Exploring the environmental context of recent Didymosphenia geminata proliferation in Gaspésie, Quebec, using paleolimnology

2014 ◽  
Vol 71 (4) ◽  
pp. 616-626 ◽  
Author(s):  
J.M. Lavery ◽  
J. Kurek ◽  
K.M. Rühland ◽  
C.A. Gillis ◽  
M.F.J. Pisaric ◽  
...  
Keyword(s):  
Environmental Context ◽  
Life Strategy ◽  
Early 20Th Century ◽  
Diatom Assemblages ◽  
Eastern Canada ◽  
Didymosphenia Geminata ◽  
Planktonic Diatoms ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Scale Shift

Management authorities often perceive Didymosphenia geminata (didymo) as an invasive, nuisance diatom species that has been introduced to eastern Canada; however, observations from early 20th century diatom surveys challenge this characterization. We apply paleolimnological techniques to place recent didymo blooms from Gaspésie, Quebec, into historical and environmental context. Sedimentary diatom assemblages were examined from Lac Humqui (a headwater lake) and Lac au Saumon (a lake with an inflowing river currently supporting blooms). The Lac Humqui assemblage experienced a broad-scale shift in their dominant life strategy with declines in fragilarioid taxa and increases in planktonic diatoms (i.e., Cyclotella–Discostella species) that began ∼1970 and increased to modern abundances ∼1990. Strong relationships between this diatom shift and increases in regional air temperatures and earlier river ice-out dates are consistent with longer growing seasons and enhanced thermal stability in Lac Humqui. Didymo was observed throughout the Lac au Saumon core, demonstrating that it has been present in the region since at least ∼1970. Our paleolimnological evidence indicates that blooms likely form in response to regional consequences of climate warming, rather than human introduction.

Effects of Didymosphenia geminata blooms on benthic diatom assemblages in the Restigouche River Watershed, eastern Canada

Botany ◽  
2015 ◽  
Vol 93 (5) ◽  
pp. 317-323 ◽  
Author(s):  
Branaavan Sivarajah ◽  
Joshua Kurek ◽  
Kathleen M. Rühland ◽  
John P. Smol
Keyword(s):  
Benthic Diatom ◽  
Diatom Assemblage ◽  
Diatom Assemblages ◽  
Eastern Canada ◽  
Didymosphenia Geminata ◽  
Assemblage Composition ◽  
River Watershed ◽  
And Function ◽  
Riverine Systems ◽  
The Impact

Nuisance Didymosphenia geminata (Lyngbye) M. Schmidt (didymo) blooms were first reported in 2006 from the Restigouche River Watershed (RRW), eastern Canada. Although government agencies and recreational users are concerned about these blooms, little is known about the impact on biota and (or) the structure and function of the relatively pristine riverine systems of the RRW. Here, we assess whether didymo blooms affect overall benthic diatom assemblage composition by examining epilithic samples from middle stretches of the Patapedia and Upsalquitch rivers. Significant (albeit minor) differences (P < 0.05) in diatom assemblage composition between sites, with and without didymo blooms, were only observed from the Patapedia River. Rarefied diatom species diversity (Hill’s N2) and rarefied richness did not differ significantly among sites, regardless of the presence or absence of blooms. Our data show that didymo blooms have minimal effect on benthic diatom assemblage composition in the RRW.

scholarly journals Drivers of Macrophyte and Diatom Diversity in a Shallow Hypertrophic Lake

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1569
Author(s):  
Kateřina Šumberová ◽  
Ondřej Vild ◽  
Michal Ducháček ◽  
Martina Fabšičová ◽  
Jan Potužák ◽  
...  
Keyword(s):  
Fish Farming ◽  
Spatial Diversity ◽  
Spatiotemporal Variability ◽  
Water Level Fluctuations ◽  
Nutrient Requirements ◽  
Diatom Assemblages ◽  
Climatic Extremes ◽  
Growing Seasons ◽  
High Species Richness ◽  
Different Parts

We studied macrophyte and diatom assemblages and a range of environmental factors in the large hypertrophic Dehtář fishpond (Southern Bohemia, Czech Republic) over the course of several growing seasons. The spatial diversity of the environment was considered when collecting diatoms and water samples in three distinct parts of the fishpond, where automatic sensor stations continually measuring basic factors were established. Macrophytes were mapped in 30 segments of the fishpond littoral altogether. High species richness and spatiotemporal variability were found in assemblages of these groups of autotrophs. Water level fluctuations, caused by the interaction of fish farming management and climatic extremes, were identified as one of the most important factors shaping the structure and species composition of diatom and macrophyte assemblages. The distance of the sampling sites from large inflows reflected well the spatial variability within the fishpond, with important differences in duration of bottom drainage and exposure to disturbances in different parts of the fishpond. Disturbances caused by intensive wave action are most probably a crucial factor allowing the coexistence of species with different nutrient requirements under the hypertrophic conditions of the Dehtář fishpond. Due to a range of variables tested and climatic extremes encountered, our study may be considered as a basis for predictive model constructions in similar hypertrophic water bodies under a progressing climate change.

scholarly journals Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

2013 ◽  
Vol 10 (7) ◽  
pp. 4465-4479 ◽  
Author(s):  
K. L. Hanis ◽  
M. Tenuta ◽  
B. D. Amiro ◽  
T. N. Papakyriakou
Keyword(s):  
Soil Temperature ◽  
Air Temperature ◽  
Growing Season ◽  
Near Surface ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Surface Soil Temperature ◽  
Filling Method ◽  
Highly Correlated

Abstract. Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyser in four years (2008–2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with FCH4 highest when water was 2–13 cm below and lowest when it was at or above the mean peat surface.

Thermal dependence of pyrithiobac efficacy inAmaranthus palmeri

Weed Science ◽  
1999 ◽  
Vol 47 (6) ◽  
pp. 644-650 ◽  
Author(s):  
Ginger G. Light ◽  
Peter A. Dotray ◽  
James R. Mahan
Keyword(s):  
Weed Control ◽  
Acetolactate Synthase ◽  
Field Studies ◽  
Thermal Dependence ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Whole Plant ◽  
Crude Leaf Extract ◽  
Highly Correlated

Variability in weed control following pyrithiobac applications has been observed under field conditions. The influence of temperature on this variability was investigated. Results from field studies performed over two growing seasons identified plant and air temperatures at the time of herbicide treatment that correlated with whole-plant efficacy differences. Based on the field data, weed control with pyrithiobac was acceptable at application temperatures of 20 to 34 C. To investigate a potential source of thermal limitations on pyrithiobac efficacy, the thermal dependence of in vitro inhibition of acetolactate synthase (ALS), the site of action for pyrithiobac, was examined. A crude leaf extract of ALS was obtained fromAmaranthus palmeri. Relative inhibitor potency (I50) values were obtained at saturating substrate conditions for temperatures from 10 to 50 C. Regression analysis of field activity against I50values showed the two data sets to be highly correlated (R2= 0.88). The thermal dependence of enzyme/herbicide interactions may provide another means of understanding environmental factors limiting herbicidal efficacy and predicting herbicide inhibition at the whole-plant level.

Clonal Responses of Tea Shoot Extension to Temperature in Malawi

1993 ◽  
Vol 29 (1) ◽  
pp. 47-60 ◽  
Author(s):  
R. I. Smith ◽  
F. J. Harvey ◽  
M. G. R. Cannell
Keyword(s):  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Field Measurements ◽  
Empirical Method ◽  
Shoot Length ◽  
Extension Rate ◽  
Base Temperature ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Tea Shoot

SummaryAlthough the relationship between the length of a growing tea shoot and time is not truly exponential, the exponential relative shoot extension rate (ERSER) can be used for comparisons when both the initial shoot lengths and the periods of measurement are identical. An empirical method to adjust ERSER for variations in initial shoot length was developed for weekly field measurements of seven tea clones in Malawi. ERSERs, measured throughout the two growing seasons after the bushes had been pruned, were standardized to an initial shoot length of 2.5 cm and were then related to mean weekly air temperatures and to vapour pressure deficits. There were large clonal differences in the response of ERSER to temperature within the range 18–23°C. Shoots of the vigorous Malawi clone SFS 150 elongated rapidly at all temperatures, but notably at the lower temperatures (18–20°C). Two Kenyan clones, BB/35 and K6/8, did not grow well at about 18°C, which is normal for growth in Kenya but which coincides with the period of short daylengths (less than 12 h) in Malawi. A significant decrease in ERSER was found with increased vapour pressure deficit over the whole range of field measurements and ERSERs were uniformly lower in the second year after pruning. The results suggest that the usual calculations to derive an inherent base temperature for elongation are not valid unless elongation is truly exponential and therefore, in general, base temperatures should not be used for comparisons between experiments.

Neural network modelling to predict weekly yields of sweet peppers in a commercial greenhouse

2008 ◽  
Vol 88 (3) ◽  
pp. 531-536 ◽  
Author(s):  
W. C. Lin ◽  
B. D. Hill
Keyword(s):  
Neural Network ◽  
Capsicum Annuum ◽  
Sweet Pepper ◽  
Network Modelling ◽  
Greenhouse Production ◽  
Capsicum Annuum L ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Model Training ◽  
Validation Set

The production of greenhouse-grown sweet pepper (Capsicum annuum L.) is irregular with a peak-and-valley pattern of weekly yields. We monitored the yields and environment in a commercial greenhouse in British Columbia over six (2000–2005) growing seasons. Light was defined as cumulative light over the current week, with L_1, L_2, L_3, L_4, L _ 5 and L_6 representing light over previous weeks. Temperature (AvgT) was defined as the current weekly average of 24-h air temperatures, with T_1, T_2 and T_3 representing temperatures over previous weeks. Inputs were also created for the current weekly yield (Y) and previous weekly yields (Y_1, Y_2, Y_3 and Y_4). Neural network (NN) modelling with up to 21 inputs was used to predict yields 1 wk (Y + 1) and 2 wk (Y + 2) in advance of the actual fruit harvest. Data for five different years were combined for model training with the year to be predicted held separate as a validation set. The best models used 13 inputs to predict Y + 1 with an average R2 of 0.66 over the 6 yr. Y_4, Y-Y_1, Y_1, L_1, Y, Y_3, Y-Y_3 and wk (of the year) were important inputs. The environmental inputs were of lesser importance, which suggests that the cyclic nature of pepper yields is inherent in the pepper biology. Predicting Y + 2 was more difficult with an average R2 of 0.59 over the 6 yr. NN have good potential for predicting pepper yields. Key words: Capsicum annuum L., flushing, fruit, greenhouse production, neural networks

scholarly journals Molecular Detection of Blueberry Stunt Phytoplasma in Eastern Canada: a Multi-year Study

2021 ◽  
Author(s):  
Christine Hammond ◽  
Edel Perez-Lopez ◽  
Jennifer Town ◽  
Charles Vincent ◽  
Debra Moreau ◽  
...  
Keyword(s):  
Production Management ◽  
Low Cost ◽  
Lamp Assay ◽  
Vaccinium Corymbosum ◽  
Eastern Canada ◽  
Diagnostic Assays ◽  
Proactive Approach ◽  
Growing Seasons ◽  
Pathogen Load ◽  
Interactive Map

Abstract Blueberry stunt phytoplasma (BBSP; ‘Candidatus Phytoplasma asteris’) is an insect-vectored plant pathogen that causes severe yield losses in blueberry (Vaccinium corymbosum), which is the most valuable fruit crop in Canada. Rapid, field-based diagnostic assays are desirable tools for the control of BBSP, as part of an integrated, proactive approach to production management termed biovigilance. We designed and validated a chaperonin-60 (cpn60)-targeted LAMP assay for detection of BBSP, providing a rapid, low cost, field-deployable diagnostic option. Our validation demonstrates that the assay is reproducible, with high analytical specificity and improved sensitivity when compared with 16S rRNA nested PCR. We applied the validated LAMP assay to nearly 2000 blueberry samples from Québec and Nova Scotia over three growing seasons (2016–2018). Our surveys revealed that BBSP is present in most sites across both provinces, though detection of the pathogen in individual plants varied in different tissues across sampling dates and across years, and evidence of spread between plants was limited. To quantify pathogen load in select plants, we designed additional qPCR and ddPCR assays, also based on cpn60. We found that pathogen load fluctuates in a given plant within and between growing seasons. Finally, we designed an interactive map to visualize the results of our surveys. These results provide a validated diagnostic assay that can be used as part of a biovigilance strategy for detecting and controlling infections caused by BBSP.

scholarly journals MJO teleconnections to crop growing seasons

2020 ◽  
Vol 54 (3-4) ◽  
pp. 2203-2219 ◽  
Author(s):  
Weston Anderson ◽  
Ángel G. Muñoz ◽  
Lisa Goddard ◽  
Walter Baethgen ◽  
Xandre Chourio
Keyword(s):  
Soil Moisture ◽  
Daily Precipitation ◽  
Maximum Temperature ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Summer Hemisphere ◽  
Leaf Level ◽  
Maximum Temperatures ◽  
The Tropics

AbstractWhile many Madden–Julian Oscillation (MJO) teleconnections are well documented, the significance of these teleconnections to agriculture is not well understood. Here we analyze how the MJO affects the climate during crop flowering seasons, when crops are particularly vulnerable to abiotic stress. Because the MJO is located in the tropics of the summer hemisphere and maize is a tropical, summer-grown crop, the MJO teleconnections to maize flowering seasons are stronger and more coherent than those to wheat, which tends to be grown in midlatitudes and flowers during the spring. The MJO significantly affects not only daily average precipitation and soil moisture, but also the probability of extreme precipitation, soil moisture and maximum temperatures during crop flowering seasons. The average influence on the probability of extreme daily precipitation, soil moisture, and maximum temperature events is roughly equal. On average the MJO modifies the probability of a 5th or 95th, 10th or 90th, and 25th or 75th percentile event by $$\sim $$∼ 2.5%, $$\sim $$∼ 4% and $$\sim $$∼ 7%, respectively. This means that an exceptionally dry (10th percentile) soil moisture value, for example, would become $$\sim $$∼ 40% more common (happening 14% of the time) during certain MJO phases. That the MJO can simultaneously dry soils and raise maximum air temperatures may be particularly damaging to crops because without available soil water during times of heat stress, plants are unable to transpire to cool leaf-level temperatures as a means of avoiding long-term damage. As a result, even though teleconnections from the MJO last only a few days to a week, they likely affect crop growth.

Differential tolerance of coniferous species to the microbially produced herbicide bialaphos. I. Morphological and growth effects

1994 ◽  
Vol 24 (11) ◽  
pp. 2191-2198 ◽  
Author(s):  
Mlkaĭlou Sy ◽  
Robert Jobidon ◽  
Hank Margolis
Keyword(s):  
Active Ingredient ◽  
Black Spruce ◽  
Survival Rates ◽  
Significant Negative Correlation ◽  
Foliar Injury ◽  
Eastern Canada ◽  
Relative Growth ◽  
Growing Seasons ◽  
Application Rates ◽  
Visible Foliar Injury

Four species of boreal conifer seedlings used for reforestation in eastern Canada were tested for their tolerance to the microbially produced herbicide bialaphos under controlled conditions. The tolerance levels of white spruce (Piceaglauca (Moench) Voss), black spruce (Piceamariana (Mill.) B.S.R), Norway spruce (Piceaabies (L.) Karst.), and red pine (Pinusresinosa Ait.) were studied over two consecutive growing seasons using different morphological and growth criteria. Application rates were the equivalent of 0, 1.0, 1.5, 2.0, 2.5, and 3.0 kg active ingredient (bialaphos) per hectare in a 1400-L solution and were applied in July, August, or September. Survival rates were a linear function of the dose of bialaphos, but were greater than 95% for all treatments. Results indicated that there was no significant correlation between visible foliar injury and the amount of epicuticular wax on needles. There was also no significant correlation between visible foliar injury and initial seedling height. However, a significant negative correlation was observed between the degree of foliar injury and the relative growth rate following treatment. No additional foliar injury occurred during the second growing season. Doses of bialaphos that did not exceed the equivalent of 2.0 kg active ingredient per hectare had no effect on subsequent growth. Tolerance was greatest when the herbicide was applied in August and least when applied in July. These results, combined with the lower tolerance previously demonstrated for several species that compete with planted conifers in eastern Canada, suggest that bialaphos has a strong potential as an alternative to chemically synthesized herbicides for vegetation management in conifer plantations.

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