Cooler Phases Research Articles

VARIABLE WEATHER PATTERNS AFFECT ANNUAL SURVIVAL OF NORTHERN FLICKERS MORE THAN PHENOTYPE IN THE HYBRID ZONE

Abstract Fitness in a hybrid zone is determined both by the reproductive success and the survival of phenotypes. The hybrid zone of Northern Flickers (Colaptes auratus), a common woodpecker, is one of the largest and most well-known hybrid zones in North America. Bounded-hybrid superiority, the most widely accepted hypothesis for the persistence of the zone, suggests hybrids should have equal or higher reproduction or survival than parental types in the zone, but the latter life history trait has never been examined. We analyzed the apparent survival of 1117 flickers over nine years using capture-recapture models and found no evidence that the phenotypic hybrid index influenced survival. Instead, annual adult apparent survival was best modeled according to large-scale weather patterns such as the North Atlantic Oscillation (NAO). During warm phases of the NAO, adult flickers had lower survival compared to cooler phases of NAO. There was no evidence that phenotype influenced the local recruitment of yearli...

Physical Properties of Diffuse H° Gas in the Galaxy

The diffuse (non self-gravitating) interstellar medium of the Galaxy is almost impossibly complex and diverse. Temperatures and densities range over many orders of magnitude. The magnetic field links all regimes of the gas, including cosmic rays. Shocks from supernovae and other sources buffet the medium. Into this maelstrom, theorists have ventured. Some models emphasize time-independent thermal equilibrium between hot and cold phases of the gas. Other models stress frequent dynamical events that throw much of the medium out of thermal equilibrium. Some models include magnetic field effects, others do not. Here we report on the nature of diffuse atomic gas, emphasizing observational results from a recent, extensive survey of HI emission and absorption along random lines of sight in the local diffuse medium. We find much of the warmer diffuse atomic gas is out of thermal equilibrium, yet the medium retains a clear dichotomy between warmer and cooler phases. The warmer phase comprises about half of the total diffuse atomic hydrogen gas. Magnetic fields have a median value of about 6 μ G in the cold gas, insuring that their dynamical effects cannot be ignored. The conundrum of similar magnetic field strengths in diffuse gas at widely disparate densities remains as an observational fact and a challenge to explain theoretically.

Holocene Environmental and Climate History of Trettetjørn, a Low-alpine Lake in Western Norway, Based on Subfossil Pollen, Diatoms, Oribatid Mites, and Plant Macrofossils

ABSTRACTHolocene lake and catchment environmental history and regional climate are reconstructed from lake sediments at Trettetjørn, a small lake situated close to the present-day treeline in western Norway. Sediments began to accumulate in the lake ca. 8575 (± 115) cal yr BP. Pollen-inferred mean July temperatures (Tjul) fluctuated below 12°C with two cooler phases ca. 8400 and 8200 cal yr BP. The pollen-inferred annual precipitation (Pann) was lowest during the early Holocene and varied around 1600 mm yr−1. At the same time the highest diatom-inferred pH values (6.8) were reconstructed, probably due to input of base cations from the immature catchment soils. Betula pubescens became established around the lake ca. 8270 cal BP, soon followed by Pinus sylvestris. Maximum Tjul of ca. 12.5°C occurred from 7760 to 5200 cal yr BP. The oribatid mite assemblages confirm the vegetation development from semiopen grassland to forest. Inferred Tjul was variable after 5200 cal yr BP and declined markedly around 4175 cal yr BP. At the same time more oceanic conditions are inferred with changes in the vegetation and mite assemblages suggesting the expansion of mires. After ca. 5000 cal yr BP and towards the present, the diatom concentration in the core becomes low and variable, thickness of the valves within the same taxon varies, and sometimes diatom frustules are completely absent from the sediment column. The diatom valve dissolution has affected both the diatom assemblages and the diatom-inferred pH up to the present-day. All proxies suggest that human impact affected the catchment after ca. 2000 cal yr BP followed by more intensive impact after ca. 1555 cal yr BP. The enlargement of the settlement at Upsete during the construction of the Bergen–Oslo railway (1894–1909 AD) is reflected by a charcoal peak and the presence of spheroidal carbonaceous particles coincides with a change in the diatom assemblages.

Climate and geomorphology in the uppermost geomorphic belts of the Central Mountain Range, Taiwan

The Central Mountain Range of Taiwan is in its lower parts exposed to strong denudation by mass movements caused by extreme rainfalls and active tectonics. Even though the uppermost regions of the mountains are also influenced by earthquakes and typhoon rains, present geomorphic activity is low. Investigations based on field work and air photo study in Nanhuta Shan (3742 m) and Yushan (3952 m) and the analysis of climate data indicate the presence of a periglacial belt with a lower limit at 3600–3700 m. The upper limit of the periglacial belt in Taiwan is not met. Ground temperature measurements in Nanhuta Shan show that freeze-thaw activity at 3560 m during the winter is restricted to the top few centimetres of the ground and the maximum frost depth is ∼25 cm.The only indicator landforms within the periglacial belt are smooth slopes. The high relief energy and a lack of fine material account for the absence of other periglacial landforms. Relict solifluction terraces, debris cones and slope failures found between 3400 and 3600 m in Nanhuta Shan are strong evidence for a period of increased slope activity during the Holocene, which in two cases were dated by OSL to approx. 3 ka. At least one solifluction unit developed during a cooler phase between 3 ka and today.

A record of the Jurassic/Cretaceous boundary climatic variation on the southern margin of the Tethys : clay minerals and palynofacies of the early Cretaceous Jebel Meloussi section (Central Tunisia, Sidi Kralif Formation)

Abstract In order to precise the paleogeographic extension of the climatic variation known at the Jurassic/Cretaceous boundary, the sedimentary organic matter (palynofacies and Rock-Eval) and the clay minerals content of Berriasian sediments of the Sidi Kralif Formation are studied on the Jebel Meloussi section, central Tunisia. Standard sedimentological and palynofacies analysis allow to reconstruct the bathymetric curve and the sequence stratigraphic scheme. Using existing biostratigraphy based on calpionellids and ammonite zonation, the sequence stratigraphic interpretation can be correlated with the established eustatic chart. Clay mineral assemblages are characterized by a shift in the kaolinite content, recorded at the end of the calpionellid zone B, at the early/middle Berriasian boundary, at a time of high long-term sea-level (MFS Be2, second order eustatic peak). A contemporary change in the clay mineral assemblages, interpreted as a climatic change, is known from the boreal area, and from the northern margin of the Tethys Sea. That change is also documented southerly in southern Morocco (Agadir area), on the Atlantic domain. A late Tithonian to early Berriasian dry and cooler phase is replaced by a middle to late Berriasian more humid phase, indicated by a general increase in kaolinite in the clay mineral assemblages. The trend from a dry climatic phase to a more humid one, recorded on the boreal domain and along the northern margin of the Tethys is also recorded in lower paleolatitudes of Tunisia, on the southern margin of the Tethys, in better dated outcrops than the ones of Morocco. The results obtained in Tunisia show that the beginning of the climatic change was precisely synchronous on both margins, and occurred within the same long-term high sea-level context.

XMM-Newtonobservations of warm absorbers in PG quasars

We present XMM-Newton European Photon Imaging Camera observations of warm absorbers in the quasars PG 1114 + 445 and PG 1309 + 355, both of which exhibit evidence for absorption by warm material in the line of sight. We find the absorption in PG 1114 + 445 to be in two phases, a 'hot' phase with a log ionization parameter, xi, of 2.57, and a 'cooler' phase with log xi = 0.83; an unresolved transition array (UTA) of M-shell iron is observed in the cooler phase. The absorption in this quasar is similar to that observed in the Seyfert 1 NGC 3783. The absorption in PG 1309 + 355 consists of a single phase, with log xi = 1.87. The absorbing gas lies at distances of 10(18) -10(22) cm from the continuum radiation sources in these active galactic nuclei (AGN), which suggests that it could originate in a wind emanating from a molecular torus. We derive distances assuming that these X-ray warm absorbers have the same velocity as the ultraviolet warm absorbers observed in these quasars. The distances to the warm absorbers from the central continuum source scale approximately with the square root of the AGN ionizing luminosity, a result consistent with the warm absorber originating as a torus wind. The kinetic luminosities of these outflowing absorbers represent insignificant fractions (<10(-3)) of the energy budgets of the AGN.

Panxian Dadong, South China: Establishing a Record of Middle Pleistocene Climatic Changes

Broad-based reconstructions of the Middle Pleistocene Asian environment are valuable sources of information that can augment our understanding of prehistoric human adaptations and expansion into East Asia. The sediments, speleothems, and geochronology of Panxian Dadong Cave serve as an example of the possible integration of this broader paleoenvironmental information with more fine-grained archaeological data. The current U-series and ESR dating results for Dadong suggest that the early human activity in the cave began at least 260 kya and continued until around 142 kya. This period correlates with Oxygen Isotope Stages 7 through 6. The lower part of the breccia (Layer 2) contains very strongly weathered dark deposits, suggesting a relatively warm climatic period from 260–180 kya that corresponds to OIS 7, followed by a cooler phase with less speleothem formation corresponding to OIS 6. The Middle Pleistocene stratigraphic sequence in the Dadong cave deposits documents fluctuating and rapid changes in temperature and humidity that are also detected in general Asian, as well as South China, paleoclimatic studies based on diverse data ranging from microstratigraphic and geochemical sediment analyses to mollusk species representation.

Geographical zonation in the Neotropics of tree species characteristic of the Paraguay‐Paraná Basin

AbstractAim This paper uses data from the literature (monographs and taxonomic reviews) to investigate the geographical zonation in South America of 32 common tree species encountered in Paraguay. The actual spatial distribution of the species is then used to provide clues on the plant communities present in the past, and especially during the Wisconsinan age (Last major ice age: 80,000–10,000 bp). The floristic relatedness between the Paraguayan flora and the neighbouring floras is also investigated.Methods The main vegetation patterns were highlighted using a Discriminant Analysis of the Eigenvectors of Neighbourhood Operator to emphasize the geographical zonation in South America of 32 tree species predominant in the Paraguay‐Paraná Basin.Results Three main vegetation patterns were emphasized: the Chaco, the Paraná‐São Francisco gradient and the Peri‐Amazonian gradient. The Chaco is well defined. The Peri‐Amazonian gradient is characterized by a continuous change in species from the Colombian pole towards the São Francisco pole. The São Francisco gradient shows a continuous change from the São Francisco pole towards the Paraná pole. Some of the species are monocentric (related to only one dispersal centre), whereas others are polycentric (distributed in several poles).Main conclusions The Chaquean xeromorphic forests are considered as a climax, with a stable composition resulting of the saline soil conditions. The Chaco acts as an edaphic barrier to many species, although the migration of some non‐Chaquean species is made possible by the net of gallery‐forests and low montane forests between the Río Paraguay and the Andean Piedmont. The Cerrado and the Chaco can be considered as a barrier limiting the expansion of the Paranean forest. This latter formation is a semi‐deciduous forest made of a mix of monocentric and polycentric elements. The numerous species found both in Colombia and in Paraná indicate that bridges exist, or have existed, between these two poles. The persistence in the Paraguay‐Paraná Basin of a moist forest made of the Paranean assemblages highlighted in this study confirms the hypothesis of moister and cooler phases than today.

Silicified Microbes in a Geyser Mound: The Enigma of Low-Temperature Cyanobacteria in a High-Temperature Setting

A geyser mound, which has formed around the vent of an abandoned well-bore in the Tokaanu geothermal area (North Island, New Zealand) over the last 50 years, is formed primarily of white opal-A along with lesser amounts of black opal-A, reticulate, amorphous or poorly crystalline clay, halite, and scattered detrital quartz grains. Despite the boiling water ejected from the vent, at least 19 taxa of silicified microbes are present in the geyserite. Calothrix , Phormidium , and Synechococcus dominate. Other microbes, including local concentrations of diatoms, are widely scattered. The dominance of cyanobacteria is enigmatic given that these microbes typically are found in cooler water environments (< 60°C) on the medial to distal parts of geyser and hot-spring discharge aprons. The proximal zone around a geyser vent is environmentally unstable because it oscillates between periodic eruptions of boiling water and cooler phases in accord with the eruptive cycle of the geyser. Thus, the environmental niches on a geyser mound are temporally and spatially variable. The periodicity, duration, and magnitude of the eruptions, and the dispersal patterns of boiling water during eruptions control the distribution of the microenvironmental niches and their temporal changes. Dispersal and cooling of the ejected water will, for example, be controlled by factors such as height of the erupted water, ambient air temperature, and prevailing wind direction. Biotas compatible with relatively cool waters may thrive on geyser mounds because they inhabit areas that are not inundated constantly by boiling water. Their development and the sinter fabrics that they generate in the proximal zone of a geyser vent means that ancient deposits must be interpreted with caution.

Multi-wavelength study of the Seyfert 1 galaxy NGC 3783 with XMM-Newton

We present the analysis of multi-wavelength XMM-Newton data from the Seyfert galaxy NGC 3783, including UV imaging, X-ray and UV lightcurves, the 0.2-10 keV X-ray continuum, the iron K-alpha emission line, and high-resolution spectroscopy and modelling of the soft X-ray warm absorber. The 0.2-10 keV spectral continuum can be well reproduced by a power-law at higher energies; we detect a prominent Fe K-alpha emission line, with both broad and narrow components, and a weaker emission line at 6.9 keV which is probably a combination of Fe K-beta and Fe XXVI. We interpret the significant deficit of counts in the soft X-ray region as being due to absorption by ionised gas in the line of sight. This is demonstrated by the large number of narrow absorption lines in the RGS spectrum from iron, oxygen, nitrogen, carbon, neon, argon, magnesium, silicon and sulphur. The wide range of iron states present in the spectrum enables us to deduce the ionisation structure of the absorbing medium. We find that our spectrum contains evidence of absorption by at least two phases of gas: a hotter phase containing plasma with a log ionisation parameter xi (where xi is in erg cm/s) of 2.4 and greater, and a cooler phase with log xi centred around 0.3. The gas in both phases is outflowing at speeds of around 800 km/s. The main spectral signature of the cold phase is the Unresolved Transition Array (UTA) of M-shell iron, which is the deepest yet observed; its depth requires either that the abundance of iron, in the cold phase, is several times that of oxygen, with respect to solar abundances, or that the absorption lines associated with this phase are highly saturated. The cold phase is associated with ionisation states that would also absorb in the UV.

Magnetic susceptibility and ice-rafted debris in surface sediments of the Nordic Seas: implications for Isotope Stage 3 oscillations

Magnetic susceptibility and ice-rafted debris of surface sediments in the Nordic Seas were investigated to reconstruct source areas and recent transport pathways of magnetic minerals. From the distribution of magnetic susceptibility and ice-rafted debris and published data on petrographic tracers for iceberg drift, we reconstructed a counter-clockwise iceberg drift pattern during cooler phases in the Holocene, which is similar to conceptual and numerical models for Weichselian iceberg drift. The release of basaltic debris at Scoresby Sund played a significant role for the magnetic signature of stadial/interstadial events during isotope stage 3 recorded in sediment cores of the Nordic Seas.

Paleoclimatical interpretation ofthe quaternary small mammals of Spain

The changes in the distribution of the small mammals associations of the Pleistocene of Spain are used here tomake an environmental interpretation from this age to the present. We have taken into account the paleoenvironmental significance of some micromammals (Rodentia, Lagomorpha, Insectivora and Chiroptera), whose living representatives live in restricted habitats, as well as their evolution, immigration and extinction. Our observations allow the following remarks. After the relative cooling that happened by the late Pliocene and at the beginning of the Pleistocene, Spain was subjected to a mild climate since the Middle Pleistocene to the present. Some relatively warmer phases probably ocurred in the Middle Pleistocene, as well as some cooler phases during the glaciations of the Upper Pleistocene, even if these were less intense than in the rest of Europe. Humidity was probably greater during the Late Pliocene and the Lower Pleistocene than in preceding ages in Southern Spain. The relatively warmer phases during the Middle Pleistocene could have also been more humid in all the Peninsula, probably with an inceease of the water courses and a greater extension of the vegetation cover. The milder phases during the Upper Pleistocene would also be more humid with more wooded areas, while the cooler phases were possibly drier. There are evidences of a tendency towards a drier climate since the Upper Pleistocene until the present. As a result, a progressive decrease in the diversity of the micromammals happened which still prevails nowadays mainly in the Mediterranean area of Spain.

Lateglacial and Holocene climate and soil erosion in southeastern France: A case study from Etang du Pourra, Provence

AbstractA synthesis of pollen evidence from Etang du Pourra, a small pond in Rhodanian Provence, France, complemented by new sedimentological, mineralogical and palynological data allow a reassessment of the Lateglacial‐Holocene vegetation and climatic history of the area. The Etang du Pourra succession is shown to consist of two parts; the lower part dates from the Lateglacial and the upper reveals the Holocene pollen‐stratigraphic succession typical of the region. In the Lateglacial, a humid and cooler phase is recorded before the Younger Dryas conditions progressively set in. In the Holocene succession, the consequences of human modifications on the environment are clearly visible in changes in mineralogy and pollen stratigraphy.

Climatic Change and its Effect on Prehispanic Agriculture in the Central Peruvian Andes

The effect of climatic change on human and natural populations is most readily discernible in geographic locations where climate is a significant factor in limiting the range of activities. Today, as in the past, severe minimum temperatures at high altitudes limit the range of production of various crops in the Peruvian Andes. Periodic climatic cooling, as evidenced by the deposits from two recent glaciations, lowered the upper elevation limit of maize and significantly reduced the area available for its cultivation in the northern Mantaro River Valley. Paleoethnobotanical data from the same area suggest that during the most recent period of climatic cooling, less maize was produced compared to the warmer time periods that bracket this event. During the cooler phase, climatic constraints on maize production could have exacerbated already existing social tensions, perhaps leading to an increased establishment of more defensive settlements. This study shows how climate can affect human actions. This does not mean that climate dictated the major social and political changes seen in the archaeological record; but including environmental constraints and climatic change in discussions about the past can, given appropriate data, provide a more complete picture of cultural change.

Reponses des malacofaunes terrestres quaternaires aux contraintes climatiques en Europe septentrionale

Quaternary land snails show two major responses to climatic variations: emigration and ecophenotypism. The former is the case of the great majority of stenotopic species. Examples of migration are determined through the study of malacological associations. In northern France, cooler phases are indicated by the immigration and development of Nordic and Alpine species of which the area of distribution was invaded by ice. By contrast, interglacial temperate periods, corresponding to a recolonization of free environments, are indicated by the immigration of forest or semiforest thermophilic species. Ecophenotypism concerns some eurythermal species. They display morphological variations of the shell, mainly variations in size, which parallel climatic variations. In Pupilla muscorum, the shell is large when the climate is cold and small when it is temperate. Examples of migration and ecophenotypism are provided by joint studies of the malacological associations and Pupilla muscorum in the Achenheim site (Alsace, France).

Pollenstratigraphische, vegetations- und klimageschichtliche Gliederung des „Bölling-Alleröd-Komplexes“ in Schleswig-Holstein und ihre Bedeutung für die Spätglazial-Stratigraphie in benachbarten Gebieten

Pollenstratigraphische, vegetations- und klimageschichtliche Gliederung des „Bölling-Alleröd-Komplexes“ in Schleswig-Holstein und ihre Bedeutung für die Spätglazial-Stratigraphie in benachbarten Gebieten

Palynology in biostratigraphy and palaeoecology of Indian Lower Gondwana formations

A critical synthesis of the new palynological data from sequences out of six boreholes through the Lower Gondwana Formations in India has enabled palynostratigraphic and palaeoclimatic conclusions of significance viz.,&#x0D; (1) The Lower Gondwana sedimentation commenced with a glaciation followed by another glacial phase, interpolated with a short interglacial. The older glacial phase constitutes the Talchir Stage, the interglacial represents older Karharbari and the younger glacial phase occurred dur.ing deposition of younger Karharbari Fm followed by a long interglacial encompassing the Barakar, Ironstone Shale and Raniganj Fms. It has been found that homotaxial deposits of the later glacial phase differed in their lithological, palaeobotanical and to some extent palynological characteristics due to differences in their proximity to centres of glaciation.&#x0D; (2) In the younger part of the sequence, the Panchet Fm appears to have commenced with another cooler phase presumably due to another minor glaciation.&#x0D; (3) Immediately following the glacial phases, the interglacial commenced with humid climate which gradually or quickly declined.