scholarly journals LARGE-SCALE DISTURBANCE AND THE STRUCTURE OF MARINE SYSTEMS: FISHERY IMPACTS ON GEORGES BANK

1998 ◽  
Vol 8 (sp1) ◽  
pp. S6-S22 ◽  
Author(s):  
Michael J. Fogarty ◽  
Steven A. Murawski
Keyword(s):  
Large Scale ◽  
Georges Bank ◽  
Marine Systems ◽  
Large Scale Disturbance

Large-Scale Disturbance and the Structure of Marine Systems: Fishery Impacts on Georges Bank

1998 ◽  
Vol 8 (1) ◽  
pp. S6 ◽  
Author(s):  
Michael J. Fogarty ◽  
Steven A. Murawski
Keyword(s):  
Large Scale ◽  
Georges Bank ◽  
Marine Systems ◽  
Large Scale Disturbance

Ecological processes maintaining differential tree species distributions in an Australian subtropical rain forest: implications for models of species coexistence

2000 ◽  
Vol 16 (3) ◽  
pp. 387-415 ◽  
Author(s):  
Igor Debski ◽  
David F. R. P. Burslem ◽  
David Lamb
Keyword(s):  
Species Composition ◽  
Tree Species ◽  
Rain Forest ◽  
Large Scale ◽  
Species Coexistence ◽  
Common Species ◽  
Size Class ◽  
Differential Mortality ◽  
Mixed Composition ◽  
Large Scale Disturbance

All stems ≥ 1 cm dbh were measured, tagged, mapped and identified on a 1-ha plot of rain forest at Gambubal State Forest, south-east Queensland, Australia. The spatial patterns and size class distributions of 11 common tree species on the plot were assessed to search for mechanisms determining their distribution and abundance. The forest was species-poor in comparison to many lowland tropical forests and the common species are therefore present at relatively high densities. Despite this, only limited evidence was found for the operation of density-dependent processes at Gambubal. Daphnandra micrantha saplings were clumped towards randomly spaced adults, indicating a shift of distribution over time caused by differential mortality of saplings in these adult associated clumps. Ordination of the species composition in 25-m × 25-m subplots revealed vegetation gradients at that scale, which corresponded to slope across the plot. Adult basal area was dominated by a few large individuals of Sloanea woollsii but the comparative size class distributions and replacement probabilities of the 11 common species suggest that the forest will undergo a transition to a more mixed composition if current conditions persist. The current cohort of large S. woollsii individuals probably established after a large-scale disturbance event and the forest has not attained an equilibrium species composition.

scholarly journals Ecological Impacts of Megaprojects: Species Succession and Functional Composition

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2411
Author(s):  
Hamada E. Ali ◽  
Solveig Franziska Bucher
Keyword(s):  
Plant Species ◽  
Large Scale ◽  
Invasive Plant ◽  
Species Traits ◽  
Natural Vegetation ◽  
Ecological Impacts ◽  
Imperata Cylindrica ◽  
Dry Matter Content ◽  
Large Scale Disturbance ◽  
The Impact

Land-use changes have huge impacts on natural vegetation, especially megaprojects, as the vegetation layer is destroyed in the course of construction works affecting the plant community composition and functionality. This large-scale disturbance might be a gateway for the establishment of invasive plant species, which can outcompete the natural flora. In contrast, species occurring in the area before the construction are not able to re-establish. In this study, we analyzed the impact of a pipeline construction on a wetland nature reserve located in northern Egypt. Therefore, we analyzed the plant species occurrence and abundance and measured each plant species’ traits before the construction in 2017 as well as on multiple occasions up to 2 years after the construction had finished on altogether five sampling events. We found that the construction activity led to the establishment of an invasive species which previously did not occur in the area, namely, Imperata cylindrica, whereas five species (Ipomoea carnea, Pluchea dioscoridis, Polygonum equisetiforme, Tamarix nilotica, and Typha domingensis) could not re-establish after the disturbance. The functionality of ecosystems assessed via the analysis of plant functional traits (plant height, specific leaf area, and leaf dry matter content) changed within species over all sampling events and within the community showing a tendency to approximate pre-construction values. Functional dispersion and Rao’s quadratic diversity were higher after the megaproject than before. These findings are important to capture possible re-establishment and recovery of natural vegetation after construction and raise awareness to the impact of megaprojects, especially in areas which are high priority for conservation.

scholarly journals Large-scale disturbance legacies and the climate sensitivity of primary Picea abies forests

2018 ◽  
Vol 24 (5) ◽  
pp. 2169-2181 ◽  
Author(s):  
Jonathan S. Schurman ◽  
Volodymyr Trotsiuk ◽  
Radek Bače ◽  
Vojtěch Čada ◽  
Shawn Fraver ◽  
...  
Keyword(s):  
Picea Abies ◽  
Climate Sensitivity ◽  
Large Scale ◽  
Large Scale Disturbance

Advancing an Ecosystem Approach in the Gulf of Maine

2012 ◽  
Keyword(s):  
Large Scale ◽  
Gulf Of Maine ◽  
Critical Role ◽  
Monitoring Program ◽  
Ecosystem Dynamics ◽  
Georges Bank ◽  
Scotian Shelf ◽  
Monitoring Programs ◽  
Zooplankton Dynamics ◽  
Biological Environment

<i>Abstract</i>.—Zooplankton communities perform a critical role as secondary producers in marine ecosystems. They are vulnerable to climate-induced changes in the marine environment, including temperature, stratification, and circulation, but the effects of these changes are difficult to discern without sustained ocean monitoring. The physical, chemical, and biological environment of the Gulf of Maine, including Georges Bank, is strongly influenced by inflow from the Scotian Shelf and through the Northeast Channel, and thus observations both in the Gulf of Maine and in upstream regions are necessary to understand plankton variability and change in the Gulf of Maine. Large-scale, quasi synoptic plankton surveys have been performed in the Gulf of Maine since Bigelow’s work at the beginning of the 20th century. More recently, ongoing plankton monitoring efforts include Continuous Plankton Recorder sampling in the Gulf of Maine and on the Scotian Shelf, U.S. National Marine Fisheries Service’s MARMAP (Marine Resources Monitoring, Assessment, and Prediction) and EcoMon (Ecosystem Monitoring) programs sampling the northeast U.S. Continental Shelf, including the Gulf of Maine, and Fisheries and Oceans Canada’s Atlantic Zone Monitoring Program on the Scotian Shelf and in the eastern Gulf of Maine. Here, we review and compare past and ongoing zooplankton monitoring programs in the Gulf of Maine region, including Georges Bank and the western Scotian Shelf, to facilitate retrospective analysis and broadscale synthesis of zooplankton dynamics in the Gulf of Maine. Additional sustained sampling at greater-than-monthly frequency at selected sites in the Gulf of Maine would be necessary to detect changes in phenology (i.e. seasonal timing of biological events). Sustained zooplankton sampling in critical nearshore fish habitats and in key feeding areas for upper trophic level organisms, such as marine mammals and seabirds, would yield significant insights into their dynamics. The ecosystem dynamics of the Gulf of Maine are strongly influenced by large-scale forcing and variability in upstream inflow. Improved coordination of sampling and data analysis among monitoring programs, effective data management, and use of multiple modeling approaches will all enhance the mechanistic understanding of the structure and function of the Gulf of Maine pelagic ecosystem.

scholarly journals Seven Decades of Spontaneous Forest Regeneration after Large-Scale Clear-Cutting in Białowieża Forest do not Ensure the Complete Recovery of Collembolan Assemblages

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 948
Author(s):  
Marek Sławski ◽  
Małgorzata Sławska
Keyword(s):  
Large Scale ◽  
Life Form ◽  
Group Structure ◽  
Complete Recovery ◽  
Long Term Effects ◽  
Old Growth ◽  
Soil Microarthropods ◽  
Clear Cutting ◽  
Białowieża Forest ◽  
Large Scale Disturbance

The long-term effects of large-scale disturbance on forest ecosystem processes and structure are poorly understood. To assess the effects of large-scale clear-cutting on the taxonomic and functional structure of collembolan assemblages, 18 plots were established in the Polish part of Białowieża Forest. All plots, situated in a mixed Tilio-Carpinetum broad-leaved forest, had eutrophic Cambisol developed on rich glacial deposits. The Collembola assemblages in the stands that had naturally regenerated on large-scale clear-cuts performed at the beginning of the 20th century were compared to those in old-growth forests (i.e., the endpoint of stand development following stand-replacing disturbance). Collembolans, one of the most numerous soil microarthropods, are successfully used to assess the consequences of forest management and ecosystem restoration. Our study tested whether seven decades of spontaneous forest development after large-scale anthropogenic disturbance ensures the complete recovery of the soil Collembola. Using complementary taxonomic and life-form approaches, we provide evidence that the collembolan assemblages associated with the tree stands that had spontaneously developed in large harvesting plots distinctly differed from those in old-growth deciduous forests in this region despite seven decades of regenerative forest succession. The species diversity of the assemblages in the naturally regenerated tree stands was significantly lower, and their life-form structure was noticeably different from those in the reference forests. Moreover, the shift in the functional group structure of the collembolan assemblages in the stands that had regenerated after clear-cutting indicates that their activity seven decades after disturbance is concentrated mainly on the decomposition of the litter in the upper layers, whereas the processes controlled by these organisms in the deeper soil layers are not fully restored.

Large-Scale Disturbances and Their Mitigation Downstream of Shallow Cavities Covered by a Perforated Lid

2004 ◽  
Vol 126 (5) ◽  
pp. 851-860 ◽  
Author(s):  
Stephen A. Jordan
Keyword(s):  
Fundamental Frequency ◽  
Large Scale ◽  
Periodic Oscillation ◽  
Feedback Mechanism ◽  
Complete Disappearance ◽  
Freestream Velocity ◽  
Design Engineers ◽  
Large Scale Disturbance ◽  
Key Factor ◽  
Shallow Cavities

Flow past cavities covered by perforated lids pose a challenging problem for design engineers. Kelvin–Helmholtz waves appear early in the separated shear layers above the perforations that quickly mature into large-scale coherent structures far downstream. This evolution is sustained by a hydrodynamic feedback mechanism within the cavity even when its aft wall is far removed from the lid. Herein, the results from large-eddy simulations show analogous fundamental characteristics between open and perforated-cover cavities. Both adequately scale the fundamental frequency of the large-scale disturbance using the freestream velocity and the cavity width (or lid length). Moreover, the dimensionless frequencies jump to higher modes at equivalent length scales. Unlike the open cavity, one can invoke certain conditions that instigate the instability above the perforations but not a simultaneous long-term feedback mechanism necessary to fully sustain the periodic oscillation. The lid itself offers options for mitigating (or even eliminating) the instability. Results (for laminar separation) show the perforation spacing as the key factor. While maintaining the same fundamental frequency, one can easily dampen its spectral peak to complete disappearance by extending the perforation spacing.

The persistent presence of the dead: recent excavations at the hunter-gatherer cemetery at Zvejnieki (Latvia)

Antiquity ◽  
2013 ◽  
Vol 87 (338) ◽  
pp. 1016-1029 ◽  
Author(s):  
Liv Nilsson Stutz ◽  
Lars Larsson ◽  
Ilga Zagorska
Keyword(s):  
Detailed Analysis ◽  
Large Scale ◽  
Northern Europe ◽  
Social Differentiation ◽  
Burial Practices ◽  
Neolithic Transition ◽  
The Past ◽  
Large Scale Disturbance ◽  
The Dead ◽  
Specific Identity

The well-known Mesolithic cemeteries of Northern Europe have long been viewed as evidence of developing social complexity in those regions in the centuries immediately before the Neolithic transition. These sites also had important symbolic connotations. This study uses new and more detailed analysis of the burial practices in one of these cemeteries to argue that much more is involved than social differentiation. Repeated burial in the densely packed site of Zvejnieki entailed large-scale disturbance of earlier graves, and would have involved recurrent encounters with the remains of the ancestral dead. The intentional use of older settlement material in the grave fills may also have signified a symbolic link with the past. The specific identity of the dead is highlighted by the evidence for clay face masks and tight body wrappings in some cases.

scholarly journals Interplanetary Disturbances Affecting Space Weather

2013 ◽  
Vol 8 (S300) ◽  
pp. 297-306 ◽  
Author(s):  
Robert F. Wimmer-Schweingruber
Keyword(s):  
Space Weather ◽  
Large Scale ◽  
Interplanetary Medium ◽  
Coronal Holes ◽  
Historical Review ◽  
The Sun ◽  
High Speeds ◽  
Large Scale Disturbance ◽  
Mass Ejection ◽  
Very High

AbstractThe Sun somehow accelerates the solar wind, an incessant stream of plasma originating in coronal holes and some, as yet unidentified, regions. Occasionally, coronal, and possibly sub-photospheric structures, conspire to energize a spectacular eruption from the Sun which we call a coronal mass ejection (CME). These can leave the Sun at very high speeds and travel through the interplanetary medium, resulting in a large-scale disturbance of the ambient background plasma. These interplanetary CMEs (ICMEs) can drive shocks which in turn accelerate particles, but also have a distinct intrinsic magnetic structure which is capable of disturbing the Earth's magnetic field and causing significant geomagnetic effects. They also affect other planets, so they can and do contribute to space weather throughout the heliosphere. This paper presents a historical review of early space weather studies, a modern-day example, and discusses space weather throughout the heliosphere.

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