Stand Structure Research Articles

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.

Stand structure of Central European forests matters more than climate for transpiration sensitivity to VPD

Abstract Temperature rise and more severe and frequent droughts will alter forest transpiration, thereby affecting the global water cycle. Yet, tree responses to increased atmospheric vapour pressure deficit (VPD) and reduced soil water content (SWC) are not fully understood due to long‐term tree adjustments to local environmental conditions that modify transpiration responses to short‐term VPD and SWC changes. We analysed sap flux density (SFD) of Fagus sylvatica, Picea abies, Pinus sylvestris and Quercus ilex from 25 sites across Europe to understand how daily variation in SWC affects the sensitivity of SFD to VPD (βVPD) and the maximum SFD (S95). Furthermore, we tested whether long‐term adjustments to site climatic conditions and stand characteristics affect βVPD and S95. The studied species showed contrasting βVPD and S95 with the largest values in F. sylvatica, followed by Q. ilex, which surpassed the two conifers that showed low βVPD and low S95. We observed that βVPD and S95 dropped during days of low SWC in F. sylvatica, P. sylvestris and Q. ilex, but not in P. abies. Both βVPD and S95 were driven by tree height, and the temperature and precipitation at the sites. However, stand basal area was the most important driver of βVPD and S95, explaining 30% of their total variance. Synthesis and applications: A future warmer and drier climate will restrict tree transpiration and thereby heavily affect the soil–plant‐atmosphere coupling. However, the effect of basal area, being the largest driver of tree transpiration sensitivity to vapour pressure deficit across a broad range of conditions, provides the opportunity to pre‐adapt European forests to future climate conditions. While stand thinning can increase the soil water availability for remaining trees, it also increases transpiration sensitivity to high air temperatures and may thereby amplify tree vulnerability to heat and drought.

Stand Structure and Species Composition of Community Forests under Livelihood Transition in Two Villages in the Inle Lake Region, Myanmar

Stand Structure and Species Composition of Community Forests under Livelihood Transition in Two Villages in the Inle Lake Region, Myanmar

Stand Structure and Dynamics of the Naturally Managed Oak-Dominated Forests and Their Relation to Environmental Variables in Swat Hindu Kush Range of Pakistan

Although oak woodlands are a characteristic landscape component in the Swat Hindukush Mountain ranges, little is known about their current or historical stand population structure and regeneration dynamics related to environmental variables. Therefore, the present study assessed the stand structure, regeneration status, and relationship of oak communities with environmental variables. The study assessed 30 oak-dominated forest sites using the quadrates method, sampling 300 quadrates for evaluating the phytosociological and environmental variables. The stand structures of forests were dominated by four oak species, i.e., Quercus incana, Quercus baloot, Quercus dilatata, and Quercus semecarpifolia, distributed along with the elevation. The lower elevation stand structures were most diverse and dominated by Q. incana, having higher stand parameters, i.e., importance value index, basal area, and density. In contrast, the higher-elevation stand structures were dominated by Q. semecarpifolia, having stand parameters in moderate measures, while those at intermediate elevations have lower stand parameters. The environmental variables were negatively correlated with the stand structures, i.e., elevation (r = −0.51), precipitation (r = −0.47), and relative humidity (r = −0.77), whereas soil nutrients such as Potassium concentration have a significant negative relation with stands structure (r = −0.66) indicating their vital role in sustaining the oak communities. The communities were fairly regenerated, with an age structure between 12–36 years, indicating young communities. These results concluded that the observed wide range of variability in stand characteristics reflects the mechanisms that have shaped them. The recent anthropogenic factors, i.e., military operations and natural hazards such as the flood of 2010, have deliberately affected the communities under natural restoration.

Woody species diversity, composition, structure and carbon storage of a dry evergreen montane forest of Essimingor Nature Forest Reserve in Tanzania

Abstract. Mwakalukwa EE, Mwakisu A, Maliondo SMS. 2023. Woody species diversity, composition, structure and carbon storage of a dry evergreen montane forest of Essimingor Nature Forest Reserve in Tanzania. Intl J Trop Drylands 7: 26-36. The biodiversity status of flora and fauna of many forests found on small protruding and isolated hills in most parts of dry areas in Tanzania is largely less studied. Their contribution to climate mitigation options also remains largely unknown. This study assessed the woody species diversity, composition, structure and carbon stocks potential of a dry evergreen montane forest of Essimingor Nature Forest Reserve in Tanzania. The vegetation data were collected from 23 concentric sample plots of 5m, 15m, and 20m radius laid systematically across the entire forest area of 6,100 ha. A total of 54 trees and shrubs species belonging to 29 families were identified. Diversity indices indicated the forest to have a high diversity of woody species. The most important species were Cassipourea malosana, Diospyros abyssinica and Drypetes natalensis. Stand structure comprised 288±173 stems ha-1, basal area of 11.47±7.23 m2ha-1 and standing volume of 27.3±16.3 m3ha-1. The mean above-ground and below-ground carbon stocks were 56.93±34.60 Mg C ha-1 and 34.71±19.72 Mg C ha-1, respectively. The observed high species diversity and carbon density signify the importance of conservation efforts bestowed in this reserve. Quantification of other carbon pools for estimation of the total carbon stock potential of this forest is recommended.

Vegetation composition, diversity, stand structure and carbon stock of a dry evergreen montane forest of Lendikinya forest reserve in Tanzania

Abstract. Mwaluseke ML, Mwakalukwa EE, Maliondo SMS. 2023. Vegetation composition, diversity, stand structure and carbon stock of a dry evergreen montane forest of Lendikinya forest reserve in Tanzania. Biodiversitas 24: 551-562. There is limited information on woody plant diversity and vegetation patterns in African dry forests, particularly in East Africa, and hence increasing the interests in understanding species composition, diversity, and structural attributes of catchment forest reserves found in Tanzania. Moreover, tree species composition, species richness, and carbon stock are not well documented in most montane forests in the region, apart from Ethiopia. Their potential in terms of carbon storage is also important for understanding their productivity and the extent to which they can be used in mitigating the effects of climate change. This study assessed vegetation composition and diversity, stand structure and potential carbon stocks of Lendikinya Forest Reserve, a dry evergreen montane forest located in Monduli District in Tanzania. A total of 56 concentric circular plots with subplots of 2 m, 5 m, 10 m, 15 m and 20 m radii were used to collect woody species data on standing trees and stumps across the entire forest of 3,689 ha. A total of 79 species belonging to 36 families were identified. Drypetes natalensis (9.2%), Diospyros abyssinica (7.1%) and Dombeya rotundifolia (6.5%) were the most important species as per the Importance Value Index (IVI). The diversity indices have indicated the forest reserve to have a high diversity of woody species. Stand structure comprises 1,398 ± 679 stems ha-1, basal area of 11.42 ± 5.41 m2ha-1and standing volume of 54.47 ± 24.1 m3ha-1 while the mean carbon stocks were 16.04 ± 7.7 t C ha-1. The alarming disturbances stress the urgent need for increased conservation efforts in order to protect the existing biodiversity and increase carbon storage and enhance water conservation in the reserve.

Impact of stand- and landscape-level variables on pine wilt disease-caused tree mortality in pine forests.

Pine wilt disease (PWD) outbreaks have affected extensive areas of South China's forests, but the factors explaining landscape patterns of pine mortality are poorly understood. The objective of this study was to determine the relative importance of stand structure, topography, landscape context, and beetle pressure in explaining PWD severity. During 2020-2021, we identified 66 plots based on mapped PWD infestation severity. We built PWD infestation maps for 2019-2021 through field surveys. Stand structure and topography were obtained from Forest Resources Management 'One Map' and elevation raster data. We then used 'One Map' and PWD infestation maps to determine landscape context and beetle pressure variables at different spatial scales. The relative importance of 12 explanatory variables was analyzed using multi-model inference. In this study, we show that: (i) 1 km was the best spatial scale related to pine mortality, and (ii) models including landscape context and beetle pressure were much better at predicting pine mortality than models using only stand-level variables. Landscape-level variables, particularly beetle pressure, were the most consistent predictors of subsequent pine mortality within susceptible stands. These results may help forest managers identify locations vulnerable to PWD and improve existing strategies for outbreak control. © 2023 Society of Chemical Industry.

Stand Structure Dynamic of Logged Over Forest after Selective Timber Harvesting in Boven Digoel, Papua

Logged-over natural forest has a different stand structure and composition from primary natural forest due to logging activities. This study aimed to examine forest dynamics (upgrowth, ingrowth, and mortality) of the logged-over forest in PT. Tunas Timber Lestari (TTL) Papua in both stands with and without treatments. The data used in this study were based on the measurement in the Permanent Measurement Plots (PUP) for ten years. This study grouped data into five diameter classes of 10 cm intervals and three wood species groups (meranti timber, mixed timber, and non-commercial timber). Data analysis was carried out by forming a stand structure model and calculating the rate of ingrowth, upgrowth, and mortality. The stand structure model for each species group in stands with treatment had a significant R² value compared to those without treatment. The average ingrowth rate in the stands with treatment was smaller than without treatment. The values of upgrowth varied with the increase in diameter classes for both stands with and without treatments. The mortality rate in stands without treatment tended to be higher, especially in mixed timber and non-commercial timber groups. In contrast, in the meranti timber group, the mortality rate mostly occurred in the stands with treatment. The stand structure models resulting in this study can be used as important information in determining appropriate silvicultural options for forest stands. Keywords: Forest dynamics, logged-over forest, meranti, selective logging

Old forest structural development drives complexity of nest webs in a naturally disturbed boreal mixedwood forest landscape

Structural complexity generated by forest development processes and tree species compositional changes provide key habitat features for vertebrate communities that rely upon tree size and decay processes for foraging, denning or nesting. Complexity of forest structure in old stands could not only be key for harboring increased taxonomic species diversity but also greater functional diversity through more complexity in networks of tree cavity dependent species. Using a nest web approach that hierarchically links cavity-bearing trees with cavity formation agents (natural decay processes and avian excavators) and cavity users (non-excavator species), we compared network characteristics of nest webs along a time since fire gradient in a naturally disturbed boreal mixedwood forest landscape in eastern North America. Since 2003, twelve 24 to 40 ha plots ranging from 61 to more than 245 years after fire were surveyed at the Lake Duparquet Research and Teaching Forest in Abitibi, Quebec, Canada to detect active nesting, and denning cavities. We found that network complexity both in terms of number of vertebrate species and number of interactions among species, increased along the age gradient and was significantly higher in the older stands than predicted by chance. Whereas cavity-nesting communities in old forests used a higher diversity of tree species over a wide range of decay stages, trembling aspen remained a key cavity-bearing tree throughout the age gradient. Woodpeckers were the main cavity formation agents whereas less than 1% of cavities originated from natural decay. The structural development of older forests is thus a driver for functional diversity in cavity-using vertebrate communities through higher interaction richness in nest webs, among cavity-bearing trees, excavators and non-excavating users. The pivotal contribution of the entire gradient of old forest cover types to the overall complexity of nest webs in the boreal mixedwood zone is also a key for the resilience of the cavity-using vertebrate community to natural disturbances. We discuss how such resilience may be compromised by even-aged industrial timber harvesting with short rotations that shifts the age structure of boreal landscapes toward regenerating and young pole forests whereas old forest cover types become below their historical range of variability.

Forest management plans as data source for the assessment of the conservation status of European Union habitat types

Natura 2000 is a European network of protected sites that should enable natural habitats to be maintained or restored at a favorable conservation status. Progress toward this objective must be periodically reported by states members of the European Union. We investigated how forest management plans might provide data to support the reporting. The study was done in the forests of the Dolomites and Venetian Prealps, Italy. Here, about 200 forest management plans, divided into several forest compartments, have been drawn up and revised every 10–15 years. Stand structure variables were retrieved from past (OR, 1970–1980) and more recent revisions (NR, 2000–2010) of 331 forest compartments ranging between 0.35 and 53.1 ha. In the beech and spruce forest habitat types (coded 9130 and 9410 in Annex I of the Directive 92/43/EEC, respectively), we found an increase from OR to NR in the density of large trees (from 32 to 46/ha and from 31 to 50/ha, respectively for the two habitats), basal area (from 27.3 to 31.5 m2/ha and from 31 to 34.5 m2/ha), mean diameter (from 34.1 to 36.2 cm and from 33.9 to 36 cm) and Gini index (from 0.35 to 0.37 and from 0.33 to 0.36). Pursuant to the Directive 92/43/EEC, the conservation status of these two habitat types should be taken as “favorable” with regards to the criterion related to the habitats’ specific structure and functions that are necessary for its long-term maintenance. We conclude that forest management plans provide a great portion of the information needed for assessing and monitoring the conservation status of forest habitat types in the Natura 2000 framework.

Plant functional trait diversity and structural diversity co-underpin ecosystem multifunctionality in subtropical forests

Tree species diversity is assumed to be an important component in managing forest ecosystems because of effects on multiple functions or ecosystem multifunctionality. However, the importance of tree diversity in determining multifunctionality in structurally complex subtropical forests relative to other regulators (e.g., soil microbial diversity, stand structure, and environmental conditions) remains uncertain. In this study, effects of aboveground (species richness and functional and structural diversity) and belowground (bacterial and fungal diversity) biodiversity, functional composition (community-weighted means of species traits), stand structure (diameter at breast height and stand density), and soil factors (pH and bulk density) on multifunctionality (including biomass production, carbon stock, and nutrient cycling) were examined along a tree diversity gradient in subtropical forests. The community-weighted mean of tree maximum height was the best predictor of ecosystem multifunctionality. Functional diversity explained a higher proportion of the variation in multifunctionality than that of species richness and fungal diversity. Stand structure -played an important role in modulating the effects of tree diversity on multifunctionality. The work highlights that species composition and maximizing forest structural complexity are effective strategies to increase forest multifunctionality while also conserving biodiversity in the management of multifunctional forests under global environmental changes.

Александр Владимирович Тюрин: к 140-летию со дня рождения

In 2022, the foresters of our country are celebrating the 140th anniversary of the scientific, pedagogical, industrial and social activities of Professor Alexander Vladimirovich Tyurin. A.V. Tyurin worked in Voronezh for 24 years, foresters note the meaningful, fruitful life of a forester, scientist, educator of youth. Created with his participation, the Voronezh Higher Forestry School gradually transformed into a large forestry university of federal significance. He was characterized by broad erudition, benevolence, a sensitive attitude towards people - this is the attractive force that attracted him to solve complex problems (his students recall). Many dozens of works capture the thoughts of a veteran of Russian forestry. The work "Fundamentals of economy in pine forests" entered the treasury of classic works on forestry; Tables of the progress of plantation growth are widely used by every practical arborist and serve as a standard for comparison in the study of the structure of stands by arborists-scientists.

Current Status and Stand Structure of Riverine Forests of Sukkur, Sindh

Current Status and Stand Structure of Riverine Forests of Sukkur, Sindh

The Use of an Airborne Laser Scanner for Rapid Identification of Invasive Tree Species Acer negundo in Riparian Forests

Invasive species significantly impact ecosystems, which is fostered by global warming. Their removal generates high costs to the greenery managers; therefore, quick and accurate identification methods can allow action to be taken with minimal impact on ecosystems. Remote sensing techniques such as Airborne Laser Scanning (ALS) have been widely applied for this purpose. However, many species of invasive plants, such as Acer negundo L., penetrate the forests under the leaves and thus make recognition difficult. The strongly contaminated riverside forests in the Vistula valley were examined in the gradient of the center of Warsaw and beyond its limits within a Natura 2000 priority habitat (91E0), namely, alluvial and willow forests and poplars. This work aimed to assess the potentiality of a dual-wavelength ALS in identifying the stage of the A. negundo invasion. The research was carried out using over 500 test areas of 4 m diameter within the riparian forests, where the habitats did not show any significant traces of transformation. LiDAR bi-spectral data with a density of 6 points/m2 in both channels were acquired with a Riegl VQ-1560i-DW scanner. The implemented approach is based on crown parameters obtained from point cloud segmentation. The Adaptive Mean Shift 3D algorithm was used to separate individual crowns. This method allows for the delineation of individual dominant trees both in the canopy (horizontal segmentation) and undergrowth (vertical segmentation), taking into account the diversified structure of tree stands. The geometrical features and distribution characteristics of the GNDVI (Green Normalized Vegetation Index) were calculated for all crown segments. These features were found to be essential to distinguish A. negundo from other tree species. The classification was based on the sequential additive modeling algorithm using a multi-class loss function. Results with a high accuracy, exceeding 80%, allowed for identifying and localizing tree crowns belonging to the invasive species. With the presented method, we could determine dendrometric traits such as the age of the tree, its height, and the height of the covering leaves of the trees.

Mastication Fuels Did Not Alter Fire Severity or Stand Structure in an Upland Oak Woodland

Abstract In the eastern deciduous forest region, open oak woodlands once occupied significant areas that are now closed-canopy forests, negatively affecting wildlife habitat and biodiversity. We superimposed midstory mastication and prescribed fire treatments onto sites with ice storm damage, subsequently subjected to sanitation thinning for management restoration. Mastication reduced stem density and basal area, created a variable cover of masticated material, and increased cover of forbs, graminoids, and tree regeneration. Prescribed fire was implemented two years after mastication treatment. We examined fuel changes and whether masticated fuels altered fire severity. Masticated duff depth decreased significantly two years after treatment; no change occurred on nonmasticated treatments. Masticated 1-hour fuels decreased 80% compared to 35% in nonmasticated treatments and masticated 10 h fuels decreased 45% compared to 9.6% in treatments without mastication. Prescribed fire reduced 1, 10, and 100 h fuels on the burn only treatment, and 10 h fuels on the mastication/burn treatment. Burn severity, measured by composite burn index, did not differ between treatments, nor did we measure significant effects of mastication on fire temperature or char height. Fire had no significant effect on stand structure but should be reexamined in three to five years. Repeated burning at three to five y intervals may also be beneficial.

Stand structure and environmental factors of mangroves of Abdasa, Gujarat, India

Marine biology,marine ecology,Phytoplankton, marine algae, zooplankton, nekton, benthos, corals and coral reefs, ecology, zoogeography and systematics, primary production and experimental work on ecosystem including energy flow at different trophic levels, population dynamics and theoretical models, recycling of matter, influence of environmental factors on metabolic activity, marine microbiology, mariculture and experimental work on propagation of cultivable species, biology of fishes, marine reptiles, sea birds and mammals, physical, chemical, geological and meteorological features of the environments related to marine biology, marine environmental damage caused by pollution and engineering works, underwater observations, conservation of living resources, modifications in methodology and techniques and development of new apparatus related to marine sciences

Recruitment of European beech, Norway spruce and silver fir in uneven-aged forests: optimal and critical stand, site and climatic conditions

Tree recruitment models are important for predicting the dynamics of uneven-aged forests. Previous studies of recruitment of European beech, Norway spruce and silver fir have shown different ecological amplitudes of these species. However, recruitment in uneven-aged stands and the values of environmental factors at which the greatest and poorest recruitment can be expected remain poorly explained. The main objectives of this study were to 1) explain how 39 stand, site and climatic factors and their interactions influence the number of recruited trees in uneven-aged forests; 2) determine the optimal and critical ranges of influential factors, including stand basal area, number of trees, proportion of tree species, shade casting, soil pH, site productivity, temperature and precipitation; and 3) estimate the maximum expected response of recruitment to changes in stand density while controlling for the effect of other limiting factors. A Tobit censored regression model was used to consider that the observed range of the number of recruited trees is censored at zero. The models were parametrized and validated using 30,963 forest inventory plots (200 m2 each) in uneven-aged forests in Slovenia. The models, which used 9 stand, 6 site and 3 climatic factors, explained 15 %, 10 % and 8 % of the total variation of the number of recruited spruce, fir and beech, respectively. Stand structure was the most important factor, with stand basal area (BA) and the proportion of the studied species having the greatest effect. Site factors including soil pH and rockiness were important for fir recruitment. The number of recruited beech and spruce was positively influenced by decadal precipitation. Higher temperatures decreased recruitment of spruce. Beech was the only species sensitive to shade casting. Recruitment of beech was higher if shade was imposed by tree species other than beech. The optimal and critical ranges of limiting factors differ between species. The model suggests that the optimal stand basal area for recruitment of beech is ≤ 19 m2/ha, which is higher than that for spruce (≤ 16 m2/ha) but lower than that for fir (≤ 28 m2/ha). The maximum predicted response of the studied species to changes in stand basal area shows that stand density control is efficient for regulating recruitment of spruce and beech, but not for fir. The suggested sensitivities and threshold values may be used in individual tree growth models or simulation–optimization studies in support of forest management decisions.

The Influence of Stand Structure on Understory Herbaceous Plants Species Diversity of Platycladus orientalis Plantations in Beijing, China

Species diversity is a crucial index used to evaluate the stability and complexity of forest ecosystems. Studying the relationship between stand structure and understory herbaceous plants species diversity is useful for managers to formulate the best forest structure optimization method with the goal of improving herbaceous species diversity. In this research, Platycladus orientalis plantations in Beijing were taken as the research object. Pearson’s correlation analysis was used to explore the single-factor correlation between stand structure and understory herbaceous plants species diversity; furthermore, a typical correlation analysis and multiple linear regression were used to explore the multi-factor correlation and analyze the dominant stand structure parameters affecting understory herbaceous plants species diversity. In the range of stand structures studied, the results showed that canopy density was negatively correlated with the Shannon–Wiener index and Simpson index (p < 0.01), and tree density was negatively correlated with the Shannon–Wiener index (p < 0.05). In terms of stand spatial structure, the mingling degree was positively correlated with the Shannon–Wiener index, Simpson index, Margalef richness index and Pielou evenness index (p < 0.05), while the uniform angle was negatively correlated with the Pielou evenness index (p < 0.05). The correlation coefficient of the first group of typical variables in the typical correlation analysis was 0.90 (p < 0.05); from this group of typical variables, it can be concluded that canopy density is the most influential indicator affecting the comprehensive index of understory herbaceous plants species diversity, with a load of −0.690, and the Shannon–Wiener index and Simpson index are the most responsive indicators of changes in the comprehensive index of stand structure, with loads of 0.871 and 0.801, respectively. In the process of the management of Platycladus orientalis plantations under a low altitude, south slope, thin soil layer and hard soil parent material, in order to improve the herbaceous species diversity, the canopy density of the overstory and tree density should be appropriately reduced. Additionally, it is necessary to regulate the horizontal spatial structure of stands. When the trees are randomly distributed and the mingling degree is high, the species diversity of herbs can be increased.

Stand structure adjustment influences the biomass allocation in naturally generated Pinus massoniana seedlings through environmental factors.

The natural regeneration of seedlings is a key factor for forest succession. Nevertheless, studies explaining the mechanism of growth and biomass allocation in regenerated seedlings after disturbance are lacking. Therefore, we measured the growth, biomass accumulation, and biomass allocation in current-age seedlings of Pinus massoniana after selective logging (logging of competitive trees, LCT; logging of inferior trees, LIT; and unlogged control, CK), and established structural equation models (SEMs) among the spatial structure characteristic indexes of the stand, environmental factors, and biomass allocation in different organs. As compared to the CK, the mingling index (M), uniform angle index (W), opening degree (O), soil organic carbon (SOC), available nitrogen (SAN), available phosphorus (SAP), available potassium (SAK), and bulk density (SBD) significantly increased (p < 0.05), while the competition index (CI) and neighborhood comparison (U) significantly decreased after logging (p < 0.05). After the LCT, seedling branch biomass improved, with an increase in the ground-diameter, crown-root ratio, and seedling quality index. More biomass was allocated to foliage and roots by an increase in the height and height-diameter ratio under the LIT. In the CK, increasing stem biomass helped the seedlings absorb and utilize more light. The Pearson correlation coefficient showed that biomass allocation to organs was independent, and seedlings adopted the strategies of heterogeneous adaptation and growth, thereby resulting in the separation of the allocation patterns among the organs. As per the redundancy analysis (RDA), CI was the main factor in biomass allocation. Environmental factors had direct effects on biomass allocation to organs, while the stand spatial structure characteristic indexes had indirect effects on biomass allocation based on SEMs. In summary, the LCT had significant, albeit indirect, effects on SOC, SAN, and SBD by reducing the CI for the regeneration and growth of seedlings in the stand, which was of great significance to the sustainable development of the forest stand of P. massoniana.

Seeing past the green: Structure, composition, and biomass differences in high graded and silviculture-managed forests of similar stand density

Forests of the eastern United States (US) mostly comprise a mix of stands managed following silvicultural principles and stands managed with exploitative timber harvesting practices. These stands can have similar stand densities (e.g., basal area per hectare) but vary vastly in structure, composition, and biomass and carbon storage. High grading, a prevalent exploitative timber harvesting practice in the eastern US, is of particular concern because it can negatively affect future forest health and productivity. This study quantifies differences in forest structure, composition, and biomass and carbon storage between high graded stands and stands that received a seed/establishment cut of a uniform shelterwood regeneration sequence treatment, which is a comparable and well-established silvicultural method used to regenerate mixed-oak forests. It focuses on mixed-oak forests (mixed-Quercus), where the effects of high grading have been understudied, and uses a sample with broader spatial coverage than previous studies. The sample comprised nine stands that were known to have been high graded 8–15 years ago and nine stands that received the seed/establishment cut of a uniform shelterwood regeneration sequence. Stand were systematically sampled using fixed-area plots. Field measurements were collected and used to calculate metrics describing forest structure and function. The structure of high graded stands was characterized by a higher proportion of trees with poor health and/or form compared to shelterwood stands, with 18.3 % less acceptable growing stock and trees with lower crown compaction. Diameter distributions of high graded stands were characterized by numerous small trees and few large-diameter trees. Spatial variability of overstory trees was contingent on the tree size range evaluated, with a larger variability of sawtimber-sized trees (trees ≥ 29.2 cm in diameter at breast height) in high graded stands. High graded stands also had 2.2 times fewer oak trees (Quercus spp.) in the overstory canopy, 17,897 fewer seedlings per hectare (ha), and 45 Mg/ha less biomass than shelterwood stands. These results indicate that high grading generally degrades mixed-oak forests and impairs their long-term capacity to supply vital ecosystem services such as habitat for specific wildlife species, carbon storage, and high-quality wood products.