Population dynamics of muskrats in experimental marshes at Delta, Manitoba

1993 ◽  
Vol 71 (8) ◽  
pp. 1620-1628 ◽  
Author(s):  
William R. Clark ◽  
Darryl W. Kroeker
Keyword(s):  
Water Level ◽  
Mass Gain ◽  
Winter Survival ◽  
Spatial And Temporal Variation ◽  
Open Population ◽  
Wetland Complex ◽  
Estimate Population Size ◽  
Different Levels ◽  
Natural Prairie

Muskrat populations were studied in relation to water level and vegetation succession in an experimental wetland complex at Delta Marsh, Manitoba, Canada, flooded to three different levels: normal (long-term average elevation); medium (30 cm above normal); and high (60 cm above normal). Trapping in October and May, combined with closed and open population estimators, was usesd to estimate population size, survival, and recruitment. Muskrat densities reached > 30/ha after the second growing season. Populations in medium and high treatments initially reached densities greater than in normal cells, but all populations decreased to < 1/ha in May 1988. Winter survival declined from 0.31 in 1986 to 0.09 in 1987 and recruitment had declined significantly by May 1988. Winter survival, per-capita recruitment, body condition, and winter mass changes were inversely related to population density, but not consistently related to water level treatments. Survival was directly related to winter mass gain although recruitment the following spring was not. The most influential demographic factor in observed declines in density was decreased winter survival, which was consistently low in all treatments once flooding reduced the emergent vegetation. In natural prairie marsh systems, spatial and temporal variation in vegetation response to flooding contributes to variation in the density dependence of both the survival and recruitment of muskrats.

Habitat selection by muskrats in experimental marshes undergoing succession

1994 ◽  
Vol 72 (4) ◽  
pp. 675-680 ◽  
Author(s):  
William R. Clark
Keyword(s):  
Habitat Selection ◽  
Water Depth ◽  
Plant Succession ◽  
Habitat Types ◽  
Wetland Succession ◽  
Wetland Complex ◽  
Density Dependent Habitat Selection ◽  
Different Levels ◽  
Selection Of

I analyzed habitat selection by muskrats (Ondatra zibethicus) in relation to density and plant succession in an experimental wetland complex flooded to three different levels: normal (long-term average elevation), medium (30 cm above normal), and high (60 cm above normal) at Delta, Manitoba. Locations where muskrats were trapped or built lodges were superimposed on vegetation types and water depth, in a geographic information system, to determine habitat selection. More than 60% of all individuals were captured in stands of Scirpus, Scolochloa, or Typha, and muskrats significantly avoided areas with water < 1 cm that were dominated by annuals and Hordeum. Muskrats preferred Typha and Scirpus stands for lodges, although some lodges were built in Scolochloa and Phragmites. Water depth at lodges averaged 38 cm, and > 90% of lodges were located in water ≥ 10 cm. Tall dense emergent growth trapped the most snow, resulting in the ice being less thick. Muskrats first captured in Typha or Scirpus stands gained significantly more mass during winter than did those captured in all other habitat types. As emergent vegetation changed and muskrat population density increased, the selection of habitat such as Typha in moderately deep water changed less than did the selection of habitat in shallow water or of those dominated by Scolochloa or sparse Scirpus. These data confirm density-dependent habitat selection by muskrats and suggest that spatial complexity induced by wetland succession is important in muskrat population dynamics.

Use Of Tai Chi Elements To Increase Respiratory Amplitude

2019 ◽  
pp. 11-20
Author(s):  
Mihai-Alexandru Citea ◽  
Marius Neculaes
Keyword(s):  
High Performance ◽  
Tai Chi ◽  
Sports Club ◽  
Optimal Functioning ◽  
Physiological Adaptations ◽  
Competitive Activity ◽  
Abdominal Breathing ◽  
Study Participants ◽  
Different Levels

High performance sport has a major impact on the physiological adaptations of the respiratory system. The importance of the optimal functioning of this system is essential to achieve top results in high performance sport but also in maintaining a long term health status. Science journals present numerous studies that highlight the benefits of practicing Tai Chi on the general population, with effects ranging from improving cardiac function, to influencing the immune system. The purpose of this study is to identify whether by practicing Tai Chi forms a athlete can change their breathing pattern and develop their respiratory amplitude. The subjects of the study were 22 fencing practitioners, accredited at the Iași Municipal Sports Club (C.S.M. Iași), aged between 14 and 18 years, with over 3 years of competitive activity. Materials and method: The study participants were evaluated initially and at the end of 7 months of practice. The frequency was 3 sessions per week, and the duration of each session was 20-30 minutes. The evaluation consisted in measuring the circumference of the thorax at 3 different levels: subaxillary, medial thorax (T6-T7) and lower rib (diaphragmatic) in maximal inspiration and expiration. Conclusions: A constant evolution is observed in most of the exposed cases. In cases where this evolution is not visible, a change in the breathing mode can be noticed, transforming from an upper rib breathing into a thoracic or abdominal breathing. With the exception of one case, all subjects had an improvement of the value in the lower rib level.

scholarly journals Effects of disk tillage on soil condition, crop yield and weed infestation

2011 ◽  
Vol 48 (No. 1) ◽  
pp. 20-26
Author(s):  
M. Birkás ◽  
T. Szalai ◽  
C. Gyuricza ◽  
M. Gecse ◽  
K. Bordás
Keyword(s):  
Winter Wheat ◽  
Crop Yield ◽  
Field Experiments ◽  
Soil Layer ◽  
Soil Condition ◽  
Perennial Weeds ◽  
Weed Infestation ◽  
Set Up ◽  
Different Levels

This research was instigated by the fact that during the last decade annually repeated shallow disk tillage on the same field became frequent practice in Hungary. In order to study the changes of soil condition associated with disk tillage and to assess it is consequences, long-term tillage field experiments with different levels of nutrients were set up in 1991 (A) and in 1994 (B) on Chromic Luvisol at G&ouml;d&ouml;ll&ouml;. The effects of disk tillage (D) and disk tillage combined with loosening (LD) on soil condition, on yield of maize and winter wheat, and on weed infestation were examined. The evaluation of soil condition measured by cone index and bulk density indicated that use of disking annually resulted in a dense soil layer below the disking depth (diskpan-compaction). It was found, that soil condition deteriorated by diskpan-compaction decreased the yield of maize significantly by 20 and 42% (w/w), and that of wheat by 13 and 15% (w/w) when compared to soils with no diskpan-compaction. Averaged over seven years, and three fertilizer levels, the cover % of the total, grass and perennial weeds on loosened soils were 73, 69 and 65% of soils contained diskpan-compaction.

scholarly journals Spatial and Temporal Variation Characteristics of Snowfall in the Haihe River Basin from 1960 to 2016

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1798
Author(s):  
Xu Wu ◽  
Su Li ◽  
Bin Liu ◽  
Dan Xu
Keyword(s):  
Temporal Variation ◽  
River Basin ◽  
Spatial And Temporal Variation ◽  
Haihe River Basin ◽  
Temperature Threshold ◽  
Threshold Method ◽  
Exponential Equation ◽  
Haihe River ◽  
The Haihe River Basin ◽  
Different Levels

The spatio-temporal variation of precipitation under global warming had been a research hotspot. Snowfall is an important part of precipitation, and its variabilities and trends in different regions have received great attention. In this paper, the Haihe River Basin is used as a case, and we employ the K-means clustering method to divide the basin into four sub-regions. The double temperature threshold method in the form of the exponential equation is used in this study to identify precipitation phase states, based on daily temperature, snowfall, and precipitation data from 43 meteorological stations in and around the Haihe River Basin from 1960 to 1979. Then, daily snowfall data from 1960 to 2016 are established, and the spatial and temporal variation of snowfall in the Haihe River Basin are analyzed according to the snowfall levels as determined by the national meteorological department. The results evalueted in four different zones show that (1) the snowfall at each meteorological station can be effectively estimated at an annual scale through the exponential equation, for which the correlation coefficient of each division is above 0.95, and the relative error is within 5%. (2) Except for the average snowfall and light snowfall, the snowfall and snowfall days of moderate snow, heavy snow, and snowstorm in each division are in the order of Zones III > IV > I > II. (3) The snowfall and the number of snowfall days at different levels both show a decreasing trend, except for the increasing trend of snowfall in Zone I. (4) The interannual variation trend in the snowfall at the different levels are not obvious, except for Zone III, which shows a significant decreasing trend.

scholarly journals Assessing Stream-Aquifer Connectivity in a Coastal California Watershed

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 416
Author(s):  
Bwalya Malama ◽  
Devin Pritchard-Peterson ◽  
John J. Jasbinsek ◽  
Christopher Surfleet
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Water Level ◽  
Time Series Data ◽  
Series Data ◽  
Low Permeability ◽  
Pumping Tests ◽  
Stream Flows ◽  
The Impact

We report the results of field and laboratory investigations of stream-aquifer interactions in a watershed along the California coast to assess the impact of groundwater pumping for irrigation on stream flows. The methods used include subsurface sediment sampling using direct-push drilling, laboratory permeability and particle size analyses of sediment, piezometer installation and instrumentation, stream discharge and stage monitoring, pumping tests for aquifer characterization, resistivity surveys, and long-term passive monitoring of stream stage and groundwater levels. Spectral analysis of long-term water level data was used to assess correlation between stream and groundwater level time series data. The investigations revealed the presence of a thin low permeability silt-clay aquitard unit between the main aquifer and the stream. This suggested a three layer conceptual model of the subsurface comprising unconfined and confined aquifers separated by an aquitard layer. This was broadly confirmed by resistivity surveys and pumping tests, the latter of which indicated the occurrence of leakage across the aquitard. The aquitard was determined to be 2–3 orders of magnitude less permeable than the aquifer, which is indicative of weak stream-aquifer connectivity and was confirmed by spectral analysis of stream-aquifer water level time series. The results illustrate the importance of site-specific investigations and suggest that even in systems where the stream is not in direct hydraulic contact with the producing aquifer, long-term stream depletion can occur due to leakage across low permeability units. This has implications for management of stream flows, groundwater abstraction, and water resources management during prolonged periods of drought.

The influence of immersed water level on the short- and long-term mechanical behavior of sandstone

2021 ◽  
Vol 138 ◽  
pp. 104631
Author(s):  
Peizhao Chen ◽  
Shibin Tang ◽  
Xin Liang ◽  
Yongjun Zhang ◽  
Chunan Tang
Keyword(s):  
Mechanical Behavior ◽  
Water Level ◽  
Short And Long Term

Time-Dependent Changes in Excitability After One-Trial Conditioning of Hermissenda

1997 ◽  
Vol 78 (6) ◽  
pp. 3460-3464 ◽  
Author(s):  
Terry Crow ◽  
Vilma Siddiqi
Keyword(s):  
Time Dependent ◽  
Control Group ◽  
Type B ◽  
Control Groups ◽  
Phototactic Behavior ◽  
Parallel Processes ◽  
Short And Long Term ◽  
A Site ◽  
Different Levels

Crow, Terry and Vilma Siddiqi. Time-dependent changes in excitability after one-trial conditioning of Hermissenda. J. Neurophysiol. 78: 3460–3464, 1997. The visual system of Hermissenda has been studied extensively as a site of cellular plasticity produced by classical conditioning. A one-trial conditioning procedure consisting of light paired with the application of serotonin (5-HT) to the exposed, but otherwise intact, nervous system produces suppression of phototactic behavior tested 24 h after conditioning. Short- and long-term enhancement (STE and LTE) of excitability in identified type B photoreceptors is a cellular correlate of one-trial conditioning. LTE can be expressed in the absence of STE suggesting that STE and LTE may be parallel processes. To examine the development of enhancement, we studied its time-dependent alterations after one-trial conditioning. Intracellular recordings from identified type B photoreceptors of independent groups collected at different times after conditioning revealed that enhanced excitability follows a biphasic pattern in its development. The analysis of spikes elicited by 2 and 30 s extrinsic current pulses at different levels of depolarization showed that enhancement reached a peak 3 h after conditioning. From its peak, excitability decreased toward baseline control levels 5–6 h after conditioning followed by an increase to a stable plateau at 16 to 24 h postconditioning. Excitability changes measured in cells from unpaired control groups showed maximal changes 1 h posttreatment that rapidly decremented within 2 h. The conditioned stimulus (CS) elicited significantly more spikes 24 h postconditioning for the conditioned group as compared with the unpaired control group. The analysis of the time-dependent development of enhancement may reveal the processes underlying different stages of memory for this associative experience.

scholarly journals Evaluating Simple Methodology for Piezoelectric Level Sensors Protection

Proceedings ◽  
2019 ◽  
Vol 48 (1) ◽  
pp. 30
Author(s):  
Luis Hamilton Pospissil Garbossa ◽  
Argeu Vanz ◽  
Matias Guilherme Boll ◽  
Hamilton Justino Vieira
Keyword(s):  
Water Level ◽  
Flood Control ◽  
Low Cost ◽  
Solid Particles ◽  
Storm Events ◽  
Sewer Systems ◽  
Continuous Monitor ◽  
Level Monitoring ◽  
Water Level Monitoring

The increasing frequency of extreme storm events has implications for the operation of sewer systems, storm water, flood control monitoring and tide level variations. Accurate and continuous monitor water level monitoring is demanded in different environments. Piezoelectric sensors are widely used for water level monitoring and work submerged in waters subject to the presence of solid particles, biological fouling and saltwater oxidation. This work aimed to develop a simple, low-cost methodology to protect sensors over long-term deployment. The results show that simple actions, costing less than 2 EUR, can protect and extend the lifecycle of equipment worth over 2000 EUR, ensuring continuous monitoring and maintaining quality measurements.

The British General Election of 1970 - Impressions of an Academic Candidate

1971 ◽  
Vol 6 (1) ◽  
pp. 36-57
Author(s):  
William Wallace
Keyword(s):  
General Election ◽  
The Political ◽  
Political Scientist ◽  
Ideal Types ◽  
Political Behaviour ◽  
Levels Of Reality ◽  
Political Scene ◽  
Different Levels ◽  
Political Battle

THE STUDENT OF POLITICS AND THE PRACTITIONER OF POLITICS approach the same problem from different ends. The student is concerned with searching for the underlying realities which can explain the surface shifts of political ephemera; or perhaps with disentangling the different levels of reality which he discerns from his dispassionate observation of the political scene. The practitioner is concerned above all with the intricacies of day-to-day politics. He is interested in long-term patterns of political behaviour only insofar as they affect his political chances, or insofar as foreknowledge will enable him to change and shape the developing pattern. At the opposite ends of this division of interest in the phenomena of politics one may imagine, as ideal types, the ‘pure’ political scientist, the neutral observer of the political battle whose attitude to the contestants and their fluctuating fortunes is one of scholarly detachment, and the dedicated politician, glorying in the clash and chaos of the battlefield, with little more than contempt for those who stand aside and watch. For those who stand towards either end of this division, there are now two separate worlds of politics.

Contradictions of the upcoming period: points for developing the agenda for medium- and long-term perspective

2021 ◽  
pp. 72-80
Author(s):  
D.M. Belousov ◽  
Keyword(s):  
Social Order ◽  
Social Situation ◽  
Regional Conflicts ◽  
Global Nature ◽  
Multi Level ◽  
Object Of Control ◽  
Trade Wars ◽  
New Social Order ◽  
Different Levels

Analysis of the economic and social situation allows for the conclusion that the world is entering an era of global instability and contradictions. There is clearly a crisis of compensatory and basic institutions. Humans cease to be the subjects of the historical process and instead are becoming the object of control. Contradictions are sharply increasing at different levels. We are witnessing the conflict between labor and capital related to the national nature of labor and the global nature of capital. Production, security and regional applied science are changing, but financial and institutional systems remain global. Information and trade wars are intensifying. During a multi-level crisis, it is difficult to predict what a new social order will be like, but the transition to it will be difficult and highly possibly rife with (macro-) regional conflicts.

Sign in / Sign up

Export Citation Format

Share Document