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Heinz G Stefan - One of the best experts on this subject based on the ideXlab platform.
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Projected Climate Change Effects on Winterkill in Shallow Lakes in the Northern United States
Environmental Management, 2000Co-Authors: Xing Fang, Heinz G StefanAbstract:was obtained from the output of the Canadian Climate Center General Circulation Model. To illustrate the effect of projected climate change on lake DO characteristics, we present herein DO information simulated, respectively, with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario, as well as differences of those values. Specific parameters obtained were minimum under-ice and lake bottom DO concentration in winter, duration of under-ice anoxic conditions (
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projected climate change effects on Winterkill in shallow lakes in the northern united states
Environmental Management, 2000Co-Authors: Xing Fang, Heinz G StefanAbstract:was obtained from the output of the Canadian Climate Center General Circulation Model. To illustrate the effect of projected climate change on lake DO characteristics, we present herein DO information simulated, respectively, with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario, as well as differences of those values. Specific parameters obtained were minimum under-ice and lake bottom DO concentration in winter, duration of under-ice anoxic conditions (<0.1 mg/liter) and low DO conditions (<3 mg/liter), and percentage of anoxic and low DO lake volumes during the ice cover period. Under current climate conditions Winterkill occurs typically in shallow eutrophic lakes of the northern contiguous United States. Climate warming is projected to eliminate Winterkill in these lakes. This would be a positive effect of climate warming. Fish species under ice may still experience periods of stress and zero growth due to low DO (<3 mg/liter) conditions under projected climate warming.
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Simulation and validation of fish thermal DO habitat in north-central US lakes under different climate scenarios
Ecological Modelling, 1999Co-Authors: Xing Fang, Heinz G Stefan, Shoeb R. AlamAbstract:Fish habitat in lakes is strongly constrained by water temperature and available dissolved oxygen (DO). Suitable fish habitat for three fish assemblages (cold-, cool-, and warm-water) in Minnesota (US) lakes was therefore determined from simulated daily water temperature and dissolved oxygen profiles. A total of 27 types of lakes were simulated under past (1961‐1979) and a projected 2CO2 climate scenarios. The projected climate scenario was derived from the output of the Canadian Climate Center General Circulation Model for a doubling of atmospheric CO2. A verified, process-oriented, unsteady and one-dimensional (vertical) year-round lake water quality model (MINLAKE96) was used for the temperature and DO simulations, which were run in a continuous mode over 19 years. Water temperature and DO criteria for survival and good-growth of each fish guild were provided by the United States Environmental Protection Agency. Simulated suitable fish habitats were compared with fish observations in 3002 Minnesota lakes. Winterkill was simulated to occur in shallow eutrophic and mesotrophic lakes under past climate conditions, and predicted to disappear under the projected 2 CO2 climate scenario due to a shortening of the ice cover period. Sensitivity of the simulated Winterkill to three DO survival limits was analyzed. A lower DO (less than 0.5 mg:1) limit for Winterkill produced better agreement with a fish observation database than higher limits. Dependence of the simulated good-growth habitat areas (GGHA) and volumes (GGHV) on the geometry (surface area and maximum depth) and trophic state of a lake was also examined. Fish habitat parameters were found to depend more strongly on geometry and less on trophic state. Climate change is projected to increase GGHA in seasonaly stratified (medium-depth and deep) lakes on the average by 50 and 115% for cool-water and warm-water fish guilds, respectively. It is also projected that cold-water fish species will have a small percentage loss in weakly stratified (medium-depth) lakes, but a small percentage gain of GGHA in deep, strongly stratified lakes. © 1999 Elsevier Science B.V. All rights reserved.
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Simulated climate change effects on ice and snow covers on lakes in a temperate region
Cold Regions Science and Technology, 1997Co-Authors: Heinz G Stefan, Xing FangAbstract:Abstract A simulation model for ice and snow covers is applied to dimictic and polymictic lakes of the temperate zone to project the effects of possible climate warming on ice and snow covers. The winter cover model is associated with a deterministic, one-dimensional water temperature model. The lake parameters required as model input are surface area (AS), maximum depth (Hmax), summer and Secchi depth as a measure of radiation attenuation and trophic state. The model is driven by daily weather data. The model has been validated with extensive data. Standard errors between simulated and measured values are 0.12 m for ice thicknesses, 0.07 m for snow covers and less than 6 days for ice formation dates. The model is applied to simulate effects of projected climate change on winter ice and snow covers on different types of lakes in Minnesota. Lake depth and latitude are shown to have the strongest influence on freeze-over dates. Lake morphometry causes variations of up to 6 days in the mean value of ice-in dates. The trophic state and shape of a lake have little effect on ice-out date, but latitude is important. The projected climate change due to a doubling of atmospheric carbon dioxide (2 × CO2) is obtained from the output of the Canadian Climate Center Global Circulation Model (CCC GCM) and the Goddard Institute of Space Studies at Columbia University (GISS GCM). The 2 × CO2 climate delays the ice formation by as much as 20 days, reduces maximum ice and snow thicknesses by 50%, and shortens the ice cover period by up to 60 days. These changes would eliminate fish Winterkill in most shallow lakes, but would endanger snowmobiles and ice fishermen. To illustrate the effect of projected climate change on winter ice/snow cover characteristics, separate graphs are presented for values simulated with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario. Independent variables used on these plots are a lake geometry ratio A S 0.25 H max and Secchi depth. The lake geometry ratio measures the susceptibility of a lake to stratification.
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Hydraulic Design of Winter Lake Aeration System
Journal of Environmental Engineering, 1990Co-Authors: Christopher Ellis, Heinz G StefanAbstract:Shallow, eutrophic lakes in the upper Midwest of the United States are subject to fish mortality due to oxygen depletion under ice Winterkill. Current practices employed to prevent this phenomenon ...
Xing Fang - One of the best experts on this subject based on the ideXlab platform.
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Projected Climate Change Effects on Winterkill in Shallow Lakes in the Northern United States
Environmental Management, 2000Co-Authors: Xing Fang, Heinz G StefanAbstract:was obtained from the output of the Canadian Climate Center General Circulation Model. To illustrate the effect of projected climate change on lake DO characteristics, we present herein DO information simulated, respectively, with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario, as well as differences of those values. Specific parameters obtained were minimum under-ice and lake bottom DO concentration in winter, duration of under-ice anoxic conditions (
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projected climate change effects on Winterkill in shallow lakes in the northern united states
Environmental Management, 2000Co-Authors: Xing Fang, Heinz G StefanAbstract:was obtained from the output of the Canadian Climate Center General Circulation Model. To illustrate the effect of projected climate change on lake DO characteristics, we present herein DO information simulated, respectively, with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario, as well as differences of those values. Specific parameters obtained were minimum under-ice and lake bottom DO concentration in winter, duration of under-ice anoxic conditions (<0.1 mg/liter) and low DO conditions (<3 mg/liter), and percentage of anoxic and low DO lake volumes during the ice cover period. Under current climate conditions Winterkill occurs typically in shallow eutrophic lakes of the northern contiguous United States. Climate warming is projected to eliminate Winterkill in these lakes. This would be a positive effect of climate warming. Fish species under ice may still experience periods of stress and zero growth due to low DO (<3 mg/liter) conditions under projected climate warming.
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Simulation and validation of fish thermal DO habitat in north-central US lakes under different climate scenarios
Ecological Modelling, 1999Co-Authors: Xing Fang, Heinz G Stefan, Shoeb R. AlamAbstract:Fish habitat in lakes is strongly constrained by water temperature and available dissolved oxygen (DO). Suitable fish habitat for three fish assemblages (cold-, cool-, and warm-water) in Minnesota (US) lakes was therefore determined from simulated daily water temperature and dissolved oxygen profiles. A total of 27 types of lakes were simulated under past (1961‐1979) and a projected 2CO2 climate scenarios. The projected climate scenario was derived from the output of the Canadian Climate Center General Circulation Model for a doubling of atmospheric CO2. A verified, process-oriented, unsteady and one-dimensional (vertical) year-round lake water quality model (MINLAKE96) was used for the temperature and DO simulations, which were run in a continuous mode over 19 years. Water temperature and DO criteria for survival and good-growth of each fish guild were provided by the United States Environmental Protection Agency. Simulated suitable fish habitats were compared with fish observations in 3002 Minnesota lakes. Winterkill was simulated to occur in shallow eutrophic and mesotrophic lakes under past climate conditions, and predicted to disappear under the projected 2 CO2 climate scenario due to a shortening of the ice cover period. Sensitivity of the simulated Winterkill to three DO survival limits was analyzed. A lower DO (less than 0.5 mg:1) limit for Winterkill produced better agreement with a fish observation database than higher limits. Dependence of the simulated good-growth habitat areas (GGHA) and volumes (GGHV) on the geometry (surface area and maximum depth) and trophic state of a lake was also examined. Fish habitat parameters were found to depend more strongly on geometry and less on trophic state. Climate change is projected to increase GGHA in seasonaly stratified (medium-depth and deep) lakes on the average by 50 and 115% for cool-water and warm-water fish guilds, respectively. It is also projected that cold-water fish species will have a small percentage loss in weakly stratified (medium-depth) lakes, but a small percentage gain of GGHA in deep, strongly stratified lakes. © 1999 Elsevier Science B.V. All rights reserved.
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Simulated climate change effects on ice and snow covers on lakes in a temperate region
Cold Regions Science and Technology, 1997Co-Authors: Heinz G Stefan, Xing FangAbstract:Abstract A simulation model for ice and snow covers is applied to dimictic and polymictic lakes of the temperate zone to project the effects of possible climate warming on ice and snow covers. The winter cover model is associated with a deterministic, one-dimensional water temperature model. The lake parameters required as model input are surface area (AS), maximum depth (Hmax), summer and Secchi depth as a measure of radiation attenuation and trophic state. The model is driven by daily weather data. The model has been validated with extensive data. Standard errors between simulated and measured values are 0.12 m for ice thicknesses, 0.07 m for snow covers and less than 6 days for ice formation dates. The model is applied to simulate effects of projected climate change on winter ice and snow covers on different types of lakes in Minnesota. Lake depth and latitude are shown to have the strongest influence on freeze-over dates. Lake morphometry causes variations of up to 6 days in the mean value of ice-in dates. The trophic state and shape of a lake have little effect on ice-out date, but latitude is important. The projected climate change due to a doubling of atmospheric carbon dioxide (2 × CO2) is obtained from the output of the Canadian Climate Center Global Circulation Model (CCC GCM) and the Goddard Institute of Space Studies at Columbia University (GISS GCM). The 2 × CO2 climate delays the ice formation by as much as 20 days, reduces maximum ice and snow thicknesses by 50%, and shortens the ice cover period by up to 60 days. These changes would eliminate fish Winterkill in most shallow lakes, but would endanger snowmobiles and ice fishermen. To illustrate the effect of projected climate change on winter ice/snow cover characteristics, separate graphs are presented for values simulated with inputs of past climate conditions (1961–1979) and with a projected 2 × CO2 climate scenario. Independent variables used on these plots are a lake geometry ratio A S 0.25 H max and Secchi depth. The lake geometry ratio measures the susceptibility of a lake to stratification.
Alireza Navabi - One of the best experts on this subject based on the ideXlab platform.
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Application of image-based phenotyping tools to identify QTL for in-field winter survival of winter wheat (Triticum aestivum L.)
Theoretical and Applied Genetics, 2019Co-Authors: Yi Chen, Harwinder S. Sidhu, Mina Kaviani, Michel S. Mcelroy, Curtis J. Pozniak, Alireza NavabiAbstract:Key message Genome-wide association on winter survival was conducted using data from image-based phenotyping method. Nine QTL were observed and three of them with candidate gene identified. Abstract Winter survival is an essential trait of winter wheat ( Triticum aestivum L.) grown in regions with high risk of Winterkill. We characterized a diversity panel of 450 Canadian wheat varieties that included mostly winter-growth habit wheats to identify key genetic factors that contribute to higher winter survival under field conditions. To more accurately quantify winter survival differences among varieties, image-based phenotyping methods, captured by unmanned aerial vehicle (UAV) and on ground level, were used to estimate the winter survival of each varieties. Winter survival index was developed to correct for emergence when evaluating winter survival. Winter survival measurement estimated by visual estimation, UAV imagery and ground imagery showed strong correlation with each other and had comparable broad-sense heritability. Genome-wide association studies resulted in the identification of seven quantitative trait loci (QTL) for winter survival including Vrn - A1 . By using the recently released annotated sequence of the wheat genome and the available RNA-Seq data, two putative candidate genes underlying the QTL for winter survival were identified. However, our study showed that certain QTL was unique to specific winter survival measurement. Collectively, our study demonstrated the feasibility of using UAV-based imagery for the identification of loci associated with winter survival in wheat. The complexity of in-field condition make our result a valuable complement to indoor frost-tolerance studies in the identification of genetic factors not directly linked to freezing tolerance.
Thomas Mehner - One of the best experts on this subject based on the ideXlab platform.
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Contrasting response of two shallow eutrophic cold temperate lakes to a partial Winterkill of fish
Hydrobiologia, 2015Co-Authors: Sabine Hilt, Thomas Wanke, Kristin Scharnweber, Mario Brauns, Jari Syväranta, Soren Brothers, Ursula Gaedke, Jan Köhler, Betty Lischke, Thomas MehnerAbstract:Food-web effects of Winterkill are difficult to predict as the enhanced mortality of planktivorous fish may be counterbalanced by an even higher mortality of piscivores. We hypothesised that a Winterkill in a clear and a turbid shallow lake would equalise their fish community composition, but seasonal plankton successions would differ between lakes. After a partial Winterkill, we observed a reduction of fish biomass by 16 and 43% in a clear-water and a turbid small temperate lake, respectively. Fish biomass and piscivore shares (5% of fish biomass) were similar in both lakes after this Winterkill, but young-of-the-year (YOY) abundances were higher in the turbid lake. Top-down control by crustaceans was only partly responsible for low phytoplankton biomass at the end of May following the Winterkill in both lakes. Summer phytoplankton biomass remained low in the clear-water lake despite high abundances of YOY fish (mainly roach). In contrast, the crustacean biomass of the turbid lake was reduced in summer by a high YOY abundance (sunbleak and roach), leading to a strong increase in phytoplankton biomass. The YOY abundance of fish in shallow eutrophic lakes may thus be more important for their summer phytoplankton development after Winterkill than the relative abundance of piscivores.
R. A. Butts - One of the best experts on this subject based on the ideXlab platform.
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Effect of fall infestations of Russian wheat aphid (Homoptera: Aphididae) on winter wheat yield and quality on the Canadian prairies.
Journal of Economic Entomology, 1997Co-Authors: R. A. Butts, J. B. Thomas, O. Lukow, B. D. HillAbstract:The effect of fall infestations of Russian wheat aphid, Diuraphis noxia (Mordvilko), was investigated in winter wheat in southern Alberta, Canada. In 3 trials, yield losses ranging from 25 to 37% were prevented by insecticide treatment of the Russian wheat aphid. The highest yield loss was associated with aphid densities of 4.81 ± 0.61 aphids per plant in the early seedling stage (Zadoks 13) on 11 September 1990; subsequently, aphid densities in the control plots increased to 90.68 ± 7.68 per plant by the last sampling date on 19 November. In all 3 trials, aphids did not survive the winter, but the fall infestations resulted in stand reductions through Winterkill ranging from 28 to 35%. On a per plant basis, those plants that survived the winter fully recovered from aphid damage during the growing season. Quality analyses indicated that the overall effects on bread making quality were minor. There were no significant relationships between aphid densities and yield. However, yield was significantly con-elated with plant stand in the spring, which in turn was significantly correlated with aphid densities during the previous fall. These data support the conclusion that, in southern Alberta, Russian wheat aphid damage is expressed in stand reductions through Winterkill and that yield reductions occur primarily when stand reductions become significant. Once they survive winter, previously infested plants recover from aphid damage and yield losses are minimal, provided plants are not reinfested in the spring.
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effect of russian wheat aphid on cold hardiness and Winterkill of overwintering winter wheat
Canadian Journal of Plant Science, 1990Co-Authors: J. B. Thomas, R. A. ButtsAbstract:Russian wheat aphid (RWA) (Diruaphis noxia (Mordvilko)) is a new and cold-hardy pest of temperate cereals in western Canada. In view of the risk of fall infestation of winter wheat (Triticum aestivum L. em. Thell.), this study was made to establish whether feeding by RWA can interfere with cold hardening and plant survival of overwintering winter wheat. Feeding by RWA significantly increased the LT50 of field-hardened Norstar winter wheat by + 2 to + 4 °C. Application of 400 g (a.i.) ha−1 of the insecticide chlorpyrifos in mid-October to control severe RWA infestations in two different fields of Norstar winter wheat significantly improved winter survival of the crop. The pattern of Winterkill within the two fields suggested that this protective effect of chlorpyrifos was greatest in areas where microtopography resulted in the least accumulations of snow and cold stress was most intense. It was concluded that heavy RWA infestation in the fall significantly reduced freezing tolerance of winter wheat and inc...
