scholarly journals High Summer Temperatures Have No Role in Breaking Physical Dormancy Among Seeds of Fireprone Cistaceae: A Reinterpretation of Luna (2020)

2021 ◽  
Author(s):  
Byron B. Lamont ◽  
Geoffrey E. Burrows ◽  
Dylan Korczynskyj
Keyword(s):  
Heat Pulse ◽  
Summer Temperature ◽  
Ambient Conditions ◽  
Physical Dormancy ◽  
Future Studies ◽  
Retarding Effect ◽  
Temperature Regimes ◽  
Summer Temperatures ◽  
Unique Study ◽  
The Mediterranean Basin

Abstract In a unique study, Luna (2020) examined the viability and germination of 12 hard-seeded Cistaceae in the Mediterranean Basin by alternating a prolonged summer-type-temperature (50/20°C at 12 h cycles) treatment with a fire-type heat pulse. A re-analysis of their data shows that the summer treatment applied before the heat pulse was superfluous as similar high levels of germination under ambient conditions were attained with the heat pulse only. The abundance of hard seeds remaining when the summer treatment was applied after the heat pulse is better explained by ungerminated seeds having become hard again rather than not responding, i.e., showing secondary physical dormancy, and thus became ‘desensitized’ to their environment. While this response is adaptive, such a retarding effect will be limited in practice as most fires are expected in autumn, at least historically, and are thus close to the start of optimal winter conditions for germination. Future studies should concentrate on the fate of the water-gap plug during such alternating treatments and also ensure that realistic summer temperature regimes are used.

Bats under a hot tin roof: comparing the microclimate of eastern cave bat (Vespadelus troughtoni) roosts in a shed and cave overhangs

2007 ◽  
Vol 55 (1) ◽  
pp. 49 ◽  
Author(s):  
B. S. Law ◽  
M. Chidel
Keyword(s):  
Energy Savings ◽  
Early Summer ◽  
Ambient Conditions ◽  
South Wales ◽  
Lactating Females ◽  
Summer Temperatures ◽  
The Cost ◽  
Maternity Roost ◽  
Diurnal Temperatures ◽  
Microclimate Conditions

We compared the microclimate experienced by maternity groups of eastern cave bats (Vespadelus troughtoni) in northern New South Wales between roosts in overhang caves versus a nearby maternity roost beneath the corrugated iron roof of a farm shed. The shed’s microclimate differed dramatically from that of the caves. Caves provided well-buffered microclimate conditions, which were cooler and more humid than ambient conditions during the day, but were warmer and less humid than ambient at night. Early summer temperatures remained between 20 and 25°C in the maternity caves. In contrast, the microclimate at the shed was not buffered, with conditions varying enormously over a 24-h period, being hotter than ambient during the day (mean = 30°C, maximum = 40°C in the middle of the day), and similar to ambient at night (mean = 18°C at dawn). Rather than selecting thermal stability, lactating females selected warm, but variable, diurnal temperatures in the shed, presumably to sustain lactation. Under this situation, we estimated considerable energetic savings by roosting in the shed (27–35%, assuming normothermia) compared with that for caves, and even higher savings if bats were torpid in the mornings and passively rewarmed later (60–69%). Lactating bats therefore presumably traded-off the cost of leaving juveniles behind in a cool roost at night with these energetic benefits. In late autumn bats continued to roost in the shed with day temperatures rising above 30°C, compared with unoccupied caves, which were considerably cooler at this time (~20°C). Clarification of the estimated energy savings and the possible costs in terms of milk production requires further research to measure concurrently body temperatures, roost temperature and energy expenditure, together with juvenile growth in different types of roosts.

Cores and Peripheries Revisited: The Mining Landscapes of Wadi Faynan (Southern Jordan) 5000 BC–AD 700

2007 ◽  
Author(s):  
Graeme Barker ◽  
David Mattingly
Keyword(s):  
Roman Empire ◽  
Iron Age ◽  
Summer Temperature ◽  
Research Interest ◽  
Annual Rainfall ◽  
Winter Temperatures ◽  
Mountain Front ◽  
Summer Temperatures ◽  
The Mean ◽  
Landscape Survey

One of Barry Cunliffe’s major areas of research interest has been societies in transition, especially in the context of core/periphery relationships between expanding states and societies on their margins. Much of this work has been on the relationships between Rome and the Iron Age societies of southern Britain on the northwestern margins of the empire, and the subsequent pathways of resistance, interaction, and transformation. In this chapter we focus on events and processes on the opposite margins of the Roman empire in the Levant, where the Nabataean state was formally incorporated into the Roman imperial system some sixty years after the Claudian invasion of Britain. We draw on the results of the Wadi Faynan Landscape Survey (1996–2000), an interdisciplinary and diachronic investigation of evidence of environmental and climatic change, settlement pattern, and human activity in the Wadi Faynan in southern Jordan (figure 7.1). Situated about 40 kilometres from the Nabataean capital of Petra, the Wadi Faynan lies in the hot and hyper-arid Jordanian Desert, at a distinctive and spectacular mountain front that reaches 1500m above the desert floor. This landform marks the eastern margin of the desert lowlands of the great Jordanian rift valley, with the trough of the Wadi ‘Arabah to the south and west, and the highlands of the Mountains of Edom and the Jordanian tablelands to the east and north (Bienkowski and Galor 2006). The mean summer temperature on the Jordanian tablelands is in the order of 178c, compared with winter temperatures of about 12ºc (Bruins 2006; Rabb’a 1994). Winter temperatures on the desert floor in the Wadi Faynan are much the same as on the plateau, but in summer temperatures frequently reach 40ºc. Seasonality is strong, with most rain falling between December and March and virtually no precipitation occurring between June and September. Annual rainfall in the lower Wadi Faynan is around 63mm and even less in theWadi ‘Arabah (‘Aqaba receives 30mm for example), whereas the Jordanian Tablelands have an average precipitation exceeding 200mm per year.

Physical dormancy in seeds of Dodonaea viscosa (Sapindales, Sapindaceae) from Hawaii

2004 ◽  
Vol 14 (1) ◽  
pp. 81-90 ◽  
Author(s):  
Jerry M. Baskin ◽  
Barbara H. Davis ◽  
Carol C. Baskin ◽  
Sean M. Gleason ◽  
Susan Cordell
Keyword(s):  
Seed Coat ◽  
White Light ◽  
Red Light ◽  
Dodonaea Viscosa ◽  
Physical Dormancy ◽  
Critical Moisture Content ◽  
Temperature Regimes ◽  
Wide Range ◽  
Critical Moisture ◽  
Impermeable Seed Coat

Dormancy in seeds ofDodonaea viscosais due to a water-impermeable seed coat (physical dormancy, PY). Thus, mechanically scarified seeds imbibed water (c.95% increase in mass) and germinated to high percentages over a wide range of temperature regimes in both white light and darkness, whereas non-scarified seeds did not take up water. Dry heat at 80–160°C and dipping in boiling water for 1–60 s also broke dormancy in a high percentage of the seeds, and continuous far-red light was not inhibitory to germination. However, dry storage in the laboratory for >1 year did not overcome dormancy. Seeds made water-permeable by boiling imbibed water, and thus germinated, at a much slower rate than those made water-permeable by mechanical scarification. We suggest that boiling opened the ‘water gap’ in the seed coat (not yet described inSapindaceaebut present in other taxa with PY) and that water entered the seed only through this small opening, thereby accounting for the slow rate of imbibition and subsequent germination. Physical dormancy has now been shown to occur in seeds of this polymorphic, worldwide species from Australia, Brazil, Hawaii, Mexico and New Zealand. The low level of dormancy reported for seed lots ofD. viscosain China, India and Pakistan is probably due to collection of seeds before they dried to the critical moisture content for development of water-impermeability of the seed coat. Germination of non-dormant seeds over a wide range of temperatures and in white light, far-red (leaf-canopy shade) light and darkness are part of the germination strategy ofD. viscosaand of other taxa whose seeds have PY at maturity.

scholarly journals Seed dormancy in Camellia sinensis L. (Theaceae): effects of cold-stratification and exogenous gibberellic acid application on germination

Botany ◽  
2017 ◽  
Vol 95 (2) ◽  
pp. 147-152 ◽  
Author(s):  
Danping Song ◽  
Ganesh K. Jaganathan ◽  
Yingying Han ◽  
Baolin Liu
Keyword(s):  
Gibberellic Acid ◽  
Camellia Sinensis ◽  
Summer Temperature ◽  
Cold Stratification ◽  
Morphophysiological Dormancy ◽  
Temperature Regimes ◽  
Physiological Dormancy ◽  
Radicle Emergence ◽  
Persistent Seed Bank ◽  
Natural Dispersal

There are several different opinions regarding dormancy in tea (Camellia sinensis L.), but there is no strong evidence available to conclude whether or not these seeds are dormant. Freshly matured tea seeds collected from Hangzhou, China, at the natural dispersal time did not germinate in light at daily alternative temperature regimes of 10/15, 15/20, 20/25, or 25/35 °C, or at a constant temperature of 25 °C. Seeds were permeable to water and the embryos did not grow prior to radicle emergence, thus, the seeds have no physical, morphological, or morphophysiological dormancy. When cold-stratified at 4 °C for 1, 2, and 3 months, 64%, 88%, and 93% of the seeds germinated, respectively. Intact fresh seeds failed to germinate after treatment with 0, 10, 500, and 1000 ppm GA3, whereas 3%, 4%, 61%, and 86% of cracked seeds germinated, respectively. Thus, the seeds have nondeep and intermediate physiological dormancy. Seeds cold-stratified for 2 months that were buried at soil depths of 0, 1, and 5 cm in pots showed that seeds at 1 cm depth established significantly higher number of seedlings (P < 0.05) than at other two depths. Because tea seeds are susceptible to summer temperature drying, these seeds do not establish a persistent seed bank.

scholarly journals A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

2011 ◽  
Vol 75 (3) ◽  
pp. 451-460 ◽  
Author(s):  
P.G. Langdon ◽  
C.J. Caseldine ◽  
I.W. Croudace ◽  
S. Jarvis ◽  
S. Wastegård ◽  
...  
Keyword(s):  
Temperature Reconstruction ◽  
Summer Temperature ◽  
Temperature Measurements ◽  
Ice Age ◽  
Data Set ◽  
Ice Cap ◽  
Catchment Disturbance ◽  
Summer Temperatures ◽  
Percentage Abundance ◽  
Instrumental Temperature

AbstractFew studies currently exist that aim to validate a proxy chironomid-temperature reconstruction with instrumental temperature measurements. We used a reconstruction from a chironomid percentage abundance data set to produce quantitative summer temperature estimates since AD 1650 for NW Iceland through a transfer function approach, and validated the record against instrumental temperature measurements from Stykkishólmur in western Iceland. The core was dated through Pb-210, Cs-137 and tephra analyses (Hekla 1693) which produced a well-constrained dating model across the whole study period. Little catchment disturbance, as shown through geochemical (Itrax) and loss-on-ignition data, throughout the period further reinforce the premise that the chironomids were responding to temperature and not other catchment or within-lake variables. Particularly cold phases were identified between AD 1683–1710, AD 1765–1780 and AD 1890–1917, with relative drops in summer temperatures in the order of 1.5–2°C. The timing of these cold phases agree well with other evidence of cooler temperatures, notably increased extent of Little Ice Age (LIA) glaciers. Our evidence suggests that the magnitude of summer temperature cooling (1.5–2°C) was enough to force LIA Icelandic glaciers into their maximum Holocene extent, which is in accordance with previous modelling experiments for an Icelandic ice cap (Langjökull).

Cryoplanation Terraces: Indicators of a Permafrost Environment

1976 ◽  
Vol 6 (1) ◽  
pp. 99-109 ◽  
Author(s):  
Richard D. Reger ◽  
Troy L. Péwé
Keyword(s):  
Mass Movement ◽  
Indirect Evidence ◽  
Summer Temperature ◽  
Climatic Data ◽  
Mass Wasting ◽  
Fine Grained ◽  
Permafrost Environment ◽  
Summer Temperatures ◽  
The Mean ◽  
July Temperature

Cryoplanation terraces are bedrock steps or terraces on ridge crests and hilltops. The tread or “flat” area is 10 to several hundred meters wide and long and slopes from 1 to 5° parallel to the ridge crests. Terrace scarps may be from 1 to 75 m high. Terraces are cut into all bedrock types and are best developed on closely jointed, fine-grained bedrock. The scarps and treads are covered with frost-rived rubble 1 to 2 m thick. The rubble on treads is perennially frozen at a depth of 1 to 2 m or less on sharp but inactive terraces in Alaska.Cryoplanation terraces exist in many parts of the world in present or past periglacial environments. They occur chiefly in nonglaciated regions and near the general altitude of snowline. Cryoplanation terraces form by scarp retreat as the result of nivation. Surficial debris is removed across the terrace tread by mass-wasting. Terrace morphology depends mainly upon climate, bedrock type, and terrace orientation.No climatic data are available from active terraces. Indirect evidence indicates that climatic requirements include low snowfall and cold summer temperatures. Shallow permafrost is necessary to provide moisture and a base for mass movement as well as a base for nivation.Hundreds of sharp but inactive terraces occur in some areas in Alaska where the summer temperature is colder than 10°C. When these terraces were active, temperatures were colder. Recent work in Alaska indicates that terraces were active in some areas when the mean July temperature was about 4°C. The mean annual air temperature probably was in the neighborhood of -12°C or colder.

scholarly journals Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

2010 ◽  
Vol 58 (7) ◽  
pp. 539 ◽  
Author(s):  
Victor M. Santana ◽  
Ross A. Bradstock ◽  
Mark K. J. Ooi ◽  
Andrew J. Denham ◽  
Tony D. Auld ◽  
...  
Keyword(s):  
Seed Dormancy ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Physical Dormancy ◽  
Temperature Regimes ◽  
Open Canopy ◽  
Eastern Australia ◽  
Soil Temperatures ◽  
Different Depths ◽  
Charred Wood

In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0–2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues.

scholarly journals Quantitative mismatch between empirical temperature-size rule slopes and predictions based on oxygen limitation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sigurd Einum ◽  
Claus Bech ◽  
Øystein Nordeide Kielland
Keyword(s):  
Body Size ◽  
Phenotypic Plasticity ◽  
Supply And Demand ◽  
Oxygen Limitation ◽  
Size Distributions ◽  
Deterministic Models ◽  
Future Studies ◽  
Temperature Regimes ◽  
Order Of Magnitude

AbstractIn ectotherms, adult body size commonly declines with increasing environmental temperature, a pattern known as the temperature-size rule. One influential hypothesis explaining this observation is that the challenge of obtaining sufficient oxygen to support metabolism becomes greater with increasing body size, and more so at high temperatures. Yet, previous models based on this hypothesis do not account for phenotypic plasticity in the physiology of organisms that counteracts oxygen limitation at high temperature. Here, we model the predicted strength of the temperature-size response using estimates of how both the oxygen supply and demand is affected by temperature when allowing for phenotypic plasticity in the aquatic ectotherm Daphnia magna. Our predictions remain highly inconsistent with empirical temperature-size responses, with the prior being close to one order of magnitude stronger than the latter. These results fail to provide quantitative support for the hypothesis that oxygen limitation drives temperature-size clines in aquatic ectotherms. Future studies into the role of oxygen limitation should address how the strength of the temperature-size response may be shaped by evolution under fluctuating temperature regimes. Finally, our results caution against applying deterministic models based on the oxygen limitation hypothesis when predicting future changes in ectotherm size distributions under climate change.

How Ambient Environment Influences Olfactory Orientation in Search and Rescue Dogs

2020 ◽  
Vol 45 (8) ◽  
pp. 625-634
Author(s):  
Judy Jinn ◽  
Erin G Connor ◽  
Lucia F Jacobs
Keyword(s):  
Air Temperature ◽  
Search Strategy ◽  
Mammalian Species ◽  
Meteorological Conditions ◽  
Search And Rescue ◽  
Ambient Conditions ◽  
Olfactory Orientation ◽  
Natural Landscape ◽  
Future Studies ◽  
Natural Statistics

Abstract Under natural conditions, an animal orienting to an air-borne odor plume must contend with the shifting influence of meteorological variables, such as air temperature, humidity, and wind speed, on the location and the detectability of the plume. Despite their importance, the natural statistics of such variables are difficult to reproduce in the laboratory and hence few studies have investigated strategies of olfactory orientation by mobile animals under different meteorological conditions. Using trained search and rescue dogs, we quantified the olfactory orientation behaviors of dogs searching for a trail (aged 1–3 h) of a hidden human subject in a natural landscape, under a range of meteorological conditions. Dogs were highly successful in locating the human target hidden 800 m from the start location (93% success). Humidity and air temperature had a significant effect on search strategy: as air conditions became cooler and more humid, dogs searched significantly closer to the experimental trail. Dogs also modified their speed and head position according to their search location distance from the experimental trail. When close to the trail, dogs searched with their head up and ran quickly but when their search took them farther from the trail, they were more likely to search with their nose to the ground, moving more slowly. This study of a mammalian species responding to localized shifts in ambient conditions lays the foundation for future studies of olfactory orientation, and the development of a highly tractable mammalian species for such research.

scholarly journals Quantitative Mismatch Between Empirical Temperature-Size Rule Slopes and Predictions Based on Oxygen Limitation

2021 ◽  
Author(s):  
Sigurd Einum ◽  
Claus Bech ◽  
Øystein Nordeide Kielland
Keyword(s):  
Body Size ◽  
Phenotypic Plasticity ◽  
Supply And Demand ◽  
Oxygen Limitation ◽  
Size Distributions ◽  
Deterministic Models ◽  
Future Studies ◽  
Temperature Regimes ◽  
Order Of Magnitude

Abstract In ectotherms, adult body size commonly declines with increasing environmental temperature, a pattern known as the temperature-size rule. One influential hypothesis explaining this observation is that the challenge of obtaining sufficient oxygen to support metabolism becomes greater with increasing body size, and more so at high temperatures. Yet, previous models based on this hypothesis do not account for phenotypic plasticity in the physiology of organisms that counteracts oxygen limitation at high temperature. Here, we model the predicted strength of the temperature-size response using estimates of how both the oxygen supply and demand is affected by temperature when allowing for phenotypic plasticity in the aquatic ectotherm Daphnia magna. Our predictions remain highly inconsistent with empirical temperature-size responses, with the prior being close to one order of magnitude stronger than the latter. These results fail to provide quantitative support for the hypothesis that oxygen limitation drives temperature-size clines in aquatic ectotherms. Future studies into the role of oxygen limitation should address how the strength of the temperature-size response may be shaped by evolution under fluctuating temperature regimes. Finally, our results caution against applying deterministic models based on the oxygen limitation hypothesis when predicting future changes in ectotherm size distributions under climate change.

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