Forest Spatial Structure Research Articles

Exploring the influence of large trees on temperate forest spatial structure from the angle of mingling

Large trees have been found to directly affect spatial patterns in forests and understanding forest spatial structure is important for developing effective forest management practices. We examined two primary broad-leaved Korean pine forests in Heilongjiang Province, China, to investigate the effects of large-diameter trees on the distribution of adjacent conspecific trees and to assess whether the effect is related to the conspecific negative density dependence hypothesis in temperate forest. We classified the tree with the widest diameter (diameter at breast height ≥ 50 cm) as the central tree and then surveyed the distribution of adjacent trees around each central tree. The degree of mingling between the central tree and adjacent trees was the lowest at 5–7 m. As the diameter of the adjacent trees increased the degree of mingling declined. This revealed that around the central tree, there was a ring of small trees conspecific to the central tree. The ring-like structure around large-diameter trees is consistent with the conspecific negative density dependence hypothesis. Thus, we propose that a ring-like structure promotes the succession and regeneration of the temperate forest.

Mapping trees along urban street networks with deep learning and street-level imagery

Planning and managing urban forests for livable cities remains a challenge worldwide owing to sparse information on the spatial distribution, structure and composition of urban trees and forests. National and municipal sources of tree inventory remain limited due to a lack of detailed, consistent and frequent inventory assessments. Despite advancements in research on the automation of urban tree mapping using Light Detection and Ranging (LiDAR) or high-resolution satellite imagery, in practice most municipalities still perform labor-intensive field surveys to collect and update tree inventories. We present a robust, affordable and rapid method for creating tree inventories in any urban region where sufficient street-level imagery is readily available. Our approach is novel in that we use a Mask Regional Convolutional Neural Network (Mask R-CNN) to detect and locate separate tree instances from street-level imagery, thereby successfully creating shape masks around unique fuzzy urban objects like trees. The novelty of this method is enhanced by using monocular depth estimation and triangulation to estimate precise tree location, relying only on photographs and images taken from the street. Experiments across four cities show that our method is transferable to different image sources (Google Street View, Mapillary) and urban ecosystems. We successfully detect >70% of all public and private trees recorded in a ground-truth campaign across Metro Vancouver. The accuracy of geolocation is also promising. We automatically locate public and private trees with a mean error in the absolute position ranging from 4 to 6 m, which is comparable to ground-truth measurements in conventional manual urban tree inventory campaigns.

Spatial and compositional structure of European oak urban forests in Kyiv city, Ukraine

Forest dimensional structure and tree species composition strictly define ecosystem resilience, success of its functioning and development. Spatial structure of forest compartments provides an additional information on the forest stand heterogeneity. The aim of this study is to examine structural patterns (both spatial and nonspatial ones) in European oak (Quercus robur L.) urban forests located in Kyiv city, Ukraine. We compared two middle-aged (~ 80 years) and two mature (~ 180 years) oak stands in terms of structural metrics collecting a data from geo-referenced trees on the established permanent sample plots. Younger stands reached similar tree diameter diversity (9.07 and 10.45 vs. 11.42 and 14.05 of Shannon indices), while the compositional diversity was driven by the dominance of either oak or European hornbeam (Carpinus betulus L.). We have not found any differences in the species mingling and deadwood distribution indices except a clear occurrence pattern for the stand located near roads. Herewith, the largest distance between the plot and park pathways was an indicator of changed spatial variation and tree dimensional differentiation within one middle-aged stand. We hypothesize that human impacts can alter structural development in urban deciduous forests providing both positive (gap formation, deadwood occurrence and ecosystem complexity) and negative (shifts in compositional and successional trajectories) effects on such forest stands.

Close-to-nature management positively improves the spatial structure of Masson pine forest stands

Abstract. Close-to-nature management (CTNM) has been proposed as a promising forestry management approach to improve the structure and quality of forests, which integrates wood production and ecological service functions. Research on the effect of CTNM on the univariate and bivariate distribution of the spatial structure of forest stands provides a scientific basis for the evaluation of CTNM implemented in forestry. Here, we analyzed and compared the spatial-structure characteristics of Masson pine (Pinus massoniana) plantations (young, middle-age, and near-mature stages) under CTNM 8 years after selective cutting and unmanaged control. We used univariate and bivariate distribution of three spatial-structure parameters: mingling (M), dominance (U), and uniform-angle index (W). Results showed that the effect of CTNM on spatial structure was more remarkable in middle-aged and near-mature Masson pine forests compared with the young forest. CTNM significantly improved mingling degree and promoted the horizontal distribution, thereby changing from a cluster to a random distribution. Moreover, CTNM improved the proportion of trees with a high mixing degree and random distribution and the proportion of trees having a micro-structure of random distribution with a high degree of mixture and dominance with a high degree of mixture in middle-aged and near-mature Masson pine forest. Overall, the implementation of CTNM 8 years ago showed a positive effect on the improvement of the spatial structure of Masson pine forest, but the present spatial structure is suboptimal. Further implementation of CTNM to adjust the mingling and uniform-angle index is necessary, and CTNM according to this method of frequency distribution of stand structure parameters can improve the success of forest management.

Introducing tree neighbouring relationship factors in forest pattern spatial analysis: weighted Delaunay triangulation method

It is important to quantify and analyze forest spatial patterns for studying biological characteristics, population interaction and the relationship between the population and environment. In this study, the forest spatial structure unit was generated based on the Delaunay triangulation model (DTM), and the weights were generated using the comprehensive values of the tree diameter at breast height, total height and crown width. The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates. Then, a weighted spatial pattern (WSP) was developed. After weighting, the neighboring trees were replaced, the replacement ratio was 38.3%, and there was 57.4% of the central tree. Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity (r = 0.932) and randomness (r = 0.711). The DTM method not only considers the spatial distance between trees, but also considers the non-spatial attributes of trees. By changing the spatial topological relation between trees, this method further improves the spatial structure measurement of forest.

天目山常绿阔叶林空间结构动态变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 天目山常绿阔叶林空间结构动态变化特征 DOI: 10.5846/stxb201912312841 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（31870617） Analysis on spatial structure dynamic characteristics of evergreen broad-leaved forest in Tianmu Mountain Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用固定样地重复监测的方法，2005-2015年每5年1次对天目山国家级自然保护区内1hm2常绿阔叶林固定样地进行3次样地调查，按优势度分析法确定群落优势树种，根据树种类别将优势树种分为常绿阔叶树种、常绿针叶树种和落叶阔叶树种3个优势树种组，利用聚集指数、树种多样性混交度和Hegyi竞争指数3个空间结构指数，分析群落和优势树种在2005-2015年期间的空间结构动态变化特征。结果表明：（1）群落表现为低度聚集、中度混交和中度竞争状态。群落聚集程度和竞争强度降低，混交程度保持稳定。群落空间结构动态变化总体特征是混交度稳定性最高，其次是分布格局，竞争态势稳定性最低。（2）群落优势种组成变化不大，3个优势树种组均呈低度聚集分布；常绿阔叶树种表现为低度混交、中度竞争状态；常绿针叶和落叶阔叶树种均表现为中度混交、低度竞争状态。常绿阔叶树种的聚集程度和竞争强度降低，混交程度保持稳定，与群落空间结构动态变化特征基本一致。常绿针叶和落叶阔叶树种的3种空间结构均保持稳定。在常绿阔叶林经营或人工林近自然改造过程中，应重视群落和优势树种的空间结构变化规律，确定阶段性空间结构优化目标，逐步促进群落进展演替。 Abstract:In order to analyze the spatial structure dynamic characteristics of the evergreen broad-leaved forest in Tianmu Mountain, a permanent sample plot (1 hm2) in Tianmu Mountain National Nature Reserve was surveyed every 5 years from 2005 to 2015. Based on the filed data collected from these three surveys, dominance index analysis was applied to determine the dominant tree species. For easy analysis, the dominant tree species were divided into three dominant species groups: evergreen broad-leaved species, evergreen conifer species, and deciduous broad-leaved species. Then, spatial structure parameters such as aggregation index, tree species diversity mingling, Hegyi competition index were used to analyze the spatial structure dynamic characteristics of the whole community and dominant tree species during 2005-2015. The results showed that: (1) the spatial structure of community was characterized by low-level aggregation, moderate mingling and moderate competition. The degree of aggregation and competition decreased, whereas the mingling degree remained stable. And the dynamic change overall characteristics of community spatial structure were as follows: the stability of mingling degree was the highest, followed by distribution pattern, and competitive situation was the lowest. (2) The composition of dominant tree species in community did not change significantly. Three dominant species groups all represented a low-level aggregated distribution pattern. Furthermore, evergreen broad-leaved species showed a low degree of mingling and moderate competition. Both evergreen conifer species and deciduous broad-leaved species showed a moderate mingling degree and low-level competition. The spatial structure dynamic characteristics of evergreen broad-leaves species was that the degree of aggregation and competition decreased, and mingling degree remained stable. It was basically consistent with the spatial structure dynamic characteristics of community. But, the spatial structure of evergreen conifer species and deciduous broad-leaved species had remained stable from 2005 to 2015. During the management of evergreen broad-leaved forest or the close-to-nature transformation management of plantation, attention should be paid to the dynamic characteristic of spatial structure of community and dominant tree species and determine the staged spatial structure optimization goals to gradually promote community succession. At present, there are few studies on dynamic monitoring of evergreen broad-leaved forest spatial structure. In the future, the establishment of a permanent sample plot network of evergreen broad-leaved forest with spatial structure as the goal will play an important role in understanding the relationship between structure and function of evergreen broad-leaved forest, revealing the formation mechanism and succession law of community. 参考文献 相似文献 引证文献

Structural and Tree Species Diversification as a Challenging Task in Forests of the Air-polluted Jizera Mountains, Czech Republic

The Jizera Mountains (Jizerske hory) are a part of the Black Triangle, which, in the past, was one of Europe's most polluted regions. Situated on the Czech–Polish border, these mountains were heavily affected by extreme SO2 and NOx loads emitted from coal power plants in the piedmont. During the 1970s and 1980s, the upper plateau of the Jizera Mountains experienced substantial forest decline due to air pollution. Dying stands were felled on more than 12,000 ha. Modernization of the energy industry after 1989 has led to a significant reduction in air pollution in the Black Triangle. Therefore, replanting the clear-cut areas in the Jizera Mountains became possible during the 1990s, and a new generation of forests has covered the upper plateau of the mountains. However, these even-aged, mainly spruce stands urgently need to be diversified in terms of age, structure, and species composition. This is not an easy task due to extreme microclimate, acidified soils, and damage to plants by rodents and deer. In 2007, a project aimed at the diversification of local ecosystems was initiated. The project is based on a system of diversification centers and corridors containing a species admixture (broadleaf trees and silver fir), which is protected from game, to form a web that enriches the age and spatial structure of forests on the upper plateau and complements their species composition. Initially, these centers and corridors were placed in more sheltered and accessible places and planted with the standard planting stock in combination with large-sized transplants (<100 cm). Through silvicultural measures, the web became successively denser and expanded to sites with less environmental protection. Supportive measures like initial fertilization of plantations and the biochemical amelioration of depleted soils have also been implemented.

Characterizing spatial structure of Abies marocana forest through point pattern analysis

Aim of study: Understanding small-scale patterns caused by stochastic factors or community interactions driving forest structure and diversity of Moroccan fir Abies marocana Trab.Area of study: Talassemtane fir forest, Talassemtane National Park, Rif Mountains, northern Morocco.Material and methods: Eight plots representative of the structural variability of A. marocana forests were selected, and all tree individuals with diameter at breast height (dbh) ≥2 cm were mapped and measured. We performed four types of spatial point pattern analyses: (1) Univariate analyses to explore the overall trees spatial pattern, (2) bivariate analyses to assess the spatial relationship between juveniles and A. marocana adults, (3) correlation between tree sizes (dbh) and distance between points pairs using the univariate mark correlation function, and (4) random labeling analyses between dominant and suppressed Moroccan fir individuals to assess competition patterns.Main results: We found a strong spatial aggregation of fir individuals and a positive intraspecific association between juveniles and adult trees. However, there were weak but significant distance-dependent effect on tree size and density-dependent effect on suppression pattern.Research highlights: Shade-tolerance, seed dispersal and/or microsite heterogeneity might play important roles in the observed fir patterns. Our results provide a basic knowledge on within-stand Moroccan fir spatial distribution, with implications for adaptive management of these relic forests, and prompting to further research to test advanced hypotheses.Additional key words: Moroccan fir; Talassemtane National Park; Rif forest; Spatial analysis; summary statistics; facilitation; aggregation.Abbreviations used: MF (Moroccan fir); Talassemtane National Park (TNP); dbh (diameter at breast height); Univariate pair-correlation function (g(r)); Heterogeneous Poisson (HP); Bivariate pair-correlation function (g12(r)); Univariate mark correlation function (kmm(r)), Mark connection function (p12(r)).

Using space syntax measures to assess the human impact on ground cover plant communities in recreational forests

This study used space syntax theory to predict the recreational impact on natural forest ecosystems. We assumed a correlation between specific space syntax measures and parameters that describe the recreational impact on forest ecosystems. For constructing a model of spatial structure of recreational forest, we chose an angular segment map of a road network. Most of the recreational impact is caused by trampling which we used to evaluate the visitors traffic. Field observations of ground cover were made on transects. For the road network we used the natural logarithm of the T1024 Choice measure, called LNchoice, and divided the range of values into two subsets. The subset ‘zone 0’ included segments where LNchoice was lower than the mean value of LNchoice, while the subset ‘zone 1’ included all other segments. Comparative analysis of the field data and indicators of the road network confirmed that zone 1 had higher trampling impacts than zone 0. In zone 1, degree of coverage by typical forest plants and their degree of dominance were lower than in zone 0, and the percentage of dead ground cover was greater. These results show that space syntax theory has great potential for landscape design and management of recreational forests.

FLiES-SIF version 1.0: three-dimensional radiative transfer model for estimating solar induced fluorescence

Abstract. Global terrestrial ecosystems control the atmospheric CO2 concentration through gross primary production (GPP) and ecosystem respiration processes. Chlorophyll fluorescence is one of the energy release pathways of excess incident light in the photosynthetic process. Over the last 10 years, extensive studies have revealed that canopy-scale Sun-induced chlorophyll fluorescence (SIF), which potentially provides a direct pathway to link leaf-level photosynthesis to global GPP, can be observed from satellites. SIF is used to infer photosynthetic capacity of plant canopy; however, it is not clear how the leaf-level SIF emission contributes to the top-of-canopy directional SIF. Plant canopy radiative transfer models are useful tools to understand the mechanism of anisotropic light interactions such as scattering and absorption in plant canopies. One-dimensional (1-D) plane-parallel layer models (e.g., the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model) have been widely used and are useful to understand the general mechanisms behind the temporal and seasonal variations in SIF. However, a 1-D model does not explain the complexity of the actual canopy structures. Three-dimensional models (3-D) have a potential to delineate the realistic directional canopy SIFs. Forest Light Environmental Simulator for SIF (FLiES-SIF) version 1.0 is a 3-D Monte Carlo plant canopy radiative transfer model to understand the biological and physical mechanisms behind the SIF emission from complex forest canopies. The FLiES-SIF model is coupled with leaf-level fluorescence and a physiology module so that users are able to simulate how the changes in environmental and leaf traits as well as canopy structure affect the observed SIF at the top of the canopy. The FLiES-SIF model was designed as three-dimensional model, yet the entire modules are computationally efficient: FLiES-SIF can be easily run by moderate-level personal computers with lower memory demands and public software. In this model description paper, we focused on the model formulation and simulation schemes, and showed some sensitivity analysis against several major variables such as view angle and leaf area index (LAI). The simulation results show that SIF increases with LAI then saturated at LAI&gt;2–4 depending on the spectral wavelength. The sensitivity analysis also shows that simulated SIF radiation may decrease with LAI at a higher LAI domain (LAI&gt;5). These phenomena are seen in certain Sun and view angle conditions. This type of nonlinear and nonmonotonic SIF behavior towards LAI is also related to spatial forest structure patterns. FLiES-SIF version 1.0 can be used to quantify the canopy SIF in various view angles including the contribution of multiple scattering which is the important component in the near-infrared domain. The potential use of the model is to standardize the satellite SIF by correcting the bidirectional effect. This step will contribute to the improvement of the GPP estimation accuracy through SIF.

Modeling the natural regeneration of Cedrus libani A. Richard in Slenfeh, Syria, using binary logistic regression

Species distributions and abundances are undergoing rapid changes worldwide. This highlights the significance of reliable, integrated information for guiding and assessing actions and policies aimed at managing and sustaining the many functions and benefits of species. Mapping and monitoring of forest extent is a common requirement of regional forest inventories and public land natural resource management which requires generation of an accurate database on spatial forest structure distribution and environmental variables. Remote Sensing and Geographic Information Systems (GIS) technology is an effective tool in modern management programs for forest ecosystems. The environmental factors which probably affect in the natural regeneration of Cedrus libani A. Richard in its natural distribution forest in Slenfeh, Syria, were modeled using the binary logistic regression (BLR) model. The effect of environmental factors (spatial and forest structure factors, topographic factors, and spectral indicators) was studied, each one as single set and then their combined effect with each other on the probability of the presence of C. libani seedlings in Slenfeh. The accuracy of the model was clearly improved by studying the effect of environmental factors combined together (84%), while the accuracy of the other studied models did not exceed 70%. The results showed that the forest cover (Cedrus libani, broad leaved except oaks, mixed) is considered a good condition for natural regeneration of C. libani, while the lack of soil moisture in summer was a negative factor in the possibility of the presence of C. libani seedlings in Slenfeh.

Soundscape mapping for spatial-temporal estimate on bird activities in urban forests

Soundscape mapping provides a unique perspective to explain the complicated spatial-temporal change of bird activities in urban forests. Most studies of soundscapes have used multi-point distribution to record sounds, which is challenging for explaining complex interferences factors in urban areas. In this study, we used soundscape mapping to explore the habitat selection of bird communities in the context of spatial-temporal structural changes. We selected the transition area from city to forest in Shenzhen, China, as the study area, set up 30 recording points which arranged in grid patterns (5 × 6), and used synchronic recording methodology to collect sounds. Aural species identification, power spectral density (PSD), and normalized-difference sound index (NDSI) were used to quantify sounds. Passerine birds (92.11 %) were found to comprise the first acoustic communities. Changes in bird species populations among seasons were noted, with spring having the most abundant bird species number (n = 59) and the most abundant ecoacoustic events. Bird communities with different frequency band clusters having different preferences for vegetation characteristics were detected. A significant two-way interaction between the accessibility of recording points and seasons on bird activities was found in this study. Urban forest spatial structure had a great effect on bird activities, and specifically through the shape of forest vertical structure complexity and forest edge effect. Our study shows the broader application potential of soundscape mapping in urban forest ecosystem research.

Wildfire and drought moderate the spatial elements of tree mortality

AbstractBackground tree mortality is a complex process that requires large sample sizes and long timescales to disentangle the suite of ecological factors that collectively contribute to tree stress, decline, and eventual mortality. Tree mortality associated with acute disturbance events, in contrast, is conspicuous and frequently studied, but there remains a lack of research regarding the role of background mortality processes in mediating the severity and delayed effects of disturbance. We conducted an empirical study by measuring the rates, causes, and spatial pattern of mortality annually among 32,989 individual trees within a large forest demography plot in the Sierra Nevada. We characterized the relationships between background mortality, compound disturbances (fire and drought), and forest spatial structure, and we integrated our findings with a synthesis of the existing literature from around the world to develop a conceptual framework describing the spatio‐temporal signatures of background and disturbance‐related tree mortality. The interactive effects of fire, drought, and background mortality processes altered the rate, spatial structuring, and ecological consequences of mortality. Before fire, spatially non‐random mortality was only evident among small (1 &lt; cm DBH ≤ 10)‐ and medium (10 &lt; cm DBH ≤ 60)‐diameter classes; mortality rates were low (1.7% per yr), and mortality was density‐dependent among small‐diameter trees. Direct fire damage caused the greatest number of moralities (70% of stems ≥1 cm DBH), but the more enduring effects of this disturbance on the demography and spatial pattern of large‐diameter trees occurred during the post‐fire mortality regime. The combined effects of disturbance and biotic mortality agents provoked density‐dependent mortality among large‐diameter (≥60 cm DBH) trees, eliciting a distinct post‐disturbance mortality regime that did not resemble the pattern of either pre‐fire mortality or direct fire effects. The disproportionate ecological significance of the largest trees renders this mortality regime acutely consequential to the long‐term structure and function of forests.

Role of Silviculture in the Formation of Norway Spruce Forests along the Southern Edge of Their Range in the Central Russian Plain

East European forests dominated by Norway spruce (Picea abies (L.) H. Karst.) in the broad-leaved–coniferous zone should be considered as secondary communities formed under the influence of centuries-long activities (logging, fires and planting) and extended outside their natural range. The study raises an issue—how stable is the current state of Norway spruce forests in the center of the Russian plain and what is the effect of silviculture on the forest cover of the large urban agglomeration—the Moscow Region? Current study is based on multidisciplinary research and consequently concerns the age dynamics of spruce plantation forests, the species and typological diversity of mature spruce forests and spatial pattern of spruce forests along the south edge of their range. The composition and structure of Norway spruce plantations have been studied for various age classes and compared with mature natural spruce forests and pine plantations on the basis of field data. Remote sensing data and modeling approach were applied to estimate the spatial structure of spruce forests. It is found that mature plantations (over 80 years) become similar to natural forests in terms of structure and composition. The relationship between the distribution of spruce formations and the climatic and geomorphological conditions are confirmed. The proportion of spruce and spruce–aspen/birch communities follows the pattern of zones—the transition from the coniferous and broad-leaved forest zone to the broad-leaved forest zone. Despite the significant anthropogenic impact and the high proportion of plantations in the composition of Norway spruce forests (about 60–80%), their floristic and typological diversities correspond to such properties of zonal broad-leaved–coniferous communities. Over-matured plantations can provide valuable habitats for the re-establishment of native typological diversity. This makes it possible to use silviculture stands as an accelerated alternative to the natural recovery of disturbed habitats.

Spatial Structure Evaluation of Natural Secondary Forest around Dongting Lake Based on Entropy Weight - Cloud Model

Li, X.; Zhang, G., and Li, J., 2020. Spatial structure evaluation of natural secondary forest around Dongting Lake based on entropy weight - cloud model. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 484–489. Coconut Creek (Florida), ISSN 0749-0208.In order to provide theoretical support for the formulation of optimized measures of stand spatial structure, 15 sample plots are set up in Daweishan Nature Reserve, Longhushan national forest farm in Yuanjiang City and Lutou national forest farm in Pingjiang County to analyze and evaluate the stand spatial structure of natural secondary forest around Dongting Lake. After determining the spatial structure unit of trees by Voronoi diagram, the five indicators including mingling degree, neighborhood comparison, openness comparison index, neighborhood pattern and angle competition index are segmented to correspond to the five grades of stand spatial structure divided by the combination of qualitative and quantitative methods. Then through the comprehensive assessment on stand spatial structure by entropy weight-cloud model, the fifteen plots are evaluated as grade III and grade IV, respectively accounting for two-thirds and one-thirds of all plots, which indicates that the reasonable stand spatial structure of natural secondary forest around Dongting Lake is above the average. As a new evaluation method of stand spatial structure, the entropy weight-cloud model has solved the issue of qualitative and quantitative conversion, and objectively calculate the weights of indicators, so as to enrich the evaluation methods of stand spatial structure, overcome the one-way evaluation by single indicator, improve the objectivity and scientificity of evaluation results, and provide theoretical basis for the scientific guidance of stand spatial structure optimization.

Estimation of the Restored Forest Spatial Structure in Semi-Arid Mine Dumps Using Worldview-2 Imagery

Forest monitoring is critical to the management and successful evaluation of ecological restoration in mined areas. However, in the past, available monitoring has mainly focused on traditional parameters and lacked estimation of the spatial structural parameters (SSPs) of forests. The SSPs are important indicators of forest health and resilience. The purpose of this study was to assess the feasibility of estimating the SSPs of restored forest in semi-arid mine dumps using Worldview-2 imagery. We used the random forest to extract the dominant feature factor subset; then, a regression model and mind evolutionary algorithm-back propagation (MEA-BP) neural network model were established to estimate the forest SSP. The results show that the textural features found using 3 × 3 window have a relatively high importance score in the random forest model. This indicates that the 3 × 3 texture factors have a relatively strong ability to explain the restored forest SSPs when compared with spectral factors. The optimal regression model has an R2 of 0.6174 and an MSRE of 0.1001. The optimal MEA-BP neural network model has an R2 of 0.6975 and an MSRE of 0.0906, which shows that the MEA-BP neural network has greater accuracy than the regression model. The estimation shows that the tree–shrub–grass mode with an average of 0.7351 has the highest SSP, irrespective of the restoration age. In addition, the SSP of each forest configuration type increases with the increase in restoration age except for the single grass configuration. The increase range of SSP across all modes was 0.0047–0.1471 after more than ten years of restoration. In conclusion, the spatial structure of a mixed forest mode is relatively complex. Application cases show that Worldview-2 imagery and the MEA-BP neural network method can support the effective evaluation of the spatial structure of restored forest in semi-arid mine dumps.

Do smaller trees easily form a ring structure around larger trees in temperate forests?

Forest spatial structure has always been an important topic of ecological research. Large trees directly affect the spatial patterns in forest stands. In this study, we used the data from seven sample plots in natural mixed forests of Korean pine (Pinus koraiensis Siebold &amp; Zucc.) and broad-leaved trees in Heilongjiang Province, China, to examine the effect of large trees on the spatial distribution of adjacent trees and to explore whether this effect is related to the gap dynamics theory. We classified trees with wide diameter (diameter at breast height (DBH) ≥ 50 cm) as central trees and then surveyed the distribution of adjacent trees around each central tree. The results revealed a ring structure of small trees (size class 2 (5.0 ≤ DBH &lt; 10.0 cm) and size class 3 (10.0 ≤ DBH &lt; 30.0 cm)) surrounding large trees. In the two northern sample plots, the trees formed the ring structures with radii of 4–7 m from the large-diameter trees. In the two central sample plots, the ring structures had the radii of 5–9 m and 5–8 m. Analogously, in the three southern sample plots, the ring structures had the radii of 7–11 m and 6–10 m. The formation of a ring structure is closely related to the competition among individuals, and there is an internal relationship between the formation of this structure and the dynamic theory.

Реконструкция истории древостоев и оценка воздействия инвазивного короеда в пихтовых лесах с помощью анализа пространственной структуры

The most devastating insect invasion of forest ecosystems in Russia is the recent mass reproduction of the four-eyed fir bark beetle (Polygraphus proximus Blandf.) in southern Siberian fir (Abies sibirica Ledeb.) forests. The objective of our research was to study the spatial structure of fir forests and their change under the impact of the four-eyed fir bark beetle in its secondary (invasive) distribution range. We selected two fir stands located near the villages of Itatka and Malinovka in the Tomsk region. Both stands represent natural ripe succession forests on sites that previously experienced logging activities, which were triggered by settlement activities in the second half of the nineteenth century. We used Field-Map technology for gathering non-spatial and spatial stand data. The analysis showed that height, diameter and radial increment of fir trees, killed or severely weakened by attacks of the four-eyed fir bark beetle, were significantly lower than that of healthy individuals. The social status of fir trees, seriously attacked or already killed by Polygraphus proximus was indicated by the Ui index as moderately suppressed. In contrast to the distribution pattern of living firs, the pattern of dead or severally weakened firs killed by the four-eyed fir bark beetle was significantly clumped over short distances (sample plots (SP) Itatka and Malinovka). This finding coincides with visual observations in other stands, that dead trees are grouped to some extent. However, the hypothesis of spatial independence of the tree positions of living and dead firs was accepted for both plots.Funding: The research was funded by the Russian Foundation for Basic Research and the government of Tomsk region, grant No. 16-44-700782, and carried out as part of a state assignment of the Center for Forest Ecology and Productivity of the Russian Academy of Sciences (No. АААА-А18-118052400130-7).For citation: Debkov N.M., Gradel A., Aleinikov A.A. Reconstruction of Stand History and Impact Evaluation of an Invasive Bark Beetle in Siberian Fir Forests with the Help of Spatial Structure Analysis. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 3, pp. 24–41. DOI: 10.37482/0536-1036-2020-3-24-41

Optimizing Forest Spatial Structure with Neighborhood-Based Indices: Four Case Studies from Northeast China

The fine-scale spatial patterns of trees and their interactions are of paramount importance for controlling the structure and function of forest ecosystems; however, few management techniques can be employed to adjust the structural characteristics of uneven-aged mixed forests. This research provides an accurate, efficient, and impersonal comprehensive thinning index (P-index) for selecting candidate harvesting trees; the index was proposed by weighting the commonly used quantitative indices with respect to stand fine-scale structures, competition status, tree vigor, and tree stability. The applications of the proposed P-index in evaluating and simulating the process of thinning operations were examined using four 1-ha mapped plots with different forest types, namely, natural secondary forest, natural pine-broadleaved mixed forest, natural larch-birch mixed forest, and natural oak forest, which were widely distributed across the Heilongjiang Province in Northeast China. The results indicated that the proposed P-index could effectively affect the structural differentiations between different forest types and alternative thinning intensities. The marginal benefits of alternative thinning intensities on the integrated forest structure indicated that removing 10% of the trees from the plots might be the optimal thinning intensity from the perspective of optimizing stand structure, in which the P-index values could be increased by approximately 5%–11% for the four tested plots. The main conclusion from this paper was that the proposed P-index could be used as a quantitative tool to manage uneven-aged mixed forests.

Automatic Windthrow Detection Using Very-High-Resolution Satellite Imagery and Deep Learning

Wind disturbances are significant phenomena in forest spatial structure and succession dynamics. They cause changes in biodiversity, impact on forest ecosystems at different spatial scales, and have a strong influence on economics and human beings. The reliable recognition and mapping of windthrow areas are of high importance from the perspective of forest management and nature conservation. Recent research in artificial intelligence and computer vision has demonstrated the incredible potential of neural networks in addressing image classification problems. The most efficient algorithms are based on artificial neural networks of nested and complex architecture (e.g., convolutional neural networks (CNNs)), which are usually referred to by a common term—deep learning. Deep learning provides powerful algorithms for the precise segmentation of remote sensing data. We developed an algorithm based on a U-Net-like CNN, which was trained to recognize windthrow areas in Kunashir Island, Russia. We used satellite imagery of very-high spatial resolution (0.5 m/pixel) as source data. We performed a grid search among 216 parameter combinations defining different U-Net-like architectures. The best parameter combination allowed us to achieve an overall accuracy for recognition of windthrow sites of up to 94% for forested landscapes by coniferous and mixed coniferous forests. We found that the false-positive decisions of our algorithm correspond to either seashore logs, which may look similar to fallen tree trunks, or leafless forest stands. While the former can be rectified by applying a forest mask, the latter requires the usage of additional information, which is not always provided by satellite imagery.