The effects of winter food addition on the population dynamics of Clethrionomys rutilus

1995 ◽  
Vol 73 (3) ◽  
pp. 419-426 ◽  
Author(s):  
Sabine Schweiger ◽  
Stan Boutin

Peaks in red-backed vole (Clethrionomys rutilus) populations are associated with high survival in the previous winter and we tested the hypothesis that winter persistence is determined by food supply. We supplied sunflower seeds to voles in a replicated design during winter in two consecutive years. The study began when voles were at peak density and the pattern of change was one of decline to low density over the first winter followed by constant low densities. Food addition increased persistence of individuals slightly in the first winter and significantly in the second winter. Despite higher numbers in spring and greater production of young on food grids, densities did not increase to a peak in autumn. We conclude that the food additions created local patches of high density, but these were too small to have widespread effects on vole dynamics in the area.

Rangifer ◽  
1984 ◽  
Vol 4 (2) ◽  
pp. 39 ◽  
Author(s):  
Terje Skogland

<p>Fetal growth rates and birth weights were studied in four wild reindeer areas in Southern Norway (Hardangervidda, Hallingskarvet, Knutsh&oslash;, Forelhogna), representing high and low density populations, with a 5-fold difference in mean lichen winter-food availability. Fetal growth was depressed by 42% in the high-densitv Hardangervidda population, and mean birth weights were 3.7 vs. 6.2 kg, with a 10 days difference in mean birth dates. Fetal size was better correlated with maternal weight, than age. Maternal weights increased until 5 yrs. of age and then decreased in the high-density Hardangervidda population (but not so in the low density Knutsh&oslash;-Forclhogna populations). 55% of the offspring died before weaning in the Hardangervidda herd, but no significant calf losses were found amont the large-sized does in the food-abundant areas.</p><p>Effekter av ern&aelig;ring og simlas kondisjon p&aring; vekst og st&oslash;rrelse av foster hos villrein.</p><p>Abstract in Norwegian / Sammendrag: Fostervekst og f&oslash;dselsvekter ble unders&oslash;kt i fire villreinomr&aring;der i S&oslash;r-Norge (Hardangervidda, Hallingskarvet, Knutsh&oslash; og Forelhogna) som representerer h&oslash;g- og l&aring;gtetthetsstammer, med en 5-foldig forskjell i gjennomsnittlig lavbeite-tilgang om vinteren. Fosterveksten ble nedsatt med 42% i h&oslash;gtetthetsstammen p&aring; Hardangervidda og f&oslash;dselsvektene var i gjennomsnitt 3,7 kg, mot 6,2 kg i det beste omr&aring;det, og med en 10 dagers forsinkelse i midlere f&oslash;dselsdato. Fosterets st&oslash;rrelse var korrelert med morens vekt, som igjen var avhengig av hennes alder. Hos de minste simlene i det d&aring;rligste omr&aring;det &oslash;kte vektene til 5-&aring;rs alder, for deretter &aring; avta for hvert gjenlevende &aring;r. Hos simlene i det beste omr&aring;det &oslash;kte vektene til 10-&aring;rs alder, og var da dobbelt s&aring; tunge som fra det d&aring;rligste omr&aring;det. 55% av avkommet d&oslash;de f&oslash;r de var avvent med diing hos Hardangervidda-simlene, mens det ikke var noen statistisk m&aring;lbar d&oslash;delighet hos kalvene i Knutsh&oslash;-Forelhogna.</p><p>Ravinnon vaikutus ja naarasporon kunto porosikion kasvuun ja suuruuteen.</p><p>Abstract in Finnish / Yhteenveto: Etel&aring;-Norjan neljall&aring; peura-alueella, jotka ovat Hardangervidda, Hallingskarvet, Knutsho ja Forelhogna, tutkittiin porosikion kasvua ja syntym&aring;painoja. Alueet edustavat ylint&aring; ja alinta tiheyskantaa ja loytyy 5-kertainen eroavaisuus keskim&aring;arin j&aring;k&aring;l&aring;laiduntaan talvisaikaan. Sikion kasvu aleni 42% ylemm&aring;ss&aring; tiheyskannassa Hardangervidda-alueella ja syntym&aring;painot olivat keskim&aring;arin 3,7 kg mutta 6,2 kg parhaimmalla alueella, ja 10 p&aring;iv&aring;n myohastyminen keskim&aring;&aring;r&aring;isesta syntym&aring;p&aring;ivayksest&aring;. Sikion suuruus oli vastaavuussuhteessa emon painoon, joka oli taas riippuvainen sen i&aring;st&aring;. Huonoimmalla alueella pieninpien naaraiden painot lis&aring;antyiv&aring;t 5-ik&aring;vuoteen asti, vahet&aring;kseen sen j&aring;lkeen jokaista j&aring;ljell&aring;olevaa elovuotta kohden. Parhaimmalla alueella naaraiden painot lis&aring;antyiv&aring;t 10-ik&aring;vuoteen asti, ja oli silloin kaksi kertaa niin raskaita kuin huonoimman alueen naarasporot. 55% j&aring;lkel&aring;isist&aring; kuoli ennenkuin ne olivat vierottuneet Hardangervidda-naarasporoista. Sit&aring;vastoin ei ollut mit&aring;&aring;n tilastollisesti mitattavissa olevaa Knutsho - Forelhogna-alueiden vasakuolevaisuudesta.</p>


2009 ◽  
Vol 364 (1520) ◽  
pp. 1049-1058 ◽  
Author(s):  
S.J Plaistow ◽  
T.G Benton

Parental effects arise when either the maternal or paternal phenotype influences the phenotypes of subsequent generations. Simple analytical models assume maternal effects are a mechanism creating delayed density dependence. Such models predict that maternal effects can very easily lead to population cycles. Despite this, unambiguous maternal-effect mediated cycles have not been demonstrated in any system. Additionally, much evidence has arisen to invalidate the underlying assumption that there is a simple positive correlation between maternal performance and offspring performance. A key issue in understanding how maternal effects may affect population dynamics is determining how the expression of parental effects changes in different environments. In this study, we tested the hypothesis that maternal effects influence population dynamics in a context-dependent way. Populations of the soil mite, Sancassania berlesei , were set up at high density (500 eggs) or low density (50 eggs), with eggs that were either laid by young mothers or old mothers (a previously documented maternal effect in this system). The influence of maternal age on both population and egg and body-size dynamics was only observed in the populations initiated under low density rather than high density. This difference was attributable to the context-dependence of maternal effects at the individual level. In low-density (high food) conditions, maternal effects have an impact on offspring reproductive performance, creating an impact on the population growth rate. In high density (low food), maternal effects impact more on juvenile survival (not adult size or reproduction), creating a smaller impact on the population growth rate. This context dependence of effects at the population level means that, in fluctuating populations, maternal effects cause intermittent delayed density dependence that does not lead to persistent cycles.


Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).


1975 ◽  
Vol 33 (02) ◽  
pp. 256-270
Author(s):  
R. M Howell ◽  
S. L. M Deacon

SummaryElectron microscopy and particle electrophoresis were found to be complementary techniques with which to complete the physical data from an earlier study on barium sulphates used to adsorb clotting factors from serum. The differences revealed by scanning electron microscopy (S. E. M.) in the physical shape of low and high density grades of barium sulphate particles appear to be of greater significance than charge as expressed by electrophoretic mobility, in determining whether or not precursor or preformed factor Xa is eluted.This conclusion was based on the finding that at pH values close to 7, where the adsorption from serum occurs, all samples with the exception of natural barytes were uncharged. However as the high-density, or soil-grade, was found by S. E. M. to consist of large solid crystals it was suggested that this shape might induce activation of factor X as a result of partial denaturation and consequent unfolding of the adsorbed protein. In contrast, uptake of protein into the centre of the porous aggregates revealed by S. E. M. pictures of low-density or X-ray grade barium sulphate may afford protection against denaturation and exposure of the enzyme site.The porous nature of particles of low-density barium sulphate compared with the solid crystalline forms of other grades accounts not only for its lower bulk density but also for its greater surface/gram ratio which is reflected by an ability to adsorb more protein from serum.Neither technique produced evidence from any of the samples to indicate the presence of stabilising agents sometimes used to coat particles in barium meals.


Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1821
Author(s):  
Ildar I. Salakhov ◽  
Nadim M. Shaidullin ◽  
Anatoly E. Chalykh ◽  
Mikhail A. Matsko ◽  
Alexey V. Shapagin ◽  
...  

Low-temperature properties of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and their blends were studied. The analyzed low-temperature mechanical properties involve the deformation resistance and impact strength characteristics. HDPE is a bimodal ethylene/1-hexene copolymer; LDPE is a branched ethylene homopolymer containing short-chain branches of different length; LLDPE is a binary ethylene/1-butene copolymer and an ethylene/1-butene/1-hexene terpolymer. The samples of copolymers and their blends were studied by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), 13С NMR spectroscopy, and dynamic mechanical analysis (DMA) using testing machines equipped with a cryochamber. It is proposed that such parameters as “relative elongation at break at −45 °C” and “Izod impact strength at −40 °C” are used instead of the ductile-to-brittle transition temperature to assess frost resistance properties because these parameters are more sensitive to deformation and impact at subzero temperatures for HDPE. LLDPE is shown to exhibit higher relative elongation at break at −45 °C and Izod impact strength at −20 ÷ 60 °C compared to those of LDPE. LLDPE terpolymer added to HDPE (at a content ≥ 25 wt.%) simultaneously increases flow properties and improves tensile properties of the blend at −45 °C. Changes in low-temperature properties as a function of molecular weight, MWD, crystallinity, and branch content were determined for HDPE, LLDPE, and their blends. The DMA data prove the resulting dependences. The reported findings allow one to understand and predict mechanical properties in the HDPE–LLDPE systems at subzero temperatures.


2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Hee Young Kwon ◽  
Kyung Mee Song ◽  
Juyoung Jeong ◽  
Ah-Yeon Lee ◽  
Seung-Young Park ◽  
...  

AbstractThe discovery of a thermally stable, high-density magnetic skyrmion phase is a key prerequisite for realizing practical skyrmionic memory devices. In contrast to the typical low-density Néel-type skyrmions observed in technologically viable multilayer systems, with Lorentz transmission electron microscopy, we report the discovery of a high-density homochiral Néel-type skyrmion phase in magnetic multilayer structures that is stable at high temperatures up to 733 K (≈460 °C). Micromagnetic simulations reveal that a high-density skyrmion phase can be stabilized at high temperature by deliberately tuning the magnetic anisotropy, magnetic field, and temperature. The existence of the high-density skyrmion phase in a magnetic multilayer system raises the possibility of incorporating chiral Néel-type skyrmions in ultrahigh-density spin memory devices. Moreover, the existence of this phase at high temperature shows its thermal stability, demonstrating the potential for skyrmion devices operating in thermally challenging modern electronic chips.


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