Critical Temperature Threshold Research Articles

Heat transfer test method development: Consideration for design and safety of household oven mitts

The purpose of this study was to develop a test method – an apparatus and a protocol for evaluating the rate of heat transfer across a sample of layered materials commonly used in oven mitts. Using the apparatus, effects of contact temperature and pressure as well as design features such as quilting stitching pattern of the sample on heat transfer were examined. The apparatus featured a round wooden base with three silicone-covered wooden “fingers” equipped with thermocouples where the test samples were mounted. The device was lowered with the samples down onto a hot plate kept at stable high “pan” contact temperature. Upon contact, changes of the “skin” contact temperatures (at the “fingers”) were recorded at 10 Hz for 300 s. Tests were carried out at six levels of pressure on the sample (exerted by variable weights), 3 levels of “pan” contact temperature, and 3 different quilting stitch patterns of the material. Time to reach critical skin threshold temperature was affected by stitch pattern; it decreased exponentially with increasing pressure and increasing hot plate contact temperature. The shape of the temperature-time curve indicated how the material configuration of the sample affects the transfer of heat.

Applying the Generalized Pareto Principle to Predict Peak Temperatures in Northeast Algeria

This study employs the Generalized Pareto Distribution (GPD) to model high temperature events at the Batna station, strategically applying varying thresholds to enhance accuracy and mitigate tail distribution bias. This was done by analyzing historical rainfall data from 1981 to 202. Using maximum likelihood estimation and an innovative approach to fitting multi-threshold GPDs, stable thresholds were established, particularly identifying the Pareto II type as the most suitable model for temperatures exceeding 25°C. Analysis revealed a consistent average temperature of 27.52°C, with a negative skewness indicating a bias toward lower values within extreme temperatures. The study also predicts return levels for different periods, providing critical temperature thresholds expected to be exceeded every 2, 20, 50, and 100 years. These findings contribute to understanding extreme temperature dynamics in the region, supporting urban planning, infrastructure design, and climate resilience strategies.

Climate Change‐Driven Long‐Term Stability Risks of Ubiquitous Moraine Dams in Glacial Lakes on Qinghai‐Tibet Plateau: A Multiphysics Coupling Evolution Perspective

AbstractGlacial lake‐moraine dam systems are widespread in cold alpine environments such as the Qinghai‐Tibet Plateau (QTP). Without climate change, the lake‐dam system exhibits stably dynamic evolution on a hydrological annual cycle. However, climate change may drive subtle alterations in the system's evolution. We developed a fully coupled Thermal‐Hydraulic‐Mechanical simulation platform considering ice‐water phase change, showing robust performance under CMIP6‐derived boundary conditions. Using this platform, we simulated climate warming‐driven multiphysics responses and dam stability evolutions of a homogeneous, simplified conceptual model of the lake‐dam system. We identified critical temperature thresholds for permanently frozen area thawing and abrupt changes in dam stability of this lake‐dam system. Considering the current slope stability situations on the QTP, the SSP 5–8.5 climate warming scenario is conservatively anticipated to pose significant geological safety risks due to potential disaster chains from glacial lake failures. Our study provides insights into profound geological process evolutions driven by climate change.

Comparison of measured and calculated high-viscosity crude oil temperature values in a pipeline during continuous pumping and shutdown modes

The paper investigates the stationary and non-stationary cooling processes of high-viscosity crude oil temperature in the Severnye Buzachi – Karazhanbas pipeline during both pump operations and pump shutdowns. To transport high-viscosity crude oil through pipelines, the hot pumping method is employed. During oil transportation and pump shutdowns, the oil temperature decreases due to heat exchange with the environment, leading to an increase in oil viscosity. As viscosity rises, more power is required from the pumps to move the thickened oil, resulting in higher electricity consumption. To avoid increased operational costs after pump shutdowns, it is crucial to accurately calculate the oil cooling temperature in order to determine the safe shutdown duration and a critical temperature threshold. The Shukhov formula is used to calculate oil temperature during transportation, while a modified version is applied during pump shutdowns. To verify the accuracy of the obtained oil temperature results, the calculated values were compared with the measured values from pipeline sensors in both stationary and non-stationary cases. The novelty of the work is in determining the methodology for calculating the safe shutdown time of a pipeline for high-viscosity oil. The proposed formula was validated using experimental data from SCADA system sensors in real-time.

Coupled thermo-hydro-mechanical analysis of porous rocks: Candidate of surrounding rocks for deep geological repositories

Deep geological sequestration is widely recognized as a reliable method for nuclear waste management, with expanded applications in thermal energy storage and adiabatic compressed air energy storage systems. This study evaluated the suitability of granite, basalt, and marble as reservoir rocks capable of withstanding extreme high-temperature and high-pressure conditions. Using a custom-designed triaxial testing apparatus for thermal-hydro-mechanical (THM) coupling, we subjected rock samples to temperatures ranging from 20 °C to 800 °C, triaxial stresses up to 25 MPa, and seepage pressures of 0.6 MPa. After THM treatment, the specimens were analyzed using a Real-Time Load-Synchronized Micro-Computed Tomography (MCT) Scanner under a triaxial stress of 25 MPa, allowing for high-resolution insights into pore and fissure responses. Our findings revealed distinct thermal stability profiles and microscopic parameter changes across three phases—slow growth, slow decline, and rapid growth—with critical temperature thresholds observed at 500°C for granite, 600 °C for basalt, and 300 °C for marble. Basalt showed minimal porosity changes, increasing gradually from 3.83% at 20 °C to 12.45% at 800 °C, indicating high structural integrity and resilience under extreme THM conditions. Granite shows significant increases in porosity due to thermally induced microcracking, while marble rapidly deteriorated beyond 300 °C due to carbonate decomposition. Consequently, basalt, with its minimal porosity variability, high thermal stability, and robust mechanical properties, emerges as an optimal candidate for nuclear waste repositories and other high-temperature geological engineering applications, offering enhanced reliability, structural stability, and long-term safety in such settings.

Micro container made of levitated liquid bead

Liquid bead, an emerging digital microfluidic platform offers a wide range of applications in research and industry. Making liquid beads using acoustic levitation technology allows for the fabrication of micro container. Extensive insight into levitated liquid beads is essential for determining their performance. Firstly, this paper unfolds the unique interface of the levitated liquid bead, which has thin membrane of shell material on top and thus serves as a micro container. Next, we characterised the puncture toughness of liquid beads to assess the capability of releasing the liquid content. Liquid bead with larger corresponding shell volume and lower core volume recorded the highest resistance against needle penetration. Finally, we observed the thermal behaviour of liquid beads at elevated temperature. The liquid beads showed no morphological change over 10-minutes period at 50 °C. At 65 °C, liquid bead exceeded the critical temperature threshold, which resulted in breaking the thin membrane and releasing the liquid from the core.

Dynamics of soil water potential as a function of stand types in a temperate forest: Emphasis on flash droughts

In the context of a changing climate and the increasing occurrences of extreme events, including droughts, field evidence, and models suggest that cases of forest decline and migration of tree species to more suitable climates will augment in the 21st century. In northeastern North America, an expansion of American beech at the expense of maples has been observed since the 1970s and has been associated to several causes. Through an analysis of time series leveraging thousands of data collected in a temperate forest in southern Quebec, Canada, dynamics of soil water potential were analyzed in interaction with soil temperature, meteorological variables and forest types, including hardwoods (mostly maple) with a large presence of beech trees (hardwood-beech stands), hardwoods (maple and birch) and mixedwoods (maple and fir). During flash drought events with a net precipitation deficit and water stress, the presence of beech led to a decrease in soil temperature and favored the maintenance of low soil water potential and faster restoration of water reserves compared to mixedwoods. Using machine learning-based approaches, distinct critical soil temperature thresholds in regard to water potential were identified for the various forest types, and the temporality in soil water regime changes was more favorable under hardwood-beech stands. The presence of beech appears to render greater resilience in regard to water stress in this forest. A greater capacity of beech to preserve and restore soil water not only offers an additional explanation for its establishment in hardwoods in the last decades, but greater water conservation in the presence of beech, assuming it remains in the landscape, could also help local plant species adapt to climate change and to the predicted increased water deficits, as well as species migrating northward to find more suitable environmental envelopes.

Critical environmental core temperature limits and heart rate thresholds across the adult age span (PSU HEAT Project).

The frequency, duration, and severity of extreme heat events have increased and are projected to continue to increase throughout the next century. As a result, there is an increased risk of excessive heat- and cardiovascular-related morbidity and mortality during these extreme heat events. Therefore, the purposes of this investigation were to establish 1) critical environmental core temperature (Tc) limits for middle-aged adults (MA), 2) environmental thresholds that cause heart rate (HR) to progressively rise in MA and older (O) adults, and 3) examine critical environmental Tc limits and HR environmental thresholds across the adult age span. Thirty-three young (Y) (15 F; 23 ± 3 yr), 28 MA (17 F; 51 ± 6 yr), and 31 O (16 F; 70 ± 3 yr) subjects were exposed to progressive heat stress in an environmental chamber in a warm-humid (WH, 34-36°C, 50-90% rh) and a hot-dry (HD, 38°C-52°C, <30% rh) environment while exercising at a low metabolic rate reflecting activities of daily living (∼1.8 METs). In both environments, there was a main effect of age on the critical environmental Tc limit and environmental HR thresholds (main effect of age all P < 0.001). Across the lifespan, critical environmental Tc and HR thresholds decline linearly with age in HD environments (R2 ≥ 0.3) and curvilinearly in WH environments (R2 ≥ 0.4). These data support an age-associated shift in critical environmental Tc limits and HR thresholds toward lower environmental conditions and can be used to develop evidence-based safety guidelines to minimize future heat-related morbidity and mortality across the adult age span.NEW & NOTEWORTHY This study is the first to identify critical environmental core temperature and heart rate thresholds across the adult age spectrum. In addition, our data demonstrate that the rate of decline in Tc and HR limits with age is environmental-dependent. These findings provide strong empirical data for the development of safety guidelines and policy decisions to mitigate excessive heat- and cardiovascular-related morbidity and mortality for impending heat events.

The burden of heat in arid regions of the Middle East: an analysis from Jordan and Kuwait

The Middle East, with its vast arid landscape, is facing escalating health risks due to intensifying heat under climate change. Kuwait and Jordan, two representative countries from the region, have no heat action plan in place. This study aims to (1) quantify the mortality burden of extreme heat in these countries, and hence (2) identify critical temperature thresholds. We collected 17 years of daily mortality records from 2000 to 2016 in Amman, Jordan, and the entire state of Kuwait. We fitted a time series design restricted to the summer months (June–August) for each location. We used distributed lag non-linear models to estimate non-linear associations and lagged effects of temperature on mortality. We then calculated attributable mortality for a range of temperature percentiles. We analyzed a total of 56 654 (39 996 all-cause deaths in Amman and 16 658 non-accidental deaths in Kuwait). Kuwait’s average summer temperature (38.7 °C) was higher than Amman (26.5 °C). In Kuwait, 202.1 (95% eCI: 17.7, 344.8) attributable heat deaths occurred over 79 d at temperatures above 41.9 °C (>95th percentile), averaging 2.6 heat deaths per day. Amman experienced 500.7 (95% eCI: 17.7, 344.8) attributable heat deaths over 77 d at temperatures above 30.75 °C, with an average of 6.5 deaths per day. This study equips Kuwait and Jordan with critical data to develop and implement targeted heat action plans. The two Middle Eastern countries face extreme heat challenges and are undergoing serious demographic changes with an influx of migrant workers and refugees. We provide an essential quantification of the mortality burden attributable to extreme heat in Kuwait and Jordan, two countries in the Middle East facing unprecedented heat and yet without existing heat action plans. Policymakers face the question of which thresholds represent negligible risk and which cannot be ignored. By analyzing 56 654 deaths, we reveal the number of deaths per day attributable to specific temperatures. This study presents the first step towards establishing targeted heat action plans to mitigate the health risks posed by intensifying heat. The methods used for Kuwait and Amman can be replicated in similar Middle Eastern countries.

The Critical Ambient Temperature Threshold for Safe Fan Use in Young Adults During Extreme Heat Exposure

Introduction: The electric fan may be an effective, low-cost heat resilience solution during extreme heat. Fans have been shown to attenuate the rise in cardiovascular and thermal strain relative to still air in young adults, particularly during exposure to more humid conditions. When ambient temperature exceeds skin temperature, a fan improves sweat evaporation from the skin surface, which counterbalances the increased rate of convective heat gain. However, at higher air temperatures, the increased convective heat gain may exceed the rate of evaporative heat loss resulting in net heat gain and increasing physiological strain. The purpose of the present study was to identify the critical ambient temperature limit, where increased physiological strain will be observed, with a fan in comparison to still air. Method: To date, 6 participants (4 females; 24±9 y; 72.8±17.8 kg; 1.8±0.2 m) have completed two 180-minute temperature ramp heat-exposures (37°C to 47°C at ~0.05°C/min, 25%RH) on separate days. Wearing standardized t-shirts and shorts, the participants remained seated while either i) facing an electric fan (5.3±0.9 m/s) or ii) in still air (0.1±0.0 m/s). Rectal and skin temperature, heart rate, blood pressure, whole-body sweat loss, thermal comfort, and thermal sensation were measured every 10 minutes. Results: Rectal temperature was similar between fan and still air up to 43°C (P&gt;0.92), however was greater with a fan from 44°C onwards (p&lt;0.05). Skin temperature was higher with a fan compared to still air throughout the exposure (p&lt;0.001). Heart rate was similar between fan and still air until 44°C (P&gt;0.61), after which heart rate was higher with a fan (p&lt;0.05). Mean arterial pressure was not different between fan and still air at any air temperature (P=0.53). The rate pressure product was higher with a fan compared to still air when the ambient temperature exceeded 44°C (p&lt;0.05). Whole-body sweat losses were greater with a fan (1215±250 g) compared to still air (675±103 g, P=0.006). No differences between fan and still air were observed for thermal comfort (P=0.22) or thermal sensation (P=0.73) throughout the temperature ramp protocol. Conclusion: When ambient temperature exceeds 43°C, electric fan use results in greater physiological strain at rest in young healthy adults relative to still air. This research was supported by Dr. Ravanelli’s Natural Sciences and Engineering Research Council of Canada Discovery Grant (PIN#2022-05096). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thermal Effects of 445 nm Laser Irradiation on the Bovine Tongue Tissues Ex Vivo

The purpose of this study was to employ the use of thermographic techniques to compare temperature changes and thermal heat transfer patterns in soft tissues when using the 445nm-diode laser with initiated and non-initiated tips. Methods: Bovine tongue slices measuring 5 mm in thickness were placed in between two microscopy glass slides at a distance of 11 cm from a thermographic camera. Fifteen 2 cm long incisions were made along the surface of the soft tissue parallel to the glass slides and the camera capture field. Incisions were performed using a 445nm diode laser (continuous wave at 2 watts) with 320μm-thick glass initiated and non-initiated fiber tips for a total 30-second irradiation period. The maximum temperature changes in oC (ΔT) in the soft tissues, as well as the vertical and lateral heat transfer (in mm), were recorded at 10-second intervals for a duration of 30 seconds, using the thermographic images captured using the infrared camera and a special image analysis software. Descriptive statistical analysis occurred to evaluate the temperature changes over the critical temperature threshold. Results: The maximum ΔT in oC for the initiated lasers was 17.48 ± 9.05 and for non-initiated lasers was 10.72 ± 2.29. The heat transfer in the two groups for vertical/lateral was 7.50 ± 1.4/18.30 ± 4.01 for the initiated lasers and 7.10 ± 1.82/19.24 ± 3.86 for the non-initiated lasers. Conclusion: Initiated tips and non-initiated tips of 445nm laser present deep penetration depths and high temperatures in bovine homogenous soft tissues. The irradiation period and clinical indication must be strictly followed to avoid complications from overheating in soft tissues. Received: 29 January 2024 | Revised: 15 April 2024 | Accepted: 23 April 2024 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement Data available on request from the corresponding author upon reasonable request.

Impact of flowering temperature on litchi yield under climate change: A case study in Taiwan

Litchi is a subtropical fruit tree that undergoes flower bud differentiation under low-temperature conditions. However, climate change has affected litchi production in Taiwan, causing litchi farmers to experience economic losses. This study explored the influence of flowering temperature on litchi yield under climate change in Taiwan by analyzing litchi production data from 2001 to 2020 and observation data from meteorological stations in litchi-producing areas. Historical observed data were used to construct several regression models relating temperature to yield, with the performance of the models used to determine critical temperature thresholds for litchi flower bud differentiation. Analytical climate data (CMIP5) were used to project yield changes in Taiwan’s litchi-producing regions under anticipated low-temperature conditions for the mid- (2036–2065) and late- (2071–2100) 21st century. The variable that exhibited the highest correlation with yield changes was the number of days with an average flowering temperature below 16 °C. The production yield, in terms of yield variation per hectare, is expected to decrease by 12 % to 35 % by the end of the 21st century (2071–2100). Given the projected decline in the number of cooler days due to climate change, existing litchi cultivars may become unsuitable for cultivation in production areas in southern Taiwan. Practical ImplicationsSome fruit trees require a period of low temperature before their flowering stage. Climate change is expected to cause warming of winter temperatures in Taiwan, which is likely to lead to reduced litchi flowering. The current study assessed the potential effects of climate change on litchi flowering in the future.Historical observed data were used to establish models, and critical temperature thresholds for litchi flowering were determined on the basis of model performance. Days with average temperatures below 16 °C exhibited the highest correlation with litchi yield among the tested thresholds. According to our results, farmers can use this 16 °C threshold to evaluate the potential effects of future climate change at their current farm locations and to identify other areas with similar or more favorable conditions for litchi cultivation. For agricultural researchers, this temperature threshold could provide a target for new litchi variety breeding and a reference basis for research on optimal cultivation methods.Notably, because climate change projection data have a high degree of uncertainty, the results of this study may differ from those of studies using different databases. In this study, we used an ensemble of CMIP5 projections incorporating data from models from various research centers around the world, which can provide more robust results based on an ensemble mean than those obtainable from a single model or a few models. In addition, rainfall is a crucial factor during the flowering growth stage. Future studies should consider the effects of rainfall and temperature on yield and should consider using a model with yield being considered a function of both of these variables to improve model accuracy.To conclude, the present study provides researchers, policymakers, and other stakeholders with insights into the primary effects of climate change on litchi production. It also lays the groundwork for future climate adaptation strategies in Taiwan’s litchi industry.

Are tropical forests approaching critical temperature thresholds?

There is growing concern about the fate of tropical forests in the face of rising global temperatures. Doughty etal. (2023) suggest that an increase in air temperature beyond ∼4 °C will result in massive death of tropical forest leaves and potentially tree death. However, this prediction relies on assumptions that likely underestimate the heat tolerance of tropical leaves.

Imperfection-induced internal resonance in nanotube resonators

Through molecular dynamics simulations, we demonstrate the possibility of internal resonances in single-walled carbon nanotubes. The resonant condition is engineered with a lack of symmetry in the boundary condition and activated by increasing the energy exchange with a coupled thermal bath. The critical temperature threshold for initiating modal interaction is found to be chirality-dependent. By applying the proper orthogonal decomposition algorithm to molecular dynamics time responses, we show how the thermal fluctuations influence the vibrational behaviour of the nanotube leading to both flexural–flexural and flexural–longitudinal resonances. Understanding the interaction between nanotube resonators and the thermal bath is crucial for designing and optimizing their performance for various nanoscale sensing, actuation, and signal processing applications.

Characteristic Identification of Heat Exposure Based on Disaster Events for Single-Season Rice along the Middle and Lower Reaches of the Yangtze River, China

As global warming continues, heat stress events are expected to increase and negatively affect rice production. Spatiotemporal changes in single-season rice exposure to heat stress were explored along the middle and lower reaches of the Yangtze River (MLRYR) in China during 1971–2020 based on created heat thresholds in different phenological stages, derived from comparison of historical heat records for single-season rice and agro-meteorological data. The feature importance (IF) provided by the Random Forest model was used to modulate the relationship between threshold accumulated temperature and yield reduction rate caused by heat stress. In addition, critical temperature thresholds at different phenological stages were determined by combining Overall Accuracy and the Receiver Operating Characteristic (ROC) curve. According to historical disaster records, the heat stress occurred before the reproductive phase (i.e., the tillering–jointing stage) and ended in the filling stage. Critical temperature thresholds of Tmax at tillering–jointing, booting, flowering and filling were quantified as 36, 35, 35 and 38 °C, with higher IF values of 13.14, 10.93, 17.15 and 13.15, respectively. The respective values of Overall Accuracy and the areas under the ROC curve were greater than 0.85 and 0.930, implying that each threshold performed excellently in identifying heat occurrence. Based on the determined critical thresholds, accumulated harmful temperature (Tcum), number of heat days (HD), first heat date (FHD) and last heat date (LHD) were presented to characterize heat exposure. It was clear that Tcum and HD exhibited a north-to-south increasing trend from 1971 to 2020, with the obvious increasing occurrence in most parts of the study region through the period of 2010 to 2020. FHD occurred earlier in most stations except the northeast parts, while LHD ended later in southern MLRYR. Exploring heat critical thresholds at different phenological stages highlighted in this study can help decision-makers monitor and evaluate heat exposure to single-season rice in MLRYR and further develop mitigation strategies to ensure rice production security.

Tropical forests are approaching critical temperature thresholds.

The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7 °C (Tcrit)1. However, it remains unclear whether leaf temperatures experienced by tropical vegetation approach this threshold or soon will under climate change. Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34 °C during dry periods, with a long high-temperature tail that can exceed 40 °C. Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed Tcrit 0.01% of the time. Furthermore, upper canopy leaf warming experiments (+2, 3 and 4 °C in Brazil, Puerto Rico and Australia, respectively) increased leaf temperatures non-linearly, with peak leaf temperatures exceeding Tcrit 1.3% of the time (11% for more than 43.5 °C, and 0.3% for more than 49.9 °C). Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9 ± 0.5 °C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of Tcrit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. The 4.0 °C estimate is within the 'worst-case scenario' (representative concentration pathway(RCP) 8.5) of climate change predictions2 for tropical forests and therefore it is still within our power to decide (for example, by not taking the RCP 6.0 or 8.5 route) the fate of these critical realms of carbon, water and biodiversity3,4.

Determining the critical threshold of meteorological heat damage to tea plants based on MODIS LST products for tea planting areas in China

Tea (Camellia sinensis (L.) Kuntze) is a daily drink in modern life throughout the world. Global warming increases the exposure of tea plants to elevated heat conditions during the summer picking period. Therefore, it is a fundamental function of the meteorological service to determine the critical temperature threshold that triggers heat damage (HD) to tea plants. In this study, MODIS daytime land surface temperature (LST) products obtained from the Aqua satellite (MYD11A1), annual land cover type products (MCD12Q1), and actual HD records were jointly used to determine the critical LST threshold resulting in HD to tea planting areas in China. An LST dataset of HD and HD-free samples was constructed based on actual HD records. The box-plot method was then used to delineate the range of LST outliers in HD to tea plants. The cumulative frequency distribution (CFD) method was adopted to determine the critical LST threshold by searching for the maximum slope of CFD within the range of LST outliers based on 2901 actual HD samples from 42 agrometeorological stations in 11 provinces in China. Results showed that the critical LST threshold triggering HD to tea plants was 30.1 °C. Two different HD data sources (i.e., 68 counties in eight provinces from the Meteorological Disaster Management System (MDMS) and 37 counties in six cities from a published book) were used as HD validation samples. Validation accuracy analysis revealed that a critical LST threshold of 30.1 °C was reasonable, with an average accuracy of between 60% and 90% for the published-book dataset, and 75.7% in the northern Yangtze River area and 86.3% in the southern Yangtze River area for the MDMS dataset. This study confirmed that using remotely sensed LST products is an effective method for identifying temperature-related agrometeorological disasters owing to the method's ability to intuitively capture the surface temperature distribution of the disaster-affected object. The findings will be helpful for identifying the timing and location of HD to tea plants, and thereby potentially preventing HD to tea plants.

Assessment of microbial biocontrol agents (BCA) viability to mechanical and thermal stress by simulating spray application conditions.

To improve the biological control agent (BCA) efficacy, stress factors threatening the microorganisms viability during spray application need to be determined. The effect of spray mixture temperature and exposure time on Trichoderma harzianum T 22 and Bacillus amyloliquefaciens QST713 viability were tested. Concurrently the combined effect of mechanical and thermal stress effect on BCAs viability were tested at two initial spray mixture temperatures (14°C and 25°C) by simulating a spray application using airblast sprayers featured by different tank capacity and a spray liquid circuit (without and with hydraulic agitation system). To assess the BCA microorganisms viability, spray mixture samples were collected at time intervals along trials and plated to count the colony forming units (CFU). The critical temperature threshold that inhibited BCA viability was 35°C with 30 min of exposure. The sprayer type, the initial temperature of the spray mixture and the temperature increment during the trials significantly decreased the number of the CFU recovered. When simulating a spray application, the spray mixture temperature increasing rate was mainly determined by the residual amount of spray mixture in the tank. Even if the tank capacity does not substantially affect the final temperature reached by the spray mixture, the higher residual spray mixture in bigger tanks can expose the BCA for a longer time to critical temperatures. Experimental trials allowed to identify the effect of factors affecting the viability of tested BCA, providing information about the actual chance to guarantee the biological efficacy of BCA treatments. This article is protected by copyright. All rights reserved.

Trees in planters – Growth, structure and ecosystem services of Platanus x hispanica and Tilia cordata and their reaction to soil drought

Urban environments are often characterized by extensive paved surfaces, exacerbating the urban heat island effect. At the same time, limited root space due to underground infrastructure poses a challenge for planting new trees in these areas. Trees in planters have emerged as popular design elements, offering innovative and sustainable greening solutions, particularly in urban environments with limited rooting space. However, growing conditions in planters may strongly impact tree growth and the provision of environmental ecosystem services (ES). In this 3-year study, we analyzed tree growth and ecosystem services (cooling by shading, CO2-fixation) of London plane (Platanus x hispanicaMünchh.) and small-leaved lime (Tilia cordataMill.) in four planting treatments: in-ground (G), planters in the ground (PG), non-insulated plastic planters (P), and insulated planters (PI). We also recorded soil temperature throughout the experiment and implemented soil drought conditions by reducing soil irrigation for half of the trees after one year. Our findings revealed higher thermal fluctuations in soil temperature within non-insulated plastic planters (P), reaching a maximum of 45 °C, surpassing the critical temperature threshold for plant growth (>38 °C). In contrast, insulated planters (PI) effectively mitigated soil temperatures, staying below 33.8 °C. When planted in the ground (G), P. x hispanica exhibited a significantly higher stem diameter increment (52–66%) compared to other planting treatments, aligning with the provision of ecosystem services. However, T. cordata trees showed a more moderate response to planting treatments in terms of growth and ecosystem service provision. Furthermore, the implementation of soil drought conditions resulted in a reduction of up to 34% in stem diameter increment for P. x hispanica and up to 25% for T. cordata. Our results underscore the necessity of tree species-specific knowledge about growth responses to different planting treatments for effective urban planning perspectives, as the provision of ecosystem services may be influenced differently.

Urban Warming Challenges Verification of Frost Advisories and Freeze Warnings in Madison, Wisconsin

Abstract Urban heat islands (UHIs) may increase the likelihood that frost sensitive plants will escape freezing nighttime temperatures in late spring and early fall. Using data from 151 temperature sensors in the Madison, Wisconsin, region during March 2012–October 2016, we found that during time periods when the National Weather Service (NWS) issued freeze warnings (threshold of 0.0°C) or frost advisories (threshold of 2.22°C) were valid, temperatures in Madison’s most densely populated, built-up areas often did not fall below the respective temperature thresholds. Urban locations had a mean minimum temperature of 0.72° and 1.39°C for spring and fall freeze warnings, respectively, compared to −0.52° and −0.53°C for rural locations. On average, 31% of the region’s land area experienced minimum temperatures above the respective temperature thresholds during freeze warnings and frost advisories, and the likelihood of temperatures falling below critical temperature thresholds increased as the distance away from core urban centers increased. The urban–rural temperature differences were greatest in fall compared to spring, and when sensor temperatures did drop below thresholds, the maximum time spent at or below thresholds was highest for rural locations during fall freeze warnings (6.2 h) compared to urban locations (4.8 h). These findings potentially have widely varying implications for the general public and industry. UHIs create localized, positive perturbations to nighttime temperatures that are difficult to account for in forecasts; therefore, freeze warnings and frost advisories may have varying degrees of verification in medium-sized cities like Madison, Wisconsin, that are surrounded by cropland and natural vegetation. Significance Statement The purpose of this study was to understand whether the urban heat island effect in Madison, Wisconsin, creates localized temperature patterns where county-scale frost advisories and freeze warnings may not verify. Approximately one-third of Madison’s urban core area and most densely populated region experienced temperatures that were consistently above critical low temperature thresholds. This is important because gardening and crop management decisions are responsive to the perceived risk of cold temperatures in spring and fall that can damage or kill plants. These results suggest that urban warming presents forecast challenges to the issuance of frost advisories and freeze warnings, supporting the need for improved numerical weather prediction at higher spatial resolution to account for complex urban meteorology.