Successional pathways on different surficial deposits in the coniferous boreal forest of the Quebec Clay Belt

To infer successional pathways on different surficial deposits in northwestern Quebec, we combined the chronosequence approach to the study of within-stand species' vertical distribution. The deposits sustained different frequencies of postfire stand composition types and successional trajectories. After fire, Picea mariana (Mill.) B.S.P. dominated all stands on organic deposits, while shade-intolerant species dominated the canopy in over 30% and 60% of stands, respectively, on fine- and coarse-textured deposits. In the absence of fire, P. mariana eventually dominates the canopy of all stands on every deposit. However, as the frequency of Larix laricina (DuRoi) K. Koch and Abies balsamea (L.) Mill. in old stands (>100 years) are, respectively, positively and negatively correlated with the deposits' paludification potential, changes in composition in this landscape appear to be driven by the species' tolerance to shade and paludification. Structural changes were characterized by the replacement of closed dense stands by open stands. The diversity of P. mariana stand structures within the youngest age-classes suggests that fire severity may also explain the diversity of stand structures within this landscape. As among-stand structural diversity decreases with increasing time elapsed since fire, converging structural development pathways may be occurring in this landscape.

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Effects of fire severity and initial tree composition on stand structural development in the coniferous boreal forest of northwestern Québec, Canada

Ecoscience ◽

10.2980/i1195-6860-13-2-152.1 ◽

2006 ◽

Vol 13 (2) ◽

pp. 152-163 ◽

Cited By ~ 65

Author(s):

Nicolas Lecomte ◽

Martin Simard ◽

Yves Bergeron

Keyword(s):

Boreal Forest ◽

Fire Severity ◽

Structural Development ◽

Coniferous Boreal Forest ◽

Tree Composition

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Does Variable-Density Thinning Increase Wind Damage in Conifer Stands on the Olympic Peninsula?

Western Journal of Applied Forestry ◽

10.1093/wjaf/22.4.285 ◽

2007 ◽

Vol 22 (4) ◽

pp. 285-296 ◽

Cited By ~ 8

Author(s):

Scott D. Roberts ◽

Constance A. Harrington ◽

Karl R. Buermeyer

Keyword(s):

Structural Diversity ◽

Variable Density ◽

Canopy Gaps ◽

Wind Damage ◽

Olympic Peninsula ◽

Growing Seasons ◽

Silvicultural Treatments ◽

Stand Structural Diversity ◽

Risk Of Wind Damage ◽

Damage Risk

Abstract Silvicultural treatments designed to enhance stand structural diversity may result in increased wind damage. The ability to avoid conditions that might lead to excessive wind damage would benefit forest managers. We analyzed wind damage following implementation of a variable-density thinning at four sites on the Olympic National Forest in northwest Washington. The prescription created small canopy gaps and retained unthinned patches within a uniformly thinned matrix, thus creating substantial amounts of internal edge. Our objective was to determine whether variable-density thinning resulted in elevated wind damage and whether the damage was spatially related to elements of the treatment, i.e., canopy gaps and uncut patches. Wind damage on the thinned plots averaged slightly more than 8.0 trees/ha. Although precise determinations of residual stem densities were not available, we estimate that total wind damage amounted to 1.3% of total stems remaining following treatment. Approximately 80% of the wind damage was blowdown, the remaining damage being stem breakage, leaning, or bowing. Nearly 54% of the damaged stems were less than 20 cm dbh. The maximum amount of damage observed was 51 trees/ha, but only 3 of 13 thinned plots had wind damage exceeding 7 trees/ha. The overall level of wind damage across all thinned plots after two growing seasons was not statistically greater than on unthinned control plots. Internal edges created by gaps, skid trails, and unthinned patches did not inherently increase wind damage risk; however, where gaps were located in topographically vulnerable positions, greater wind damage did occur. Overall wind damage was not excessive on any of the plots, and after 2 years, all residual stands remained intact and in a manageable condition. Our preliminary results suggest that variable-density thinning that includes creation of small canopy gaps does not necessarily predispose stands to greater risk of wind damage than uniform thinning. However, care must be taken in locating gaps and skid trails away from topographically vulnerable positions.

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Zebrafish structural development in Mueller-matrix scanning microscopy

Scientific Reports ◽

10.1038/s41598-019-56610-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 5

Author(s):

Aymeric Le Gratiet ◽

Marta d’Amora ◽

Marti Duocastella ◽

Riccardo Marongiu ◽

Artemi Bendandi ◽

...

Keyword(s):

Structural Changes ◽

Molecular Mechanisms ◽

Developmental Stages ◽

Mueller Matrix ◽

Fluorescence Probes ◽

Imaging Method ◽

Structural Development ◽

Matrix Formalism ◽

Label Free ◽

Biological Organization

AbstractZebrafish are powerful animal models for understanding biological processes and the molecular mechanisms involved in different human diseases. Advanced optical techniques based on fluorescence microscopy have become the main imaging method to characterize the development of these organisms at the microscopic level. However, the need for fluorescence probes and the consequent high light doses required to excite fluorophores can affect the biological process under observation including modification of metabolic function or phototoxicity. Here, without using any labels, we propose an implementation of a Mueller-matrix polarimeter into a commercial optical scanning microscope to characterize the polarimetric transformation of zebrafish preserved at different embryonic developmental stages. By combining the full polarimetric measurements with statistical analysis of the Lu and Chipman mathematical decomposition, we demonstrate that it is possible to quantify the structural changes of the biological organization of fixed zebrafish embryos and larvae at the cellular scale. This convenient implementation, with low light intensity requirement and cheap price, coupled with the quantitative nature of Mueller-matrix formalism, can pave the way for a better understanding of developmental biology, in which label-free techniques become a standard tool to study organisms.

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Шумпетерова теорија економска раста: Предузетништво као одговор на економску стагнацију // Schumpeterian growth theory: Entrepreneurship - a response to the economic downturn

ACTA ECONOMICA ◽

10.7251/ace1318219a ◽

2013 ◽

Vol 11 (18) ◽

pp. 219

Author(s):

Јово Атељевић

Keyword(s):

Structural Changes ◽

Marxist Theory ◽

Growth Theory ◽

Economic Downturn ◽

Structural Development ◽

Economic Cycles ◽

Relevant Today ◽

Perfect Model ◽

Anglo American ◽

Schumpeterian Growth Theory

Резиме: Игнорисање и неразумијевање Шумпетеровог писања су главни разлози зашто је британско-америчка школа, као доминантна у контексту неокласичне економије, била и још увијек јесте одвојена од њемачке историјске школе. Међутим, Шумпетерове поставке су и данас релевантне будући да систем опште економске равнотеже нема праву теорију ендогеног или структуралног развоја коју је предложио Шумпетер. Његова теорија економског развоја може послужити као кохерентни одговор на марксистичку теорију. За Шумпетера, унутаркапиталистичка конкуренција у потпуности објашњава структурне промјене у економији. Он тврди да је конкуренција динамички процес разлика и борбе међу компанијама, а не статична конкуренција Валрасовог система. У Шумпетеровој властитој визији економског система, теорија економских циклуса и теорија раста су нераздвојне. Циљ овог рада је да кроз синтезу теоретских анализа потврди релевантност Шумпетерове теорије у контексту дигиталне економије.Summary: Ignorance and misunderstanding of Schumpeter’s writing are the main reasons why the Anglo-American School, as dominant in the context of neoclassical economics, was and still is separate from the German Historical School. However, Schumpeter’s arguments are relevant today because the system of general economic equilibrium has no adequate theory able to explain neither endogenous nor structural development proposed by Schumpeter. His theory of economic development can serve as a coherent response to Marxist theory. For Schumpeter, the intra-capitalist competition fully explains the structural changes in the economy. He argues that competition is a dynamic process of differences and struggles between companies, and not static competition as proposed by the Walrasian mathematical perfect model. Schumpeter argues that the theory of economic cycles and the growth theory are inseparable. The overarching aim of this paper is to through synthesize of theoretical analysis confirms the relevance of Schumpeter’s theory in the context of the digital economy.

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EVALUATION OF NANOCRYSTALLINE BA(ZRXTI1-X)O3 PRODUCED BY MECHANICAL ALLOYING

International Journal of Modern Physics Conference Series ◽

10.1142/s201019451200236x ◽

2012 ◽

Vol 05 ◽

pp. 472-479

Author(s):

M. Hajfathalian ◽

Z. A. Nemati ◽

H. R. Madaah Hosseini

Keyword(s):

Electron Microscopy ◽

Mechanical Alloying ◽

Structural Changes ◽

Ferroelectric Properties ◽

High Energy ◽

Structural Development ◽

Transition Electron Microscopy ◽

Nano Crystalline ◽

High K ◽

Different Temperatures

BaTiO 3-based solid solutions involve high piezoelectric and ferroelectric properties. One of the most favorable systems of this material is Ba ( Zr x Ti 1- x ) O 3. While nano structured ceramics of which have a great potential for using them in capacitors, actuators, transducers and dielectrics to reach high K values. In this study, nano crystalline Ba ( Zr x Ti 1- x ) O 3( x =0.1-0.8) which is called BZT composite has been prepared by mechanical alloying. The parameters affecting the process and properties were evaluated. The starting powders that are used here were nano sized high pure ZrO 2; submicron sized high pure TiO 2 and BaCO 3. The prepared powder was calcined, compacted and sintered at different temperatures and in various times. The structural changes and phase developments during mechanical alloying were studied by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) and Transition Electron Microscopy (TEM). The results showed that by using mechanical alloying method, high dense nano crystalline BZT ceramics were obtained successfully at very low sintering temperature. The dielectric constant of BZT was much great, because of using nano materials in this method at the temperatures of 1250-1400°C. The effect of high energy milling in micro structural development of nano crystalline BZT has been discussed as well as dielectric properties.

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Interactions between xylem traits linked to hydraulics during xylem development optimize growth performance in conifer seedlings

10.1101/2021.12.24.474017 ◽

2021 ◽

Author(s):

Jehova Lourenco ◽

Daniel Houle ◽

Louis Duchesne ◽

Daniel Kneeshaw

Keyword(s):

Climate Change ◽

Plant Growth ◽

Growth Performance ◽

Structural Changes ◽

Abies Balsamea ◽

Jack Pine ◽

Future Research ◽

Hydraulic Architecture ◽

Environmental Filters ◽

Xylem Development

Climate change has threatened forests globally, challenging tree species ability to track the rapidly changing environment (e..g., drought and temperature rise). Conifer species face strong environmental filters due to climatic seasonality. Investigating how conifers change their hydraulic architecture during xylem development across the season may shed light on possible mechanisms underlying hydraulic adaptation in conifers. Laser microscopy was used to assess the three-dimensional hydraulic architecture of balsam fir (Abies balsamea (Linnaeus) Miller), jack pine (Pinus banksiana Lambert), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Miller) Britton, Sterns & Poggenburgh) seedlings. We measured hydraulic-related xylem traits from early to latewood, during four years of plant growth. The xylem development of jack pine seedlings contrasts with the other species for keeping torus overlap (a hydraulic safety-associated xylem trait), relatively constant across the season (from early to latewood) and the years. The tracheids and torus expansion are positively associated with plant growth. Pit aperture-torus covariance is central to the seasonal dynamics of jack pine xylem development, which jointly with a rapid tracheid and pit expansion seems to boost its growth performance. Linking xylem structural changes during xylem development with hydraulics is a major issue for future research to assess conifers vulnerability to climate change.

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Stand structural diversity and species with leaf nitrogen conservative strategy drive aboveground carbon storage in tropical old-growth forests

10.21203/rs.3.rs-27540/v1 ◽

2020 ◽

Author(s):

Genzhu Wang ◽

Yuguo Liu ◽

Xiuqin Wu ◽

Danbo Pang ◽

Xiao Yang ◽

...

Keyword(s):

Carbon Storage ◽

Structural Equation ◽

Structural Diversity ◽

Old Growth ◽

Elevation Gradients ◽

Niche Complementarity ◽

Aboveground Carbon ◽

Old Growth Forest ◽

Stand Structural Diversity ◽

Aboveground Carbon Storage

Abstract Background: Tropical old-growth forest ecosystems are essential for global carbon regulation. Even there are mounting evidences for the significance of species and functional composition, stand structure and elevation gradients on aboveground carbon storage, the relative strengths of these drivers and whether elevation effects via biotic factors are not clear. Furthermore, the mechanisms (the mass-ratio hypothesis or niche complementarity hypothesis) are still poorly understood. Methods: We analyzed aboveground carbon storage, species diversity, stand structural diversity, community-weighted mean (CWM) of functional traits and functional diversity (FDvar) using date from 56 old-growth forest communities with different elevation gradients in Dawei mountain of southwestern China. Multiple regression models were used to test the relative importance of the predictor variables and structural equation model was used to explore the direct and indirect influences on the aboveground carbon storage. Results: Our optimal multiple regression model show aboveground carbon storage is mostly affected by diameter at breast height (DBH) diversity, followed by FDvar of dry matter concentration in mature leaves and CWM nitrogen concentration in young leaves. The final structural equation model indicates elevation indirectly affected aboveground carbon storage via DBH diversity. The stand structural diversity, but not species diversity or functional diversity, enhanced aboveground carbon storage. Conclusions: Our results indicate mass-ratio and niche complementarity effect promote aboveground carbon storage simultaneously. The complex stand structure and species with leaf nitrogen conservative strategy were the crucial drivers of aboveground carbon storage in tropical old-growth forests.

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Palynostratigraphie et paléoenvironnements du Pléistocène supérieur dans la région du lac Bras d'Or, île du Cap-Breton, Nouvelle-Écosse

Canadian Journal of Earth Sciences ◽

10.1139/e86-051 ◽

1986 ◽

Vol 23 (4) ◽

pp. 491-503 ◽

Cited By ~ 14

Author(s):

A. de Vernal ◽

R. J. Mott

Keyword(s):

Boreal Forests ◽

Mixed Forest ◽

Abies Balsamea ◽

Sensu Stricto ◽

Fagus Grandifolia ◽

Last Interglacial ◽

Humid Climate ◽

Climatic Fluctuations ◽

Coniferous Species ◽

Coniferous Boreal Forest

The East Bay and Castle Bay stratigraphic sections along the northeastern shore of Bras d'Or Lake, despite some discontinuities, represent an important part of the Upper Pleistocene. Pollen analysis of these deposits provides a record that can be subdivided into three main units: (1) The first unit reflects the spread of rich forests dominated by thermophilous species such as Quercus, Ostrya, and Pinus strobus. It indicates a warmer and certainly drier climate than the present one. Th/U ages of the order of 120 000 years support a correlation of unit I with the Sangamonian (sensu stricto) interglacial (substage 5 in oceanic climato-stratigraphy). (2) The lower part of unit II, characterized by Abies balsamea, Fagus grandifolia, Tsuga canadensis, and Pinus, reflects the predominance of a mixed forest in the regional landscape. A cool and humid climate, probably not dissimilar to that of present is inferred. Th/U ages of approximately 85 000 years permits correlation of this forest stage with a relatively warm interval of the last interglacial, probably substage 5a. The upper part of unit II reflects a cooler climate and is characterized by pollen assemblages of the coniferous species Abies balsamea and Picea. (3) The lower stratigraphic part of unit III represents the spreading of coniferous boreal forests dominated by Picea, Pinus, and Abies during a cooler interval than at present. An approximate Th/U age of 60 000 years was obtained. Unit III reflects several cycles interpreted as alternating successions of tundra–forest and coniferous boreal forest. It suggests minor climatic fluctuations during a relatively cold interval. The third polynostratigraphic unit covers a significant part of the middle Wisconsinan (stage 3).

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Leaf Area and Structural Changes after Thinning in Even-AgedPicea rubensandAbies balsameaStands in Maine, USA

International Journal of Forestry Research ◽

10.1155/2012/181057 ◽

2012 ◽

Vol 2012 ◽

pp. 1-9

Author(s):

R. Justin DeRose ◽

Robert S. Seymour

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Structural Changes ◽

Abies Balsamea ◽

Picea Rubens ◽

Area Index ◽

Precommercial Thinning ◽

Density Reduction

We tested the hypothesis that changes in leaf area index (LAI m2 m−2) and mean stand diameter following thinning are due to thinning type and residual density. The ratios of pre- to postthinning diameter and LAI were used to assess structural changes between replicated crown, dominant, and low thinning treatments to 33% and 50% residual density in even-agedPicea rubensandAbies balsameastands with and without a precommercial thinning history in Maine, USA. Diameter ratios varied predictably by thinning type: low thinnings were <0.7, crown thinnings were >0.7 but <1.0, and dominant thinnings were >1.0 . LAI change was affected by type and intensity of thinning. On average, 33% density reduction removed <50% of LAI, whereas 50% density reduction removed >50% of LAI. Overall reduction of LAI was generally greatest in dominant thinnings (54%), intermediate in crown thinnings (46%), and lowest in low thinnings (35%). Upon closer examination by crown classes, the postthinning distribution of LAI between upper and lower crown classes varied by thinning history, thinning method, and amount of density reduction.

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