A temporal dimension to the stress gradient hypothesis for intraspecific interactions

Oikos ◽  
2014 ◽  
Vol 123 (11) ◽  
pp. 1323-1330 ◽  
Author(s):  
Shekhar R. Biswas ◽  
Helene H. Wagner
Keyword(s):  
Stress Gradient ◽  
Intraspecific Interactions ◽  
Temporal Dimension

scholarly journals Changes in niche differentiation and environmental filtering over a hydric stress gradient

2020 ◽  
Vol 13 (2) ◽  
pp. 185-194
Author(s):  
Alejandra Martínez-Blancas ◽  
Carlos Martorell
Keyword(s):  
Interspecific Competition ◽  
Interspecific Interactions ◽  
General Pattern ◽  
Stress Gradient ◽  
Niche Differentiation ◽  
Intraspecific Interactions ◽  
Soil Pathogens ◽  
Southern Mexico ◽  
Environmental Filter ◽  
Hydric Stress

Abstract Aims Diversity in communities is determined by species’ ability to coexist with each other and to overcome environmental stress that may act as an environmental filter. Niche differentiation (ND) results in stronger intra- than interspecific competition and promotes coexistence. Because stress affects interactions, the strength of ND may change along stress gradients. A greater diversity of plant growth forms has been observed in stressful habitats, such as deserts and alpine regions, suggesting greater ND when stress is strong. We tested the hypothesis that niche differences and environmental filters become stronger with stress. Methods In a semiarid grassland in southern Mexico, we sowed six annual species in the field along a hydric stress gradient. Plants were grown alone (without interactions), with conspecific neighbors (intraspecific interactions) or with heterospecific neighbors (interspecific interactions). We analyzed how the ratio of intra- to interspecific competition changed along the gradient to assess how water availability determines the strength of ND. We also determined if hydric stress represented an environmental filter. Important Findings We observed stronger intra- than interspecific competition, especially where hydric stress was greater. Thus, we found ND in at least some portion of the gradient for all but one species. Some species were hindered by stress, but others were favored by it perhaps because it eliminates soil pathogens. Although strong ND was slightly more frequent with stress, our species sample was small and there were exceptions to the general pattern, so further research is needed to establish if this is a widespread phenomenon in nature.

Time in International Organizations and International Organizations in Time

2019 ◽  
Author(s):  
Eugénia C. Heldt
Keyword(s):  
International Organizations ◽  
Path Dependence ◽  
Time Pressure ◽  
Temporal Dimension ◽  
Incremental Change ◽  
Critical Junctures ◽  
Pressure Time ◽  
Multilateral System ◽  
System Time ◽  
Over Time

Time plays a central role in international organizations (IOs). Interactions among actors are embedded in a temporal dimension, and actors use formal and informal time rules, time discourses, and time pressure to obtain concessions from their counterparts. By the same token, legacies and innovations within and outside IOs can be examined as a dynamic process evolving over time. Against this background, this chapter has a twofold aim. First, it examines how actors use time in IOs with a particular focus on multilateral negotiations to justify their actions. Drawing on international relations studies and negotiation analysis, this piece explores six different dimensions of time in the multilateral system: time pressure, time discourse, time rules, time costs, time horizons, and time as a resource. Second, this chapter delineates the evolution of IOs over time with the focus on innovations that emerge to adapt their institutional system to new political and economic circumstances. This piece looks particularly at endogenous and exogenous changes in IOs, recurring to central concepts used by historical institutionalism, including path dependence, critical junctures, and sequencing. This allows us to map patterns of incremental change, such as displacement, conversion, drift, and layering.

scholarly journals From scenario-based seismic hazard to scenario-based landslide hazard: fast-forwarding to the future via statistical simulations

2021 ◽  
Author(s):  
Luigi Lombardo ◽  
Hakan Tanyas
Keyword(s):  
Ground Motion ◽  
Landslide Susceptibility ◽  
Additive Model ◽  
Landslide Hazard ◽  
Northridge Earthquake ◽  
Ground Acceleration ◽  
Temporal Dimension ◽  
Earthquake Scenario ◽  
The Mean ◽  
Ground Motion Scenarios

AbstractGround motion scenarios exists for most of the seismically active areas around the globe. They essentially correspond to shaking level maps at given earthquake return times which are used as reference for the likely areas under threat from future ground displacements. Being landslides in seismically actively regions closely controlled by the ground motion, one would expect that landslide susceptibility maps should change as the ground motion patterns change in space and time. However, so far, statistically-based landslide susceptibility assessments have primarily been used as time-invariant.In other words, the vast majority of the statistical models does not include the temporal effect of the main trigger in future landslide scenarios. In this work, we present an approach aimed at filling this gap, bridging current practices in the seismological community to those in the geomorphological and statistical ones. More specifically, we select an earthquake-induced landslide inventory corresponding to the 1994 Northridge earthquake and build a Bayesian Generalized Additive Model of the binomial family, featuring common morphometric and thematic covariates as well as the Peak Ground Acceleration generated by the Northridge earthquake. Once each model component has been estimated, we have run 1000 simulations for each of the 217 possible ground motion scenarios for the study area. From each batch of 1000 simulations, we have estimated the mean and 95% Credible Interval to represent the mean susceptibility pattern under a specific earthquake scenario, together with its uncertainty level. Because each earthquake scenario has a specific return time, our simulations allow to incorporate the temporal dimension into any susceptibility model, therefore driving the results toward the definition of landslide hazard. Ultimately, we also share our results in vector format – a .mif file that can be easily converted into a common shapefile –. There, we report the mean (and uncertainty) susceptibility of each 1000 simulation batch for each of the 217 scenarios.

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