scholarly journals Onshore–offshore gradient in metacommunity turnover emerges only over macroevolutionary time-scales

2014 ◽  
Vol 281 (1795) ◽  
pp. 20141533 ◽  
Author(s):  
Adam Tomašových ◽  
Stefano Dominici ◽  
Martin Zuschin ◽  
Didier Merle
Keyword(s):  
Time Scales ◽  
Thermal Gradients ◽  
Short Term ◽  
Northeast Atlantic ◽  
Atlantic Province ◽  
Temporal Turnover ◽  
Warm Temperate ◽  
Molluscan Species

Invertebrate lineages tend to originate and become extinct at a higher rate in onshore than in offshore habitats over long temporal durations (more than 10 Myr), but it remains unclear whether this pattern scales down to durations of stages (less than 5 Myr) or even sequences (less than 0.5 Myr). We assess whether onshore–offshore gradients in long-term turnover between the tropical Eocene and the warm-temperate Plio-Pleistocene can be extrapolated from gradients in short-term turnover, using abundances of molluscan species from bulk samples in the northeast Atlantic Province. We find that temporal turnover of metacommunities does not significantly decline with depth over short durations (less than 5 Myr), but significantly declines with depth between the Eocene and Plio-Pleistocene (approx. 50 Myr). This decline is determined by a higher onshore extinction of Eocene genera and families, by a higher onshore variability in abundances of genera and families, and by an onshore expansion of genera and families that were frequent offshore in the Eocene. Onshore–offshore decline in turnover thus emerges only over long temporal durations. We suggest that this emergence is triggered by abrupt and spatially extensive climatic or oceanographic perturbations that occurred between the Eocene and Plio-Pleistocene. Plio-Pleistocene metacommunities show a high proportion of bathymetric generalists, in contrast to Eocene metacommunities. Accordingly, the net cooling and weaker thermal gradients may have allowed offshore specialists to expand into onshore habitats and maintain their presence in offshore habitats.

scholarly journals Short-Term and Long-Term Surface Soil Moisture Memory Time Scales Are Spatially Anticorrelated at Global Scales

2019 ◽  
Vol 20 (6) ◽  
pp. 1165-1182 ◽  
Author(s):  
Kaighin A. McColl ◽  
Qing He ◽  
Hui Lu ◽  
Dara Entekhabi
Keyword(s):  
Soil Moisture ◽  
Time Scales ◽  
Time Scale ◽  
Surface Soil ◽  
Satellite Observations ◽  
Surface Soil Moisture ◽  
Short Term ◽  
Term Memory ◽  
Memory Time

Abstract Land–atmosphere feedbacks occurring on daily to weekly time scales can magnify the intensity and duration of extreme weather events, such as droughts, heat waves, and convective storms. For such feedbacks to occur, the coupled land–atmosphere system must exhibit sufficient memory of soil moisture anomalies associated with the extreme event. The soil moisture autocorrelation e-folding time scale has been used previously to estimate soil moisture memory. However, the theoretical basis for this metric (i.e., that the land water budget is reasonably approximated by a red noise process) does not apply at finer spatial and temporal resolutions relevant to modern satellite observations and models. In this study, two memory time scale metrics are introduced that are relevant to modern satellite observations and models: the “long-term memory” τL and the “short-term memory” τS. Short- and long-term surface soil moisture (SSM) memory time scales are spatially anticorrelated at global scales in both a model and satellite observations, suggesting hot spots of land–atmosphere coupling will be located in different regions, depending on the time scale of the feedback. Furthermore, the spatial anticorrelation between τS and τL demonstrates the importance of characterizing these memory time scales separately, rather than mixing them as in previous studies.

scholarly journals Trends and Persistence of Dry–Wet Conditions in Northeast Brazil

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1134
Author(s):  
Antonio Samuel Alves da Silva ◽  
Moacyr Cunha Filho ◽  
Rômulo Simões Cezar Menezes ◽  
Tatijana Stosic ◽  
Borko Stosic
Keyword(s):  
Time Scales ◽  
Water Resource Management ◽  
Standardized Precipitation Index ◽  
Kendall Test ◽  
Spatially Explicit ◽  
Fluctuation Analysis ◽  
Short Term ◽  
Agricultural Planning ◽  
Detrended Fluctuation

We analyze trend and persistence in Standardized Precipitation Index (SPI) time series derived from monthly rainfall data at 133 gauging stations in Pernambuco state, Brazil, using a suite of complementary methods to address the spatially explicit tendencies, and persistence. SPI was calculated for 1-, 3-, 6-, and 12-month time scales from 1950 to 2012. We use Mann–Kendall test and Sen’s slope to determine sign and magnitude of the trend, and detrended fluctuation analysis (DFA) method to quantify long-term correlations. For all time scales significant negative trends are obtained in the Sertão (deep inland) region, while significant positive trends are found in the Agreste (intermediate inland), and Zona da Mata (coastal) regions. The values of DFA exponents show different scaling behavior for different time scales. For short-term conditions described by SPI-1 the DFA exponent is close to 0.5 indicating weak persistency and low predictability, while for medium-term conditions (SPI-3 and SPI-6) DFA exponents are greater than 0.5 and increase with time scale indicating stronger persistency and higher predictability. For SPI-12 that describes long-term precipitation patterns, the values of DFA exponents for inland regions are around 1, indicating strong persistency, while in the shoreline the value of the DFA exponent is between 1.0 and 1.5, indicating anti-persistent fractional Brownian motion. These results should be useful for agricultural planning and water resource management in the region.

scholarly journals Short term changes in methanol emission and pectin methylesterase activity are not directly affected by light in <i>Lycopersicon esculentum</i>

2011 ◽  
Vol 8 (4) ◽  
pp. 1023-1030 ◽  
Author(s):  
P. Y. Oikawa ◽  
L. Li ◽  
M. P. Timko ◽  
J. E. Mak ◽  
M. T. Lerdau
Keyword(s):  
Time Scales ◽  
Pectin Methylesterase ◽  
Light Activation ◽  
Short Term ◽  
Substrate Limitation ◽  
Emission Models ◽  
Seasonal Time Scale ◽  
Short Time ◽  
Cell Wall Expansion

Abstract. Plants are an important source of atmospheric methanol (MeOH), the second most abundant organic gas after methane. Factors regulating phytogenic MeOH production are not well constrained in current MeOH emission models. Previous studies have indicated that light may have a direct influence on MeOH production. As light is known to regulate cell wall expansion, it was predicted that light would stimulate MeOH production through the pectin methylesterase (PME) pathway. MeOH emissions normalized for stomatal conductance (gs) did not, however, increase with light over short time scales (20–30 min). After experimentally controlling for gs and temperature, no light activation of PME activity or MeOH emission was observed. The results clearly demonstrate that light does not directly influence short-term changes in MeOH production and emission. Our data suggest that substrate limitation may be important in regulating MeOH production over short time scales. Future investigation of the long-term impacts of light on MeOH production may increase understanding of MeOH emission dynamics at the seasonal time scale.

scholarly journals Psychological Momentum During and Across Sports Matches: Evidence for Interconnected Time Scales

2016 ◽  
Vol 38 (1) ◽  
pp. 82-92 ◽  
Author(s):  
Ruud J. R. Den Hartigh ◽  
Paul L. C. Van Geert ◽  
Nico W. Van Yperen ◽  
Ralf F. A. Cox ◽  
Christophe Gernigon
Keyword(s):  
Dynamical Systems ◽  
Time Scales ◽  
Self Efficacy ◽  
Short Term ◽  
The Third ◽  
Psychological Momentum ◽  
Rowing Ergometer ◽  
Competitive Athletes ◽  
Dynamical Nature

This study on psychological momentum (PM) in sports provides the first experimental test of an interconnection between short-term PM (during a match) and long-term PM (across a series of matches). Twenty-two competitive athletes were striving to win a prize during a rowing-ergometer tournament, consisting of manipulated races. As hypothesized, athletes who had developed long-term positive PM after two successful races were less sensitive to a negative momentum scenario in the third race, compared with athletes who had developed long-term negative PM after two unsuccessful races. More specifically, the exerted efforts, perceptions of momentum, and self-efficacy were higher for participants who had developed long-term positive PM, and their perceptions of momentum and self-efficacy decreased less rapidly. These results illustrate a typical complex dynamical systems property, namely interconnected time scales, and provide deeper insights into the dynamical nature of PM.

scholarly journals Design droughts as planning tool for ecosystem establishment in post-mining landscapes

2014 ◽  
Vol 11 (5) ◽  
pp. 4809-4849 ◽  
Author(s):  
D. Halwatura ◽  
A. M. Lechner ◽  
S. Arnold
Keyword(s):  
Time Scales ◽  
Standardized Precipitation Index ◽  
Distribution Functions ◽  
Drought Indices ◽  
Minor Role ◽  
Short Term ◽  
Eastern Australia ◽  
Recurrence Intervals ◽  
Different Time Scales

Abstract. Eastern Australia has considerable mineral and energy resources and areas of high biodiversity value co-occurring over a broad range of agro-climatic environments. Water is the primary abiotic stressor for (agro)ecosystems in many parts of Eastern Australia. In the context of mined land rehabilitation quantifying the severity-duration-frequency (SDF) of droughts is crucial for successful ecosystem rehabilitation to overcome challenges of early vegetation establishment and long-term ecosystem resilience. The objective of this study was to quantify the SDF of short-term and long-term drought events of 11 selected locations across a broad range of agro-climatic environments in Eastern Australia by using three drought indices at different time scales: the Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), and the Standardized Precipitation-Evapotranspiration Index (SPEI). Based on the indices we derived bivariate distribution functions of drought severity and duration, and estimated the recurrence intervals of drought events at different time scales. The correlation between the simple SPI and the more complex SPEI or RDI was stronger for the tropical and temperate locations than for the arid locations, indicating that SPEI or RDI can be replaced by SPI if evaporation plays a minor role for plant available water. Both short-term and long-term droughts were most severe and prolonged, and occurred most frequently in arid regions, but were relatively rare in tropical and temperate regions. Our approach is similar to intensity-duration-frequency (IDF) analyses of rainfall crucial to design infrastructure. In this regard, we propose to apply SDF analyses of droughts to design ecosystem components in post-mining landscapes. Together with design rainfalls, design droughts should be used to assess rehabilitation strategies and ecological management based on drought recurrence intervals, thereby minimising the risk of failure of initial ecosystem establishment due to ignorance of fundamental abiotic and site-specific environmental barriers.

scholarly journals On the importance of time scales when studying adaptive evolution

2018 ◽  
Author(s):  
Charles Perrier ◽  
Anne Charmantier
Keyword(s):  
Time Scales ◽  
Quantitative Traits ◽  
Field Studies ◽  
Data Series ◽  
Wild Populations ◽  
Short Term ◽  
Trait Variation ◽  
Bill Length ◽  
Term Field

AbstractLong-term field studies coupled with quantitative genomics offer a powerful means to understand the genetic bases underlying quantitative traits and their evolutionary changes. However, analyzing and interpreting the time scales at which adaptive evolution occurs is challenging. First, while evolution is predictable in the short term, with strikingly rapid phenotypic changes in data series, it remains unpredictable in the long term. Second, while the temporal dynamics of some loci with large effect on phenotypic variation and fitness have been characterized, this task can be complicated in cases of highly polygenic trait architecture implicating numerous small effect size loci, or when statistical tests are sensitive to the heterogeneity of some key characteristics of the genome, like recombination rate variations. After introducing these aforementioned challenges, we discuss a recent investigation of the genomic architecture and spatio-temporal variation in great tit bill length, which was related to the recent use of bird feeders. We discuss how this case study illustrates the importance of considering different temporal scales and evolutionary mechanisms both while analyzing trait temporal trends and when searching for and interpreting the signals of putative genomic footprints of selection. More generally this commentary discusses interesting challenges for unraveling the time scale at which adaptive traits evolve and their genomic bases.Impact summaryAn important goal in evolutionary biology is to understand how individual traits evolve, leading to fascinating variations in time and space. Long-term field studies have been crucial in trying to understand the timing, extent, and ecological determinants of such trait variation in wild populations. In this context, recent genomic tools can be used to look for the genetic bases underlying such trait variation and can provide clues on the nature and timing of their evolution. However, the analysis and the interpretation of the time scales at which evolution occurs remain challenging. First, analyzing long-term data series can be tricky; short-term changes are highly predictable whereas long-term evolution is much less predictable. A second difficult task is to study the architecture of complex quantitative traits and to decipher the timing and roles of the several genomic mechanisms involved in their evolution. This commentary introduces these challenges and discusses a recent investigation of the nature and timing of ecological and genomic factors responsible for variation in great tit bill length. Overall, we raise cautionary warnings regarding several conceptual and technical features and limitations when coupling analyses of long-term and genomic data to study trait evolution in wild populations.

scholarly journals The lateral growth and coalesence of magma systems

2019 ◽  
Vol 377 (2139) ◽  
pp. 20180005 ◽  
Author(s):  
Juliet Biggs ◽  
Catherine Annen
Keyword(s):  
Time Scales ◽  
Thermal Relaxation ◽  
Magma Reservoir ◽  
Growth Stages ◽  
Short Time Scale ◽  
Conductive Heat ◽  
Short Term ◽  
Deformation Patterns ◽  
Over Time

Thermal and mechanical models of magma reservoir growth need to be reconciled with deformation patterns and structural relationships observed at active magma systems. Geophysical observations provide a series of short time-scale snap-shots (10 0 –10 2 years) of the long-term growth of magmatic bodies (10 3 –10 6 years). In this paper, we first review evidence for the growth of magmatic systems along structural features and the associated deformation patterns. We then define three distinct growth stages, (1) aligned melt pockets, (2) coalesced reservoirs, (3) highly evolved systems, which can be distinguished using short-term surface observations. We use two-dimensional thermal models to provide first-order constraints on the time scales and conditions associated with coalescence of individual magma bodies into large-scale reservoirs. We find that closely spaced intrusions (less than 1 km apart) can develop combined viscoelastic shells over time scales of 10s kyr and form laterally extensive mush systems over time scales of 10–100 kyr. The highest temperatures and melt fractions occur during a period of thermal relaxation after melt injection has ceased, suggesting that caldera-forming eruptions may preferentially occur long after the main intrusive activity. The coalescence of eruptible melt-rich chambers only occurs for the highest melt supply rates and deepest systems. Thus, these models indicate that, in most cases, conductive heat transfer alone is not sufficient for a full coalescence of magma chambers and that other processes involving mechanical ruptures and mush mobilization are necessary; individual melt lenses can remain isolated for long periods within growing mush systems, and will only mix during eruption or other catastrophic events. The long-term history of the magmatic system is therefore critical in determining rheological structure and hence short-term behaviour. This framework for the development of magmatic systems in the continental crust provides a mechanical basis for the interpretation of unrest at the world's largest volcanoes. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics'.

scholarly journals Diurnal, seasonal and long-term behaviour of high arctic tundra-heath ecosystem dynamics inferred from model ensembles constrained by time-integrated CO<sub>2</sub> fluxes

2017 ◽  
Author(s):  
Wenxin Zhang ◽  
Per-Erik Jansson ◽  
Bo Elberling
Keyword(s):  
Time Scales ◽  
High Arctic ◽  
Ecosystem Dynamics ◽  
Co2 Fluxes ◽  
Short Term ◽  
C Cycle ◽  
Short And Long Term ◽  
Model Ensembles ◽  
Different Time Scales

Abstract. Ecosystem CO2 fluxes in high Arctic are rather dynamic, as they are sensitive to climatic variability through multiple ecosystem processes, for instance, vegetation and snow dynamics as well as permafrost thawing, operating at different time scales. Uncertainties from both high-frequency measurements and model assumptions challenge model calibration to describe both short- and long-term phenomena related to weather and climate variabilities. In this study, we generated three model ensembles using a Monte-Carlo based uncertainty approach with acceptance criteria for 15 years of eddy covariance CO2 measurements of a high Arctic heath ecosystem based on the time-integrated CO2 fluxes within the day, the year and the entire period. The temporal distribution of residuals between the model and measurements indicated that the three model ensembles reasonably simulated diurnal, seasonal and long-term behaviours of CO2 fluxes respectively. The inter-annual variation of CO2 fluxes over 15 years showed the current ecosystem is at a transition from being a C sink to a C neutral balance. The long-term behaviour model ensemble simulated a more intensified diurnal C cycle than the short-term behaviour model ensembles. The intensified C cycle was mainly attributed to a faster depletion of the soil C pools. The sensitivities of posterior parameters to the model performance index (coefficient of determination, R2) reflected that parameters in the processes of soil water and heat transfer and snow dynamics regulated the short-term behaviour of CO2 fluxes, while parameters in the process of soil decomposition regulated the long-term behaviour of CO2 fluxes. Our results suggest that the development of ecosystem models should diagnose their effectiveness in capturing ecosystem CO2 exchange behaviour across different time scales. A clear trade-off may exist when the model is tuned to capture both the short- and long-term variation of CO2 fluxes. To constrain the model with the time-integrated CO2 fluxes is a simple and useful method to reduce the non-explained errors and to identify the crucial link to controlling parameters and processes.

Synaptic Dynamics on Different Time Scales in a Parallel Fiber Feedback Pathway of the Weakly Electric Fish

2004 ◽  
Vol 91 (2) ◽  
pp. 1064-1070 ◽  
Author(s):  
John E. Lewis ◽  
Leonard Maler
Keyword(s):  
Time Scales ◽  
Electric Fish ◽  
Parallel Fiber ◽  
Weakly Electric Fish ◽  
Short Term ◽  
Parallel Fibers ◽  
Short Term Plasticity ◽  
Synaptic Dynamics ◽  
Weakly Electric

Synaptic dynamics comprise a variety of interacting processes acting on a wide range of time scales. This enables a synapse to perform a large array of computations, from temporal and spatial filtering to associative learning. In this study, we describe how changing synaptic gain via long-term plasticity can act to shape the temporal filtering of a synapse through modulation of short-term plasticity. In the weakly electric fish, parallel fibers from cerebellar granule cells provide massive feedback inputs to the pyramidal neurons of the electrosensory lateral line lobe. We demonstrate a long-term synaptic enhancement (LTE) of these synapses that is biochemically similar to the presynaptic long-term potentiation expressed by parallel fibers in the mammalian cerebellum. Using a novel stimulation protocol and a simple modeling paradigm, we then quantify the changes in short-term plasticity during the induction of LTE and show that these changes can be explained by gradual changes in only one model parameter, that which is associated with the baseline probability of transmitter release. These changes lead to a shift in the spike frequency preference of the synapse, suggesting that long-term plasticity is not only involved in controlling the gain of the parallel fiber synapse, but also provides a means of controlling synaptic filtering over multiple time scales.

scholarly journals Linking long- and short-term emission variability in pulsars

2019 ◽  
Vol 488 (4) ◽  
pp. 5702-5712 ◽  
Author(s):  
P R Brook ◽  
A Karastergiou ◽  
S Johnston
Keyword(s):  
Time Scales ◽  
Radio Pulsars ◽  
Physical Processes ◽  
Short Term ◽  
Monitoring Technique ◽  
Wide Range ◽  
Statistical Detection ◽  
Short Time

ABSTRACT It is now known that the emission from radio pulsars can vary over a wide range of time-scales, from fractions of seconds to decades. However, it is not yet known if long- and short-term emission variability are caused by the same physical processes. It has been observed that long-term emission variability is often correlated with rotational changes in the pulsar. We do not yet know if the same is true of short-term emission variability, as the rotational changes involved cannot be directly measured over such short time-scales. To remedy this, we propose a continuous pulsar monitoring technique that permits the statistical detection of any rotational changes in nulling and mode-changing pulsars with certain properties. Using a simulation, we explore the range of pulsar properties over which such an experiment would be possible.

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