Cooler Nights Research Articles

Modeling the impacts of extreme climate scenarios on soil acidity (pH and exchangeable aluminum) in Abbay River Basin, Ethiopia

The Abbay River Basin faces the looming threat of extreme climate events, including prolonged droughts and erratic rainfall patterns, which can significantly affect soil health and fertility. This study aimed to explore the influence of extreme climate conditions on soil pH and exchangeable aluminum, aiming to promote sustainable agricultural practices in Ethiopia. The Africa Soil Information Service (ASIS) provided datasets on soil pH and exchangeable aluminum. The European Copernicus Climate Change Data Store was used to download historical and future datasets of extreme climatic indices from 1980 to 2010 and 2015–2050, respectively. The Coupled Model Intercomparison Project Phase 6 model ensemble was used to predict future climate impacts under three shared socioeconomic scenarios: SSP1-2.6, SSP2-4.3, and SSP5-8.5. Data extraction, quality control, and clustering were conducted before analysis, and the model was validated for its accuracy and reliability in predicting soil parameter changes. An artificial neural network model was utilized to predict the effects of extreme climate indices on soil pH and exchangeable aluminum concentrations. The model was designed to accurately and reliably predict changes in soil parameters. This study compared the changes in soil pH and aluminum concentrations using paired t tests. The model's diagnostic results indicated a significant impact of extreme climate scenarios on soil pH and exchangeable aluminum. Extreme climate factors such as heavy precipitation and cooler night time temperatures significantly contribute to soil acidification and an increase in aluminum concentration. Under the SSP1-2.6 and SSP2-4.5 emission scenarios, soil pH levels are expected to increase by 8.38 % and 3.79 %, respectively. These changes in soil pH are expected to have significant impacts on the exchangeable aluminum content in the soil, with increases of 37 % and 5.38 %, respectively, under the same emission scenarios. However, the SSP5.8 scenario predicted a 45 % increase in exchangeable aluminum and a 9.36 % decrease in soil pH. Therefore, this study significantly enhances our understanding of the influence of climate change on soil health. The development of strategies to mitigate climate change impacts on agriculture in the region must consider the effects of extreme climate indices.

Investigating an Enhanced Approach for Greenhouse Climate Control: Optimising Cooling and Heating Systems

This study aimed to enhance greenhouse climate regulation by optimizing the efficiency of existing cooling and heating systems while considering external temperature and humidity conditions. We introduced an automated system capable of regulating the internal greenhouse environment, which underwent testing across 30 days in September 2021, with temperatures ranging from 26°C to 31°C and humidity from 65% to 70%. The system consistently monitored and adjusted the microclimate, with sensors capturing temperature and humidity data at 30-second intervals, amassing over 83,000 data entries for enhanced control accuracy. The automated regulation effectively maintained desired humidity, significantly reducing nighttime levels by 80% while carefully increasing daytime humidity to counteract external heat. Temperature control was largely successful, sustaining daytime levels around 32°C, but faced challenges in maintaining the target of 26°C during cooler nights. Energy consumption was optimized, with the automation leading to a significant 4-33% energy saving for cooling and an 8% saving in heating compared to traditional methods. Additionally, the system was accessible via a web interface, allowing for real-time climate tracking and prompt anomaly identification. In conclusion, the developed greenhouse automation system exhibited efficiency in equipment usage and improved temperature and humidity control. Further enhancements are required for lamp-based heating. This research contributes to the efficiency and reliability of greenhouse automation systems, mitigating risks associated with external environmental factors and enhancing stability, productivity, and disease and pest prevention.

Investigating an Enhanced Approach for Greenhouse Climate Control: Optimising Cooling and Heating Systems

This study aimed to enhance greenhouse climate regulation by optimizing the efficiency of existing cooling and heating systems while considering external temperature and humidity conditions. We introduced an automated system capable of regulating the internal greenhouse environment, which underwent testing across 30 days in September 2021, with temperatures ranging from 26°C to 31°C and humidity from 65% to 70%. The system consistently monitored and adjusted the microclimate, with sensors capturing temperature and humidity data at 30-second intervals, amassing over 83,000 data entries for enhanced control accuracy. The automated regulation effectively maintained desired humidity, significantly reducing nighttime levels by 80% while carefully increasing daytime humidity to counteract external heat. Temperature control was largely successful, sustaining daytime levels around 32°C, but faced challenges in maintaining the target of 26°C during cooler nights. Energy consumption was optimized, with the automation leading to a significant 4-33% energy saving for cooling and an 8% saving in heating compared to traditional methods. Additionally, the system was accessible via a web interface, allowing for real-time climate tracking and prompt anomaly identification. In conclusion, the developed greenhouse automation system exhibited efficiency in equipment usage and improved temperature and humidity control. Further enhancements are required for lamp-based heating. This research contributes to the efficiency and reliability of greenhouse automation systems, mitigating risks associated with external environmental factors and enhancing stability, productivity, and disease and pest prevention.

Viticultural Climate Indexes and Their Role in The Prediction of Anthocyanins and Other Flavonoids Content in Seedless Table Grapes

Background: Viticulture bioclimatic indexes like the Heliothermal Index (HI), Cool Night Index (CI), and Dryness Index (DI), can be used to assess the influence of climate on grapes’ quality. Methods: HI, CI, and DI + total seasonal irrigation were utilized to assess the effect of climate on the flavonoids content and composition of two Vitis vinifera seedless varieties, ‘Summer Royal’ and ‘Crimson Seedless’, both grown in Apulia (Southern Italy). Results: The flavonoids content was significantly affected by variety and climate conditions on the base of HI, CI, and DI + total seasonal irrigation. Factor analysis applied to climate indexes and flavonoids showed that anthocyanins and flavonols were negatively and positively correlated to CI in both varieties, respectively. Additionally, warmer night temperatures determined higher fla-van-3-ols. HI increase promoted anthocyanins, flavonols, and flavan-3-ols content in Crimson Seedless, whilst it induced an opposite trend in Summer Royal. Finally, DI + total seasonal irrigation showed to be positively linked to flavonols content and negatively linked to anthocyanins content just in the case of Crimson Seedless. Significant regression models were also determined between climate indexes and productive parameters (i.e., yield, TSS, TA, pH, bunch, and berry weight). Conclusions: Climate indexes HI, CI, and DI + total seasonal irrigation showed an effect on quality grape parameters like flavonoids and contributed to building predictive models when new climatic zones are going to be evaluated for the production of table grapes.

Phenology and radial growth of poplars in wide alley agroforestry systems and the effect on yield of annual intercrops in the first four years of tree age

Silvoarable agroforestry systems have the potential to combat the negative effects of climate change while also enhancing productivity per unit land. Although the growth rate of large-spaced trees remains poorly investigated and the yield of annual intercrops uncertain, silvoarable agroforestry systems with poplar are receiving an ever-growing interest. This study assessed the growth of the new HES (High Environmental Sustainability) poplar clone, Moncalvo, arranged in 40-m spaced parallel alleys with a density of 35 trees ha−1 (SA, silvoarable). Their growth was compared to those cultivated in a specialized poplar plantation (C, control) with 277 trees ha−1, and the agronomic impact on wheat and soybean as intercrops was explored. Measurements took place between 2018 and 2021 during the first 4 years, which represents the midpoint of the expected poplar rotation. Here it was demonstrated that at the end of the investigated period, diameter at breast height was significantly greater (23.8 vs. 20.5 cm, +16%) and the plant height lower (14.3 vs. 15.5 m, −8%) in poplar grown in SA as compared to those in C, likely due to reduced intraspecific competition for environmental resources. In SA, seasonal tree phenology was delayed by approximately two weeks in spring, possibly due to the high sensitivity of poplar to low soil water content and cooler night air temperatures in springtime. The grain yield of wheat was not impaired by tree shading but instead occasionally improved when neighboring the poplar alley (e.g., year 2021: +28% at 12 m from the tree row vs. full sun conditions), while soybean yield was generally reduced (maximum −38% at 6 m from the tree row). This study innovatively studied the growth response of HES poplar clones in silvoarable systems by providing valuable insights into the growth dynamics of trees grown in combination with field crops. It is concluded that poplars in wide spaced alleys of silvoarable systems in temperate climates grow faster than poplars in plantations of high population density due to enhanced access to resources, while future investigations will allow for the identification of clone-specific rotation durations. In the arable tree interrow, winter crops more readily benefit from such agroforestry system than summer crops due to reduced cycle overlap and light competition with the tree canopy.

Seasonal Changes in Amylose and Starch Compositions in ‘Ambrosia’ Apples Associated with Rootstocks and Orchard Climatic Conditions

The dynamics of amylose (AM) and total starch content (TSC) have been studied in several apple varieties; however, their responses to environmental variables and rootstocks are less understood in new low-climacteric varieties. In addition, the pertinence of AM and TSC to fruit dry matter content (DMC), fruit quality at harvest, and quality retention after storage is little understood. In this study, we investigated the seasonal changes in AM and TSC of ‘Ambrosia’ apples grafted onto dwarfing rootstocks Malling 9 (M.9) and Budagovsky 9 (B.9) in two consecutive years, 2016 and 2017, in the Okanagan-Similkameen Valley, British Columbia, Canada. Enzymatic methods with Megazyme® kits were used to analyze the fruit samples collected from four orchards in the growing season. In 2016, the orchard microclimate exhibited cooler nights and greater diurnal temperature ranges (DTRs) compared to 2017. As a result, the AM content and AM portion in TSC were significantly higher in 2016, with levels peaking over 40% compared to the values observed in 2017. However, there were no significant differences in peak values of TSC between the two years. Additionally, the apples grown on the B.9 rootstock consistently showed higher levels of AM and AM percentage compared to those grown on the M.9 rootstock. The study also used Felix 750 Produce Quality Meter, a handheld infrared spectrometer, to assess the dry matter content (DMC) of growing fruit, which showed a strong correlation with AM content (r > 0.8). After being harvested at commercial maturity and stored in controlled atmospheric chambers (CA) for 8 months, fruit quality analysis suggested that the AM level and its percentage in TSC played an important role in determining ‘Ambrosia’ apple quality after long-term storage.

Cool, dry nights and short heatwaves during growth result in longer telomeres in temperate songbird nestlings.

Exposure to rising sublethal temperatures can affect development and somatic condition, and thereby Darwinian fitness. In the context of climate warming, these changes could have implications for population viability, but they can be subtle and consequently difficult to quantify. Using telomere length (TL) as a known biomarker of somatic condition in early life, we investigated the impact of pre-hatching and nestling climate on six cohorts of wild nestling superb fairy wrens (Malurus cyaneus) in temperate south-eastern Australia. Models incorporating only climate information from the nestling phase were best supported compared to those including the (pre-)laying to incubation phase (previously shown to affect mass) or both phases combined. This implies that nestling TL is most sensitive to ambient climate in the nestling phase. The top model showed a negative relationship between early-life TL and nestling mean daily minimum temperature when rainfall was low which gradually became positive with increasing rainfall. In addition, there was a positive relationship between TL and the frequency of hot days (daily maximum temperature ≥35°C), although these temperatures were rare and short-term. Including other pre-hatching and nestling period, climate variables (e.g., mean daily maximum temperature and mean diurnal temperature variability) did not improve the prediction of nestling TL. Overall, our results suggest that cooler nights when conditions are dry and short-term temperature spikes above 35°C during development are conducive for somatic maintenance. While these findings indicate a potential pathway for climate warming to impact wildlife fitness, they emphasize the need to elucidate the mechanisms underlying these complex associations.

Relocation of bioclimatic suitability of Portuguese grapevine varieties under climate change scenarios.

Climate change has been driving warming trends and changes in precipitation patterns and regimes throughout Europe. Future projections indicate a continuation of these trends in the next decades. This situation is challenging the sustainability of viniculture and, thus, significant efforts towards adaptation should be then carried out by local winegrowers. Ecological Niche Models were built, using the ensemble modelling approach, to estimate the bioclimatic suitability of four main wine-producing European countries, namely France, Italy, Portugal, and Spain, in the recent past (1989-2005), for the cultivation of twelve Portuguese grape varieties. The models were then used to project the bioclimatic suitability to two future periods (2021- 2050 and 2051-2080) to better understand the potential shifts related to climate change (modeled after Intergovernmental Panel on Climate Change's Representative Concentration Pathways 4.5 and 8.5 scenarios). The models were obtained with the modeling platform BIOMOD2, using four bioclimatic indices, namely the "Huglin Index", the "Cool Night index", the "Growing Season Precipitation index", and the "Temperature Range during Ripening index" as predictor variables, as well as the current locations of the chosen grape varieties in Portugal. All models performed with high statistical accuracy (AUC > 0.9) and were able to discriminate several suitable bioclimatic areas for the different grape varieties, in and around where they are currently located but also in other parts of the study area. The distribution of the bioclimatic suitability changed, however, when looking at future projections. For both climatic scenarios, projected bioclimatic suitability suffered a considerable shift to the north of Spain and France. In some cases, bioclimatic suitability also moved towards areas of higher elevation. Portugal and Italy barely retained any of the initially projected varietal areas. These shifts were mainly due to the overall rise in thermal accumulation and lower accumulated precipitation in the southern regions projected for the future. Ensemble models of Ecological Niche Models were shown to be valid tools for winegrowers who want to adapt to a changing climate. The long-term sustainability of viniculture in southern Europe will most likely have to go through a process of mitigation of the effects of increasing temperatures and decreasing precipitation.

Twenty-first century climate extremes’ projections and their spatio-temporal trend analysis over Pakistan

Study regionThe study area comprising Pakistan is distributed in five homogeneous climatic zones. Study focusAn integrated five step approach has been used for zonal climate extreme analysis. Seven out of thirteen most appropriate Global Climate Models (GCMs) were selected using Posterior Inclusion Probability in the Bayesian model averaging approach. The output of selected GCMs is then downscaled using statistical downscaling. Climate extremes are projected for the baseline and future time periods. Spatio-temporal trend and statistical significance analysis were performed for climate extremes. New hydrological insights for the regionMost of the climate extremes have heterogeneous trends for the precipitation under RCP4.5 and RCP8.5. The increasing trends in climate extreme are noted in the northern region, monsoon region, and south-west parts of Pakistan. Significantly increasing trend is observed in TMAXmean and TMINmean across the country. TN10P (Cool nights) and TX10P (Cool days) have decreasing trends in the future for most of the GCMs across the country for RCP4.5 and RCP8.5. In contrast, TN90P (warm nights) and TX90P (warm days) have increasing trends for all GCMs in future under both scenarios. For RCP8.5, temperature extremes have significantly increased except TN10P and TX10P indicating significantly decreasing trends. There is notable increase in the number of summer days in future under both scenarios.

Sensitivity of coastal southern African climate to changes in coastline position and associated land extent over the last glacial

Paleoclimatic changes in South Africa, especially around the southern Cape region, are of intense interdisciplinary interest; as this is an important area in the context of human evolution, hosting several prominent archaeological sites such as Blombos Cave (located near today's shoreline). In this study, we investigate the sensitivity of climate of coastal southern Africa to changes in glacial variations in sea level and associated land extent, by performing a model sensitivity experiment. Employing a high-resolution (12 km grid spacing) regional climate model (WRF), output from a global model simulation at 70 thousand years ago (ka) is downscaled twice: First using the present-day coastline, then with an estimated coastline position at 70 ka; keeping all other forcing factors identical. Thus we focus on the response of the local climate to an expanded land surface area equivalent to a glacial sea level low stand scenario. Our results reveal that the climate of previously coastal localities shows strong continental characteristics when sea level drops, as the coastline moves away, and a coastal plain is exposed. This is most evident from the year-round warmer days and cooler nights, with up to 6 °C increases (decreases) in daily maximum (minimum) temperatures. This result also extends to extremes. For instance, at the archaeological site of Blombos Cave, temperature extremes (1st and 99th percentiles) of the modelled marine climate become 25- to 75-fold more probable as the coastline shifts. We also find year-round reductions (5–40%) in the amount of precipitation within the region, owing to local modifications in near-surface atmospheric circulation caused by the exposed land. The reductions in precipitation are accompanied by a significant drop in the annual number of rainy days (31 days locally at Blombos Cave). Simulated changes also vary seasonally, with more pronounced and widespread changes in temperature and precipitation occurring during summer. Through isolating and quantifying the effects of land extent variation, our approach demonstrates, for the first time, the role of coastline position in shaping local climate around near-coastal environs. Our results have significant implications for future studies exploring the influence of local coastline changes on early human settlement and mobility patterns.

Assessing impact of weather variability and changing climate on oil-palm yield in major growing regions of southern Thailand


 Oil palm yield is very responsive to weather fluctuations in the growing season. The purpose of this study was to investigate the relationship between yield variation and climate trends in the major oil palm-growing regions, especially in Southern Thailand (Chumphon; CP, Ranong; RN, Krabi; KB, Trang; TR, Satun; ST, Phang-Nga; PN, SuratThani; SR and Nakhon Si Thammarat; NS) where oil palm has been grown in a large plantation. Monthly weather variables from 16 agricultural meteorological stations were analyzed by linear and non-linear regressions over 28 years in each major oil palm-producing region. To evaluate the trends of changes in weather parameters and yield, a statistical model was developed for estimating oil palm yield based on climatic trends during 1994-2017. The results showed that warming trends were observed at all major oil palm-growing regions. There were pieces of evidence of significant correlation in temperature trends which had the strongest values in KB (Tmax, R2=0.534**) and PN (Tmin, R2=0.670**). The highest trends of ET and RH were also markedly increased in SR (R2=0.618**). Whereas precipitation trend had slightly increasing changes in CP (R2=0.220**) and PN (R2=0.233**). In addition, the annual trends in the values of Heliothermal Index, Dryness Index and Cool Night Index were markedly increased in NS, RN and KB, respectively. Comparing climate variables and yield variations over 19 years, the study indicated that the relationships between observed yield and estimated yield had highly significant differences in CP (R2=0.468**), SR (R2=0.735***) and NS (R2=0.579***), but there was lower value in KB (R2=0.098*) than those of the other regions. Therefore, this study indicates that recent climate trends have had an implicit effect on oil palm yield in the major producing regions in Southern Thailand. This study could be a guideline to further planning for oil palm management. 

Climate change in a typical Apulian region for table grape production: spatialisation of bioclimatic indices, classification and Future Scenarios

The present research focused on the characterisation of climate evolution in a typical Apulian region for table grape production under the protected geographical indication, “Uva di Puglia I.G.P.”Two thirty-year time window period (TW) were analysed: 1961-1990 and 1991-2020. Georeferenced maps for both TWs were produced to delimit homogeneous zones and to evaluate the climate variability within the investigated area by means of the two bioclimatic indices, Heliothermal Index (HI) and Winkler Index (WI). Spatial analysis of HI and WI was performed using the regression-kriging (RK) interpolation method and the Digital Elevation Model/DEM (10 x 10 m) as a prediction attribute.An increase in both the minimum and maximum temperatures was observed, and locations above 300 m a.s.l. shifted from HI+1 “temperate warm” to HI+2 “warm” according to the Geoviticulture Multicriteria Climatic Classification System. WI values similarly increased between the periods 1961–1990 and 1991–2020, shifting all the sites grouped in the Elevation Classes defined as being below 300 m a.s.l. from Region IV to Region V of the Winkler Classification.According to HI and WI, presumed maturity was calculated as being reached 9 to 15 (HI) and 12 to 28 days (WI) earlier in 1991–2020 than in 1961–1990, taking into account the heat requirements of cv. Italia table grape (representative of Apulian table grape production), were set at 2200 for both indices on the basis of literature data.Moreover, three table grape vineyards, located in the three main producing provinces of Apulia (Bari, Taranto and Barletta-Andria-Trani (BAT)), were considered for future scenarios analysis on the basis of two different Representative Concentration Pathways (RCPs), 4.5 and 8.5, and classified according to the Geoviticulture Multicriteria Climatic Classification System (MCC). Future scenarios scored WI values that exceeded the threshold of 2700 in the BAT and TA provinces in the 2061–2090 time window period for RCP 8.5. In contrast, RCP 4.5 led to a mitigating effect, which was not noticeable until 2040, with a consequent reclassification of the investigated areas on the basis of HI and Cool Night Index (CI).These findings suggest that in order to prevent or overcome heat stress, it will be necessary to implement strategies, such as vineyard relocation to unexplored elevations or latitudes and/or the exploitation of new table grape varieties able to fulfill the optimal maturity parameters, even when the duration of the phenological phases is shorter.

Additive and non-additive effects of day and night temperatures on thermally plastic traits in a model for adaptive seasonal plasticity.

Developmental plasticity can match organismal phenotypes to ecological conditions, helping populations to deal with the environmental heterogeneity of alternating seasons. In contrast to natural situations, experimental studies of plasticity often use environmental conditions that are held constant during development. To explore potential interactions between day and night temperatures, we tested effects of circadian temperature fluctuations on thermally plastic traits in a seasonally plastic butterfly, Bicyclus anynana. Comparing phenotypes for four treatments corresponding to a full-factorial analysis of cooler and warmer temperatures, we found evidence of significant interaction effects between day and night temperatures. We then focused on comparing phenotypes between individuals reared under two types of temperature fluctuations (warmer days with cooler nights, and cooler days with warmer nights) and individuals reared under a constant temperature of the same daily mean. We found evidence of additive-like effects (for body size), and different types of dominance-like effects, with one particular period of the light cycle (for development time) or one particular extreme temperature (for eyespot size) having a larger impact on phenotype. Differences between thermally plastic traits, which together underlie alternative seasonal strategies for survival and reproduction, revealed their independent responses to temperature. This study underscores the value of studying how organisms integrate complex environmental information toward a complete understanding of natural phenotypic variation and of the impact of environmental change thereon.

Unbalanced exchange flow and its implications for the night cooling of buildings by displacement ventilation

Passive ventilation of buildings at night forms an essential part of a low-energy cooling strategy, enabling excess heat that has accumulated during the day to self-purge and be replaced with cooler night air. Instrumental to the success of a purge are the locations and areas of ventilation openings, and openings positioned at low and at high levels are a common choice as there is then the expectation that a buoyancy-driven displacement flow will establish and persist. Desirable for their efficiency, displacement flows guide excess heat out through high-level openings and cooler air in through low-level openings. Herein we show that displacement flow cannot be maintained for the full duration of a purge. Instead, the flow must transition to an ‘unbalanced exchange flow’, whereby the cool inflow of air at low level is maintained but there is now a warm outflow and a cool inflow occurring simultaneously at the high-level opening. The internal redistribution of heat caused by this exchange alters the rate at which heat is self-purged and the time thought necessary to complete a purge. We develop a theoretical model that captures and predicts these behaviours. Our approach is distinct from all others which assume that a displacement flow will persist throughout the purge. Based on this enhanced understanding, and specifically that the transition to unbalanced exchange flow changes the rate of cooling and resultant emptying times, we anticipate that practitioners will be better placed to design passive systems that meet their target specifications for cooling.

Unbalanced Exchange Flow and its Implications

Passive ventilation of buildings at night forms an essential part of a low-energy cooling strategy, enabling excess heat that has accumulated during the day to self-purge and be replaced with cooler night air. Instrumental to the success of a purge are the locations and areas of ventilation openings, and openings positioned at low and at high levels are a standard choice as there's then the expectation that a buoyancy-driven displacement flow will establish and persist. Desirable for his or her efficiency, displacement flows guide excess heat out through high-level openings and cooler air in through low-level openings. Herein we show that displacement flow can't be maintained for the complete duration of a purge. Instead, the flow must transition to an ‘unbalanced exchange flow’, whereby the cool inflow of air at low level is maintained but there's now a warm outflow and a cool inflow occurring simultaneously at the high-level opening. The internal redistribution of heat caused by this exchange alters the rate at which heat is self-purged and the time thought necessary to complete a purge. We develop a theoretical model that captures and predicts these behaviours. Our approach is distinct from all others which assume that a displacement flow will persist throughout the purge. Based on this enhanced understanding, and specifically that the transition to unbalanced exchange flow changes the rate of cooling and resultant emptying times, we anticipate that practitioners will be better placed to design passive systems that meet their target specifications for cooling.

Transient daily heat stress during the early reproductive phase disrupts pod and seed development in Brassica napus L.

AbstractTransient daily heat stress during flowering of canola (Brassica napus L.) as a result of global warming is an increasing threat to grain production in this important oilseed crop. We investigated the intensity and duration of transient daily heat stress treatment at different stages of reproductive development in three B. napus genotypes under controlled environment conditions. Heat stress treatments during the week before first open flower on the main stem (S0) or during the first week (S1) or second week (S2) following first open flower greatly reduced pod number and seed yield on the main stem. Heat stress treatment during the third week (S3), fourth week (S4), or fifth week (S5) reduced seed yield more on the branches and less on the main stem as time progressed. Pod number and seed yield were reduced by moderate heat stress (TC2; 32°C/22°C) and high heat stress (TC3; 35°C/25°C), compared with the control (TC1, 25°C/15°C). Each duration of heat stress treatment (3, 5 or 7 days) caused the same reduction in pod number and seed per pod on the main stem. Leaf stomatal conductance, leaf chlorophyll index, plant height, and dry weight of above‐ground biomass increased from TC1 to TC3, which indicates that heat stress in the absence of drought stress does not inhibit vegetative growth. Cool night temperatures (15°C) resulted in recovery of pod number and seed yield after moderate (32°C) but not high (35°C) daily transient heat stress. The range of genotype responses to heat stress was greater under TC2 than under TC3. This research brings forward the critical period for heat stress sensitivity in B. napus to one week before first open flower and defines the conditions for controlled environment screening for heat tolerance in B. napus.

Changes of Extreme Temperature and Its Influencing Factors in Shiyang River Basin, Northwest China

The increase in the frequency and intensity of extreme weather events around the world has led to the frequent occurrence of global disasters, which have had serious impacts on the society, economic and ecological environment, especially fragile arid areas. Based on the daily maximum temperature and daily minimum temperature data of four meteorological stations in Shiyang River Basin (SRB) from 1960 to 2015, the spatio-temporal variation characteristics of extreme temperature indices were analyzed by means of univariate linear regression analysis, Mann–Kendall test and correlation analysis. The results showed that the extreme temperatures warming indices and the minimum of daily maximum temperature (TXn) and the minimum of daily minimum temperature (TNn) of cold indices showed an increasing trend from 1960 to 2016, especially since the 1990s, where the growth rate was fast and the response to global warming was sensitive. Except TXn and TNn, other cold indices showed a decreasing trend, especially Diurnal temperature (DTR) range, which decreased rapidly, indicating that the increasing speed of daily min-temperature were greater than of daily max-temperature in SRB. In space, the change tendency rate of the warm index basically showed an obvious altitude gradient effect that decreased with the altitude, which was consistent with Frost day (FD0) and Cool nights (TN10p) in the cold index, while Ice days (ID0) and Cool days (TX10p) are opposite. The mutation of the cold indices occurred earlier than the warm indices, illustrating that the cold indices in SRB were more sensitive to global warming. The change in extreme temperatures that would have a significant impact on the vegetation and glacier permafrost in the basin was the result of the combined function of different atmospheric circulation systems, which included the Arctic polar vortex, Western Pacific subtropical high and Qinghai-tibet Plateau circulation.

Vocal activity of the Ferruginous pygmy-owl (Glaucidium brasilianum) is strongly correlated with moon phase and nocturnal temperature

Bird vocal activity is affected by endogenous and exogenous factors. Owl surveys are mainly based on the detection of nocturnal calls, and therefore, the impact of exogenous factors on owls’ vocal activity may have consequences in conservation planning and behavioural studies. However, our current knowledge about the impact of climatic factors and the moon phase on owl calling behaviour is very limited, especially in the Neotropics. We used autonomous recording units to evaluate the effect of air temperature, rainfall, relative air humidity, and percent of the moon illuminated on the vocal occurrence (active/inactive) of the Ferruginous pygmy-owl (Glaucidium brasilianum) over three consecutive moon cycles in the Brazilian Pantanal. Vocal activity was positively associated with the percent of the moon illuminated, with 75% of the nights on which the species was vocally active having a moon illumination percentage higher than 77%. The vocal activity of the species was negatively associated with the nocturnal air temperature, with more vocal activity observed on cooler nights. Relative air humidity and daily rainfall were not associated with the vocal activity of the Ferruginous pygmy-owl. Our study improves the knowledge about the impact of exogenous factors on the calling behaviour of Neotropical owls. We conclude that future surveys aiming to detect the Ferruginous pygmy-owl should be carried out on nights with a high percent of moon illumination (>75%) and nights with low average temperature (< 18 °C).

Atmospheric layering during peak pine pollen season

Pollen release by Northern Hemisphere pine forests is well-documented yet little is known about its atmospheric layering. At what altitudes are these atmospheric layers and how do they influence pollen dispersal? To answer this, pollen concentrations were analysed using radiosonde soundings and LiDAR imagery over the Pamlico Sound, a large marine body at 35.4062° N, 76.3259° W between coastal of North Carolina, USA and its barrier islands. Pollen sampled over the sound ranged from 11 to 861 pollen m−3. During daylight, the planetary boundary layer (PBL) height was 1932 m and it was capped by a warm, dry inversion from 2015 to 3072 m. Similarly, PBL height was estimated at 2000 m using a CALIPSO LiDAR image. Mixed-phase clouds could form above the PBL starting at 5650 m where temperatures were less than −13.5 °C and wind speeds exceeded 29.8 m s−1. During cooler night hours, the PBL height dropped to 724 m and its inversion cap also dropped to 1027–1904 m. Strong westerly winds with a low vertical shear drove pollen across water on a cloudless sunny day. Wind speeds below the PBL stayed strong at night while rising relative humidity influenced pollen deposition. Structuring atmospheric layers during pollen dispersal provided more understanding of how long-distance pollen is dispersed at a land–atmosphere interface.

Nutrient Acquisition, Rather Than Stress Response Over Diel Cycles, Drives Microbial Transcription in a Hyper-Arid Namib Desert Soil.

Hot desert surface soils are characterized by extremely low water activities for large parts of any annual cycle. It is widely assumed that microbial processes in such soils are very limited. Here we present the first metatranscriptomic survey of microbial community function in a low water activity hyperarid desert soil. Sequencing of total mRNA revealed a diverse and active community, dominated by Actinobacteria. Metatranscriptomic analysis of samples taken at different times over 3 days indicated that functional diel variations were limited at the whole community level, and mostly affected the eukaryotic subpopulation which was induced during the cooler night hours. High levels of transcription of chemoautotrophic carbon fixation genes contrasted with limited expression of photosynthetic genes, indicating that chemoautotrophy is an important alternative to photosynthesis for carbon cycling in desiccated desert soils. Analysis of the transcriptional levels of key N-cycling genes provided strong evidence that soil nitrate was the dominant nitrogen input source. Transcriptional network analyses and taxon-resolved functional profiling suggested that nutrient acquisition processes, and not diurnal environmental variation, were the main drivers of community activity in hyperarid Namib Desert soil. While we also observed significant levels of expression of common stress response genes, these genes were not dominant hubs in the co-occurrence network.