Distribution and abundance of attached, littoral algae in 21 lakes and streams in the Northwest Territories

1979 ◽  
Vol 57 (6) ◽  
pp. 568-577 ◽  
Author(s):  
James W. Moore
Keyword(s):  
Northwest Territories ◽  
Growth Curve ◽  
Littoral Zone ◽  
Growing Season ◽  
Predominant Species ◽  
Maximum Abundance ◽  
Collection Sites ◽  
Achnanthes Minutissima

Collections of epilithic, epipelic, epiphytic, and epipsammic algae were made from the littoral zone of 21 lakes and streams in the Northwest Territories during 1975 and 1976. Tabellaria flocculosa was the predominant species in the epilithon and epipelon, reaching maximum densities of 0.5–2.5 × 109 μm3/cm2 depending on watercourse. It was followed in importance by Achnanthes minutissima, Navicula spp., and Nitzschia frustulum, all of which occurred at densities of 0.1–0.3 × 109 μm3/cm2. While the only two common taxa in the epiphyton, A. minutissima and T. flocculosa, maintained populations of 1.0–1.3 × 109 μm3/cm2, the most frequently encountered epipsammic species, Amphora ovalis var. pediculus, Fragilaria construens var. venter, Achnanthes minutissima, and Achnanthes pinnata, reached maximum levels of 4 × 107 μm3/cm2. The growing season for the attached flora extended from June to October throughout the study area. All four communities displayed a unimodal growth curve during this period, reaching maximum abundance in either July or August. The end of the growing season came during the middle of October when the collection sites were frozen to the bottom.

Influence of Oxadiazon on Peanuts and Weeds1

1977 ◽  
Vol 4 (1) ◽  
pp. 37-41 ◽  
Author(s):  
Gale A. Buchanan ◽  
Paul A. Backman ◽  
R. Rodriguez-Kabana
Keyword(s):  
Weed Control ◽  
Arachis Hypogaea ◽  
Growing Season ◽  
Mixed Population ◽  
Annual Grass ◽  
Predominant Species ◽  
Time Treatment ◽  
Arachis Hypogaea L ◽  
Substantial Control

Abstract Oxadiazon [2-tert-butyl-4-(2, 4-dichloro-5-isopropoxyphenyl)- Δ2-1,3,4-oxadiazolin-5-one] was applied alone as a preemergence treatment and in combination with dinoseb (2-sec-butyl-4,6-dinitrophenol) as a cracking-time treatment to peanuts (Arachis hypogaea L.). During the years 1970 to 1972 the experimental area was heavily infested with a mixed population of annual grass and broadleaf weeds. During the years 1973 to 1975, the predominant species present were sicklepod (Cassia obtusifolia L.) and Florida beggarweed [Desmodium tortuosum (Sw.) D.C.]. Grass control was acceptable with 3.36 kg/ha of oxadiazon in 2 of the 3 years when benefin (N-butyl-N-ethyl-∝, ∝, ∝ -trifluoro-2, 6-dinitro-p-toluidine) was not included. Commercially acceptable control of Florida beggarweed and sicklepod occurred with application of 3.36 kg/ha of oxadiazon. Substantial control was obtained with an application of 1.68 kg/ha. Generally, the addition of 1.68 kg/ha dinoseb to oxadiazon resulted in slightly improved weed control, particularly at lower rates of oxadiazon. Oxadiazon at rates of 6.7 kg/ha or more was phytotoxic to peanuts during the early part of the growing season. This phytotoxicity generally did not result in lower peanut yields. However, treated plants were more compact.

scholarly journals Tree-ring Reconstruction of Early-growing Season Precipitation from Yellowknife, Northwest Territories, Canada

2009 ◽  
Vol 41 (4) ◽  
pp. 486-496 ◽  
Author(s):  
Michael F. J. Pisaric ◽  
Sonia M. St-Onge ◽  
Steven V. Kokelj
Keyword(s):  
Northwest Territories ◽  
Tree Ring ◽  
Growing Season ◽  
Tree Ring Reconstruction ◽  
Growing Season Precipitation

Freshwater shelled invertebrate indicators of paleoclimate in northwestern Canada during late glacial times

1977 ◽  
Vol 14 (9) ◽  
pp. 2029-2046 ◽  
Author(s):  
L. D. Delorme ◽  
S. C. Zoltai ◽  
L. L. Kalas
Keyword(s):  
Northwest Territories ◽  
Potential Evapotranspiration ◽  
Growing Season ◽  
Late Glacial ◽  
Annual Precipitation ◽  
Time Interval ◽  
Mean Annual Temperature ◽  
The Mean

Paleoclimatic interpretations based on shelled invertebrates from four sites in the northwest corner of the Northwest Territories, Canada, during the time interval 14 410–6820 years BP, indicate that the mean annual temperature was about 8.2–11.6 °C higher than at present, and that the annual precipitation was about 55–234 mm greater than at the present time. Based on potential evapotranspiration, it can be computed that the length of the growing season was about 156 days long as compared to between 90 and 135 growing days at the present time for the same area.

The effects of an Arctic winter on benthic invertebrates in the littoral zone of Char Lake, Northwest Territories

1985 ◽  
Vol 63 (12) ◽  
pp. 2825-2834 ◽  
Author(s):  
Daniel Andrews ◽  
Frank H. Rigler
Keyword(s):  
Northwest Territories ◽  
Benthic Invertebrates ◽  
Littoral Zone ◽  
Growth Efficiency ◽  
Reproductive Period ◽  
Life Cycles ◽  
Conclusive Evidence ◽  
Subzero Temperatures ◽  
Program Temperature ◽  
Population Energetics

A method was devised for sampling the frozen benthos in the littoral zone of Char Lake, Northwest Territories, a polar lake that was studied during the International Biological Program. Temperature probes indicated that during the winter benthic invertebrates in sediments at 0.5 and 1.75 m were exposed to temperatures as low as −18 and −8 °C, respectively. Mortality in animals that had overwintered in the frozen samples ranged from 13 to 84% (mean 46%) and was attributed mostly to sample processing. With the possible exception of chironomids, no conclusive evidence was found that benthic invertebrates avoid freezing by emigrating to deeper portions of the lake. Exposure to subzero temperatures for 8 months or more increased the synchrony in development of the population of the harpacticoid Attheyella nordenskioldii and shifted its peak reproductive period by about 4 months. These changes implied increases in the population's gross production, growth efficiency, and ecological efficiency. The exposure of shallow-dwelling benthic invertebrates to subzero temperatures is a widespread phenomenon, the effects of which on life cycles and population energetics are poorly known.

scholarly journals Warming Increases Nitrous Oxide Emission from the Littoral Zone of Lake Poyang, China

2020 ◽  
Vol 12 (14) ◽  
pp. 5674
Author(s):  
Junxiang Cheng ◽  
Ligang Xu ◽  
Mingliang Jiang ◽  
Jiahu Jiang ◽  
Yanxue Xu
Keyword(s):  
Nitrous Oxide ◽  
Soil Moisture ◽  
Littoral Zone ◽  
Abiotic Factors ◽  
Growing Season ◽  
N2o Emission ◽  
N2o Emissions ◽  
N2o Flux ◽  
Lake Poyang ◽  
Littoral Wetlands

Littoral wetlands are globally important for sustainable development; however, they have recently been identified as critical hotspots of nitrous oxide (N2O) emissions. N2O flux from subtropical littoral wetlands remains unclear, especially under the current global warming environment. In the littoral zone of Lake Poyang, a simulated warming experiment was conducted to investigate N2O flux. Open-top chambers were used to raise temperature, and the static chamber-gas chromatograph method was used to measure N2O flux. Results showed that the littoral zone of Lake Poyang was an N2O source, with an average flux rate of 8.9 μg N2O m−2 h−1. Warming significantly increased N2O emission (13.8 μg N2O m−2 h−1 under warming treatment) by 54% compared to the control treatment. N2O flux in the spring growing season was also significantly higher than that of the autumn growing season. In addition, temperature was not significantly related to N2O flux, while soil moisture only explained about 7% of N2O variation. These results imply that N2O emission experiences positive feedback effect on the ongoing warming of the climate, and abiotic factors (e.g., soil temperature and soil moisture) were not main controls on N2O variation in this littoral wetland.

The influence of hydromorphological modifications of the littoral zone in lakes on macrophytes

2014 ◽  
Vol 43 (1) ◽  
Author(s):  
Szymon Jusik ◽  
Aurelia Macioł
Keyword(s):  
Vegetation Cover ◽  
Littoral Zone ◽  
Dominant Species ◽  
Field Research ◽  
Growing Season ◽  
Ecological Factor ◽  
Average Level ◽  
Filamentous Algae ◽  
Starting Point ◽  
Morphological Transformations

AbstractThe study aimed at determining the influence of hydromorphological modifications of the littoral zone in lakes on the occurrence and quantitative diversity of macrophytes. The field research was carried out at the peak of the growing season (June – September) between 2006 and 2009. Altogether, 457 transects were studied, located in 5 lakes. Studies on the hydromorphology were performed with the method of Lake Habitat Survey (LHS), and on macrophytes — with the method of transects. The studied sites were divided into 3 groups of different intensity of morphological transformations. The identified groups constituted the starting point for the analysis of influence exerted by transformations on macrophytes. The obtained results indicate that hydromorphological modifications of lakes are an important ecological factor affecting the occurrence and quantitative diversity of macrophytes. The transformations recorded in the studied reservoirs resulted mostly from recreational exploitation. They were responsible for mechanical elimination of dominant species, which led to an increased number of taxa, synanthropization and an average level of hemeroby as well as a decrease in the total vegetation cover. Helophytes were the most negatively affected group by the transformations, which reduce their contribution in the vegetation cover, whereas macroscopic filamentous algae and elodeids were positively affected.

scholarly journals Characterization of Curtoviruses Associated with Curly Top Disease of Tomato in California and Monitoring for These Viruses in Beet Leafhoppers

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 99-108 ◽  
Author(s):  
Li-Fang Chen ◽  
Kelly Brannigan ◽  
Rod Clark ◽  
Robert L. Gilbertson
Keyword(s):  
Central Valley ◽  
Growing Season ◽  
Fresh Market ◽  
California Department ◽  
Tomato Production ◽  
Predominant Species ◽  
Food And Agriculture ◽  
High Concentrations ◽  
Species Specific ◽  
Reservoir Hosts

Curly top disease is caused by a complex of curtoviruses (family Geminiviridae), and it continues to plague tomato production in California. To better understand the etiology of curly top of tomatoes in California, polymerase chain reaction (PCR)-based methods were developed and used to characterize the curtoviruses involved, and to monitor for these viruses in the beet leafhopper vector, Circulifer tenellus. From 2002 to 2008, 86 processing and fresh market tomato fields in the Central Valley of California were surveyed for the incidence of curly top symptoms. Representative samples with curly top symptoms were collected from the surveyed fields, as well as from another 24 fields. The incidence of curly top symptoms in most fields ranged from trace (<1%) to low (1 to 5%); however, in 2002, 2003, and 2008, some fields had medium (5 to 20%) or high (>20%) incidences. PCR with general and species-specific primers was used to establish that the predominant species associated with tomato curly top disease were Beet mild curly top virus (BMCTV) and, to a lesser extent, Beet severe curly top virus (BSCTV). The incidence, relative amount, and species of curly top virus in leafhoppers, collected at monthly intervals by the California Department of Food and Agriculture (CDFA) personnel during 2003 to 2008, was also determined. The predominant species detected were BMCTV and BSCTV. The highest incidences of curly top in tomato fields were associated with high populations of leafhoppers (e.g., in 2003 when populations were two times greater than average) having high incidences and levels of curly top virus early in the growing seasons (e.g., March to May 2003 and 2008). Detection of curly top virus in leafhoppers early in the growing season was consistent with acquisition of virus from reservoir hosts in the foothills. However, continued detection of curly top virus in leafhoppers throughout the growing season and development of curly top in late-planted fresh market tomatoes were consistent with the presence of inoculum sources (e.g., weeds or crop plants) in the agricultural areas of the Central Valley. Geographical locations or “hotspots” having higher proportions of curly top virus–positive leafhoppers were identified, which may reveal areas having high concentrations of curly top virus reservoir hosts. The application of these molecular tools has provided new insight into curly top of tomato in California, and may lead to improved curly top management.

Problem gambling symptomatology and alcohol misuse among adolescents: A parallel-process latent growth curve model.

2017 ◽  
Vol 31 (4) ◽  
pp. 447-456 ◽  
Author(s):  
Seema Mutti-Packer ◽  
David C. Hodgins ◽  
Nady el-Guebaly ◽  
David M. Casey ◽  
Shawn R. Currie ◽  
...  
Keyword(s):  
Problem Gambling ◽  
Growth Curve ◽  
Alcohol Misuse ◽  
Parallel Process ◽  
Latent Growth Curve ◽  
Growth Curve Model ◽  
Latent Growth ◽  
Latent Growth Curve Model ◽  
Curve Model

Health Promotion Strategy of the Northwest Territories

2000 ◽  
Author(s):  
Elsie de Roose ◽  
Rick Tremblay ◽  
Lona Hegeman
Keyword(s):  
Health Promotion ◽  
Northwest Territories ◽  
Promotion Strategy ◽  
Health Promotion Strategy

Latent Growth Curve Modeling of the Development of Leadership Performance

2006 ◽  
Author(s):  
Rosalie J. Hall ◽  
Robert G. Lord ◽  
Hsien-Yao Swee ◽  
Barbara A. Ritter ◽  
David A. DuBois
Keyword(s):  
Growth Curve ◽  
Growth Curve Modeling ◽  
Latent Growth Curve Modeling ◽  
Latent Growth Curve ◽  
Latent Growth ◽  
Leadership Performance ◽  
Curve Modeling
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