scholarly journals Distinctive patterns and signals at major environmental events and collapse zone boundaries

2021 ◽  
Vol 193 (10) ◽  
Author(s):  
Melinda Pálinkás ◽  
Levente Hufnagel
Keyword(s):  
Climate Change ◽  
Cluster Analysis ◽  
Species Richness ◽  
Relative Abundance ◽  
Large Scale ◽  
Hierarchical Cluster ◽  
Small Scale ◽  
Total Abundance ◽  
First Order ◽  
Environmental Events

AbstractWe studied the patterns of pre-collapse communities, the small-scale and the large-scale signals of collapses, and the environmental events before the collapses using four paleoecological and one modern data series. We applied and evaluated eight indicators in our analysis: the relative abundance of species, hierarchical cluster analysis, principal component analysis, total abundance, species richness, standard deviation (without a rolling window), first-order autoregression, and the relative abundance of the dominant species. We investigated the signals at the probable collapse triggering unusual environmental events and at the collapse zone boundaries, respectively. We also distinguished between pulse and step environmental events to see what signals the indicators give at these two different types of events. Our results show that first-order autoregression is not a good environmental event indicator, but it can forecast or indicate the collapse zones in climate change. The rest of the indicators are more sensitive to the pulse events than to the step events. Step events during climate change might have an essential role in initiating collapses. These events probably push the communities with low resilience beyond a critical threshold, so it is crucial to detect them. Before collapses, the total abundance and the species richness increase, the relative abundance of the species decreases. The hierarchical cluster analysis and the relative abundance of species together designate the collapse zone boundaries. We suggest that small-scale signals should be involved in analyses because they are often earlier than large-scale signals.

scholarly journals The collapse indicators of the dominant species outperform community-level critical slowing down indicators

2020 ◽  
Author(s):  
Melinda Pálinkás ◽  
Levente Hufnagel
Keyword(s):  
Species Richness ◽  
Standard Deviation ◽  
Dominant Species ◽  
Large Scale ◽  
Community Level ◽  
Critical Slowing Down ◽  
Small Scale ◽  
Warning Signals ◽  
Slowing Down ◽  
Environmental Events

AbstractWe studied similarities of collapses and concluded that dominant species have a universal effect on the pattern of collapses. We used open paleoecological and modern data to detect ‘early warning signals’ of collapses. We tested and ranked collapse indicators at the community level (abundance, species richness, constancy, dominance, Shannon’s H, standard deviation, variance, lag-1 autocorrelation of community abundance, lag-1 autocorrelation of Shannon’s H) and at the level of the dominant species (total changes of pre-collapse and collapse dominant species, lag-1 autocorrelation of pre-collapse and collapse dominant species) based on their performances. We distinguished between small-scale signals (sharp drops and peaks) and large-scale signals (trend changes). Small-scale signals and large-scale signals can be at the same time, however, small-scale signals can also precede large-scale signals. Small-scale signals indicate environmental events. Large-scale trend changes refer to the decline and eventually the collapse of the community. Our results show that the collapse indicators of the dominant species outperform community-level critical slowing down indicators, which suggests that the dominant species probably have an important role in community-level collapses triggered by environmental events. We also concluded that unusual environmental events might be the number one cause of collapses therefore small-scale signals should be involved in analyses.

Urea stress is more akin to EGF exposure than to hypertonic stress in renal medullary cells

2002 ◽  
Vol 283 (3) ◽  
pp. F388-F398 ◽  
Author(s):  
Wei Tian ◽  
David M. Cohen
Keyword(s):  
Cluster Analysis ◽  
Large Scale ◽  
Hierarchical Cluster ◽  
Immunoblot Analysis ◽  
Activating Transcription Factor 3 ◽  
Expression Array ◽  
Hypertonic Stress ◽  
Activating Transcription Factor ◽  
Medullary Cells

Although urea is considered to be a cell stressor even in renal medullary cells perpetually exposed to this solute in vivo by virtue of the renal concentrating mechanism, aspects of urea signaling resemble that of a peptide mitogen. Urea was compared with epidermal growth factor and hypertonic NaCl or hypertonic mannitol using a large-scale expression array-based approach. The expression profile in response to urea stress more closely resembled that of EGF treatment than hypertonic stress, as determined by hierarchical cluster analysis; the effect of urea+NaCl was equidistant from that of either solute applied individually. Among the most highly urea- and hypertonicity-responsive transcripts were genes that had previously been shown to be responsive to these solutes, validating this approach. Increased expression of the activating transcription factor 3 by urea was newly detected via expression array and confirmed via immunoblot analysis. Earlier, we noted an abrogation of tonicity-dependent gene regulation by urea, primarily in a transient transfection-based model (Tian W and Cohen DM. Am J Physiol Renal Physiol 280: F904–F912, 2001). Here we applied K-means cluster analysis to demonstrate that the genes most profoundly up- or downregulated by hypertonic stress were partially restored toward basal levels in the presence of urea pretreatment. These global expression data are consistent with our earlier biochemical studies suggesting that urea affords cytoprotection in this context. In the aggregate, these data strongly support the hypothesis that the urea effect in renal medullary cells resembles that of a peptide mitogen in terms of the adaptive program of gene expression and in terms of cytoprotection from hypertonicity.

Reverberation Intensity Decaying in Range-Dependent Waveguide

2019 ◽  
Vol 27 (03) ◽  
pp. 1950007
Author(s):  
J. R. Wu ◽  
T. F. Gao ◽  
E. C. Shang
Keyword(s):  
Large Scale ◽  
Back Propagation ◽  
Normal Modes ◽  
Small Scale ◽  
Signal Pulse ◽  
First Order ◽  
Orthogonal Property ◽  
Short Signal ◽  
Scale Roughness ◽  
Special Case

In this paper, an analytic range-independent reverberation model based on the first-order perturbation theory is extended to range-dependent waveguide. This model considers the effect of bottom composite roughness: small-scale bottom rough surface provides dominating energy for reverberation, whereas large-scale roughness has the effect of forward and back propagation. For slowly varying bottom and short signal pulse, analytic small-scale roughness backscattering theory is adapted in range-dependent waveguides. A parabolic equation is used to calculate Green functions in range-dependent waveguides, and the orthogonal property of local normal modes is employed to estimate the modal spectrum of PE field. Synthetic tests demonstrate that the proposed reverberation model works well, and it can also predict the reverberation of range-independent waveguide as a special case.

scholarly journals Testing biodiversity theory using species richness of reef-building corals across a depth gradient

2019 ◽  
Vol 15 (10) ◽  
pp. 20190493 ◽  
Author(s):  
T. Edward Roberts ◽  
Sally A. Keith ◽  
Carsten Rahbek ◽  
Tom C. L. Bridge ◽  
M. Julian Caley ◽  
...  
Keyword(s):  
Species Richness ◽  
Large Scale ◽  
Coral Species ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Empirical Support ◽  
Null Model ◽  
Local Scale ◽  
Small Scale ◽  
Energy Availability

Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

scholarly journals How Much Should Climate Model Output Be Smoothed in Space?

2011 ◽  
Vol 24 (3) ◽  
pp. 867-880 ◽  
Author(s):  
Jouni Räisänen ◽  
Jussi S. Ylhäisi
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Climate Model ◽  
Future Climate Change ◽  
Small Scale ◽  
Model Output ◽  
Climate Change Projections ◽  
Local Conditions ◽  
Climate Model Output ◽  
Mean Climate

Abstract The general decrease in the quality of climate model output with decreasing scale suggests a need for spatial smoothing to suppress the most unreliable small-scale features. However, even if correctly simulated, a large-scale average retained by the smoothing may not be representative of the local conditions, which are of primary interest in many impact studies. Here, the authors study this trade-off using simulations of temperature and precipitation by 24 climate models within the Third Coupled Model Intercomparison Project, to find the scale of smoothing at which the mean-square difference between smoothed model output and gridbox-scale reality is minimized. This is done for present-day time mean climate, recent temperature trends, and projections of future climate change, using cross validation between the models for the latter. The optimal scale depends strongly on the number of models used, being much smaller for multimodel means than for individual model simulations. It also depends on the variable considered and, in the case of climate change projections, the time horizon. For multimodel-mean climate change projections for the late twenty-first century, only very slight smoothing appears to be beneficial, and the resulting potential improvement is negligible for practical purposes. The use of smoothing as a means to improve the sampling for probabilistic climate change projections is also briefly explored.

scholarly journals Hydraulic diversity stabilizes productivity in a large-scale subtropical tree biodiversity experiment

2021 ◽  
Author(s):  
Florian Schnabel ◽  
Xiaojuan Liu ◽  
Matthias Kunz ◽  
Kathryn E. Barry ◽  
Franca J. Bongers ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Richness ◽  
Tree Species ◽  
Structural Equation ◽  
Large Scale ◽  
Structural Equation Models ◽  
Forest Productivity ◽  
Climate Mitigation ◽  
Climate Change Effects ◽  
Tree Species Richness

AbstractExtreme climatic events threaten forests and their climate mitigation potential globally. Understanding the drivers promoting ecosystems stability is therefore considered crucial to mitigate adverse climate change effects on forests. Here, we use structural equation models to explain how tree species richness, asynchronous species dynamics and diversity in hydraulic traits affect the stability of forest productivity along an experimentally manipulated biodiversity gradient ranging from 1 to 24 tree species. Tree species richness improved stability by increasing species asynchrony. That is at higher species richness, inter-annual variation in productivity among tree species buffered the community against stress-related productivity declines. This effect was mediated by the diversity of species’ hydraulic traits in relation to drought tolerance and stomatal control, but not the community-weighted means of these traits. Our results demonstrate important mechanisms by which tree species richness stabilizes forest productivity, thus emphasizing the importance of hydraulically diverse, mixed-species forests to adapt to climate change.

scholarly journals The need for large-scale distribution data to estimate regional changes in species richness under future climate change

2017 ◽  
Vol 23 (12) ◽  
pp. 1393-1407 ◽  
Author(s):  
Nicolas Titeux ◽  
Dirk Maes ◽  
Toon Van Daele ◽  
Thierry Onkelinx ◽  
Risto K. Heikkinen ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Richness ◽  
Large Scale ◽  
Future Climate ◽  
Future Climate Change ◽  
Distribution Data

scholarly journals Response of orthopterans to macroclimate changes: A 15-year case study in Central European humid grasslands

2019 ◽  
Vol 28 (2) ◽  
pp. 187-193
Author(s):  
Zoltán Kenyeres ◽  
Gábor Takács ◽  
Norbert Bauer
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Species Richness ◽  
Land Management ◽  
Relative Abundance ◽  
The Other ◽  
Central European ◽  
Thermophilic Species ◽  
Orthopteran Species

Orthoptera is a good indicator taxon of macroclimate changes. In our case study, we analyzed data of orthopterans, vegetation, and macroclimate collected yearly from 2002 through 2017 in Central European humid grasslands. During the study period, the annual mean temperature increased, while the relative abundance of moderately hygrophilic orthopteran species decreased significantly. On the other hand, the species richness and diversity of the assemblages increased due, mostly, to an increase of graminicole/thermophilic species. According to our results, the conservation of the hygrophilic orthopteran assemblages of Central European humid grasslands under global warming can only be ensured by adequate land management, which can at least mitigate the effects of climate change resulting in the warming and drying of humid habitats.

scholarly journals Contribution of ocean physics and dynamics at different scales to heat uptake in low-resolution AOGCMs

2020 ◽  
pp. 1-62
Author(s):  
Oleg A. Saenko ◽  
Jonathan M. Gregory ◽  
Stephen M. Griffies ◽  
Matthew P. Couldrey ◽  
Fabio Boeira Dias
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Large Scale ◽  
Heat Budget ◽  
Heat Content ◽  
Ocean Dynamics ◽  
Small Scale ◽  
Upper Ocean ◽  
Ocean Heat Uptake ◽  
Heat Uptake

AbstractUsing an ensemble of atmosphere-ocean general circulation models (AOGCMs) in an idealized climate change experiment, this study quantifies the contributions to ocean heat uptake (OHU) from ocean physical parameterizations and resolved dynamical processes operating at different scales. Analysis of heat budget diagnostics reveals a leading-order global heat balance in the sub-surface upper ocean in a steady state between the large-scale circulation warming it and mesoscale processes cooling it, and shows that there are positive contributions from processes on all scales to the subsurface OHU during climate change. There is better agreement among the AOGCMs in the net OHU than in the individual scales/processes contributing to it. In the upper ocean and at high latitudes, OHU is dominated by small-scale diapycnal processes. Below 400 m, OHU is dominated by the super-residual transport, representing large-scale ocean dynamics combined with all parameterized mesoscale and submesoscale eddy effects. Weakening of the AMOC leads to less heat convergence in the subpolar North Atlantic and less heat divergence at lower latitudes, with a small overall effect on the net Atlantic heat content. At low latitudes, the dominance of advective heat redistribution is contrary to the diffusive OHU mechanism assumed by the commonly used upwelling-diffusion model. Using a density watermass framework, it is found that most of the OHU occurs along isopycnal directions. This feature of OHU is used to accurately reconstruct the global vertical ocean warming profile from the surface heat flux anomalies, supporting advective (rather than diffusive) models of OHU and sea-level rise.

scholarly journals Analysis of the Attitude Within Asia-Pacific Countries Towards Disaster Risk Reduction: Text Mining of the Official Statements of 2018 Asian Ministerial Conference on Disaster Risk Reduction

2019 ◽  
Vol 14 (8) ◽  
pp. 1024-1029 ◽  
Author(s):  
Daisuke Sasaki ◽  
Keyword(s):  
Climate Change ◽  
Cluster Analysis ◽  
Text Mining ◽  
Risk Reduction ◽  
Word Frequency ◽  
Hierarchical Cluster Analysis ◽  
Disaster Risk Reduction ◽  
Hierarchical Cluster ◽  
Disaster Risk ◽  
Asia Pacific

This study aims to investigate the attitude within Asia-Pacific countries towards disaster risk reduction (DRR) through text mining of the official statements of the 2018 Asian Ministerial Conference on Disaster Risk Reduction. The official statements can be considered as a proxy of the participating countries’ stances on DRR. As methodology, four different kinds of text mining techniques were adopted; namely, word frequency list, hierarchical cluster analysis, co-occurrence network, and correspondence analysis for the sake of quantitative content analysis. Consequently, the word frequency list showed that words such as “development (develop)” and “climate change” seemed to be distinctive of the conference focusing on DRR issues. The result of hierarchical cluster analysis seemed to imply that the participating countries, namely their governments, had appeared to be keen to implement the Sendai Framework for Disaster Risk Reduction 2015–2030 (SFDRR) along with their national DRR policies and to connect DRR with their development, while climate change had not been directly linked to the SFDRR and was stated as another global issue closely related to DRR. Considering that the SFDRR is closely related to the SDGs and the Paris Agreement, the observation of these contrasting results of the text mining analysis is a noteworthy finding. The result is also consistent with that of the co-occurrence network. The result of the correspondence analysis implied that the statement announced by Japan had appeared to have a characteristic feature in comparison to other statements. One possible reason for this is that there was no explicit reference to climate change, while the countries faced with disasters caused by climate change, such as those in the Pacific Islands, tended to focus on it.

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