Drought Events Research Articles

Leaf gas exchange responses to combined heat and drought stress in wheat genotypes with varied stomatal density

Stomata regulate the plant’s gas exchange and water balance, and their density may be a crucial factor in the response to abiotic stresses. The aim of this study was to investigate the response of leaf gas exchange of three spring wheat genotypes with different stomatal density to progressive drought and combined heat and drought stress. The stomatal conductance (gs) was the most sensitive parameter that declined with increasing drought stress. This negatively affected transpiration and leaf cooling, and limited photosynthesis (A) when gs decreased to < 550 mmol m−2 s−1. The treatments affected all three genotypes similarly over time irrespective of stomatal density. However, when related to the fraction of transpirable soil water (FTSW) in the pot, gs and A of the low and high stomatal density cultivars responded differently when heat was added to the drought stress. The high stomatal density cultivar showed no difference in maximum gs at FTSW > 0.3, and a similar decline of gs and A at FTSW < 0.3 in drought alone and combined drought and heat. The low stomatal density cultivar showed a higher maximum gs and the most severe decline of gs under combined heat and drought stress and a significantly slower decline of gs under drought alone, which was also reflected in a significantly slower reduction in A under drought compared to the combined stress. Overall, the drought response of stomatal closure dominated the physiological response under simultaneous heat and drought irrespective of stomatal density, and it was only in the combined stress that the maximum photochemical efficiency Fv/Fm was negatively affected. In conclusion, to elucidate the effect of drought and combined drought and heat on the leaf gas exchange in wheat cultivars with varied stomatal density, it is crucial to relate the parameters to the available soil water, not the duration of the drought.

The 2019–21 drought in southern Madagascar

Two consecutive failed rainy seasons in the southern part of Madagascar in 2019–21 had devastating impacts on the population, including an amplification of the ongoing food insecurity in the area. The drought events were second in severity only to the 1990–92 drought and were estimated in a previous study to have a return period of 135 years. In this study, the physical mechanisms that led to these consecutive drought events are investigated.We found that the anomalously cold sea surface temperatures (SSTs) that persisted to the south of Madagascar between December 2019 and December 2020 led to a decrease in the transport of moist air over land. These cold SST anomalies were the most negative anomalies in the past four decades and intensified the rainfall deficit resulting from a negative Subtropical Indian Ocean Dipole (SIOD) mode during the rainy season of December 2019 to March 2020 and during December 2020. We also found that the rainfall response to the SST anomaly south of Madagascar was three times greater than that of a canonical SIOD.A weak Mozambique Channel Trough and a strong Angola low system, on the other hand, modulated the expected above-normal rainfall from a La Niña event in January–February 2021. Our study demonstrates how local factors can modulate the impacts of large-scale drivers, and that both local and global drivers, and their interactions, should be considered when producing seasonal forecasts and advisories, as well as climate change adaptation and mitigation plans for southern Madagascar.

Water controls the divergent responses of terrestrial plant photosynthesis under nitrogen enrichment

Abstract Quantifying leaf photosynthetic response to nitrogen (N) deposition under contrasting water conditions is important for reliably modelling terrestrial carbon and water cycles, a topic that has not been well understood. Here, we analysed 737‐paired observations from 102 publications to assess the response of 11 leaf photosynthesis‐related properties to N addition under different water conditions. Our research includes global experiments, with 19 conducted in the field and 83 in greenhouses. Treatments without water reduction were classified as ‘no water change’, while those with reduced water or precipitation causing physiological drought were categorized as ‘drought’. We found that, compared to the control group, N addition significantly increased leaf photosynthetic rate (Pn; 20.9%), leaf transpiration (E; 8.3%) and stomatal conductance (gs; 14.1%). However, the decrease in Pn (−11.6%), E (−24.7%) and gs (−23.9%) under the combination of N addition and drought indicated that N addition could not offset the negative effects of drought. Furthermore, N addition significantly enhanced water‐use efficiency (WUE) by 19.8% under no water change conditions and by 21.1% under drought conditions. Within plant functional groups, herbaceous species exhibited greater susceptibility to N addition than woody species, especially under drought conditions. The observed patterns of increase in Pn with longer experimental duration and WUE with higher N rate under drought conditions showed that plants would gradually adapt to long‐term water stress in the context of N deposition. Furthermore, our results showed that drought could strengthen the correlations between leaf photosynthetic properties. Lastly, our study demonstrated that N addition and drought significantly impacted leaf nitrogen content and SPAD, respectively, and further affected gs, Pn and WUE. Synthesis. Our results emphasize the crucial role of water conditions in shaping the response of leaf photosynthesis to nitrogen (N) enrichment and also acknowledge the significance of leaf functional traits in regulating the dynamics of leaf photosynthetic processes.

Early leaf senescence under drought conditions in the Northern hemisphere

Changes in the dates of autumn foliar senescence (DFS) have significant impacts on regional carbon uptake, while current approaches for the estimation of DFS are still lacking. The most important issue is that there are complicated factors that affect the DFS, among which drought effects probably have contributed the most. Using long-term DFS observations derived from the third-generation normalized difference vegetation index dataset (NDVI3g), we found a wider spread of earlier DFS trends over the Northern Hemisphere from 1999 to 2015, three times larger than that from 1982 to 1998. The five multivariate analysis of variance approaches consistently suggest the key role of drought in regulating these changes. We therefore derived a new DFS algorithm with the standardized precipitation evapotranspiration index (SPEI) to characterize these drought effects, and validations from both NDVI3g and MODIS data demonstrated that our new algorithm provided significantly improved estimates of DFS for all plant functional types, with higher accuracy for water-limited ecosystems. We further applied this new algorithm to predict DFS under various shared socioeconomic pathways (SSPs) by the end of this century, and we found overall earlier DFS than the current expectations. Our results therefore highlight the importance of drought in the modeling of plant phenology using remote sensing observations and thus are highly important for understanding the relationships between land carbon sinks and climate change, especially given that droughts are projected to be more severe and frequent in the future.

Enhanced effects of species richness on resistance and resilience of global tree growth to prolonged drought

The increasing duration of drought induced by global climate change has reduced forest productivity. Biodiversity is believed to mitigate the effects of drought, thereby enhancing the stability of tree growth. However, the effects of species richness on tree growth stability under droughts with different durations remain uncertain. Here, we used tree ring data from 4,072 sites globally, combined with climate and plant richness data, to evaluate the effects of species richness on the resistance and resilience of trees to short-term and prolonged droughts. We found that species richness enhanced resistance but weakened resilience of trees to drought globally. Compared to short-term drought, species richness further increased tree growth during prolonged drought but reduced the growth afterward, resulting in stronger effects on resistance and resilience. In addition, as the degree of drought intensified and regional aridity levels increased, the effects of richness on resistance and resilience under short-term drought were enhanced, but these trends were reduced or even reversed under prolonged drought. These results reveal the global effects of species richness on resistance and resilience of tree growth to droughts with different durations and highlight that species richness plays a crucial role in resisting prolonged drought.

Global Health Emergencies of Extreme Drought Events: Historical Impacts and Future Preparedness

Global Health Emergencies of Extreme Drought Events: Historical Impacts and Future Preparedness

Human activities increased compound drought and heat events over China during 1961–2014

AbstractCompared to independent drought or extreme heat events, compound drought and heat events (CDHEs) can pose more adverse impacts on ecosystems and human society. As the anthropogenic influence on CDHEs in China remains largely unquantified, we analyse both observed and simulated changes in the occurrence of CDHEs over China from 1961 to 2014, and perform detection and attribution analyses utilizing an optimal fingerprinting method, based on observations, reanalysis data and numerical experiments from seven Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Upward trends are found in observed CDHEs during 1961–2014 over the majority of China, especially in the last two decades. The increase in CDHEs is largely attributed to human influence. Anthropogenic forcing is detectable in the observed CDHEs changes in the whole China and its eastern region. Furthermore, a three‐signal analysis indicates that greenhouse gases play a key role in increasing CDHEs over China, while natural forcing has a negligible effect. Anthropogenic aerosol emissions also play a detectable role in offsetting the greenhouse gas‐induced increase of CDHEs over China.

Biostimulators with marine algae extracts and their role in increasing tolerance to drought stress in highbush blueberry cultivation

Drought is one of the most serious challenges facing agriculture and ecosystems around the world. With more frequent and more extreme weather events, the effects of drought are becoming more severe, leading to yield losses, soil depletion and environmental degradation. In this work, we present an analysis of the impact of a marine algae biostimulanat andits ability to offset the effects of drought stress in blueberry cultivation. The aim of the research was to evaluate various fertilisation programs in increasing plant resistance to abiotic stress such as drought. It was tested whether the algal biostimulator provides the same tolerance to drought stress in highbush blueberry plants as regular fertilisers without biostimulation. The research was conducted in 2022 in a greenhouse in controlled drought conditions. Three-year-old highbush blueberry bushes (12 pieces) were used in the experiment. Highbush blueberry bushes (Vaccinium corymbosum) ’Brigitta Blue’ varieties were planted in plastic pots with a capacity of 10 dm3 containing an acidic substrate and placed in a greenhouse. Controlled lighting conditions were maintained using sodium lamps and a temperature of 25°C/20°C day/night. The substrate in pots was maintained at 80% of field water capacity by manual watering and weekly supply of nutrient solution for 5 weeks until water deficit occurred. Half of the plants were sprayed weekly with biostimulant at a concentration of 1%, three times 1 week apart (1 application per week). The biostimulant was evenly applied to the entire plant. Seven days after the third application of the product, half of the unsprayed and sprayed plants were subjected to water deficit stress by holding thewatering until 40% of the field water capacity (FC) was reached. The experimental layout included four combinations: C—Control—no biostimulation, no water deficit; CS—Stress control—water deficit up to 40% FC, no biostimulation; B—Biostimulator—no water deficit, biostimulation; BS—Stress plus biostimulator—water deficit up to 40% FC, biostimulation. Fertilisers with seaweed extracts show the ability to reduce the adverse effects of stress, promoting plant resilience, including tolerance to drought stress. The following were evaluated in the experiment: catalase activity, peroxidase activity, free malondialdehyde content, photosynthetic activity and leaf mineral content. The biostimulant used in experiment increased the oxidative activity of the enzymes pe-roxidase and catalase under simulated drought stress conditions. The algal biostimulant increased the average value of catalase activity by 20% in comparison to the control plants, in both combinatinations. The tested biostimulator had no effect on the chlorophyll content in the leaves or the concentration of nutrients in the leaves. The effect of marine algae products on the yield quantity and high quality is related among other to bioactive substances which helps to prevent drought stress.

Extreme drought events and land surface temperature variations on the northeastern Tibetan Plateau over the last 350 ka

The northeastern Tibetan Plateau (NETP) is located in the ecologically vulnerable northwestern China, with semi-humid and semi-arid conditions. Long-term paleo-hydrological and paleo-temperature variations and their mechanisms over the NETP remain ambiguous, primarily due to the limited availability of well-dated, long-term depositional archives and suitable proxies. In this paper, we investigate climate variations and their underlying mechanisms in the region using Glycerol Dialkyl Glycerol Tetraethers (GDGTs) spanning the last 350 ka. Our results suggest that the NETP underwent substantial drying during glacial periods, with the driest period occurring during the last glacial period. The intensity of drought during glacial periods is comparable to that in the Westerlies-dominated region but differs from that in the East Asian monsoon region. This suggests that the influence of the Westerlies surpassed that of the East Asian summer monsoon (EASM), becoming the major driver of warm-season drought events on the NETP during glacial periods. Additionally, the peaks of aridity events coincide with summer insolation maxima during glacial periods, which may be related to the direct influence of local insolation on regulating evaporation. The reconstructed land surface temperatures were about 6.7 °C during interglacial periods and 2.6 °C during glacial periods, which may be linked to a combination of variations in insolation, CO2 levels, and other internal feedback mechanisms. However, an unusual warming occurred during the last glaciation, with an average temperature of about 4.8 °C. This warming may be related to variations in soil moisture and vegetation resulting from extreme drought. Our study highlights the sensitivity of hydrological variations over the NETP to insolation and Westerlies, as well as the critical roles of soil moisture and vegetation in land surface temperature variations.

Cumulative and Lagged Effects: Seasonal Characteristics of Drought Effects on East Asian Grasslands

With the acceleration of global warming, droughts are expected to both intensify and become more frequent. More so than forests, the productivity of grasslands is largely controlled by soil moisture and is highly susceptible to drought. Drought can impact grasslands though the effects may lag and accumulate over time. Because prior research has mainly focused on the annual or growing season scale, it remains unclear whether there are seasonal differences in the cumulative and lagged effects (CALEs) of drought. This study uses Normalized Difference Vegetation Index (NDVI) and Standardized Precipitation Evapotranspiration Index (SPEI) data to explore the seasonal characteristics of the CALEs of drought on grassland growth in East Asia from 2001 to 2020. The main results include the following: (1) More than 40% of grasslands are significantly affected by the CALEs of drought for all three seasons (spring, summer, and autumn). (2) Grasslands are more sensitive to the CALEs of drought in summer. The spatial variability of the cumulative time scale is the greatest in spring, whereas the spatial variability of the lagged time scale is the greatest in summer. The lag time scale gradually shortens as moisture decreases in summer and autumn but shows an inverted U-shape in spring. As drought conditions intensify, the cumulative time scale gradually increases in spring and autumn, while gradually decreasing in summer. (3) The dominant drought effects vary among different seasons: the lagged effect (LE) predominates in spring and autumn, whereas in summer it is the cumulative effect (CE) that dominates. The LE exceeds the CE in 54.89% of the study area during the growing season. We emphasize that annual- or growing season-scale studies of drought CE and LE may obscure seasonal response characteristics. Given the seasonal nature of droughts and the seasonally varying sensitivities of grassland growth to these droughts, the impacts on vegetation fluctuate significantly across different seasons. The results help us more accurately predict grassland ecosystem changes under the background of global warming and the increasing probability of severe drought, providing important reference values for future grassland ecological protection and planning.

Effect of Drought and Rehydration on Physiological Characteristics of Agriophyllum squarrosum (L.) Moq. in Different Habitats.

Agriophyllum squarrosum (L.) Moq. is a highly prevalent xerophytic species found throughout northern China. It is suitable for cultivation in semi-arid sandy environments and may establish roots in arid desert locations. This species plays a pioneering and exploratory role in the colonization of desert plants. In this study, we selected A. squarrosum from the Urat desert steppe (UD) and Horqin sandy land (HS) to explore their adaptation mechanisms to drought and rehydration environments by using the pot weighing control method to simulate an arid environment. The findings showed that the control (watering to 60-65% of field capacity) exceeded its required amount and the leaves turned yellow. The chlorophyll content was lower than those under moderate and severe drought, and rehydration caused a decrease. However, the contents of malondialdehyde, soluble sugar, and proline in the drought treatment were higher than those in the control. Under moderate and severe drought, the chlorophyll content and the quantum efficiency of photosystem II (Fv/Fm) of A. squarrosum from UD were higher than those from HS. During drought and rehydration processes, the proline content was relatively lower, while the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) and the content of soluble sugar and soluble protein were higher. However, antioxidant enzymes and osmoregulators from UD were higher than those from HS. The results suggest that the stronger ability of A. squarrosum to endure drought environments in UD is due to the high level of antioxidant enzymes and osmoregulators, which are conducive to relieving cell membrane damage when subjected to drought and rehydration.

Fat storage and drought tolerance in a seasonally‐adapted primate: Implications for modeling the effects of animal responses to global climate change

AbstractGlobal warming is changing habitats and affecting biodiversity, and is expected to exacerbate aridification in many regions. Animals and plants in seasonally dry tropical forests often exhibit adaptations to cope with seasonal resource limitation. However, whether these adaptations will facilitate drought tolerance or increase drought vulnerability is unclear. Here, we combine long‐term individual‐based data on phenology, morphometrics, and demographics to investigate how drought impacts the food resources, health, reproduction, and behavior of a population of Verreaux's sifaka (Propithecus verreauxi), a critically endangered lemur inhabiting dry deciduous forests in Madagascar. Between December 2010 and May 2023, the population experienced 3 years of severe drought (2016, 2017, 2022). During green periods in severe drought, the availability of high‐quality sifaka foods (young leaves, fruit) was significantly reduced and fruit tree mortality increased. This reduced availability of fruit persisted in the year after a drought, despite typical rainfall. Yet surprisingly, we found no negative effects on body condition or commonly‐used metrics for reproductive success during drought years or years following a drought. Instead, sifaka exhibited significantly higher levels of subcutaneous body fat during severe droughts. We observed little change in sifaka behavior between drought and non‐drought periods. However, they were more likely to lick dew during severe drought, and spent significantly less time feeding on young and mature leaves. They also significantly increased their time feeding on flowers and fruits, despite the reduced abundance of fruit in the habitat. Together, our results suggest that increased consumption of water‐rich fruit and flowers during severe droughts could facilitate physiological mechanisms that help sifaka cope with water scarcity, including fructose‐mediated fat storage, metabolic water production, and water conservation. These results provide new insights into how critically endangered animals may respond to climate change, suggesting that behavioral and physiological adaptations to seasonal resource limitation may buffer some mammals from the effects of severe drought or other extreme weather events.

Drought impairs detritivore feeding activity more strongly in northern than in southern European latitudes

Soil detritivores play key roles in decomposition processes closely related to ecosystem services. Drought and soil organic carbon depletion due to agricultural management are detrimental to soil biodiversity, but their interactive effects on soil biota and associated processes have not been thoroughly investigated. In 2018, we used rain-out shelters to experimentally induce drought in wheat fields of contrasting levels of organic carbon in Sweden, Germany and Spain. That year Europe experienced a climatic dipole, with exceptionally severe droughts in northern latitudes. We assessed the feeding activity of soil detritivores by bait-lamina tests, and measured several abiotic and biotic soil parameters. In the peak of the dipole drought (summer) southern fields had the driest soils. Nonetheless, detritivore feeding activity responded to the experimental drought by shifting to deeper soil layers there. Low soil organic carbon (SOC) levels exacerbated the latter effect. However, in this same period, feeding activity in northern and central Europe was two orders of magnitude lower than in the south, and failed to respond to either the experimental treatment and/or SOC levels. Using mixed-effects longitudinal random forests, we detected various candidate drivers of detritivore feeding activity: soil moisture, phosphorus content, bacteria and nematodes. Different bacterial taxa were associated to detritivory in each country, but their potential influence was pervasive. Thus, our results suggest that drought had adverse effects on detritivore feeding, which were exacerbated northwards due to the climatic dipole. Increased SOC levels mitigated drought effects only in southern soils. Regional adaptation of soil biota to aridity could explain the response of detritivores in southern Europe to drought. Machine learning algorithms arise as useful tools for exploring potential drivers relating biodiversity to soil processes. Overall, future research on the effects of drought on soil biodiversity and processes will be key for tackling climate change impacts in terrestrial ecosystems.

Mitigating the negative effects of droughts on alpine grassland productivity in the northern Xizang Plateau via degradation-combating actions

The Qinghai-Xizang Plateau, hosting the world’s largest alpine pastures, plays a pivotal environmental role in Asia. These ecosystems face alterations driven by both climate change and anthropogenic activities, resulting in the widespread consideration of grassland degradation. From 2000 to 2020, the northern Xizang Plateau experienced a pronounced escalation in drought conditions, particularly following a management policy aimed at combating grassland degradation, via restricting livestock numbers and implementing fencing enclosures, initiated in 2009. Specially, following the enforcement of this policy (2010–2020), there was a substantial 13.5 % reduction in soil moisture levels compared to the pre-implementation period (2000–2009), accompanied by a 42.8 % increase in drought severity (measured by the Palmer Drought Severity Index, PDSI) and an 11.6 % rise in drought duration. Under these challenging drought conditions, we identified negative trends of potential grassland Net Primary Productivity (NPP) which in absence of anthropogenic influence, as simulated by terrestrial ecosystem model (TEM). Contrary to this simulation, satellite time series observations revealed a widespread increase in actual grassland productivity. Remarkably, despite the challenging drought conditions between 2010 and 2020, we observed a substantial increase of 4.8 % in actual NPP (measured by light use efficiency model), 2.7 % in Normalized Difference Vegetation Index (NDVI), 10 % in solar-induced chlorophyll fluorescence (SIF), and 7.95 % in Gross Primary Productivity (GPP), respectively. Much of this enhancement in grassland productivity occurred in areas where livestock populations had markedly declined. Notably, the percentage of NPP increase mainly caused by degradation-combating actions doubled from 24.8 % during 2000–2009 to 49.8 % during 2010–2020 across the northern Xizang Plateau. In conclusion, our findings highlight the potential of large-scale degradation-combating actions to mitigate the negative impacts of climate change and contribute to a greener Earth.

Assessment and pre-assessment of compound hot and drought events over Yangtze River Basin

Abstract The severe compound hot and drought event (CHDE) in 2022 had serious impacts on water resources, agriculture, power supply, and ecosystems in the Yangtze River Basin (YRB). Have similar spatiotemporally overlapping compound events, like the one observed in 2022, occurred historically in the basin? How can we pre-assess the impacts of such potential events on subseasonal timescales? To address these, regional CHDEs in the YRB since 1961 were systematically identified and comprehensively assessed using a modified Intensity-Area-Duration (IAD) technique and hazard assessment method. Additionally, the subseasonal pre-assessment capability for CHDEs in the YRB using the China Meteorological Administration's third-generation climate model prediction system (CPSv3-S2S) was demonstrated. A total of 140 CHDEs occurred during 1961 to 2022, with the 21st century showing a remarkably high risk of such events. Among these, 2022 was the most intense year, with the event from July 26th to August 30th being unprecedented in severity. CPSv3-S2S effectively forecast this event’s occurrence within a 1-25 lead days, particularly in pre-assessing its extensively impacted area and high-hazard centers in the upper and middle reaches of the main river course. This pre-assessment method serves as a valuable reference in decision-making to anticipate and mitigate risks of hydropower supply shortages and heightened electricity demand during extremely high temperatures in the upstream area.

Seasonal Variability and Hydrological Patterns Influence the Long-Term Trends of Nutrient Loads in the River Po

This study investigates the long-term trends (1992–2022) of nitrogen and phosphorus loadings exported by the River Po to the Adriatic Sea, to better analyse how changes in hydrology are affecting the timing and magnitude of river nutrient loads. We used 30 years of monitoring data in order to (a) identify the main temporal patterns and their interactions at a decadal, annual and seasonal scale, (b) estimate precipitation effects on load formation and evaluate whether and to which extent the hydrological regime affects nutrient export across the years and (c) analyse the nutrient export regime at a monthly scale and the main transport dynamic of N and P chemical species (hydrological vs. biogeochemical control). The long-term analysis shows a general decrease of both P and N loadings, but the trends are different between the elements and their chemical species, as well as undergoing different seasonal variations. We found a statistically significant relationships between precipitation and loads, which demonstrates that precipitation patterns drive the exported load at the intra- and interannual time scales considered in this study. Precipitation-induced load trends trigger seasonal changes in nutrient deliveries to the sea, peaking in spring and autumn. The nitrogen decrease is mainly concentrated in the summer dry period, while total phosphorus diminishes mainly in spring and autumn. This mismatch of N and P results in variable molar N:P ratios within the year. The effects of extreme drought and flood events, along with the progressive decrease in the snowmelt contribution to water fluxes, are expected to exacerbate the variability in the N and P loadings, which in turn is expected to perturbate the biodiversity, food webs and trophic state of the Northern Adriatic Sea.

Gleaning Rural Journalism: Rural Journalists' Agricultural and Environmental Reporting Utilizing Community Storytelling Networks☆

AbstractEnvironmental concerns are growing in parts of the rural United States as drinking water wells become contaminated with agrichemicals, and climate change impacts such as drought and extreme rain events disrupt farming practices. Analyzing in‐depth interviews with 29 U.S. rural journalists, we explore the role rural journalists play when reporting on the environment as it relates to agricultural issues. Findings show that reporting about the environment—such as weather, climate change, water shortages, and droughts—appear in rural journalists' stories given those topics' relevance to their rural communities and the social systems forces exerting influence on journalists, yet rural journalists often do not perceive themselves as doing environmental reporting. Rural journalists also report lacking training and resources to do environmental reporting. This study points to the need for more support for rural journalists' environmental reporting as one way to build social change and maintain local community.

Assessing the impact of turnip yellows virus infection and drought on canola performance: implications under a climate change scenario

IntroductionCanola (Brassica napus L.) is one of the most important crops worldwide. Turnip yellows virus (TuYV), transmitted by aphids, is one of the most damaging viruses affecting canola crops and is challenging to control. With the prediction of more intense and prolonged drought events due to future climate change, an additional factor may extensively impact the epidemiology of plant diseases. This study aimed to understand the impact of drought on canola plants infected with TuYV and to explore the relationship between virus infection and drought.MethodsTwo glasshouse experiments were conducted: 1. Competition: Four plants (two infected, two non-infected) were grown in the same pot. 2. No Competition: One plant was grown per pot. In both experiments, infected and non-infected canola plants were exposed to well-watered conditions, water stress (simulated drought), and terminal drought. Various plant traits were recorded, including biomass, leaf area, height, number of leaves, chlorophyll content, water use efficiency, and virus symptom expression.ResultsBoth virus infection and water stress reduced dry biomass, leaf area, and height. Virus infection alone reduced canola biomass by up to 49% compared to non-infected, well-watered controls. Under water stress or terminal drought, the biomass of TuYV-infected plants was further reduced by up to 71% and 65%, respectively. Virus infection also reduced the number of leaves, although water treatment alone did not. Chlorophyll content was higher in water-stressed and terminal drought plants compared to well-watered ones, while virus infection reduced chlorophyll content. The impact of drought and virus infection was more pronounced when plants were under competition.DiscussionGiven the expected increase in prolonged and frequent droughts in many canola-growing regions due to climate change, a significant detrimental effect on canola production due to the combined influence of drought and TuYV is anticipated. This study underscores the need for developing mitigation strategies to protect canola production in a changing climate.

Interannual Variation of Summer Compound Hot and Drought Events in Xinjiang and Its Relationship with the North Atlantic Sea Surface Temperature

Abstract Xinjiang suffers compound hot and drought events under global warming. However, less attention has been paid to physical mechanisms of the variability of compound hot and drought events in this region. This article investigates the interannual variation of summer (June–August) compound hot and drought events in Xinjiang and its relationship with the sea surface temperature (SST) over the North Atlantic. The results show that its first empirical orthogonal function (EOF) mode features a spatially homogenous pattern. This mode is closely connected with the simultaneous meridional negative–positive–negative SST anomalies over the North Atlantic. The summer North Atlantic tripole SST anomalies can trigger a remarkable wave train extending from the North Atlantic to Eurasia, consequently inducing an anomalous high pressure system over the Iran–Pamir Plateau, which is conducive to the increase in air temperature from the surface to the upper troposphere over Xinjiang. The warmer troposphere further strengthens the western Asian subtropical meridional temperature gradient and thereby enhances the westerly wind to the north flank of the West Asian subtropical westerly jet (WASWJ). As a result, the WASWJ is displaced northward, which intensifies the sinking motion and prevents the water vapor transport to Xinjiang, leading to a decrease in precipitation in the target region. The higher temperature and less precipitation contribute to the occurrence of compound hot and drought events over Xinjiang. Numerical simulations based on the Community Atmosphere Model, version 4 (CAM4), further confirm the relationship between the North Atlantic tripole SST anomalies and compound hot and drought events in Xinjiang during summer on the interannual time scale. Significance Statement Xinjiang, located in northwest China, suffers from frequent and intense compound hot and drought events in recent decades. It is thus urgent to understand the physical mechanisms associated with its occurrence in order for disaster prevention and mitigation. In this study, we reveal that the leading mode of summer compound hot and drought events over Xinjiang, featuring a spatially homogenous pattern, is closely correlated with the simultaneous meridional negative–positive–negative SST anomalies over the North Atlantic. The North Atlantic tripole SST anomalies can lead to an anomalous high pressure system over the Iran–Pamir Plateau and a northward shift of the West Asian subtropical westerly jet through exciting a wave train propagating from the North Atlantic to Eurasia, which consequently contributes to the occurrence of compound hot and drought events over Xinjiang.

UV-C Priming Enhances Water Stress Tolerance in Broccoli (Brassica Oleracea, L.) and Its Germination Rate

Germination of broccoli seeds exposed to UV-C radiation (priming) for a 30-minute period and tolerance to water stress was evaluated. These findings suggest that the adverse effect of drought on the germination rate can be circumvented by seeds primed with a UV-C radiation at a wavelength of 254 nm during 30 min.