Journal articles on the topic 'Stand structural complexity'
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1
Bradford, John B., and Douglas N. Kastendick. "Age-related patterns of forest complexity and carbon storage in pine and aspen–birch ecosystems of northern Minnesota, USA." Canadian Journal of Forest Research 40, no. 3 (March 2010): 401–9. http://dx.doi.org/10.1139/x10-002.
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Forest managers are seeking strategies to create stands that can adapt to new climatic conditions and simultaneously help mitigate increases in atmospheric CO2. Adaptation strategies often focus on enhancing resilience by maximizing forest complexity in terms of species composition and size structure, while mitigation involves sustaining carbon storage and sequestration. Altered stand age is a fundamental consequence of forest management, and stand age is a powerful predictor of ecosystem structure and function in even-aged stands. However, the relationship between stand age and either complexity or carbon storage and sequestration, especially trade-offs between the two, are not well characterized. We quantified these relationships in clearcut-origin, unmanaged pine and aspen chronosequences ranging from <10 to >130 years in northern Minnesota. Complexity generally increased with age, although compositional complexity changed more over time in aspen forests and structural complexity changed more over time in pine stands. Although individual carbon pools displayed various relationships with stand age, total carbon storage increased with age, whereas carbon sequestration, inferred from changes in storage, decreased sharply with age. These results illustrate the carbon and complexity consequences of varying forest harvest rotation length to favor younger or older forests and provide insight into trade-offs between these potentially conflicting management objectives.
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Man, Rongzhou, and Hua Yang. "Construction of neighbourhood diversity indices with stem mapping data." Canadian Journal of Forest Research 45, no. 8 (August 2015): 1137–41. http://dx.doi.org/10.1139/cjfr-2015-0108.
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Typical use of diversity indices in forest stands does not reflect within-stand variation in species and structure. Despite numerous efforts to design stand diversity indices that capture spatial variation in two- or three-dimensional space, the application of these indices is limited due to their complexity or lack of ecological relevance. In this research note, we illustrate the application of diversity indices at the neighbourhood scale using stem mapping data from a boreal mixedwood stand in northeastern Ontario, which was assessed before and after partial harvesting. Among the three diversity indices (Shannon species diversity, Shannon structural diversity by height class distribution, and structural diversity by height variation), neighbourhood structural diversity by height variation was less dependent on neighbourhood size (between 4 and 12 trees) and more sensitive to stand structural change than Shannon structural diversity by height class distribution. Despite general increases in Shannon species diversity and structural diversity by height variation at both stand and neighbourhood scales after the harvest — an indication of higher diversity — within-stand variation (coefficients of variation) in neighbourhood diversity values decreased, suggesting that residual stands were spatially more uniform after the harvest. Therefore, the neighbourhood diversity indices are useful for capturing spatial variation in species and structural diversity, especially in managed stands in which spatial distributions and patterns can be significantly modified by management interventions.
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Seidel, Dominik, Martin Ehbrecht, Peter Annighöfer, and Christian Ammer. "From tree to stand-level structural complexity — Which properties make a forest stand complex?" Agricultural and Forest Meteorology 278 (November 2019): 107699. http://dx.doi.org/10.1016/j.agrformet.2019.107699.
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Willim, Katharina, Melissa Stiers, Peter Annighöfer, Martin Ehbrecht, Christian Ammer, and Dominik Seidel. "Spatial Patterns of Structural Complexity in Differently Managed and Unmanaged Beech-Dominated Forests in Central Europe." Remote Sensing 12, no. 12 (June 12, 2020): 1907. http://dx.doi.org/10.3390/rs12121907.
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One of the main goals of modern silviculture is to emulate the structural complexity of old-growth forests. In this context, it is of advantage to identify a target state of structural complexity at the stand level and to analyze the spatial characteristics that led to the desired complexity of forest structures in primary forest references. In this study, we used 3D forest scenes captured by terrestrial laser scanning (TLS) to identify spatial patterns of structural complexity of differently managed and unmanaged European forests dominated by beech (Fagus sylvatica L.). We scanned in managed even-aged and uneven-aged stands, as well as in formerly managed forests (National Parks) and primary forests. For three different forest strata, representing the understory, the midstory, and the overstory of a forest stand, we determined the structural complexity mathematically using fractal analysis. Beyond that, we analyzed the density, as well as the horizontal and vertical distribution of plant material. For all three forest strata, we observed differences in structural complexity between the different forest types. Within the lower and middle strata, the investigated primary forests showed a random to regular distribution of plant material, as well as a complex understory structure as a result of pronounced natural decay. Compared to the primary forests, the managed uneven-aged stands showed quite similar spatial patterns of distribution of plant material, but on average a higher space occupation in the lower and middle forest stratum. Our results suggest that single tree or group selection cutting is a useful management tool to imitate old-growth structures of undisturbed beech-dominated forests.
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McElhinny, Chris, Phillip Gibbons, Cris Brack, and Juergen Bauhus. "Forest and woodland stand structural complexity: Its definition and measurement." Forest Ecology and Management 218, no. 1-3 (October 2005): 1–24. http://dx.doi.org/10.1016/j.foreco.2005.08.034.
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Seidel, Dominik, Peter Annighöfer, Martin Ehbrecht, Paul Magdon, Stephan Wöllauer, and Christian Ammer. "Deriving Stand Structural Complexity from Airborne Laser Scanning Data—What Does It Tell Us about a Forest?" Remote Sensing 12, no. 11 (June 8, 2020): 1854. http://dx.doi.org/10.3390/rs12111854.
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The three-dimensional forest structure is an important driver of several ecosystem functions and services. Recent advancements in laser scanning technologies have set the path to measuring structural complexity directly from 3D point clouds. Here, we show that the box-dimension (Db) from fractal analysis, a measure of structural complexity, can be obtained from airborne laser scanning data. Based on 66 plots across different forest types in Germany, each 1 ha in size, we tested the performance of the Db by evaluating it against conventional ground-based measures of forest structure and commonly used stand characteristics. We found that the Db was related (0.34 < R < 0.51) to stand age, management intensity, microclimatic stability, and several measures characterizing the overall stand structural complexity. For the basal area, we could not find a significant relationship, indicating that structural complexity is not tied to the basal area of a forest. We also showed that Db derived from airborne data holds the potential to distinguish forest types, management types, and the developmental phases of forests. We conclude that the box-dimension is a promising measure to describe the structural complexity of forests in an ecologically meaningful way.
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Hickey, Laura J., Jeff Atkins, Robert T. Fahey, Mark T. Kreider, Shea B. Wales, and Christopher M. Gough. "Contrasting Development of Canopy Structure and Primary Production in Planted and Naturally Regenerated Red Pine Forests." Forests 10, no. 7 (July 8, 2019): 566. http://dx.doi.org/10.3390/f10070566.
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Globally, planted forests are rapidly replacing naturally regenerated stands but the implications for canopy structure, carbon (C) storage, and the linkages between the two are unclear. We investigated the successional dynamics, interlinkages and mechanistic relationships between wood net primary production (NPPw) and canopy structure in planted and naturally regenerated red pine (Pinus resinosa Sol. ex Aiton) stands spanning ≥ 45 years of development. We focused our canopy structural analysis on leaf area index (LAI) and a spatially integrative, terrestrial LiDAR-based complexity measure, canopy rugosity, which is positively correlated with NPPw in several naturally regenerated forests, but which has not been investigated in planted stands. We estimated stand NPPw using a dendrochronological approach and examined whether canopy rugosity relates to light absorption and light–use efficiency. We found that canopy rugosity increased similarly with age in planted and naturally regenerated stands, despite differences in other structural features including LAI and stem density. However, the relationship between canopy rugosity and NPPw was negative in planted and not significant in naturally regenerated stands, indicating structural complexity is not a globally positive driver of NPPw. Underlying the negative NPPw-canopy rugosity relationship in planted stands was a corresponding decline in light-use efficiency, which peaked in the youngest, densely stocked stand with high LAI and low structural complexity. Even with significant differences in the developmental trajectories of canopy structure, NPPw, and light use, planted and naturally regenerated stands stored similar amounts of C in wood over a 45-year period. We conclude that widespread increases in planted forests are likely to affect age-related patterns in canopy structure and NPPw, but planted and naturally regenerated forests may function as comparable long-term C sinks via different structural and mechanistic pathways.
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Kane, Van R., Robert J. McGaughey, Jonathan D. Bakker, Rolf F. Gersonde, James A. Lutz, and Jerry F. Franklin. "Comparisons between field- and LiDAR-based measures of stand structural complexity." Canadian Journal of Forest Research 40, no. 4 (April 2010): 761–73. http://dx.doi.org/10.1139/x10-024.
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Forest structure, as measured by the physical arrangement of trees and their crowns, is a fundamental attribute of forest ecosystems that changes as forests progress through suc;cessional stages. We examined whether LiDAR data could be used to directly assess the successional stage of forests by determining the degree to which the LiDAR data would show the same relative ranking of structural development among sites as would traditional field measurements. We sampled 94 primary and secondary sites (19–93, 223–350, and 600 years old) from three conifer forest zones in western Washington state, USA, in the field and with small-footprint, discrete return LiDAR. Seven sets of LiDAR metrics were tested to measure canopy structure. Ordinations using the of LiDAR 95th percentile height, rumple, and canopy density metrics had the strongest correlations with ordinations using two sets of field metrics (Procrustes R = 0.72 and 0.78) and a combined set of LiDAR and field metrics (Procrustes R = 0.95). These results suggest that LiDAR can accurately characterize forest successional stage where field measurements are not available. This has important implications for enabling basic and applied studies of forest structure at stand to landscape scales.
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Kane, Van R., Jonathan D. Bakker, Robert J. McGaughey, James A. Lutz, Rolf F. Gersonde, and Jerry F. Franklin. "Examining conifer canopy structural complexity across forest ages and elevations with LiDAR data." Canadian Journal of Forest Research 40, no. 4 (April 2010): 774–87. http://dx.doi.org/10.1139/x10-064.
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LiDAR measurements of canopy structure can be used to classify forest stands into structural stages to study spatial patterns of canopy structure, identify habitat, or plan management actions. A key assumption in this process is that differences in canopy structure based on forest age and elevation are consistent with predictions from models of stand development. Three LiDAR metrics (95th percentile height, rumple, and canopy density) were computed for 59 secondary and 35 primary forest plots in the Pacific Northwest, USA. Hierarchical clustering identified two precanopy closure classes, two low-complexity postcanopy closure classes, and four high-complexity postcanopy closure classes. Forest development models suggest that secondary plots should be characterized by low-complexity classes and primary plots characterized by high-complexity classes. While the most and least complex classes largely confirmed this relationship, intermediate-complexity classes were unexpectedly composed of both secondary and primary forest types. Complexity classes were not associated with elevation, except that primary Tsuga mertensiana (Bong.) Carrière (mountain hemlock) plots were complex. These results suggest that canopy structure does not develop in a linear fashion and emphasize the importance of measuring structural conditions rather than relying on development models to estimate structural complexity across forested landscapes.
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Matsala, Maksym, Andrii Bilous, Roman Feshchenko, Raisa Matiashuk, Svitlana Bilous, and Yaroslav Kovbasa. "Spatial and compositional structure of European oak urban forests in Kyiv city, Ukraine." Journal of Forest Science 67, No. 3 (March 5, 2021): 143–53. http://dx.doi.org/10.17221/173/2020-jfs.
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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.
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Asbeck, Thomas, and Julian Frey. "Weak relationships of continuous forest management intensity and remotely sensed stand structural complexity in temperate mountain forests." European Journal of Forest Research 140, no. 3 (February 13, 2021): 721–31. http://dx.doi.org/10.1007/s10342-021-01361-4.
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AbstractUnderstanding the relationship of stand structural complexity and forest management is relevant to create desired stand structures by adapting management strategies under changing disturbance scenarios and climatic conditions. To overcome difficulties in differentiating between strict categories of silvicultural practices and to describe the impact of forest management more appropriate, we used a continuous indicator of forest management intensity (ForMI). The ForMI consists of three components including volumes of natural deadwood, non-native tree species and harvested trees. There are a great number of approaches to quantify stand structure; here we used the recently established stand structural complexity index (SSCI) which represents a density-dependent as well as vertical measure of complexity based on the distribution of points in 3D space inventoried by terrestrial laser scanning. The data collection took place in 135 one-hectare plots managed under close-to-nature forest management (CTNFM) located in the Black Forest, Germany. We build generalized additive models to test the relationship of the SSCI with the ForMI. The model results did not prove a significant relationship between the SSCI and the ForMI, but components of the ForMI showed significant relationships to the SSCI. Our results indicate that the relationship between stand structural complexity and forest management intensity is, while plausible, not trivial to demonstrate. We conclude that forest managers have a relatively wide range of choices in CTNFM to adapt forests within a similar range of management intensity as presented here to future challenges, since management intensity does not change the forest structure drastically.
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Ballauff, Johannes, Delphine Clara Zemp, Dominik Schneider, Bambang Irawan, Rolf Daniel, and Andrea Polle. "Legacy Effects Overshadow Tree Diversity Effects on Soil Fungal Communities in Oil Palm-Enrichment Plantations." Microorganisms 8, no. 10 (October 13, 2020): 1577. http://dx.doi.org/10.3390/microorganisms8101577.
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Financially profitable large-scale cultivation of oil palm monocultures in previously diverse tropical rain forest areas constitutes a major ecological crisis today. Not only is a large proportion of the aboveground diversity lost, but the belowground soil microbiome, which is important for the sustainability of soil function, is massively altered. Intermixing oil palms with native tree species promotes vegetation biodiversity and stand structural complexity in plantations, but the impact on soil fungi remains unknown. Here, we analyzed the diversity and community composition of soil fungi three years after tree diversity enrichment in an oil palm plantation in Sumatra (Indonesia). We tested the effects of tree diversity, stand structural complexity indices, and soil abiotic conditions on the diversity and community composition of soil fungi. We hypothesized that the enrichment experiment alters the taxonomic and functional community composition, promoting soil fungal diversity. Fungal community composition was affected by soil abiotic conditions (pH, N, and P), but not by tree diversity and stand structural complexity indices. These results suggest that intensive land use and abiotic filters are a legacy to fungal communities, overshadowing the structuring effects of the vegetation, at least in the initial years after enrichment plantings.
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McElhinny, C., P. Gibbons, and C. Brack. "An objective and quantitative methodology for constructing an index of stand structural complexity." Forest Ecology and Management 235, no. 1-3 (November 2006): 54–71. http://dx.doi.org/10.1016/j.foreco.2006.07.024.
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Seidel, Dominik, Melissa Stiers, Martin Ehbrecht, Maik Werning, and Peter Annighöfer. "On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode." Agroforestry Systems 95, no. 4 (April 2021): 669–85. http://dx.doi.org/10.1007/s10457-021-00620-y.
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AbstractAgroforestry systems provide important ecosystem functions and services. They have the potential to enrich agricultural monocultures in central Europe with structural elements otherwise absent, which is expected to be accompanied by a surplus of ecosystem functions. Here we used quantitative measures derived from terrestrial laser scanning in single-scan mode to describe the structural complexity, the canopy openness, the foliage height diversity and the understory complexity of four common agroforest systems in central Europe. We accessed silvopasture systems with grazing ponies and cattle as well as fellow deer, short rotation forests with agricultural use between the tree rows, tree orchards with grazing sheep and Christmas tree plantations on which chickens forage. As a reference, we used data for 65 forest sites across Germany, representing different forest types, various dominant tree species, stand ages and management systems. We found that overall stand structural complexity is ranked as follows: forest > silvopasture systems > short rotation forest > tree orchard > Christmas tree plantation. Consequently, if overall structural complexity of an agricultural landscape shall be enriched, there is now strong evidence on how this may be achieved using agroforests. However, if the focus lies on selected structures that serve specific functions, e.g. dense understory to provide animal shelter, specific types of agroforests may be chosen and the ranking in overall structural complexity may be less important.
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Park, Juhan, Hyun Seok Kim, Hyun Kook Jo, and II Bin Jung. "The Influence of Tree Structural and Species Diversity on Temperate Forest Productivity and Stability in Korea." Forests 10, no. 12 (December 6, 2019): 1113. http://dx.doi.org/10.3390/f10121113.
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Research Highlights: Using a long-term dataset on temperate forests in South Korea, we established the interrelationships between tree species and structural diversity and forest productivity and stability, and identified a strong, positive effect of structural diversity, rather than tree species diversity, on productivity and stability. Background and Objectives: Globally, species diversity is positively related with forest productivity. However, temperate forests often show a negative or neutral relationship. In those forests, structural diversity, instead of tree species diversity, could control the forest function. Materials and Methods: This study tested the effects of tree species and structural diversity on temperate forest productivity. The basal area increment and relative changes in stand density were used as proxies for forest productivity and stability, respectively. Results: Here we show that structural diversity, but not species diversity, had a significant, positive effect on productivity, whereas species diversity had a negative effect, despite a positive effect on diversity. Structural diversity also promoted fewer changes in stand density between two periods, whereas species diversity showed no such relation. Structurally diverse forests might use resources efficiently through increased canopy complexity due to canopy plasticity. Conclusions: These results indicate reported species diversity effects could be related to structural diversity. They also highlight the importance of managing structurally diverse forests to improve productivity and stability in stand density, which may promote sustainability of forests.
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Ducey, Mark J. "The Ratio of Additive and Traditional Stand Density Indices." Western Journal of Applied Forestry 24, no. 1 (January 1, 2009): 5–10. http://dx.doi.org/10.1093/wjaf/24.1.5.
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Abstract The ratio between additive and original versions of Reineke's stand density index (SDI) has been used as a descriptor of stand structural complexity. That ratio also can be informative for designing efficient sampling methods and for the design of silvicultural experiments. Previous analyses of this ratio have assumed a diameter distribution without truncation, such that trees from zero to infinite dbh are possible. Truncation of the diameter distribution, e.g., by tallying only trees larger than some minimum dbh, moves the ratio much closer to one when the stand has a classic balanced uneven-aged structure. Minimum values of the ratio are found not with classic reverse-J distributions, but with sharply bimodal distributions that might be typical of a two-cohort stand. The implications for the use of novel sampling methods and for experimental designs to test whether the additive or original SDI provides better prediction in irregular stands are discussed.
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Cannon, Jeffery B., Wade T. Tinkham, Ryan K. DeAngelis, Edward M. Hill, and Mike A. Battaglia. "Variability in Mixed Conifer Spatial Structure Changes Understory Light Environments." Forests 10, no. 11 (November 13, 2019): 1015. http://dx.doi.org/10.3390/f10111015.
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In fire-adapted conifer forests of the Western U.S., changing land use has led to increased forest densities and fuel conditions partly responsible for increasing the extent of high-severity wildfires in the region. In response, land managers often use mechanical thinning treatments to reduce fuels and increase overstory structural complexity, which can help improve stand resilience and restore complex spatial patterns that once characterized these stands. The outcomes of these treatments can vary greatly, resulting in a large gradient in aggregation of residual overstory trees. However, there is limited information on how a range of spatial outcomes from restoration treatments can influence structural complexity and tree regeneration dynamics in mixed conifer stands. In this study, we model understory light levels across a range of forest density in a stem-mapped dry mixed conifer forest and apply this model to simulated stem maps that are similar in residual basal area yet vary in degree of spatial complexity. We found that light availability was best modeled by residual stand density index and that consideration of forest structure at multiple spatial scales is important for predicting light availability. Second, we found that restoration treatments differing in spatial pattern may differ markedly in their achievement of objectives such as density reduction, maintenance of horizontal and tree size complexity, and creation of microsite conditions favorable to shade-intolerant species, with several notable tradeoffs. These conditions in turn have cascading effects on regeneration dynamics, treatment longevity, fire behavior, and resilience to disturbances. In our study, treatments with high aggregation of residual trees best balanced multiple objectives typically used in ponderosa pine and dry mixed conifer forests. Simulation studies that consider a wide range of possible spatial patterns can complement field studies and provide predictions of the impacts of mechanical treatments on a large range of potential ecological effects.
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Zenner, Eric K., Erkki Lähde, and Olavi Laiho. "Contrasting the temporal dynamics of stand structure in even- and uneven-sized Picea abies dominated stands." Canadian Journal of Forest Research 41, no. 2 (February 2011): 289–99. http://dx.doi.org/10.1139/x10-205.
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Although proposed as a means of increasing structural diversity in managed forests, the impact of single-tree selection on the temporal dynamics of three-dimensional structure has not been previously evaluated. Forest structural development in Picea-dominated stands was contrasted over 15 years in stem-mapped randomized plots in southern Finland that underwent either low thinning (creating the even-sized (ES) structure of a bell-shaped diameter distribution) or single-tree selection (maintaining the uneven-sized (UES) structure of a reverse-J-shaped distribution) through multiple harvest entries. Structure was quantified with nonspatial stand attributes (e.g., density) and indices that quantify spatially explicit relationships among neighboring trees (e.g., structural complexity index (SCI)). Over time, three-dimensional structure reflected differential tree growth and mortality, resulting in minor changes in tree composition, spatial pattern, and tree size differentiation and somewhat greater changes in the SCI. The third harvest entry simplified the forest structure in both structure types. However, structural metrics such as the variability of tree diameters, tree size differentiation, and the SCI recovered to preharvest levels within 2–4 years in UES plots, whereas no recovery was seen in the ES structure type. Single-tree selection was demonstrated to perpetuate the uneven-sized structure associated with natural nonpyrogenic Picea-dominated forests.
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Ehbrecht, Martin, Peter Schall, Christian Ammer, and Dominik Seidel. "Quantifying stand structural complexity and its relationship with forest management, tree species diversity and microclimate." Agricultural and Forest Meteorology 242 (August 2017): 1–9. http://dx.doi.org/10.1016/j.agrformet.2017.04.012.
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Ren, Siyuan, Qingsong Yang, Heming Liu, Guochun Shen, Zemei Zheng, Shuangshuang Zhou, Mengfang Liang, Huimin Yin, Zhengkang Zhou, and Xihua Wang. "The Driving Factors of Subtropical Mature Forest Productivity: Stand Structure Matters." Forests 12, no. 8 (July 28, 2021): 998. http://dx.doi.org/10.3390/f12080998.
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Forest productivity (increment of above-ground biomass) is determined by biodiversity but also by stand structure attributes. However, the relative strengths of these drivers in determining productivity remain controversial in subtropical forests. In this study, we analyzed a tree growth data from 500 plots with in a 20 ha mature subtropical forest in eastern China. We used spatial simultaneous autoregressive error models to examine the effects of diversity variables (species richness, evenness, and composition), stand structural attributes (stand density, tree size range and diversity), environmental factors (topography and soil), and initial above-ground biomass (AGB) on productivity. We also applied structural equation models to quantify the relative importance of diversity, stand structure, environmental factors, and initial AGB in determining forest productivity. Our results showed that stand structure together with diversity and initial AGB governed forest productivity. Tree size diversity (DBH Shannon’s diversity index) had the largest positive effect on forest productivity. These results provide new evidence that structural explanatory variables have greater contributions to productivity for mature subtropical forests, strongly supporting the niche complementarity hypothesis. Our work highlights the importance of tree size diversity in promoting high forest productivity, and suggests that regulating and conserving complexity of forest stand structure should be among the most important goals in subtropical forest management.
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Seidel, Dominik, Peter Annighöfer, Christian Ammer, Martin Ehbrecht, Katharina Willim, Jan Bannister, and Daniel P. Soto. "Quantifying Understory Complexity in Unmanaged Forests Using TLS and Identifying Some of Its Major Drivers." Remote Sensing 13, no. 8 (April 14, 2021): 1513. http://dx.doi.org/10.3390/rs13081513.
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The structural complexity of the understory layer of forests or shrub layer vegetation in open shrublands affects many ecosystem functions and services provided by these ecosystems. We investigated how the basal area of the overstory layer, annual and seasonal precipitation, annual mean temperature, as well as light availability affect the structural complexity of the understory layer along a gradient from closed forests to open shrubland with only scattered trees. Using terrestrial laser scanning data and the understory complexity index (UCI), we measured the structural complexity of sites across a wide range of precipitation and temperature, also covering a gradient in light availability and basal area. We found significant relationships between the UCI and tree basal area as well as canopy openness. Structural equation models (SEMs) confirmed significant direct effects of seasonal precipitation on the UCI without mediation through basal area or canopy openness. However, annual precipitation and temperature effects on the UCI are mediated through canopy openness and basal area, respectively. Understory complexity is, despite clear dependencies on the available light and overall stand density, significantly and directly driven by climatic parameters, particularly the amount of precipitation during the driest month.
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Frey, Julian, Bettina Joa, Ulrich Schraml, and Barbara Koch. "Same Viewpoint Different Perspectives—A Comparison of Expert Ratings with a TLS Derived Forest Stand Structural Complexity Index." Remote Sensing 11, no. 9 (May 13, 2019): 1137. http://dx.doi.org/10.3390/rs11091137.
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Forests are one of the most important terrestrial ecosystems for the protection of biodiversity, but at the same time they are under heavy production pressures. In many cases, management optimized for timber production leads to a simplification of forest structures, which is associated with species loss. In recent decades, the concept of retention forestry has been implemented in many parts of the world to mitigate this loss, by increasing structure in managed stands. Although this concept is widely adapted, our understanding what forest structure is and how to reliably measure and quantify it is still lacking. Thus, more insights into the assessment of biodiversity-relevant structures are needed, when aiming to implement retention practices in forest management to reach ambitious conservation goals. In this study we compare expert ratings on forest structural richness with a modern light detection and ranging (LiDAR) -based index, based on 52 research sites, where terrestrial laser scanning (TLS) data and 360° photos have been taken. Using an online survey (n = 444) with interactive 360° panoramic image viewers, we sought to investigate expert opinions on forest structure and learn to what degree measures of structure from terrestrial laser scans mirror experts’ estimates. We found that the experts’ ratings have large standard deviance and therefore little agreement. Nevertheless, when averaging the large number of participants, they distinguish stands according to their structural richness significantly. The stand structural complexity index (SSCI) was computed for each site from the LiDAR scan data, and this was shown to reflect some of the variation of expert ratings (p = 0.02). Together with covariates describing participants’ personal background, image properties and terrain variables, we reached a conditional R2 of 0.44 using a linear mixed effect model. The education of the participants had no influence on their ratings, but practical experience showed a clear effect. Because the SSCI and expert opinion align to a significant degree, we conclude that the SSCI is a valuable tool to support forest managers in the selection of retention patches.
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Kenefic, Laura S., and Ralph D. Nyland. "Sugar Maple Height-Diameter and Age-Diameter Relationships in an Uneven-Aged Northern Hardwood Stand." Northern Journal of Applied Forestry 16, no. 1 (March 1, 1999): 43–47. http://dx.doi.org/10.1093/njaf/16.1.43.
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Abstract Sugar maple (Acer saccharum Marsh.) height-diameter and age-diameter relationships are explored in a balanced uneven-aged northern hardwood stand in central New York. Results show that although both height and age vary considerably with diameter, these relationships can be described by statistically valid equations. The age-diameter relationship compares favorably to one reported by Tubbs (1977) for sugar maple in unmanaged (virgin) northern hardwoods, suggesting that periodic cuttings improved growing conditions in our stand. Deliberate attempts to control size-class distribution and tree spacing should continue to increase diameter growth rates and decrease the time needed to reach certain threshold tree sizes. Growth rates that can be reasonably expected in this and similarly structured stands are provided. Lastly, a wide range of heights and diameters are documented, confirming the structural complexity associated with the balanced selection system. An equation to predict sugar maple height from diameter is provided and may prove useful when assessing habitat or visual characteristics of complex uneven-aged stands. North. J. Appl. For. 16(1):43-47.
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Zhang, W., B. Hu, and M. Woods. "Mapping forest stand complexity for woodland caribou habitat assessment using multispectral airborne imagery." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-2 (November 11, 2014): 179–85. http://dx.doi.org/10.5194/isprsarchives-xl-2-179-2014.
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The decline of the woodland caribou population is a result of their habitat loss. To conserve the habitat of the woodland caribou and protect it from extinction, it is critical to accurately characterize and monitor its habitat. Conventionally, products derived from low to medium spatial resolution remote sensing data, such as land cover classification and vegetation indices are used for wildlife habitat assessment. These products fail to provide information on the structure complexities of forest canopies which reflect important characteristics of caribou’s habitats. Recent studies have employed the LiDAR system (Light Detection And Ranging) to directly retrieve the three dimensional forest attributes. Although promising results have been achieved, the acquisition cost of LiDAR data is very high. In this study, utilizing the very high spatial resolution imagery in characterizing the structural development the of forest canopies was exploited. A stand based image texture analysis was performed to predict forest succession stages. The results were demonstrated to be consistent with those derived from LiDAR data.
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Axelson, Jodi N., René I. Alfaro, and Brad C. Hawkes. "Changes in stand structure in uneven-aged lodgepole pine stands impacted by mountain pine beetle epidemics and fires in central British Columbia." Forestry Chronicle 86, no. 1 (February 1, 2010): 87–99. http://dx.doi.org/10.5558/tfc86087-1.
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We examined the development of lodgepole pine (Pinus contorta Dougl.) in uneven-aged stands in the Interior Douglasfir (IDF) biogeoclimatic zone of central of British Columbia (B.C.), which are currently undergoing a massive outbreak of the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB). Using historical ecological approaches, dendrochronology, and stand measurement data, we determined the roles MPB and fire disturbances have played in the ecological processes of lodgepole pine in an Interior Douglas-fir zone. We found that multiple mixed-severity fires created patchy uneven-aged stands dominated by lodgepole pine. Since fire suppression in the 20th century, multiple MPB disturbances have maintained the structural complexity of the stands and favoured regeneration of lodgepole pine in the understory despite the absence of fire, resulting in self-perpetuating multi-age lodgepole pine stands. Analysis of the stand structures remaining after multiple MPB outbreaks showed that, even with high overstory mortality, the sample stands contained several MPB-initiated cohorts, consisting of younger and smaller-diameter lodgepole pine. These surviving lodgepole pine layers, which are less susceptible to beetle, will provide important ecological legacies, and could play an important role in the mid-term timber supply chain. We concluded that, in the absence of fire, the MPB plays a more frequent role in directing stand dynamics and structure in uneven-aged lodgepole pine stands resulting in selfperpetuating complex stands in the central interior. We compared and contrasted these findings with those obtained in “even-aged” lodgepole pine stands, also in the Interior Douglas-fir zone in the southern interior, which were investigated in an earlier study. Key words: lodgepole pine, mountain pine beetle, dendroecology, complex stands, mixed-severity fire regime
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Saunders, Mike R., and Robert G. Wagner. "Long-term spatial and structural dynamics in Acadian mixedwood stands managed under various silvicultural systems." Canadian Journal of Forest Research 38, no. 3 (March 2008): 498–517. http://dx.doi.org/10.1139/x07-155.
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Using inventory data from a long-term silviculture experiment in east-central Maine, spatial models were developed to analyze 28 years (1974–2002) of stand structural dynamics. Differences in spatial pattern, species mingling, height differentiation, and relative stand complexity index (rSCI) were compared among five treatments: commercial clear-cutting, fixed diameter-limit, 5 year single-tree selection, three-stage shelterwood (both with and without precommercial thinning), and unharvested natural areas. Regardless of treatment, regeneration events (whether induced by natural breakup of the overstory or by harvesting) increased aggregation in spatial pattern and reduced species mingling, more so in the commercial clearcut and fixed diameter-limit treatments where hardwood densities were highest. Regular spatial patterns were rare. Height differentiation values for individual trees and stand-level mean rSCI were generally highest in untreated natural areas and 5 year selection treatments, intermediate in commercial clearcut and fixed diameter-limit treatments, and lowest in three-stage shelterwood treatments. After a brief adjustment period, precommercial thinning in a shelterwood treated stand generally increased species mingling, height differentiation, and rSCI. Two untreated natural areas exhibited divergent pathways of structural development. Dynamics in uneven-aged selection treatments more closely resembled that of the untreated natural areas than did the shelterwood, commercial clearcut, or fixed diameter-limit treatments.
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Smith, Kimberly J., William S. Keeton, Mark J. Twery, and Donald R. Tobi. "Understory plant responses to uneven-aged forestry alternatives in northern hardwood–conifer forests." Canadian Journal of Forest Research 38, no. 6 (June 2008): 1303–18. http://dx.doi.org/10.1139/x07-236.
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The understory layer encompasses the majority of plant species diversity in forested ecosystems and may be sensitive to timber harvest disturbance. We hypothesize that (i) uneven-aged, low-intensity silvicultural systems can maintain understory plant diversity and support late-successional species following harvest disturbance; (ii) retaining and enhancing stand structural complexity can increase understory plant diversity in northern hardwood–conifer forests; and (iii) plant responses are influenced by interactions among canopy structure, soils, and climate processes. Experimental treatments include single-tree selection and group selection, both modified to increase structural retention, and a third technique designed to promote late-successional forest structure and function, structural complexity enhancement. Four replications of each treatment were applied to 2 ha units in Vermont and New York, USA. Understory vegetation was monitored 2 years pre- and 4 years post-treatment. Results show that over time, understory responses were strongly affected by overstory treatment and less influenced by soils and drought. All treatments succeeded at maintaining overall composition and diversity. However, late-successional diversity increased significantly in structural complexity enhancement units compared with group selection units. These results indicate that while conventional uneven-aged systems can maintain understory plant diversity, variations that retain or enhance structural complexity may be more effective at retaining late-successional species.
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Michaud, Gabriel. "L’incidence d’un enseignement centré sur la forme sur la performance orale." Canadian Modern Language Review 77, no. 3 (August 1, 2021): 269–89. http://dx.doi.org/10.3138/cmlr-2020-0128.
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The present study examines the timing effect of form-focused instruction within a task on language performance. One hundred and ten university-level, French as a second language students of B1 and B2 proficiency performed a ranking task. Two groups received instruction on the subjunctive prior to completing the task, two groups received instruction during the task, and two groups received instruction after the task. Performance was analyzed along the lines of structural complexity, accuracy, fluidity, and lexical complexity. The group receiving instruction prior to task completion displayed the most structural complexity, overall accuracy, and fluidity. Instruction during the task resulted in the greatest degree of lexical complexity and accuracy with respect to the use of the subjunctive. The post-task instruction group did not stand out in any respect. The results of the study demonstrate that form-focus instruction given prior to task completion does not necessarily yield negative effects on performance, contrary to some theoretical predictions or pedagogical recommendations regarding Task-Based Language Teaching.
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McElhinny, C., P. Gibbons, C. Brack, and J. Bauhus. "Fauna-habitat relationships: a basis for identifying key stand structural attributes in temperate Australian eucalypt forests and woodlands." Pacific Conservation Biology 12, no. 2 (2006): 89. http://dx.doi.org/10.1071/pc060089.
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We review a representative sample of the literature concerning fauna-habitat relationships in temperate Australian eucalypt forests and woodlands as a basis for identifying some key stand structural attributes in these ecosystems. Our review identifies 56 studies in south-east and south-west Australia in which the presence or abundance of different fauna were significantly associated with vegetation structural attributes at the scale of a stand. The majority of these studies concern bird, arboreal mammal, and ground mammal habitat requirements, with relatively few studies addressing the habitat requirements of reptiles, invertebrates, bats or amphibians. We identify 34 key structural attributes from these 56 studies, by grouping similar attributes, and then representing each group with a single generic attribute. Relatively few of these attributes are incorporated into indices used to quantify fauna habitat. We highlight the need for a quantitative method for selecting which key attributes should form the basis for an index of structural complexity or other surrogate measure of faunal diversity.
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Palik, Brian J., and Neil Pederson. "Overstory mortality and canopy disturbances in longleaf pine ecosystems." Canadian Journal of Forest Research 26, no. 11 (November 1, 1996): 2035–47. http://dx.doi.org/10.1139/x26-229.
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We studied longleaf pine (Pinuspalustris Mill.) ecosystems to determine causes and rates of overstory mortality, size of canopy disturbances, and the effects of disturbance on canopy structure. Further, we used redundancy analysis to relate variation in characteristics of mortality across a landscape to site and stand variables. We analyzed mortality that occurred from 1990 to 1994 in 70 second-growth plots that spanned a range of site conditions and stand structures, and in five large disturbances that occurred outside the random sample of plots. Half of pine mortality over 5 years in the 70 plots was from unknown causes. Lightning was the primary identifiable cause of mortality, followed by suppression and wind. Lightning mortality was most frequent on xeric sites, while windthrow was common on wet–mesic sites. Suppression mortality was frequent on wet–mesic sites and in higher density stands. Five-year mortality rates averaged 2.3 trees/ha, or 1.9% of original density. Most mortality consisted of single trees. Large disturbances (mostly from lightning) of 15–30 trees were rare, occurring once per 1000 ha in 5 years. Variation in amount of mortality and size of disturbance were unrelated to soil or stand structural characteristics. Low mortality rates from small-scale disturbances result in slow canopy turnover. These results indicate that large openings sufficient for natural regeneration of longleaf pine develop slowly in the absence of hurricanes. Silvicultural options for longleaf pine can be designed to mimic the canopy structure that results from natural canopy disturbances, which leave many live trees standing. Such options may be desirable if a goal of silviculture is to increase structural complexity in stands managed for timber.
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Ali, Arshad, Si-Liang Lin, Jie-Kun He, Fan-Mao Kong, Jie-Hua Yu, and Hai-Sheng Jiang. "Climate and soils determine aboveground biomass indirectly via species diversity and stand structural complexity in tropical forests." Forest Ecology and Management 432 (January 2019): 823–31. http://dx.doi.org/10.1016/j.foreco.2018.10.024.
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Sharma, Ram P., Igor Štefančík, Zdeněk Vacek, and Stanislav Vacek. "Generalized Nonlinear Mixed-Effects Individual Tree Diameter Increment Models for Beech Forests in Slovakia." Forests 10, no. 5 (May 24, 2019): 451. http://dx.doi.org/10.3390/f10050451.
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Individual tree growth and yield models precisely describe tree growth irrespective of stand complexity and are capable of simulating various silvicultural alternatives in the stands with diverse structure, species composition, and management history. We developed both age dependent and age independent diameter increment models using long-term research sample plot data collected from both monospecific and mixed stands of European beech (Fagus sylvatica L.) in the Slovak Republic. We used diameter at breast height (DBH) as a main predictor and other characteristics describing site quality (site index), stand development stage (dominant height and stand age), stand density or competition (ratio of individual tree DBH to quadratic mean diameter), species mixture (basal area proportion of a species of interest), and dummy variable describing stand management regimes as covariate predictors to develop the models. We evaluated eight versatile growth functions in the first stage using DBH as a single predictor and selected the most suitable one, i.e., Chapman-Richards function for further analysis through the inclusion of covariate predictors. We introduced the random components describing sample plot-level random effects and stochastic variations on the diameter increment, into the models through the mixed-effects modelling. The autocorrelation caused by hierarchical data-structure, which is assumed to be partially reduced by mixed-effects modelling, was removed through the inclusion of the parameter accounting for the autoregressive error-structures. The models described about two-third parts of a total variation in the diameter increment without significant trends in the residuals. Compared to the age independent mixed-effects model (conditional coefficient of determination, R c 2 = 0.6566; root mean square error, RMSE = 0.1196), the age dependent model described a significantly larger proportion of the variations in diameter increment ( R c 2 = 0.6796, RMSE = 0.1141). Diameter increment was significantly influenced differently by covariate predictors included into the models. Diameter increment decreased with the advancement of stand development stage (increased dominant height and stand age), increasing intraspecific competition (increased basal area proportion of European beech per sample plot), and diameter increment increased with increasing site quality (increased site index) and decreased competition (increased ratio of DBH to quadratic mean diameter). Our mixed-effects models, which can be easily localized with the random effects estimated from prior measurement of diameter increments of four randomly selected trees per sample plot, will provide high prediction accuracies. Our models may be used for simulating growth of European beech irrespective of its stand structural complexity, as these models have included various covariate variables describing both tree-and stand-level characteristics, thinning regimes, except the climate characteristics. Together with other forest models, our models will be used as inputs to the growth simulator to be developed in the future, which is important for decision-making in forestry.
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Crotteau, Justin S., Christopher R. Keyes, Elaine K. Sutherland, David K. Wright, and Joel M. Egan. "Forest fuels and potential fire behaviour 12 years after variable-retention harvest in lodgepole pine." International Journal of Wildland Fire 25, no. 6 (2016): 633. http://dx.doi.org/10.1071/wf14223.
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Variable-retention harvesting in lodgepole pine offers an alternative to conventional, even-aged management. This harvesting technique promotes structural complexity and age-class diversity in residual stands and promotes resilience to disturbance. We examined fuel loads and potential fire behaviour 12 years after two modes of variable-retention harvesting (dispersed and aggregated retention patterns) crossed by post-harvest prescribed fire (burned or unburned) in central Montana. Results characterise 12-year post-treatment fuel loads. We found greater fuel load reduction in treated than untreated stands, namely in the 10- and 100-h classes (P = 0.002 and 0.049 respectively). Reductions in 1-h (P < 0.001), 10-h (P = 0.008) and 1000-h (P = 0.014) classes were greater in magnitude for unburned than burned treatments. Fire behaviour modelling incorporated the regenerating seedling cohort into the surface fuel complex. Our analysis indicates greater surface fireline intensity in treated than untreated stands (P < 0.001), and in unburned over burned stands (P = 0.001) in dry, windy weather. Although potential fire behaviour in treated stands is predicted to be more erratic, within-stand structural variability reduces probability of crown fire spread. Overall, results illustrate trade-offs between potential fire attributes that should be acknowledged with variable-retention harvesting.
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Azhar, Badrul, David B. Lindenmayer, Jeff Wood, Joern Fischer, Adrian Manning, Chris Mcelhinny, and Mohamed Zakaria. "The influence of agricultural system, stand structural complexity and landscape context on foraging birds in oil palm landscapes." Ibis 155, no. 2 (March 16, 2013): 297–312. http://dx.doi.org/10.1111/ibi.12025.
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Šumichrast, Ladislav, Jaroslav Vencurik, Ján Pittner, and Stanislav Kucbel. "The long-term dynamics of the old-growth structure in the National Nature Reserve Badínsky prales." Journal of Forest Science 66, No. 12 (December 21, 2020): 501–10. http://dx.doi.org/10.17221/139/2020-jfs.
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The main goal of this paper was to evaluate structure dynamics in the fir-beech, old-growth forest Badínsky prales. Measurements were taken on four permanent research plots (0.5 ha each) between 1970 and 2018, typically in ten-year intervals. In order to assess long-term structure dynamics, this study used basic stand characteristics and selected structural indices – the relative density (RD), coefficient of homogeneity (H), and structural complexity index (SCI). Species composition was quantified by the relative importance value (RIV), and a detrended correspondence analysis was carried out for the visualisation of long-term changes. The long-term mean of the stand volume reached 634 ± 99 m3·ha−1, and the mean of the basal area was 36.6 ± 4.0 m2·ha–1. Calculated values of the coefficient of homogeneity (1.46–2.54) were similar to values in other old-growth forests with a comparable tree species composition. An increasing trend in beech RIV values was observed; on the other hand, fir RIV values fell by approximately 20%–25%. In 2018, maximal values of the basal area, stand volume and relative density were recorded. These high values may indicate better growth conditions due to climate change, as well as fewer disturbance events in the last few decades.
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Tudoran, Gheorghe Marian, Alexandru Claudiu Dobre, Avram Cicșa, and Ionuț Silviu Pascu. "Development of Mathematical Models for the Estimation of Dendrometric Variables Based on Unmanned Aerial Vehicle Optical Data: A Romanian Case Study." Forests 12, no. 2 (February 9, 2021): 200. http://dx.doi.org/10.3390/f12020200.
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Research highlights: In this study, the possibility of developing predictive models for both individual trees and forest stands, based on information derived from digital surface models (DSMs), was evaluated. Background and objectives: Unmanned aerial systems (UASs) make it possible to obtain digital images with increased spectral and spatial resolution at a lower cost. Based on the variables extracted by means of the digital representation of surfaces, we aimed at generating mathematical models that would allow the prediction of the main biometric features of both individual trees and forest stands. Materials and methods: Forest stands are characterized by various structures. As such, measurements may address upper-level trees, but most often are oriented towards those belonging to the mean tree category, randomly selected from those identifiable from digital models. In the case of grouped trees, it is the best practice to measure the projected area of the entire canopy. Tree and stand volumes can be determined using models based on features measured in UAS-derived digital models. For the current study, 170-year-old mixed sessile oak stands were examined. Results: Mathematical models were developed based on variables (i.e., crown diameter and tree height) extracted from digital models. In this way, we obtained results characterized by root mean square error (RMSE) values of 18.37% for crown diameter, 10.95% for tree height, and 8.70% for volume. The simplified process allowed for the estimates of the stand volume using crown diameter or diameter at breast height, producing results with RMSE values of 9%. Conclusions: The accuracy of the evaluation of the main biometric features depends on the structural complexity of the studied plots, and on the quality of the DSM. In turn, this leads to the necessity to parametrize the used models in such a manner that can explain the variation induced by the stand structure.
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Gallo, Josef, Lukáš Bílek, Václav Šimůnek, Sonia Roig, and José Alfredo Bravo Fernández. "Uneven-aged silviculture of Scots pine in Bohemia and Central Spain: comparison study of stand reaction to transition and long-term selection management." Journal of Forest Science 66, No. 1 (January 30, 2020): 22–35. http://dx.doi.org/10.17221/147/2019-jfs.
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The achievement of sustainable forest management requires the incorporation of ongoing environmental changes into long-term planning. Moreover, in time of climatic change and changing company demands, importance of Scots pine (Pinus sylvestris L.) is still increasing at the expense of other tree species due to its low ecological requirements. The aim of the study was to compare the structure and production of Scots pine stands managed under different silvicultural systems on four research plots, assess the structural and diversity indices, and analyse the increment structure using tree-ring dating in the Czech Republic and Spain. Area of study was Western Bohemian and Guadarrama Mountain range in Central Spain. The results indicate that stand volume on the investigated plots ranged from 231 to 441 m<sup>3</sup>∙ha<sup>–1</sup> with tree density 276–996 trees∙ha<sup>–1</sup>. Intensively managed (uneven-aged) permanent research plots showed increased growth on basal area. The difference was evident also for older trees. The transition to uneven-aged forest does not negatively influence stocking and wood production and provide higher benefits for diversity and structural complexity in comparison to regular stands.
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Caviedes, Julián, and José Tomás Ibarra. "Influence of Anthropogenic Disturbances on Stand Structural Complexity in Andean Temperate Forests: Implications for Managing Key Habitat for Biodiversity." PLOS ONE 12, no. 1 (January 9, 2017): e0169450. http://dx.doi.org/10.1371/journal.pone.0169450.
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Keren, Srđan, Jurij Diaci, Renzo Motta, and Zoran Govedar. "Stand structural complexity of mixed old-growth and adjacent selection forests in the Dinaric Mountains of Bosnia and Herzegovina." Forest Ecology and Management 400 (September 2017): 531–41. http://dx.doi.org/10.1016/j.foreco.2017.06.009.
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Maguire, Chris C., Douglas A. Maguire, Tom E. Manning, Sean M. Garber, and Martin W. Ritchie. "Response of small mammals to alternative stand structures in the mixed-conifer forest of northeastern CaliforniaThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research." Canadian Journal of Forest Research 38, no. 5 (May 2008): 943–55. http://dx.doi.org/10.1139/x07-239.
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A common, but largely untested, strategy for maintaining forest biodiversity is to enhance stand structural complexity. A silvicultural experiment was implemented from 1996 to 1998 at Blacks Mountain Experimental Forest, California, to test the efficacy of two levels of structural diversity (high versus low) and two levels of prescribed underburning (burn versus no burn) for maintaining or restoring biodiversity. Small mammals were trapped and tagged in experimental units for 2 noncontiguous weeks in fall 2003 and 2004. Total number of captures and number of captured individuals varied by year (P < 0.002). No treatment effects were detected for all species lumped together or for the three most frequent species analyzed separately ( Tamias amoenus J.A. Allen, 1890, Peromyscus maniculatus (Wagner, 1845), and Spermophilus lateralis (Say, 1823)), with the exception that T. amoenus was captured more often in burned units in 2004 (P = 0.004 for year × burn interaction). Mixed-effects regression models indicated that the number of captures and captured individuals of T. amoenus and P. maniculatus decreased with increasing residual basal area of overstory trees, but opposite results were obtained for S. lateralis. After accounting for residual stand density differences, T. amoenus was captured more frequently in units of low structural diversity and S. lateralis in units of high structural diversity.
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Fall, Andrew, Marie-Josée Fortin, Daniel D. Kneeshaw, Stephen H. Yamasaki, Christian Messier, Luc Bouthillier, and Cheryl Smyth. "Consequences of various landscape-scale ecosystem management strategies and fire cycles on age-class structure and harvest in boreal forests." Canadian Journal of Forest Research 34, no. 2 (February 1, 2004): 310–22. http://dx.doi.org/10.1139/x03-143.
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At the landscape scale, one of the key indicators of sustainable forest management is the age-class distribution of stands, since it provides a coarse synopsis of habitat potential, structural complexity, and stand volume, and it is directly modified by timber extraction and wildfire. To explore the consequences of several landscape-scale boreal forest management strategies on age-class structure in the Mauricie region of Quebec, we used spatially explicit simulation modelling. Our study investigated three different harvesting strategies (the one currently practiced and two different strategies to maintain late seral stands) and interactions between fire and harvesting on stand age-class distribution. We found that the legacy of initial forested age structure and its spatial configuration can pose short- (<50 years) to medium-term (150300 years) challenges to balancing wood supply and ecological objectives. Also, ongoing disturbance by fire, even at relatively long cycles in relation to historic levels, can further constrain the achievement of both timber and biodiversity goals. For example, when fire was combined with management, harvest shortfalls occurred in all scenarios with a fire cycle of 100 years and most scenarios with a fire cycle of 150 years. Even a fire cycle of 500 years led to a reduction in older forest when its maintenance was not a primary constraint. Our results highlight the need to consider the broad-scale effects of natural disturbance when developing ecosystem management policies and the importance of prioritizing objectives when planning for multiple resource use.
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Hennon, Paul E., and Michael H. McClellan. "Tree mortality and forest structure in the temperate rain forests of southeast Alaska." Canadian Journal of Forest Research 33, no. 9 (September 1, 2003): 1621–34. http://dx.doi.org/10.1139/x03-081.
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Tree mortality in 27 old-growth stands at three locales in southeast Alaska was evaluated to determine how types of tree death contributed to stand structure and the production of woody debris and to interpret small-scale disturbance. Basal area, density of stems, and the condition of dead trees were described for each tree species. Dead trees with broken boles were observed most frequently, followed by dead standing intact and uprooted trees. The frequencies of dead trees within snag and log deterioration classes indicated that most trees died standing and subsequently broke. Reconstructed annual mortality rates for overstory trees averaged 0.30.5%·year1 for the three locales and were relatively stable through the previous century. Tree fall direction for both uprooted and broken trees aligned significantly with the downslope direction. All three types of tree mortality contributed substantially to structural diversity, reflecting a high degree of complexity associated with small-scale disturbance at these three study locales.
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B. Lindenmayer, D., A. W. Claridge, A. M. Gilmore, D. Michael, and B. D. Lindenmayer. "The ecological roles of logs in Australian forests and the potential impacts of harvesting intensification on log-using biota." Pacific Conservation Biology 8, no. 2 (2002): 121. http://dx.doi.org/10.1071/pc020121.
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A review is presented of the ecological values of logs in Australian eucalypt forests. Logs are a key component of stand structural complexity and have critical functional roles for forest biodiversity including:- (1) providing nesting and sheltering sites for biota, (2) providing foraging substrates for predators like snakes and predatory invertebrates such as velvet worms, (3) providing basking and hibernation sites for reptiles, (4) facilitating animal movement, (5) providing places for key social behaviours, (6) acting as plant germination sites, (7) providing substrates to promote the growth of fungi, (8) providing mesic refugia for organisms during drought and/or fire, and (9) contributing to heterogeneity in the litter layer and patterns of ground cover. Logs also play significant roles in nutrient cycling in forests. The role of logs is often ignored in forestry operations, including those where harvesting intensification will occur through the removal of dead and/or "defective" standing trees and logs under the guise of removing so-called waste or logging "residues". Recently proposed intensive large-scale forestry operations in the Australian native forest estate (e.g., biomass burning power plants and charcoal plants) have the potential to reduce stand structural complexity, alter forest ecosystem function and negatively impact upon log-dependent species in those part of the landscape where harvesting takes place. The risks of such impacts have not been adequately measured in Australia, but they need to be addressed urgently. Prescriptions for the retention and future recruitment of logs must be developed to avert possible losses of biodiversity.
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Li, Zheng, Duo Tao, Mengwei Li, Zhan Shu, Songshi Jing, Minjuan He, and Peng Qi. "Prediction of Damage Accumulation Effect of Wood Structural Members under Long-Term Service: A Machine Learning Approach." Materials 12, no. 8 (April 16, 2019): 1243. http://dx.doi.org/10.3390/ma12081243.
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It is well known that wood structural members can stand a relatively heavy load in the short term but will gradually get weaker if the load is applied for a longer period. This phenomenon is caused by the damage accumulation effect in wood and should be appropriately considered during the design of timber structures. Although various formulation methods (also known as classical models) have been proposed to evaluate the damage accumulation effect in wood, the calibration of model parameters is very time-consuming. Our work proposes a novel method to deal with the damage accumulation effect in wood that involves the application of machine learning algorithms. The proposed algorithm considers a multi-objective optimization process with a combination of goodness-of-fit and complexity. Long-term experimental data of typical wood species are used for developing the machine learning based damage accumulation model. Compared with existing pre-formulated models, our model managed to reduce the complexity of the model structure and give sufficiently accurate and unbiased predictions. This study aims to provide a novel tool for evaluating the damage accumulation in wood structural members, and the proposed model can further support the life-cycle performance assessment of timber structures under long-term service scenarios.
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Schneider, Eryn E., and Andrew J. Larson. "Spatial aspects of structural complexity in Sitka spruce – western hemlock forests, including evaluation of a new canopy gap delineation method." Canadian Journal of Forest Research 47, no. 8 (August 2017): 1033–44. http://dx.doi.org/10.1139/cjfr-2017-0029.
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Structural complexity in long-lived forests where stand-replacing disturbances are rare is thought to emerge from chronic small-scale disturbances and competitive interactions between trees. We analyzed tree size distributions, tree spatial patterns, and canopy gap attributes in ten 1.42 ha stem mapped plots in old-growth Sitka spruce (Picea sitchensis (Bong.) Carrière) – western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests in southeast Alaska. Most plots had rotated sigmoid or reverse-J-shaped diameter distributions. Overstory tree patterns were uniform at short distance (<5 m) and random or aggregated at larger distances (>5 m); understory trees were spatially random or aggregated at most scales. Tree patterns were highly variable across plots. Overstory and understory tree populations were spatially independent in most medium canopy cover (40%–70%) plots but spatially repelled in most high canopy cover (>70%) plots. Canopy gap delineation using a traditional geometric approach identified more gaps and greater forest area in gaps compared to a new method based on canopy tree shadow lengths. We recommend defining the lower limit of canopy gap size using overstory tree crown diameter; gap delineation based on overstory tree shadow length is overly conservative at higher latitude sites. Our analyses show that, despite their low species richness, the temperate rainforests of southeast Alaska are highly structurally diverse.
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O'Grady, Anthony P., Derek Eamus, Peter G. Cook, and Sebastien Lamontagne. "Groundwater use by riparian vegetation in the wet - dry tropics of northern Australia." Australian Journal of Botany 54, no. 2 (2006): 145. http://dx.doi.org/10.1071/bt04164.
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Within Australia and globally there is considerable concern about the potential impacts of groundwater extraction on ecosystems dependent on groundwater. In this study we have combined heat pulse and isotopic techniques to assess groundwater use by riparian vegetation along the Daly River in the Northern Territory. The riparian forests of the Daly River exhibited considerable structural and floristic complexity. More than 40 tree species were recorded during vegetation surveys and these exhibited a range of leaf phonologies, implying complex patterns of water resource partitioning within the riparian forests. Water use was a function of species and season, and stand water use varied between 1.8 and 4.1 mm day–1. In general, however, water use tended to be higher in the wet season than during the dry season, reflecting the contribution to stand water use by dry-season deciduous tree species. There was a strong relationship between stand basal area and stand water use in the wet season, but the strength of this relationship was lower in the dry season. The amount of groundwater use, as determined by analysis of deuterium concentrations in xylem sap, was principally a function of position in the landscape. Trees at lower elevations, closer to the river, used more groundwater than trees higher on the levees. By using a combination of techniques we showed that riparian vegetation along the Daly River was highly groundwater dependent and that these water-use requirements need to be considered in regional management plans for groundwater.
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Shiryaeva, E. N., M. A. Polyakov, and D. V. Terent'ev. "Analysis of interconnections between technical systems on hierarchically connected technological levels of steel sheet production by hot rolling." Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 76, no. 8 (September 3, 2020): 847–55. http://dx.doi.org/10.32339/0135-5910-2020-8-847-855.
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Complexity of modern metallurgical plants, presence of great number of horizontal and vertical interactions between their various structural subdivisions makes it necessary to apply a systems analysis to elaborate effective measures for stable development of a plant operation. Among such measures, digitalization of a plant is widespread at present. To implement the digitalization it is necessary to have clear vision about links at all the levels of the technological system of a plant. A terminology quoted, accepted in the existing regulatory documents for defining of conceptions, comprising the technological system. It was shown, that the following four hierarchical levels of technological systems are distinguished: technological systems of operations, technological systems of processes, technological systems of production subdivisions and technological systems of plants. A hierarchical scheme of technological systems of hot-rolled sheet production at an integrated steel plant presented. Existing horizontal and vertical links between the basic plant’s shops shown. Peculiarities of flows of material, energy and information at the operation “rolling” of the technological system “hot rolling of a steel sheet” considered. As a technical system of the technological process of the hot rolling, the hot rolling mill was chosen. A structural diagram of the hot rolling mill was elaborated, the mill being consisted of reheating furnaces, roughing and finishing stand groups, with an intermediate roll-table between them, and down-coilers section. Since the rolling stands are the basic structural elements of the hot rolling mill, structural diagrams of a roughing and a finishing stands were elaborated. Results of the systems analysis of the technological and technical systems, hierarchically linked in the process of steel sheet hot rolling, can be applied for perfection of organization structure of the whole plant, as well as for elaboration mathematical models of a system separate elements functioning, which is a necessary condition for a plant digitalization.
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Sabatini, F. M., S. Burrascano, M. M. Azzella, A. Barbati, S. De Paulis, D. Di Santo, L. Facioni, et al. "One taxon does not fit all: Herb-layer diversity and stand structural complexity are weak predictors of biodiversity in Fagus sylvatica forests." Ecological Indicators 69 (October 2016): 126–37. http://dx.doi.org/10.1016/j.ecolind.2016.04.012.
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Pascual, Adrián, Juan Guerra-Hernández, Diogo N. Cosenza, and Vicente Sandoval. "The Role of Improved Ground Positioning and Forest Structural Complexity When Performing Forest Inventory Using Airborne Laser Scanning." Remote Sensing 12, no. 3 (January 28, 2020): 413. http://dx.doi.org/10.3390/rs12030413.
Full textAbstract:
The level of spatial co-registration between airborne laser scanning (ALS) and ground data can determine the goodness of the statistical inference used in forest inventories. The importance of positioning methods in the field can increase, depending on the structural complexity of forests. An area-based approach was followed to conduct forest inventory over seven National Forest Inventory (NFI) forest strata in Spain. The benefit of improving the co-registration goodness was assessed through model transferability using low- and high-accuracy positioning methods. Through the inoptimality losses approach, we evaluated the value of good co-registered data, while assessing the influence of forest structural complexity. When using good co-registered data in the 4th NFI, the mean tree height (HTmean), stand basal area (G) and growing stock volume (V) models were 2.6%, 10.6% and 14.7% (in terms of root mean squared error, RMSE %), lower than when using the coordinates from the 3rd NFI. Transferring models built under poor co-registration conditions using more precise data improved the models, on average, 0.3%, 6.0% and 8.8%, while the worsening effect of using low-accuracy data with models built in optimal conditions reached 4.0%, 16.1% and 16.2%. The value of enhanced data co-registration varied between forests. The usability of current NFI data under modern forest inventory approaches can be restricted when combining with ALS data. As this research showed, investing in improving co-registration goodness over a set of samples in NFI projects enhanced model performance, depending on the type of forest and on the assessed forest attributes.
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O'Grady, A. P., D. Worledge, A. Wilkinson, and M. Battaglia. "Photosynthesis and respiration decline with light intensity in dominant and suppressed Eucalyptus globulus canopies." Functional Plant Biology 35, no. 6 (2008): 439. http://dx.doi.org/10.1071/fp08127.
Full textAbstract:
Within canopy gradients in light-saturated photosynthesis (Amax), foliar nitrogen ([N]area) and leaf dark respiration (R15) were studied in the canopies of dominant and suppressed trees within an even-aged (4-year-old) Eucalyptus globulus (Labill) stand in southern Tasmania. Despite being an even-aged stand growing in a relatively uniform environment with respect to nutrient and water availability, the stand exhibited considerable structural complexity. Diameter at 1.3 m ranged between 3 cm and 21 cm, trees average 12 m height and stand leaf area index was ~6 m2 m–2 leading to strong gradients in light availability. We were interested in understanding the processes governing canopy production in trees of contrasting dominance classes. Vertical gradients in photosynthesis and foliar respiration were studied within the canopies of dominant and suppressed trees during 2006 and 2007. Amax varied from ~18 μmol m–2 s–1 in the upper canopy to 3 μmol m–2 s–1 at lower canopy positions. On average, Amax were higher in the dominant trees than in the suppressed trees. However, at any given height, Amax were similar in suppressed and dominant trees and were strongly related to leaf nitrogen content. Dark respiration varied from ~1.4 μmol m–2 s–1 in the upper canopy to 0.2 μmol m–2 s–1 in the lower canopy positions. In contrast to the patterns for Amax, dark respiration rates in the suppressed trees were higher than dominant trees at similar canopy positions. Respiration rates were also strongly related to [N]area and to Amax.