scholarly journals Seed traits linked to differential survival of plants during the Cretaceous/Paleogene impact winter

2020 ◽  
pp. 307-322
Author(s):  
Keith Berry
Keyword(s):  
High Probability ◽  
Climate Models ◽  
Recalcitrant Seeds ◽  
Differential Survival ◽  
Asteroid Impact ◽  
Transient Period ◽  
Orthodox Seeds ◽  
The Difference ◽  
Mass Extinction Event ◽  
Screw Pine

In past investigations the pattern of differential survival of plants across the K/Pg boundary has been viewed as incompatible with severe asteroid impact winter scenarios (i.e., an impact winter lasting more than a few months), particularly the enigmatic survival of coryphoid palms and Pandanus (screw pine). Stateof- the-art climate models based on soot, sulfate and nano-sized dust aerosols predict a global impact winter that drastically reduced precipitation and resulted in a transient period of total darkness and permafrost conditions. This suggests that the plants most likely to have been affected by the global mass-extinction event were tropical phanerophytes that produce recalcitrant seeds, which by definition are desiccation-intolerant, survive less than a year, and cannot survive freezing. However, this hypothesis has never been tested. In this study I sampled over 100 plant species from the global fossil record that have a high probability of having produced either recalcitrant seeds/disseminules (n1 = 58) or orthodox seeds (n2 = 59), based on their phylogenetic relationships with extant taxa that either are monomorphic for these traits or specifically exhibit a genetic marker for abscisic acid inhibition associated with seed dormancy and recalcitrance. A one-tailed z-test for the difference between two proportions revealed that plant taxa with a high probability of having produced recalcitrant seeds had significantly lower survivorship than plant taxa with a high probability of having produced orthodox seeds (p < 0.0001). Based on these data, it can be concluded that plants which formed a frost-tolerant seed bank during the latest Maastrichtian were significantly more likely to survive the K/Pg impact winter than plants which did not (including palms). These data clearly indicate that the K/Pg impact winter probably lasted longer than a year and that it selected for seed-based traits that effectively sorted correlated functional traits of mature plants (i.e., leaf physiognomic features). This novel hypothesis stands as an alternative to J.A. Wolfe’s classic hypothesis that a mild K/Pg impact winter selected for fast-growing angiosperms with deciduous leaves and did not affect the plant communities of the Southern Hemisphere. Potential mechanisms for the rare survival of tropical, recalcitrant-seeded plants are discussed.

Mitotic Activity Dynamics in Recalcitrant Seeds Acer sachharinum during Maturation and Germination

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 479c-479
Author(s):  
L. Kozeko ◽  
V. Troyan ◽  
L. Musatenko
Keyword(s):  
Cell Division ◽  
Mitotic Activity ◽  
Quiescent State ◽  
Activity Levels ◽  
Recalcitrant Seeds ◽  
Mature Embryos ◽  
Before And After ◽  
Orthodox Seeds ◽  
Mature Seeds ◽  
Activity Dynamics

In orthodox seeds the cell division within the embryo meristems arrests during maturation at embryo moisture content (MC) 65% to 47%, and the maturation completion and transition of seeds to quiescent state occurs at MC about 10%. The arrest of cycling happens asynchronously in different meristematic tissues during desiccation: first in shoot and then in root. The aim of this work was to define a mitotic activity dynamics in recalcitrant seeds with the high MC at maturation end and the absence of quiescent state characteristic of it. The object was seeds of Acer saccharinum, using widely for planting of greenery in Kiev city. The mitotic activity was determined in 0.5 mm of the embryo root pole (RP) and 0.5 mm of the shoot pole with embryo leaves (SP). The A. sachharinum seeds completed them maturation at MC 53% (FW basis). During maturation the mitotic index (MI) in RP decreased from 3.2% in immature seeds (at embryos MC 80%) to 0 in mature seeds and in SP–from 5.4% to 3.3%, respectively. Cell division in SP arrested by dehydration of mature embryos to MC 46% by PEG 6000 (30%). The seeds lost viability by desiccation to MC 34%. The mature seeds were able to germinate immediately after abscission. During seed germination the cell division reactived in RP and increased in SP already before root protrusion. In plantlets 10–15 mm long the MI increased to 8% in RP and 12% in SP. Thus, the strategy of immediate germination of recalcitrant A. sachharinum seeds includes a preservation of cell division in SP of mature embryos, in contrast with orthodox seeds, and high mitotic activity levels in meristems of germinating embryos before and after root protrusion.

scholarly journals Climate Drift in the CMIP5 Models*

2013 ◽  
Vol 26 (21) ◽  
pp. 8597-8615 ◽  
Author(s):  
Alexander Sen Gupta ◽  
Nicolas C. Jourdain ◽  
Jaclyn N. Brown ◽  
Didier Monselesan
Keyword(s):  
Climate Models ◽  
Coupled Model ◽  
Deep Ocean ◽  
Internal Variability ◽  
Correction Method ◽  
Physical Models ◽  
Cmip5 Models ◽  
Steric Sea Level ◽  
Biogeochemical Models ◽  
The Difference

Abstract Climate models often exhibit spurious long-term changes independent of either internal variability or changes to external forcing. Such changes, referred to as model “drift,” may distort the estimate of forced change in transient climate simulations. The importance of drift is examined in comparison to historical trends over recent decades in the Coupled Model Intercomparison Project (CMIP). Comparison based on a selection of metrics suggests a significant overall reduction in the magnitude of drift from phase 3 of CMIP (CMIP3) to phase 5 of CMIP (CMIP5). The direction of both ocean and atmospheric drift is systematically biased in some models introducing statistically significant drift in globally averaged metrics. Nevertheless, for most models globally averaged drift remains weak compared to the associated forced trends and is often smaller than the difference between trends derived from different ensemble members or the error introduced by the aliasing of natural variability. An exception to this is metrics that include the deep ocean (e.g., steric sea level) where drift can dominate in forced simulations. In such circumstances drift must be corrected for using information from concurrent control experiments. Many CMIP5 models now include ocean biogeochemistry. Like physical models, biogeochemical models generally undergo long spinup integrations to minimize drift. Nevertheless, based on a limited subset of models, it is found that drift is an important consideration and must be accounted for. For properties or regions where drift is important, the drift correction method must be carefully considered. The use of a drift estimate based on the full control time series is recommended to minimize the contamination of the drift estimate by internal variability.

scholarly journals Comment on "Quantitative performance metrics for stratospheric-resolving chemistry-climate models" by Waugh and Eyring (2008)

2009 ◽  
Vol 9 (23) ◽  
pp. 9101-9110 ◽  
Author(s):  
V. Grewe ◽  
R. Sausen
Keyword(s):  
Observational Data ◽  
Confidence Intervals ◽  
Climate Models ◽  
Performance Metrics ◽  
Statistical Tests ◽  
Low Grade ◽  
Perfect Model ◽  
Special Cases ◽  
Quantitative Performance ◽  
The Difference

Abstract. This comment focuses on the statistical limitations of a model grading, as applied by D. Waugh and V. Eyring (2008) (WE08). The grade g is calculated for a specific diagnostic, which basically relates the difference of means of model and observational data to the standard deviation in the observational dataset. We performed Monte Carlo simulations, which show that this method has the potential to lead to large 95%-confidence intervals for the grade. Moreover, the difference between two model grades often has to be very large to become statistically significant. Since the confidence intervals were not considered in detail for all diagnostics, the grading in WE08 cannot be interpreted, without further analysis. The results of the statistical tests performed in WE08 agree with our findings. However, most of those tests are based on special cases, which implicitely assume that observations are available without any errors and that the interannual variability of the observational data and the model data are equal. Without these assumptions, the 95%-confidence intervals become even larger. Hence, the case, where we assumed perfect observations (ignored errors), provides a good estimate for an upper boundary of the threshold, below that a grade becomes statistically significant. Examples have shown that the 95%-confidence interval may even span the whole grading interval [0, 1]. Without considering confidence intervals, the grades presented in WE08 do not allow to decide whether a model result significantly deviates from reality. Neither in WE08 nor in our comment it is pointed out, which of the grades presented in WE08 inhibits such kind of significant deviation. However, our analysis of the grading method demonstrates the unacceptably high potential for these grades to be insignificant. This implies that the grades given by WE08 can not be interpreted by the reader. We further show that the inclusion of confidence intervals into the grading approach is necessary, since otherwise even a perfect model may get a low grade.

Make Use of the Difference of Failure and Exit to Improve the Operation Efficiency

2020 ◽  
pp. 164-184
Author(s):  
Yangyang Chen ◽  
Weiwei Dong ◽  
Dixuan Zhang ◽  
Mingwei Jin
Keyword(s):  
High Probability ◽  
Business Failure ◽  
Entrepreneurial Ecosystem ◽  
Operation Efficiency ◽  
Know How ◽  
Serial Entrepreneurship ◽  
Financial Condition ◽  
The Difference ◽  
Failure Experience ◽  
Entrepreneurial Exit

As business failure is a high probability event that influences the operation efficiency of the entrepreneurial ecosystem, it is necessary to know how to manage business failure experience to promote serial entrepreneurship and improve circulation in the ecosystem. While most scholars agree that it is different between failure and exit, DeTienne suggests that exit could be a way to avoid failure and protect the passion and financial condition of entrepreneurs. Therefore, this chapter analyzes the difference of failure and exit and conducts a model to help entrepreneurs decide whether to exit and how to choose a better way to exit entrepreneurship. In the meantime, this chapter analyzes why entrepreneurial exit can improve the operation efficiency of entrepreneurial ecosystem, and also it would give some ideas about how to bound from failure and benefit from failure to do better next time. After reading this chapter, entrepreneurs have the idea that failure is controllable and exit may be a restart to do business more successfully.

The Aftermath

Impact! ◽  
1996 ◽  
Author(s):  
Gerrit L. Verschuur
Keyword(s):  
Water Vapor ◽  
Spectral Line ◽  
Asteroid Impact ◽  
Infrared Telescope ◽  
University Of Arizona ◽  
The Difference ◽  
Life On Earth ◽  
The University ◽  
The Impact ◽  
Space Telescope Science Institute

After all the hoopla associated with Jupiter’s publicity stunt died down, planetary scientists got down to the business of analyzing their data. Simulations of the aftermath of a comet or asteroid impact had been available for years and in July 1994 many of the predictions were confirmed, albeit some more dramatically than expected. The timing of the event was almost as if to remind us to take more seriously what we have been thinking and talking about for some time. Putting aside for a moment the implications for life on earth had something similar happened here, let’s look at some of the things that were learned. Argument continues as to what actually hit Jupiter, a comet or asteroid. When the Space Telescope Science Institute sent out a press release on September 29, 1994, entitled “Hubble Observations Shed New Light on Jupiter Collision,” we were led to expect an answer. The introduction gave us further hope: “Was it a comet or an asteroid?” But the institute didn’t have the answer. Its observations slightly favored a cometary origin, but the asteroid possibility still could not be ruled out. Comets are mostly icy, or so we like to think, and asteroids are mostly rocky or metallic, or so we like to think. When you really get down to it, this business of the difference between comets and asteroids has launched a new cottage industry within astronomical circles. A more recent hint that a comet was involved came from observations made from on board the Kuiper Airborne Observatory, an airplane that carries a beautiful infrared telescope high above most of the water vapor in the atmosphere where it can then see more clearly. Ann Sprague and Donald Huntern from the University of Arizona and their colleagues found evidence for water minutes after two of the fragments smashed into Jupiter. The water signature, a spectral line, indicated it was at a temperature of 500 kelvins (degrees above absolute zero, or about 230 Celcius), much hotter than Jupiter’s usual 200 kelvins (-73 Celcius). Although they could not rule out that the water originated deep in Jupiter’s clouds, the way it came and went over a period of 20 minutes suggested that it was liberated by the impact and was part of a cometlike object.

scholarly journals Western Europe is warming much faster than expected

2009 ◽  
Vol 5 (1) ◽  
pp. 1-12 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
S. Drijfhout ◽  
A. van Ulden ◽  
R. Haarsma ◽  
A. Sterl ◽  
...  
Keyword(s):  
Western Europe ◽  
Climate Models ◽  
Signal To Noise Ratio ◽  
Warming Trend ◽  
North Atlantic Current ◽  
Climate Fluctuations ◽  
The North ◽  
The Difference ◽  
Decadal Climate ◽  
Random Fluctuations

Abstract. The warming trend of the last decades is now so strong that it is discernible in local temperature observations. This opens the possibility to compare the trend to the warming predicted by comprehensive climate models (GCMs), which up to now could not be verified directly to observations on a local scale, because the signal-to-noise ratio was too low. The observed temperature trend in western Europe over the last decades appears much stronger than simulated by state-of-the-art GCMs. The difference is very unlikely due to random fluctuations, either in fast weather processes or in decadal climate fluctuations. In winter and spring, changes in atmospheric circulation are important; in spring and summer changes in soil moisture and cloud cover. A misrepresentation of the North Atlantic Current affects trends along the coast. Many of these processes ontinue to affect trends in projections for the 21st century. This implies that climate predictions for western Europe probably underestimate the effects of anthropogenic climate change.

scholarly journals A new approach towards the so-called recalcitrant seeds

2018 ◽  
Vol 40 (3) ◽  
pp. 221-236 ◽  
Author(s):  
Claudio José Barbedo
Keyword(s):  
Plant Conservation ◽  
Point Of View ◽  
Recalcitrant Seeds ◽  
New Approach ◽  
Recalcitrant Seed ◽  
Seed Conservation ◽  
Conservation Technology ◽  
Orthodox Seeds ◽  
Standard Life ◽  
Life Behavior

ABSTRACT: Water is essential, irreplaceable, and indispensable for any kind of carbon-based-life metabolic activity. Water-dependent living beings are the expected pattern in nature. However, some organisms can survive for some time at a minimum water content, such as seeds of some species (orthodox seeds). Nevertheless, the expected standard life behavior is found in seeds of another group of species, the so-called recalcitrant seeds, which are sensitive to desiccation. A huge range of different behaviors can be found between these two groups, leading authors to consider that orthodoxy and recalcitrance is not an all-or-nothing situation. Notwithstanding, we are still too far from understanding the differences and similarities between all these kinds of seeds and this has been a serious barrier to the development of plant conservation technologies. A new approach to understanding the differences between these seeds is presented here based on seed maturation, environmental influences, and evolution. From this point of view, all kinds of seed behavior are contemplated and, consequently, some new perspectives are considered for the recalcitrant seed conservation technology, the most intensely desired technology nowadays in this area.

Enrichment of chalcophile elements in seawater accompanying the end-Cretaceous impact event

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2055-2066
Author(s):  
Teruyuki Maruoka ◽  
Yoshiro Nishio ◽  
Tetsu Kogiso ◽  
Katsuhiko Suzuki ◽  
Takahito Osawa ◽  
...  
Keyword(s):  
Organic Matter ◽  
Iron Oxides ◽  
Sedimentary Rocks ◽  
Reductive Dissolution ◽  
X Ray ◽  
Asteroid Impact ◽  
Chalcophile Elements ◽  
The Difference ◽  
Impact Heating ◽  
Fe Ions

Abstract Chalcophile elements are enriched in the Cretaceous–Paleogene (KPg) boundary clays from Stevns Klint, Denmark. As the concentrations of Cu, Ag, and Pb among several chalcophile elements such as Cu, Zn, Ga, As, Ag, and Pb are correlated with those of Ir, we suggest that these elements were supplied to the oceans by processes related to the end-Cretaceous asteroid impact. Synchrotron X-ray fluorescence images revealed that Cu and Ag exist as trace elements in pyrite grains or as 1–10-µm-sized discrete phases specifically enriched in Cu or Ag. The difference in carrier phases might depend on the materials that transported these elements to the seafloor. Based on their affinities with Cu, Ag, and Ir, iron oxides/hydroxides and organic matter were identified as the potential carrier phases that supplied these elements to the seafloor. Chalcophile elements adsorbed on iron oxides/hydroxides might have been released during reductive dissolution of iron oxides/hydroxides and incorporated into the pyrite produced simultaneously with the reductive dissolution of iron oxides/hydroxides. Both iron oxides/hydroxides and chalcophile elements were possibly released from the KPg target rocks (i.e., sedimentary rocks and/or basement crystalline rocks) by impact heating. Elements with a high affinity to organic matter would have been released upon its degradation and then converted into discrete minerals because of the deficiency in Fe ions. As such discrete minerals include the elements that form acid soluble sulfides such as Cu, Ag, and Pb, enrichment of these elements might have been induced by the intense acid rain just after the end-Cretaceous asteroid impact.

scholarly journals Tropospheric ozone in CMIP6 Simulations

2020 ◽  
Author(s):  
Paul T. Griffiths ◽  
Lee T. Murray ◽  
Guang Zeng ◽  
Alexander T. Archibald ◽  
Louisa K. Emmons ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Climate Models ◽  
Decadal Variability ◽  
Stratospheric Ozone ◽  
Coupled Model ◽  
Mean Value ◽  
Ozone Production ◽  
Chemical Production ◽  
The Difference ◽  
Using Data

Abstract. The evolution of tropospheric ozone from 1850 to 2100 has been studied using data from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). We evaluate long-term changes using coupled atmosphere-ocean chemistry-climate models, focusing on the CMIP historical and ScenarioMIP ssp370 experiments, for which detailed tropospheric ozone diagnostics were archived. The model ensemble has been evaluated against a suite of surface, sonde, and satellite observations of the past several decades, and found to reproduce well the salient spatial, seasonal and decadal variability and trends. The tropospheric ozone burden increases from 244 ± 30 Tg in 1850 to a mean value of 348 ± 15 Tg for the period 2005–2014, an increase of 40 %. Modelled present day values agree well with previous determinations (ACCENT: 336 ± 27 Tg; ACCMIP: 337 ± 23 Tg and TOAR: 340 ± 34 Tg). In the ssp370 experiments, the ozone burden reaches a maximum of 402 ± 36 Tg in 2090, before declining slightly to 396 ± 32 Tg by 2100. The ozone budget has been examined over the same period using lumped ozone production (PO3) and loss (LO3) diagnostics. There are large differences (30 %) between models in the preindustrial period, with the difference narrowing to 15 % in the present day. Both ozone production and chemical loss terms increase steadily over the period 1850 to 2100, with net chemical production (PO3-LO3) reaching a maximum around the year 2000. The residual term, which contains contributions from stratosphere-troposphere transport reaches a minimum around the same time, while dry deposition increases steadily across the experiment. Differences between the model residual terms are explained in terms of variation in tropopause height and stratospheric ozone burden.

scholarly journals Differential survival among Tahitian tree snails during a mass extinction event: persistence of the rare and fecund

Oryx ◽  
2014 ◽  
Vol 50 (1) ◽  
pp. 169-175 ◽  
Author(s):  
C.S. Bick ◽  
Diarmaid Ó Foighil ◽  
Trevor Coote
Keyword(s):  
Demographic Data ◽  
Differential Survival ◽  
Widespread Species ◽  
Field Surveys ◽  
Society Islands ◽  
Extinction Event ◽  
Snail Family ◽  
Mass Extinction Event ◽  
Euglandina Rosea ◽  
Biological Attribute

AbstractThe deliberate introduction of the rosy wolf snail Euglandina rosea to the Society Islands in the 1970s led to the mass extirpation of its rich Partulidae (Pilsbry, 1900) fauna, comprising approximately half of all species in this Pacific island tree snail family. On Tahiti ongoing field surveys have documented the survival of two of seven endemic species of Partula (P. hyalina and/or P. clara) in 38 valleys. E. rosea is now a potent extinction agent across Oceania and determining the factors enabling these two taxa to endure may have wide conservation import. We hypothesized that P. hyalina and P. clara have survived because they were the most abundant and/or widespread species and that they will eventually become extinct. We lack demographic data contemporaneous with predator introduction, but an early 20th century study by H.E. Crampton provides historical demographic data for intact Tahitian partulid populations. Crampton found that P. clara and P. hyalina, although widespread, were consistently rarer than their now-extirpated congeners, including in the 23 valleys he surveyed that retain surviving populations. Given this result, and the recent finding that P. clara and P. hyalina comprise a discrete founding lineage in Tahiti, it is plausible that some shared biological attribute(s) may have contributed to their survival. Crampton recorded the clutch sizes of thousands of gravid Tahitian partulids and found that these two taxa had higher instantaneous mean clutch sizes than did co-occurring congeners. Higher fecundities may have contributed to the survival of P. hyalina and P. clara in the valleys of Tahiti.

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