has high universality and accuracy, even in a complex stand environment with high canopy density.

Chronic Exclusion of Fire in Longleaf Pine Stands of an Urban Interface: The University of West Florida Campus Ecosystem Study

The dependence of longleaf pine (Pinus palustris) ecosystems on fire is well-understood, and the anthropogenic alteration of fire cycles within its natural range has contributed to its decline. This has been increasingly exacerbated in areas of urban interfaces, wherein the use of prescribed fire can be problematic. The purpose of this study—the University of West Florida Campus Ecosystem Study—was to examine the effects of fire exclusion on longleaf pine in the unique urban interface of a university campus. This was an interconnected series of investigations on the main campus and three associated natural areas that comprised remnant longleaf stands following the cessation of widespread longleaf pine harvesting—120 years ago. This period of chronic fire exclusion allowed for a distinct shift in the stand structure and composition. The open, savanna-like structure of fire-maintained longleaf stands has transitioned into closed-canopy forests with the increased prevalence of southern evergreen oaks (especially live oak—Quercus virginiana) and Magnolia spp., resulting in the complete absence of longleaf regeneration. Fire exclusion also appeared to decrease soil fertility. The significant variation in the mean age of longleaf pine stems on the main campus; natural areas suggest that these natural areas were likely under separate ownership with contrasting land-use history prior to its purchase by the State of Florida for campus construction in 1963.

Stand Structure Beats Age for Ground Cover Vegetation in Ageing Hemiboreal Scots Pine and Norway Spruce Stands

Intensifying forest management and a reduction in the rotation period necessitates the development of intensive biodiversity conservation strategies, such as the triad concept, which aims at ensuring habitat connectivity. Such an approach depends on the relationships between biodiversity components and manageable stand characteristics. Mostly, the biological value of stands has been associated with age, although stand structures, which are often intercorrelated with age, might be of primary importance. The relationships between ground cover vegetation, which is a principal component and indicator of the biological value of temperate conifer forests, and stand characteristics were assessed in pre-harvesting/harvesting age and old-growth coniferous stands in the eastern Baltic region (Latvia). The old-growth stands were nearly two times older than the pre-harvesting/harvesting age stands. Both stand groups showed generally similar ground cover flora, though ground cover vegetation showed higher variability in the old-growth stands. The principal gradients of ground cover vegetation were related to light, site fertility, and structural diversity, as well as the degree of deciduous (particularly Betula spp.) admixture in a tree stand. Considering the explicit contrasts, stand age did not affect ground cover vegetation, implying the principal effects of stand structure, which are manageable characteristics. This implies the potential for specific management to aid the ecological connectivity of stands in commercial forest landscapes.

Relative Humidity, Soil Phosphorus, and Stand Structure Diversity Determine Aboveground Biomass along the Elevation Gradient in Various Forest Ecosystems of Pakistan

The direct effects of relative humidity and soil on aboveground biomass (AGB) versus the indirect effects mediated by stand structural diversity remain unclear in forest ecosystems across large-scale elevation gradients. Forest inventory data containing 15,260 individual trees and 104 tree species from 200 forest plots were collected. The result shows that the relative humidity, elevation, and Coefficient of Variation of Diameter at breast height (CVD) significantly influence AGB in the Tropical Thorn Forest (TTF). Regarding elevation, CVD was positive and significant, and relative humidity and SR negatively impacted AGB in sub-tropical broad-leaved forests (STBLF). In moist temperate mixed forests (MTMF), soil phosphorus and CVD have a significant positive impact, while relative humidity, elevation, and SR negatively influence AGB. Elevation and CVD have positive, while SR and soil phosphorus have a negative and insignificant effect on AGB in Dry Temperate Conifer Forests (DTCF). Soil phosphorus and relative humidity positively affected AGB (β = 0.021), while elevation, CVD, and SR negatively affect AGB in dry temperate, pure pine forests (DTPPF). Relative humidity and soil phosphorus have a positive direct effect on AGB in multi-species forests. The current study suggests that AGB primarily depends on relative humidity, soil phosphorus, and elevation in different forest types.

Composition, Structure, and Carbon Stock of Tree in the System: Teak-Based Agroforestry in Gemawang Wonogiri Village

Background: The teak-based agroforestry system in Gemawang Wonogiri Village has the potential for various types of constituent tree vegetation that can act as carbon stock stores. This research was conducted considering the limited research on teak-based agroforestry systems, especially in the Wonogiri area. This study aims to provide information on tree vegetation's composition, structure, and diversity and determine the potential carbon stocks of tree vegetation standing in teak-based agroforestry systems. Methods: The research method used a 20 x 20 m2 plot of 1 ha, and the plots were placed using a purposive sampling approach. Results: Found nine species of tree vegetation from 8 families with 271 individuals ha-1. The species of teak tree (Tectona grandis) has the highest INP of 81.56 %. The Diversity Index is moderate, with a value of 1.79, and the Dominance Index is low at 0.21. The amount of carbon stored in tree stands is 45.71 MgC ha-1. Conclusions: This research can give information and points of reference about the structure and composition of stands in agroforestry systems and their potential to store carbon stocks. The research data is useful for the community as a source of information regarding the condition of the agroforestry area in Gemawang Village so that they can make optimal use of the area by developing suitable vegetation.

Vegetation composition, diversity, stand structure, and carbon storage of Lolkisale Village Land Forest Reserve in the Northeastern part of Tanzania

Abstract. Mwakalukwa EE, Mwakisu A, Madundo S, Maliondo SMS. 2023. Vegetation composition, diversity, stand structure, and carbon storage of Lolkisale Village Land Forest Reserve in the Northeastern part of Tanzania. Nusantara Bioscience 15: 79-90. Little is known about the effects of human activities on the condition of the Lolkisale Village land Forest reserve located in Monduli District, Arusha region, in the northeastern part of Tanzania. This study assessed the status of woody species diversity, composition, structure, and available potential of the forest on carbon storage. The vegetation data were collected from 33 concentric sample plots of 5 m, 15 m, and 20 m radius laid systematically across the forest area of 960 ha. A total of 58 plant species belonging to 30 families were identified. Diversity indices have indicated a high woody species diversity in the forest reserve. The most important species were Commiphora schimperi (O.Berg) Engl., Dombeya rotundifolia (Hochst.) Planch., Acacia tortilis (Forssk.) Hayne, and Combretum molle R.Br. ex G. Don. Stand structure comprises 190 ± 117 stems ha-1, basal area of 7.68 ± 5.17m2ha-1 and standing volume of 64.04 ± 45.85 m3ha-1, while the mean above-ground carbon stocks and the mean below-ground carbon stocks were 19.55 ± 13.38 Mg C ha-1 and 3.91 ± 2.68 Mg C ha-1 respectively. Generally, the reserve was found to be in good condition. The observed high diversity of woody species signifies the importance of legally protecting this area as a village land forest reserve. In addition, quantifying other carbon pools, such as soil, dead wood, and surface litter, should be considered for estimating this forest's total carbon stock potential. In this regard, measures to control the use of the forest as a grazing area would be useful to allow new regrowth and young trees to attain maturity stages without being interfered with by the livestock.

Analysis of the Relative Importance of Stand Structure and Site Conditions for the Productivity, Species Diversity, and Carbon Sequestration of Cunninghamia lanceolata and Phoebe bournei Mixed Forest.

Forest stand structure (the characteristics and interrelationships of live trees) and site conditions (the physical and environmental characteristics of a specific location) have been linked to forest regeneration, nutrient cycling, wildlife habitat, and climate regulation. While the effects of stand structure (i.e., spatial and non-spatial) and site conditions on the single function of Cunninghamia lanceolata and Phoebe bournei (CLPB) mixed forest have been studied in previous studies, the relative importance of stand structure and site conditions in terms of productivity, species diversity, and carbon sequestration remains unresolved. In this study, a structural equation model (SEM) was adopted to analyze the relative importance of stand structure and site conditions for the forest productivity, species diversity, and carbon sequestration of CLPB mixed forest in Jindong Forestry in Hunan Province. Our research demonstrates that site conditions have a greater influence on forest functions than stand structure, and that non-spatial structures have a greater overall impact on forest functions than spatial structures. Specifically, the intensity of the influence of site conditions and non-spatial structure on functions is greatest for productivity, followed by carbon sequestration and species diversity. In contrast, the intensity of the influence of spatial structure on functions is greatest for carbon sequestration, followed by species diversity and productivity. These findings provide valuable insights for the management of CLPB mixed forest in Jindong Forestry and have significant reference value for the close-to-natural forest management (CTNFM) of pure Cunninghamia lanceolata forests.

Stand Structure Management and Tree Diversity Conservation Based on Using Stand Factors: A Case Study in the Longwan National Nature Reserve

The management of stand structure and the protection of species diversity are crucial to forest ecosystem service functions. Changbai Mountain is one of the three major forest regions in Northeast China, and understanding the characteristics of stand structure and the allometric relationship between stand structure variables and the correlation between stand factors and species diversity is the basis for achieving effective forest management and ecological function improvement. In this study, the typical deciduous broad-leaved mixed forest and coniferous and broad-leaved mixed forest of the Longwan Nature Reserve in the Changbai Mountain were taken as the research objects, and the stand structure and diversity were investigated in detail. Allometric growth equations were established using the breast height diameter (DBH), tree height, and crown width of the main dominant species. Pearson correlation analysis was conducted on the stand structure and diversity of the forest community. The experimental results showed that young forests with small diameters and small individuals were the main part of the stands. Optimal allometric growth models of the main tree species (Acer mandshuricum, Ulmus davidiana var. japonica, Juglans mandshurica, Acer mono, and Tilia amurensis) were 0.807D0.646, 0608D0.381H0.390, 0.502D0.533H0.295, 0.795D0.540H0.157, and 0.541D0.484H0.301, respectively, with R2 values ranging between 0.6 and 0.8, indicating a good fit for the models. Furthermore, tree density, crown width, and DBH were the main factors affecting tree diversity. The research results will provide theoretical support for the efficient management of forest stand structure and diversity conservation in the Longwan Reserve.

Short-Term Effects of Anthropogenic Disturbances on Stand Structure, Soil Properties, and Vegetation Diversity in a Former Virgin Mixed Forest

Despite the sharply growing interest in the disturbances occurring in primary forests, little is known about the response of European virgin forests to anthropogenic disturbance. The present study investigated the effect of the first silvicultural interventions that took place nine years earlier in a former virgin forest (FVF). Changes in the stand structure, environmental characteristics, and diversity of ground vegetation were studied in comparison with a nearby virgin forest (VF), both consisting of a mixture of European beech and silver fir. While the tree density did not differ significantly between the two forests, the number of large trees, the basal area, and the stand volume were significantly reduced in the FVF. The deadwood volume was twice as great in the VF as in the FVF and was found in both forests, particularly from silver fir. Despite significantly better light conditions in the FVF, natural regeneration was not significantly higher than in the VF. However, a slight improvement in the proportion of silver fir and other tree species into total regeneration was reported. The soil temperature was significantly higher in the FVF, independent of the measurement season, while the soil moisture showed a higher value in the VF only in spring. The FVF is characterized by a greater soil CO2 emission, which is especially significant in summer and fall. The diversity of the ground vegetation did not yet react significantly to the silvicultural intervention. These preliminary findings are important in drawing suitable forest management practices that need to be applied in mixed beech–silver fir stands, especially in terms of maintaining species diversity. However, the short time frame since the intervention obliges further research on this VF–FVF pair over the next 10–20 years, at least regarding silver fir dynamics.