scholarly journals Exogenous disturbances and endogenous self-organized processes are not mutually exclusive drivers of spatial patterns in macroalgal assemblages

2020 ◽  
Author(s):  
J. He ◽  
L. Rindi ◽  
C. Mintrone ◽  
L. Benedetti-Cecchi
Keyword(s):  
Spatial Patterns ◽  
Empirical Work ◽  
Power Laws ◽  
Local Scale ◽  
Species Assemblages ◽  
Spatial Gradient ◽  
Gap Size ◽  
Scale Interactions ◽  
Relative Contribution ◽  
Self Organized

AbstractComplex spatial patterns are common in coastal marine systems, but mechanisms underlying their formation are disputed. Most empirical work has focused on exogeneous spatially structured disturbances as the leading cause of pattern formation in species assemblages. However, theoretical and observational studies suggest that complex spatial patterns, such as power laws in gap-size distribution, may result from endogenous self-organized processes involving local-scale interactions. The lack of studies simultaneously assessing the influence of spatially variable disturbances and local-scale interactions has fuelled the idea that exogenous and endogenous processes are mutually exclusive explanations of spatial patterns in marine ecosystems. To assess the relative contribution of endogenous and exogenous processes in the emergence of spatial patterns, an intertidal assemblage of algae and invertebrates was exposed for 2 years to various combinations of intensity and spatial patterns of disturbance. Localized disturbances impinging at the margins of previously disturbed clearings and homogenous disturbances without any spatial pattern generated heterogeneous distributions of disturbed gaps and macroalgal patches, characterized by a truncated or a pure power-law scaling. Spatially varying disturbances produced a spatial gradient in the distribution of algal patches and, to a lesser extent, also a power-scaling in both patch- and gap-size distributions. These results suggest that exogenous and endogenous processes are not mutually exclusive forces that can lead to the formation of similar spatial patterns in species assemblages.

Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

2006 ◽  
Vol 12 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Keisuke Suzuki ◽  
Takashi Ikegami
Keyword(s):  
Pattern Formation ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Spiral Structure ◽  
Scale Interactions ◽  
Micro Scale ◽  
Macro Scale ◽  
Loop Network ◽  
Spatial Pattern Formation

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

scholarly journals Associating an Entropy with Power-Law Frequency of Events

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 940 ◽  
Author(s):  
Evaldo Curado ◽  
Fernando Nobre ◽  
Angel Plastino
Keyword(s):  
Information Theory ◽  
Forest Fires ◽  
Ground State ◽  
State Energy ◽  
Power Laws ◽  
Natural Systems ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Isothermal Processes ◽  
Entropic Index

Events occurring with a frequency described by power laws, within a certain range of validity, are very common in natural systems. In many of them, it is possible to associate an energy spectrum and one can show that these types of phenomena are intimately related to Tsallis entropy S q . The relevant parameters become: (i) The entropic index q, which is directly related to the power of the corresponding distribution; (ii) The ground-state energy ε 0 , in terms of which all energies are rescaled. One verifies that the corresponding processes take place at a temperature T q with k T q ∝ ε 0 (i.e., isothermal processes, for a given q), in analogy with those in the class of self-organized criticality, which are known to occur at fixed temperatures. Typical examples are analyzed, like earthquakes, avalanches, and forest fires, and in some of them, the entropic index q and value of T q are estimated. The knowledge of the associated entropic form opens the possibility for a deeper understanding of such phenomena, particularly by using information theory and optimization procedures.

scholarly journals A Five Species Cyclically Dominant Evolutionary Game with Fixed Direction: A New Way to Produce Self-Organized Spatial Patterns

Entropy ◽  
2016 ◽  
Vol 18 (8) ◽  
pp. 284 ◽  
Author(s):  
Yibin Kang ◽  
Qiuhui Pan ◽  
Xueting Wang ◽  
Mingfeng He
Keyword(s):  
Spatial Patterns ◽  
Evolutionary Game ◽  
Self Organized ◽  
Fixed Direction

scholarly journals Modeling Spatial Patterns of Humus Forms in Montane and Subalpine Forests: Implications of Local Variability for Upscaling

2018 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Niels Hellwig ◽  
Dylan Tatti ◽  
Giacomo Sartori ◽  
Kerstin Anschlag ◽  
Ulfert Graefe ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Ground Cover ◽  
Landscape Scale ◽  
Local Scale ◽  
Mountain Forest ◽  
High Mountain ◽  
Subalpine Forests ◽  
Humus Forms ◽  
Humus Form ◽  
Local Variability

Humus forms are a distinctive morphological indicator of soil organic matter decomposition. The spatial distribution of humus forms depends on environmental factors such as topography, climate and vegetation. In montane and subalpine forests, environmental influences show a high spatial heterogeneity, which is reflected by a high spatial variability of humus forms. This study aims at examining spatial patterns of humus forms and their dependence on the spatial scale in a high mountain forest environment (Val di Sole/Val di Rabbi, Trentino, Italian Alps). On the basis of the distributions of environmental covariates across the study area, we described humus forms at the local scale (six sampling sites), slope scale (60 sampling sites) and landscape scale (30 additional sampling sites). The local variability of humus forms was analyzed with regard to the ground cover type. At the slope and landscape scale, spatial patterns of humus forms were modeled applying random forests and ordinary kriging of the model residuals. The results indicate that the occurrence of the humus form classes Mull, Mullmoder, Moder, Amphi and Eroded Moder generally depends on the topographical position. Local-scale patterns are mostly related to micro-topography (local accumulation and erosion sites) and ground cover, whereas slope-scale patterns are mainly connected with slope exposure and elevation. Patterns at the landscape scale show a rather irregular distribution, as spatial models at this scale do not account for local to slope-scale variations of humus forms. Moreover, models at the slope scale perform distinctly better than at the landscape scale. In conclusion, the results of this study highlight that landscape-scale predictions of humus forms should be accompanied by local- and slope-scale studies in order to enhance the general understanding of humus form patterns.

Power-Law Phenomena in Adhesive De-Bonding

1996 ◽  
Vol 458 ◽  
Author(s):  
G. Kendall ◽  
P. J. Cote ◽  
D. Crayon ◽  
F. J. Bonetto
Keyword(s):  
Power Law ◽  
Characteristic Length ◽  
Power Laws ◽  
Structural Features ◽  
Fractal Nature ◽  
Pressure Sensitive Adhesive ◽  
Self Organized ◽  
Pressure Sensitive ◽  
Self Organized Criticality ◽  
Glass Interface

ABSTRACTAcoustic emission (AE) events were recorded during the peeling of pressure-sensitive adhesive (PSA) tape from a silicate glass surface. The distributions of AE event durations and energies are found to have the form of power laws. Power-law dependencies (hyperbolic distributions) are recognized as a consequence of self-organized criticality (SOC), resulting from the absence of any characteristic length or time scales. In these studies, standard optical microscopy was used to characterize the fractal nature of the PSA-glass interface. The present results suggest that it is the inherent static structural features found at the fractal PSA-glass interface which produce the observed hyperbolic distributions in AE events, rather than a true SOC process.

scholarly journals The Effects of Selective Logging Behaviors on Forest Fragmentation and Recovery

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Xanic J. Rondon ◽  
Graeme S. Cumming ◽  
Rosa E. Cossío ◽  
Jane Southworth
Keyword(s):  
Forest Fragmentation ◽  
Spatial Patterns ◽  
Management Practices ◽  
Timber Harvesting ◽  
Selective Logging ◽  
Forest Landscape ◽  
Intermediate Scale ◽  
Scale Interactions ◽  
Predator Prey Model ◽  
Forest Resilience

To study the impacts of selective logging behaviors on a forest landscape, we developed an intermediate-scale spatial model to link cross-scale interactions of timber harvesting, a fine-scale human activity, with coarse-scale landscape impacts. We used the Lotka-Volterra predator-prey model with Holling’s functional response II to simulate selective logging, coupled with a cellular automaton model to simulate logger mobility and forest fragmentation. Three logging scenarios were simulated, each varying in timber harvesting preference and logger mobility. We quantified forest resilience by evaluating (1) the spatial patterns of forest fragmentation, (2) the time until the system crossed a threshold into a deforested state, and (3) recovery time. Our simulations showed that logging behaviors involving decisions made about harvesting timber and mobility can lead to different spatial patterns of forest fragmentation. They can, together with forest management practices, significantly delay or accelerate the transition of a forest landscape to a deforested state and its return to a recovered state. Intermediate-scale models emerge as useful tools for understanding cross-scale interactions between human activities and the spatial patterns that are created by anthropogenic land use.

Local-scale spatial patterns of freshwater mussels in the Upper Mississippi River

2019 ◽  
Vol 38 (4) ◽  
pp. 742-752 ◽  
Author(s):  
P. R. Ries ◽  
N. De Jager ◽  
T. J. Newton ◽  
S. J. Zigler
Keyword(s):  
Spatial Patterns ◽  
Mississippi River ◽  
Freshwater Mussels ◽  
Local Scale ◽  
Upper Mississippi River

Spatial patterns of meiofauna and diversity of nematode species assemblages in the Uvea lagoon (Loyalty Islands, South Pacific)

2008 ◽  
Vol 88 (5) ◽  
pp. 931-940 ◽  
Author(s):  
Y. Guo ◽  
M.-N. Helleouet ◽  
G. Boucher
Keyword(s):  
Species Richness ◽  
Spatial Patterns ◽  
Environmental Parameters ◽  
Nematode Species ◽  
Abundant Species ◽  
Diversity Indices ◽  
Species Assemblages ◽  
Leeward Side ◽  
Local Composition ◽  
Total Species Richness

Meiofauna assemblages were investigated at 15 stations on triplicated samples in the Uvea Atoll (Loyalty Islands) in relation to 9 selected environmental parameters. Spatial patterns and variability of meiofauna density were quantified according to location, macrofauna and nematode species assemblages. Meiofauna was dominated by ciliates and nematodes. Densities of total meiofauna and of most of the meiofauna taxa were significantly higher in the back reef North Pléiades stations than the leeward side of the Island. The highest correlation between biotic patterns and environmental parameters that best explains the pattern was with sediment thickness and to a lesser extent organic matter, C/N ratio and depth. One hundred and thirty-four nematode species were identified with four dominant species Chromadora macrolaimoides, an undescribed species of Bolbonema, Daptonema svalbardense and Prochromadorella septempapillata. Three significantly different nematode species assemblages were detected in two of the previously described macrofauna assemblages by cluster analysis and multidimensional scaling methods suggesting that nematodes are more sensible ecological indicators than macrofauna. Diversity indices based on dominance were not significantly different among the three nematode species assemblages but indices based on species richness and rarefaction were significantly higher leeward of Uvea Island. Estimates of total species richness showed no sign of stabilizing with sample size. However, rare species stabilized very quickly, whereas abundant species were added with increasing sampling coverage, indicating a high spatial variability of the local composition of nematodes.

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