scholarly journals Using Leaf Temperature to Improve Simulation of Heat and Drought Stresses in a Biophysical Model

Plants ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Ruchika S. Perera ◽  
Brendan R. Cullen ◽  
Richard J. Eckard
Keyword(s):  
Heat Stress ◽  
Air Temperature ◽  
Energy Budget ◽  
Perennial Ryegrass ◽  
Measured Data ◽  
Leaf Temperature ◽  
Biophysical Model ◽  
Controlled Environment ◽  
Air Temperatures ◽  
Environment Experiment

Despite evidence that leaf temperatures can differ by several degrees from the air, crop simulation models are generally parameterised with air temperatures. Leaf energy budget is a process-based approach that can be used to link climate and physiological processes of plants, but this approach has rarely been used in crop modelling studies. In this study, a controlled environment experiment was used to validate the use of the leaf energy budget approach to calculate leaf temperature for perennial pasture species, and a modelling approach was developed utilising leaf temperature instead of air temperature to achieve a better representation of heat stress impacts on pasture growth in a biophysical model. The controlled environment experiment assessed the impact of two combined seven-day heat (control = 25/15 °C, day/night, moderate = 30/20 °C, day/night, and severe = 35/25 °C, day/night) and drought stresses (with seven-day recovery period between stress periods) on perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.) and chicory (Cichorium intybus L.). The leaf temperature of each species was modelled by using leaf energy budget equation and validated with measured data. All species showed limited homeothermy with the slope of 0.88 (P < 0.05) suggesting that pasture plants can buffer temperature variations in their growing environment. The DairyMod biophysical model was used to simulate photosynthesis during each treatment, using both air and leaf temperatures, and the patterns were compared with measured data using a response ratio (effect size compared to the well-watered control). The effect size of moderate heat and well-watered treatment was very similar to the measured values (~0.65) when simulated using T leaf, while T air overestimated the consecutive heat stress impacts (0.4 and 0). These results were used to test the heat stress recovery function (Tsum) of perennial ryegrass in DairyMod, finding that recovery after heat stress was well reproduced when parameterized with T sum = 20, while T sum = 50 simulated a long lag phase. Long term pasture growth rate simulations under irrigated conditions in south eastern Australia using leaf temperatures predicted 6–34% and 14–126% higher pasture growth rates, respectively at Ellinbank and Dookie, during late spring and summer months compared to the simulations using air temperatures. This study demonstrated that the simulation of consecutive heat and/or drought stress impacts on pasture production, using DairyMod, can be improved by using leaf temperatures instead of air temperature.

scholarly journals Ideas and perspectives: Heat stress: more than hot air

2016 ◽  
Vol 13 (20) ◽  
pp. 5821-5825 ◽  
Author(s):  
Hans J. De Boeck ◽  
Helena Van De Velde ◽  
Toon De Groote ◽  
Ivan Nijs
Keyword(s):  
Heat Stress ◽  
Air Temperature ◽  
Climate Models ◽  
Heat Waves ◽  
Leaf Temperature ◽  
Balance Model ◽  
Plant Responses ◽  
Atmospheric Conditions ◽  
Air Temperatures ◽  
The Impact

Abstract. Climate models project an important increase in the frequency and intensity of heat waves. In gauging the impact on plant responses, much of the focus has been on air temperatures, while a critical analysis of leaf temperatures during heat extremes has not been conducted. Nevertheless, direct physiological consequences from heat depend primarily on leaf rather than on air temperatures. We discuss how the interplay between various environmental variables and the plants' stomatal response affects leaf temperatures and the potential for heat stress by making use of both an energy balance model and field data. The results demonstrate that this interplay between plants and environment can cause leaf temperature to vary substantially at the same air temperature. In general, leaves tended to heat up when radiation was high and when stomates were closed, as expected. But perhaps counterintuitively, high air humidity also raised leaf temperatures, while humid conditions are typically regarded as benign with respect to plant survival since they limit water loss. High wind speeds brought the leaf temperature closer to the air temperature, which can imply either cooling or warming (i.e. abating or reinforcing heat stress) depending on other prevailing conditions. The results thus indicate that heat waves characterized by similar extreme air temperatures may pose little danger under some atmospheric conditions but could be lethal in other cases. The trends illustrated here should give ecologists and agronomists a more informed indication about which circumstances are most conducive to the occurrence of heat stress.

An infrared-based coefficient to screen plant environmental stress: concept, test and applications

2009 ◽  
Vol 36 (11) ◽  
pp. 990 ◽  
Author(s):  
Guo Yu Qiu ◽  
Kenji Omasa ◽  
Sadanori Sase
Keyword(s):  
Heat Stress ◽  
Water Stress ◽  
Environmental Stress ◽  
Air Temperature ◽  
Canopy Temperature ◽  
Water Shortage ◽  
Leaf Temperature ◽  
Stress Index ◽  
Crop Water Stress Index ◽  
Water Stress Index

By introducing a reference dry leaf (a leaf without transpiration), a formerly proposed plant transpiration transfer coefficient (hat) was applied to detect environmental stress caused by water shortage and high temperature on melon, tomato and lettuce plants under various conditions. Results showed that there were obvious differences between leaf temperature, dry reference leaf temperature and air temperature. The proposed coefficient hat could integrate the three temperatures and quantitatively evaluate the environmental stress of plants. Experimental results showed that the water stress of melon plants under two irrigation treatments was clearly distinguished by using the coefficient. The water stress of a tomato plant as the soil dried under a controlled environmental condition was sensitively detected by using hat. A linear relationship between hat and conventional crop water stress index was revealed with a regression determination coefficient R2 = 0.97. Further, hat was used to detect the heat stress of lettuce plants under high air temperature conditions (28.7°C) with three root temperature treatments (21.5, 25.9 and 29.5°C). The canopy temperature under these treatments was respectively 26.44, 27.15 and 27.46°C and the corresponding hat value was –1.11, –0.74 and –0.59. Heat stress was also sensitively detected using hat. The main advantage of hat is its simplicity for use in infrared applications.

scholarly journals Trends in heat stress over Europe over the 20th century

2021 ◽  
Author(s):  
Joakim Kjellsson ◽  
Nils Niebaum ◽  
Robin Pilch Kedzierski
Keyword(s):  
Heat Stress ◽  
20Th Century ◽  
Heat Wave ◽  
Air Temperature ◽  
Heat Waves ◽  
Dew Point ◽  
Stress Index ◽  
Internal Climate Variability ◽  
Air Temperatures ◽  
Using Data

&lt;p&gt;We investigate how European heat waves and their associated heat stress on humans have changed over the 20th century. We find that the heat stress has increased, even in regions where heat waves have not become warmer. As heat stress increases over wide areas of Europe there is also an increase in the total population affected by the heat stress.&amp;#160;&lt;/p&gt;&lt;p&gt;Heat waves pose a serious health risk to humans by reducing our ability to shed heat. We have studied the occurrence and intensity of heat waves as well as a heat stress index based on simplified wet-bulb globe temperature using data from ERA-20C reanalysis 1900-2010. Over the 110 years of data we find an overall warming of the air temperatures and dew point. The 98th percentile of both air temperature has increased by more than 1.5&amp;#176;C over large areas of Europe.&amp;#160;&lt;/p&gt;&lt;p&gt;We find an overall increase in heat wave days per year as well as an increase of air temperature during heat waves over most of Europe. As such, many densely populated areas exhibit increased heat stress during heat waves. For example, the mean heat stress during heat wave days over Paris has increased by one level, from &amp;#8220;alert&amp;#8221; in 1900-1930 to &amp;#8220;caution&amp;#8221; in 1980-2010. The fraction of the population exposed to heat waves has increased by 10%/century in central Europe and 25%/century over the Mediterranean.&amp;#160;&lt;/p&gt;&lt;p&gt;We find more heat waves during 1920 - 1950, which may be related to the positive phase of the Atlantic Multidecadal Variation (AMV). This suggests that the heat stress during European heat waves may also be influenced by internal climate variability, and large-ensemble model simulations may be used to disentangle the effects of natural variability and anthropogenic forcing.&lt;/p&gt;

scholarly journals Decrease of Pollen Stainability of Green Bean at High Temperatures and Relationship to Heat Tolerance

2001 ◽  
Vol 126 (5) ◽  
pp. 571-574 ◽  
Author(s):  
Katsumi Suzuki ◽  
Tadashi Tsukaguchi ◽  
Hiroyuki Takeda ◽  
Yoshinobu Egawa
Keyword(s):  
Heat Stress ◽  
Phaseolus Vulgaris ◽  
High Temperatures ◽  
Air Temperature ◽  
Heat Tolerance ◽  
Green Bean ◽  
Controlled Environment ◽  
Pollen Stainability ◽  
Pod Yield ◽  
Heat Tolerant

Pod yield of `Kentucky Wonder' green bean (Phaseolus vulgaris L.) decreased at high temperatures due to a reduction of pod set. A highly positive correlation was observed between pod set and pollen stainability in flowers that were affected by heat stress about 10 days before anthesis. Pollen stainability was decreased by heat stress applied 8 to 11 days before flowering under controlled environment conditions. When mean air temperature during this period exceeded 28 °C, pollen stainability decreased under field conditions. Low pollen stainability indicated sensitivity to high temperatures about 10 days before flowering. A heat-tolerant cultivar showed higher pollen stainability than did heat-sensitive cultivars under high temperatures. These results demonstrated that heat tolerance at an early reproductive stage could be evaluated by analyzing pollen stainability using flowers developed under high temperatures.

Effect of air temperature on the abomasal and small intestinal digestion of a milk substitute diet given to young calves

1989 ◽  
Vol 48 (1) ◽  
pp. 67-74 ◽  
Author(s):  
M. S. Cockram ◽  
T. G. Rowan
Keyword(s):  
Proteolytic Activity ◽  
Air Temperature ◽  
Controlled Environment ◽  
Apparent Digestibility ◽  
Air Temperatures ◽  
Intestinal Digestion ◽  
Milk Substitute ◽  
Small Intestinal ◽  
Environment Chamber

ABSTRACTTwelve Friesian calves were each fitted with an abomasal cannula. The calves were placed in a controlled environment chamber and given a milk substitute diet in buckets at 12-h intervals. The calves were exposed to air temperatures of 25°C from 4 to 10 days of age, 5°C from 11 to 14 days of age, and 25°C at 15 days of age. At 9, 10, 11, 14 and 15 days of age, the abomasal contents of the calves were sampled at 2-h intervals and the temperature and pH of the abomasal contents were recorded at 40-min intervals for a period of 12 h. The rectal and abomasal temperatures of the calves were lower at 11 days of age than at 10 days of age, and were greater at 15 days of age than at 14 days of age (P < 0·05).In a similar experiment four Friesian calves were each fitted with an ileal re-entrant cannula. The calves were exposed to air temperatures of 25°C from 5 to 19 days of age, 5°C from 20 to 26 days of age, and 25CC at 27 days of age. At 18, 19, 20, 26 and 27 days of age the ileal contents of the calves were collected and sampled for a period of 12 h.No significant effects of the air temperatures of 25° and 5°C on the abomasal digestion (acidity and proteolytic activity of the abomasal contents) and ileal apparent digestibility of the diet were found.

scholarly journals Ideas and perspectives: Heat stress: more than hot air

2016 ◽  
Author(s):  
Hans J. De Boeck ◽  
Helena Van De Velde ◽  
Toon De Groote ◽  
Ivan Nijs
Keyword(s):  
Heat Stress ◽  
Air Temperature ◽  
Heat Waves ◽  
Balance Model ◽  
Plant Responses ◽  
Atmospheric Conditions ◽  
Change Models ◽  
Wind Speeds ◽  
Air Temperatures ◽  
The Impact

Abstract. Climate change models project an important increase in the frequency and intensity of heat waves. In gauging the impact on plant responses, much of the focus has been on air temperatures while a critical analysis of leaf temperatures during heat extremes has not been made. Nevertheless, direct physiological consequences from heat depend primarily on leaf rather than on air temperatures. We discuss how the interplay between various environmental variables and the plants' stomatal response affects leaf temperatures and the potential for heat stress by making use of both an energy balance model and field data. The results demonstrate that this interplay between plants and environment can cause leaf temperatures fluctuations in excess of 10 °C (for narrow leaves) to even 20 °C (for big broad leaves) at the same air temperature. In general, leaves tended to heat up when radiation was high and when stomates were closed, as expected. But perhaps counterintuitively, also high air humidity raised leaf temperatures, while humid conditions are typically regarded as benign with respect to plant survival since they limit water loss. High wind speeds brought the leaf temperature closer to the air temperature, which can imply either cooling or warming (i.e. abating or reinforcing heat stress) depending on other prevailing conditions. The results thus indicate that heat waves characterized by similar extreme air temperatures may pose little danger under some atmospheric conditions, but could be lethal in other cases. The trends illustrated here should give ecologists and agronomists a more informed indication about which circumstances are most conductive for heat stress to occur.

Assessing the Impacts of Future Climate on Cotton Production in the Arizona Low Desert

2020 ◽  
Vol 63 (4) ◽  
pp. 1087-1098
Author(s):  
Ibukun Timothy Ayankojo ◽  
Kelly R. Thorp ◽  
Kelly Morgan ◽  
Kritika Kothari ◽  
Srinivasulu Ale
Keyword(s):  
Heat Stress ◽  
Water Use ◽  
Air Temperature ◽  
Management Practices ◽  
Growth Yield ◽  
Future Climate ◽  
Cotton Production ◽  
Climate Conditions ◽  
Air Temperatures ◽  
The Future

HighlightsCotton yield was reduced significantly under projected future climate conditions for the Arizona low desert (ALD). Of all the weather variables, yield reduction was primarily due to projected increases in daily maximum and minimum air temperatures.Cotton reproductive stages were more susceptible to heat stress than vegetative stages. Projected increases in air temperature may result in a slight increase in cotton growth or biomass production; however, heat stress significantly reduced fruit retention, leading to lower boll number and yield.Although future increases in CO2 may improve plant growth and productivity, the potential benefit of CO2 fertilization on cotton growth and yield in the ALD was offset by the projected increase in air temperature.The projected average seasonal irrigation requirement increased by at least 10%. This suggests that greater demand for freshwater withdrawal for agriculture can be expected in the future. Therefore, given the projected change in future climate, cotton cultivars tolerant of longer periods of high air temperature, changes in planting dates, and improved management practices for higher water productivity are critical needs for sustainable cotton production in the ALD.Abstract. Cotton is an important crop in Arizona, with a total cash value of approximately $200 million for fiber and cottonseed in 2018. In recent years, heat stress from increasing air temperature has reduced cotton productivity in the Arizona low desert (ALD); however, the effects of future climate on ALD cotton production have not been studied. In this study, the DSSAT CSM-CROPGRO-Cotton model was used to simulate the effects of future climate on cotton growth, yield, and water use in the ALD area. Projected climate forcings for the ALD were obtained from nine global climate models under two representative concentration pathways (RCP 4.5 and 8.5). Cotton growth, yield, and water use were simulated for mid-century (2036 to 2065) and late century (2066 to 2095) and compared to the baseline (1980 to 2005). Results indicated that seed cotton yield was reduced by at least 40% and 51% by mid-century and late century, respectively, compared to the baseline. Of all the weather variables, the seasonal average maximum (R2 = 0.72) and minimum (R2 = 0.80) air temperatures were most correlated with yield reductions. Under the future climate conditions of the ALD, cotton growth or biomass accumulation slightly increased compared to the baseline. Irrigation requirements in the ALD increased by at least 10% and 14% by mid-century and late century, respectively. Increases in irrigation requirements were due to an increase in crop water use; hence, greater demand for freshwater withdrawal for agricultural purposes is anticipated in the future. Therefore, cotton cultivars that are tolerant of long periods of high air temperature and improved management practices that promote efficient crop water use are critical for future sustainability of cotton production in the ALD. Keywords: . Arid region, CSM-CROPGRO-Cotton, Future climate, Gossypium hirsutum L., Heat stress, Irrigation demand.

scholarly journals Using daily air temperature thresholds to evaluate snow melting occurrence and amount on Alpine glaciers by <i>T</i>-index models: the case study of the Forni Glacier (Italy)

2014 ◽  
Vol 8 (5) ◽  
pp. 1921-1933 ◽  
Author(s):  
A. Senese ◽  
M. Maugeri ◽  
E. Vuillermoz ◽  
C. Smiraglia ◽  
G. Diolaiuti
Keyword(s):  
Air Temperature ◽  
Energy Budget ◽  
Snow Depth ◽  
Lapse Rate ◽  
Positive Energy ◽  
Temperature Threshold ◽  
Snow Melting ◽  
Air Temperatures ◽  
Temperature Thresholds ◽  
The Mean

Abstract. Glacier melt conditions (i.e., null surface temperature and positive energy budget) can be assessed by analyzing data acquired by a supraglacial automatic weather station (AWS), such as the station installed on the surface of Forni Glacier (Italian Alps). When an AWS is not present, the assessment of actual melt conditions and the evaluation of the melt amount is more difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 0 °C. In this paper, we applied both energy budget and T-index approaches with the aim of solving this issue. We start by distinguishing between the occurrence of snowmelt and the reduction in snow depth due to actual ablation (from snow depth data recorded by a sonic ranger). Then we find the daily average temperature thresholds (by analyzing temperature data acquired by an AWS on Forni Glacier) which, on the one hand, best capture the occurrence of significant snowmelt conditions and, on the other, make it possible, using the T-index, to quantify the actual snow ablation amount. Finally we investigated the applicability of the mean tropospheric lapse rate to reproduce air temperature conditions at the glacier surface starting from data acquired by weather stations located outside the glacier area. We found that the mean tropospheric lapse rate allows for a good and reliable reconstruction of glacier air temperatures and that the choice of an appropriate temperature threshold in T-index models is a very important issue. From our study, the application of the +0.5 °C temperature threshold allows for a consistent quantification of snow ablation while, instead, for detecting the beginning of the snow melting processes a suitable threshold has proven to be at least −4.6 °C.

scholarly journals Air temperature thresholds to evaluate snow melting at the surface of Alpine glaciers by T-index models: the case study of Forni Glacier (Italy)

2014 ◽  
Vol 8 (2) ◽  
pp. 1563-1587 ◽  
Author(s):  
A. Senese ◽  
M. Maugeri ◽  
E. Vuillermoz ◽  
C. Smiraglia ◽  
G. Diolaiuti
Keyword(s):  
Air Temperature ◽  
Energy Budget ◽  
Snow Water Equivalent ◽  
Lapse Rate ◽  
Positive Energy ◽  
Temperature Threshold ◽  
Weather Station ◽  
Glacier Melt ◽  
Air Temperatures ◽  
The Mean

Abstract. The glacier melt conditions (i.e.: null surface temperature and positive energy budget) can be assessed by analyzing meteorological and energy data acquired by a supraglacial Automatic Weather Station (AWS). In the case this latter is not present the assessment of actual melting conditions and the evaluation of the melt amount is difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 273.15 K. In this paper, to detect the most indicative threshold witnessing melt conditions in the April–June period, we have analyzed air temperature data recorded from 2006 to 2012 by a supraglacial AWS set up at 2631 m a.s.l. on the ablation tongue of the Forni Glacier (Italian Alps), and by a weather station located outside the studied glacier (at Bormio, a village at 1225 m a.s.l.). Moreover we have evaluated the glacier energy budget and the Snow Water Equivalent (SWE) values during this time-frame. Then the snow ablation amount was estimated both from the surface energy balance (from supraglacial AWS data) and from T-index method (from Bormio data, applying the mean tropospheric lapse rate and varying the air temperature threshold) and the results were compared. We found that the mean tropospheric lapse rate permits a good and reliable reconstruction of glacier air temperatures and the major uncertainty in the computation of snow melt is driven by the choice of an appropriate temperature threshold. From our study using a 5.0 K lower threshold value (with respect to the largely applied 273.15 K) permits the most reliable reconstruction of glacier melt.

scholarly journals Experimental Study of Temperature Effect on Human Skin: Discussion of Methodology

2013 ◽  
Vol 10 ◽  
pp. 71-76 ◽  
Author(s):  
Ahmad Rasdan Ismail ◽  
Abu Bakar Rosli ◽  
Norfadzilah Jusoh
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Experimental Studies ◽  
Controlled Environment ◽  
Cooling Conditions ◽  
Air Temperatures ◽  
Local Supply ◽  
Thermoregulatory System ◽  
Environment Chamber ◽  
Basic Features

This paper present the discussion of methods used in experimental studies of thermal comfort that only focus on the effect skin temperature of human. The study was conducted human subject tests in a controlled environment chamber for cooling conditions. This study was measure in the test climate chamber at Universiti Malaysia Pahang. Three broad methodology categories are compared which are experiments in which subjects have control of air temperature, relative humidity or neither. The local supply air temperatures were at 19, 25 and 32 °C while relative humidity was at 40, 55 and 70%. Together with a previously proposed diagram of basic features of the human thermoregulatory system may be used to specify limits for air temperature and relative humidity in the indoor environment.

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