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The response of evapotranspiration (ET) to drought is essential for understanding water availability under drought conditions, which has received increasing scientific attention but remains highly uncertain. An unprecedented extreme drought sweeping the whole Yangtze River Basin during the summer and autumn of 2022 provides a novel opportunity to explore the ET response to drought within large river basins. Here, we apply multiple ET products to investigate the spatiotemporal variation of ET during the 2022 extreme drought and analyse the response of ET to drought in the Yangtze River Basin. The results show that this drought, characterized by widespread substantial precipitation deficit and high level of atmospheric evaporative demand (AED), leads to evident abnormal ET. Over the whole basin, ET exhibits a notable increase in the initial 2 months of this drought, which can significantly reduce water availability. However, despite continued high AED, the increase in ET fails to remain in the following months due to limited moisture supply. This suggests that ET response to drought varies as drought progresses. Among other drought events from 2003 to 2022, the response of ET is similar to that in the 2022 extreme drought. Specifically, for most sub‐basins, ET typically shows positive anomalies in the early stage of drought, followed by negative anomalies in the late stage. Generally, our findings improve the understanding of the dynamic response of ET to drought at the basin scale, which is crucial for basin water security. [ABSTRACT FROM AUTHOR]

Polyploid is considered an advantage that has evolved to be more environmentally adaptable than its diploid. To understand if doubled chromosome of diploid rice can improve drought tolerance, we evaluated the diploid (2X) and autotetraploid (4X) plants of three indica and three japonica varieties. Drought stress in the plastic bucket of four-leaf stage revealed that the drought tolerance of 4X plants was lower than that of its diploid donor plants. The assay of photosynthetic rate of all varieties showed that all 4X varieties had lower rates than their diploid donors. The capacity for reactive oxygen species production and scavenging varied among different 2X and 4X varieties. Further, transcriptomic analysis of 2X and 4X plants of four varieties under normal and drought condition showed that the wide variation of gene expression was caused by difference of varieties, not by chromosome ploidy. However, weighted gene co-expression network analysis (WGCNA) revealed that the severe interference of photosynthesis-related genes in tetraploid plants under drought stress is the primary reason for the decrease of drought tolerance in autotetraploid lines. Consistently, new transcripts analysis in autotetraploid revealed that the gene transcription related with mitochondrion and plastid of cell component was influenced most significantly. The results indicated that chromosome doubling of diploid rice weakened their drought tolerance, primarily due to disorder of photosynthesis-related genes in tetraploid plants under drought stress. Maintain tetraploid drought tolerance through chromosome doubling breeding in rice needs to start with the selection of parental varieties and more efforts. [ABSTRACT FROM AUTHOR]

Background: Drought is a leading environmental factor affecting plant growth. To explore the drought tolerance mechanism of asparagus, this study analyzed the responses of two asparagus varieties, namely, 'Jilv3' (drought tolerant) and 'Pacific Early' (drought sensitive), to drought stress using metabolomics and transcriptomics. Results: In total, 2,567 and 7,187 differentially expressed genes (DEGs) were identified in 'Pacific Early' and 'Jilv3', respectively, by comparing the transcriptome expression patterns between the normal watering treatment and the drought stress treatment. These DEGs were significantly enriched in the amino acid biosynthesis, carbon metabolism, phenylpropanoid biosynthesis, and plant hormone signal transduction pathways. In 'Jilv3', DEGs were also enriched in the following energy metabolism-related pathways: citrate cycle (TCA cycle), glycolysis/gluconeogenesis, and pyruvate metabolism. This study also identified 112 and 254 differentially accumulated metabolites (DAMs) in 'Pacific Early' and 'Jilv3' under drought stress compared with normal watering, respectively. The amino acid, flavonoid, organic acid, and soluble sugar contents were more significantly enhanced in 'Jilv3' than in 'Pacific Early'. According to the metabolome and transcriptome analysis, in 'Jilv3', the energy supply of the TCA cycle was improved, and flavonoid biosynthesis increased. As a result, its adaptability to drought stress improved. Conclusions: These findings help to better reveal the molecular mechanism underlying how asparagus responds to drought stress and improve researchers' ability to screen drought-tolerant asparagus varieties as well as breed new varieties. [ABSTRACT FROM AUTHOR]

This study introduces a novel Hybrid Ensemble Machine-Learning (HEML) algorithm to merge long-term satellite-based reanalysis precipitation products (SRPPs), enabling the estimation of super drought events in the Lake Victoria Basin (LVB) during the period of 1984 to 2019. This study considers three widely used Machine learning (ML) models, including RF (Random Forest), GBM (Gradient Boosting Machine), and KNN (k-nearest Neighbors), for the emerging HEML approach. The three SRPPs, including CHIRPS (Climate Hazards Group Infra-Red Precipitation with Station), ERA5-Land, and PERSIANN-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Network-Climate Data Record), were used to merge for developing new precipitation estimates from HEML model. Additionally, classification and regression models were employed as base learners in developing this algorithm. The newly developed HEML datasets were compared with other ML and SRPP products for super-drought monitoring. The Standardized precipitation evapotranspiration index (SPEI) was used to estimate super drought characteristics, including Drought frequency (DF), Drought Duration (DD), and Drought Intensity (DI) from machine learning and SRPPs products in LVB and compared with RG observation. The results revealed that the HEML algorithm shows excellent performance (CC = 0.93) compared to the single ML merging method and SRPPs against observation. Furthermore, the HEML merging product adeptly captures the spatiotemporal patterns of super drought characteristics during both training (1984–2009) and testing (2010–2019) periods. This research offers crucial insights for near-real-time drought monitoring, water resource management, and informed policy decisions. [ABSTRACT FROM AUTHOR]

Evaluating drought parameters at the basin level is one of the fundamental processes for planning sustainable crop production. This study aimed to evaluate both short-term and long-term meteorological drought parameters within the Vaippar Basin, located in southern India, by employing the standardized precipitation index (SPI). Gridded rainfall values developed from 13 rain gauge stations were employed to calculate the SPI values. Drought parameters, encompassing occurrence, intensity, duration, frequency, and trends, were assessed for both short-term and long-term droughts. The study findings indicated that the occurrence of short-term drought was 51.7%, while that of long-term drought was 49.82%. Notably, the basin experienced extreme short-term droughts in 1980, 1998 and 2016 and long-term droughts in 1981, 2013, and 2017. Utilizing an innovative trend identification method for SPI values, a significant monotonic upwards trend was identified in October and December for short-term drought and in December for long-term drought. This study defined the minimum threshold rainfall, which represents the critical amount required to prevent short-term drought (set at 390 mm) and long-term drought (set at 635 mm). The drought severity recurrence curves developed in this study indicate that when the SPI values fall below − 1.0, short-term drought affects 25% of the basin area, while long-term drought impacts 50% of the basin area at a 20-year recurrence interval. Additionally, the drought hazard index (DHI), which combines drought intensity and severity, demonstrated higher values in the northwestern regions for short-term drought and in the southern areas for long-term drought. The study's findings, highlighting areas of drought vulnerability, severity, and recurrence patterns in the basin, direct the attention for timely intervention when drought initiates. [ABSTRACT FROM AUTHOR]

In a gene chip analysis, rice (Oryza sativa) OsSMP2 gene expression was induced under various abiotic stresses, prompting an investigation into its role in drought resistance and abscisic acid signaling. Subsequent experiments, including qRT–PCR and β-glucuronidase activity detection, affirmed the OsSMP2 gene's predominant induction by drought stress. Subcellular localization experiments indicated the OsSMP2 protein primarily localizes to the cell membrane system. Overexpressing OsSMP2 increased sensitivity to exogenous abscisic acid, reducing drought resistance and leading to reactive oxygen species accumulation under drought stress. Conversely, in simulated drought experiments, OsSMP2 -silenced transgenic plants showed significantly longer roots compared with the wild-type Nipponbare. These results suggest that OsSMP2 overexpression negatively affects rice drought resistance, offering valuable insights into molecular mechanisms, and highlight OsSMP2 as a potential target for enhancing crop resilience to drought stress. [ABSTRACT FROM AUTHOR]

Drought stress is a prominent abiotic factor that adversely influences the growth and development of Bupleurum chinense during its seedling stage, negatively impacting biomass and secondary metabolite production, thus affecting yield and quality. To investigate the molecular mechanism underlying the response of B. chinense seedlings under drought stress, this study employed comprehensive physiological, transcriptomic, and metabolomic analyses. The results revealed that under drought stress, the root soluble sugar and free proline content in B. chinense seedlings significantly increased, while the activities of SOD, POD, and CAT increased in the leaves. These findings indicate the presence of distinct response mechanisms in B. chinense to cope with drought stress. Integrated analysis further identified significant correlations between genes and metabolites related to amino acid biosynthesis in the leaves, as well as genes and metabolites associated with acetaldehyde and dicarboxylic acid metabolism. In the roots, genes and metabolites related to plant hormone signaling and the tricarboxylic acid (TCA) cycle showed significant correlations. These findings provide vital views into the molecular-level response mechanisms of B. chinense under drought stress. Moreover, this study establishes the groundwork for identifying drought-tolerant genes and breeding drought-resistant varieties, which could improve the drought tolerance of medicinal plants and have broader implications for agriculture and crop production in water-scarce areas. [ABSTRACT FROM AUTHOR]

Improving the drought resistance of rice is of great significance for expanding the planting area and improving the stable yield of rice. In our previous work, we found that ROLLED AND ERECT LEAF1 (REL1) protein promoted enhanced tolerance to drought stress by eliminating reactive oxygen species (ROS) levels and triggering the abscisic acid (ABA) response. However, the mechanism through which REL1 regulates drought tolerance by removing ROS is unclear. In this study, we identified REL1 interacting protein 5 (RIP5) and found that it directly combines with REL1 in the chloroplast. We found that RIP5 was strongly expressed in ZH11 under drought-stress conditions, and that the rip5-ko mutants significantly improved the tolerance of rice plants to drought, whereas overexpression of RIP5 resulted in greater susceptibility to drought. Further investigation suggested that RIP5 negatively regulated drought tolerance in rice by decreasing the content of ascorbic acid (AsA), thereby reducing ROS clearance. RNA sequencing showed that the knockout of RIP5 caused differential gene expression that is chiefly associated with ascorbate and aldarate metabolism. Furthermore, multiple experimental results suggest that REL1 is involved in regulating drought tolerance by inhibiting RIP5. Collectively, our findings reveal the importance of the inhibition of RIP5 by REL1 in affecting the rice's response to drought stress. This work not only explains the drought tolerance mechanism of rice, but will also help to improve the drought tolerance of rice. [ABSTRACT FROM AUTHOR]

Vineyards and olive groves are two of the most important Mediterranean crops, not only for their economic value but also for their cultural and environmental significance, playing a crucial role in global agriculture. This systematic review, based on an adaptation of the 2020 PRISMA statement, focuses on the use of satellite remote sensing tools for the detection of drought in vineyards and olive groves. This methodology follows several key steps, such as defining the approach, selecting keywords and databases, and applying exclusion criteria. The bibliometric analysis revealed that the most frequently used terms included "Google Earth Engine" "remote sensing" "leaf area index" "Sentinel-2", and "evapotranspiration". The research included a total of 81 articles published. The temporal distribution shows an increase in scientific production starting in 2018, with a peak in 2021. Geographically, the United States, Italy, Spain, France, Tunisia, Chile, and Portugal lead research in this field. The studies were classified into four categories: aridity and drought monitoring (ADM), agricultural water management (AWM), land use management (LUM), and water stress (WST). Research trends were analysed in each category, highlighting the use of satellite platforms and sensors. Several case studies illustrate applications in vineyards and olive groves, especially in semi-arid regions, focusing on the estimation of evapotranspiration, crop coefficients, and water use efficiency. This article provides a comprehensive overview of the current state of research on the use of satellite remote sensing for drought assessment in grapevines and olive trees, identifying trends, methodological approaches, and opportunities for future research in this field. [ABSTRACT FROM AUTHOR]

Monitoring drought stress is crucial for estimating productivity and assessing the health status of forest ecosystems under global climate change. Solar-induced chlorophyll fluorescence (SIF) is mechanistically coupled to photosynthesis and has advantages over greenness-based vegetation indices in detecting drought. In recent years, SIF has commonly been used in monitoring drought stress in crop ecosystems. However, the response of tower-based SIF to drought stress in forest ecosystems remains unclear. In this study, we investigated the potential of tower-based SIF to monitor drought, which was quantified using the plant water stress index (PWSI) in a Chinese cork oak plantation. The results show the negative effect of drought on SIF, and afternoon depression of SIF emission under drought stress was observed. Canopy SIF (F) exhibited a nonlinear relationship with PWSI, while the quantum yield of SIF (ΦF) exhibited a significant linear relationship with PWSI at 687 nm and 760 nm (ΦF687: R2 = 0.90; ΦF760: R2 = 0.85). Incident radiation (PAR) and canopy structure affected the response of SIF to drought stress, with PAR as the main factor causing the nonlinear relationship between F and PWSI. Afternoon depression was described as the afternoon/morning ratio (AMR). AMRF and AMRΦF exhibited a negative linear response to PWSI. AMRF was less affected than F by PAR and canopy structures, and AMRΦF was more physiologically representative than ΦF. Moreover, AMRΦF was sensitive to VPD and REW, and it might be a good indicator of drought. Red SIF was more sensitive to drought than far-red SIF, as the R2 of PWSI with AMRΦF687 (R2 = 0.89) was higher than that with AMRΦF687 (R2 = 0.84). These results highlight the potential of tower-based SIF, especially red SIF, for drought monitoring in a plantation, and consideration of the physiological diurnal variation in SIF under drought stress is crucial for improving the accuracy of drought stress monitoring. [ABSTRACT FROM AUTHOR]

Red chili pepper Capsicum annuum L. var. annuum plants are one of the fruity vegetable types that are often cultivated in riparian tropical wetlands but are constrained by water stress such as waterlogging during rainy season and drought in dry season. The aim of this research was to evaluate the growth and morphophysiological responses of red chili pepper cultivars subjected to waterlogging and drought stress conditions. The experiment was carried out in a strip-plot design with two factors. The first factor was three water stress treatments, namely control (field capacity), waterlogging, and drought. The second factor was six cultivars of Indonesian red chili pepper. The findings indicated that both waterlogging and drought stress had a detrimental impact on the reduction of the growth parameters of red chili pepper such as root, shoot and total dry weight. Chili pepper defended its root weights in response to drought stress (0.653 g plant-1) whereas it preserved shoot weight in response to waterlogging (0.913 g plant-1). In the morphological characters, chili pepper exhibited an increase in specific leaf area expansion in response to both waterlogging (150.82 cm2) and drought (188.82 cm2) compared to control (140.91 cm2), but decreased specific leaf weight during stresses and recovered after 7 d in waterlogging. Leaf chlorophyll content (SPAD) and leaf relative water content (LRWC), as physiological characteristics, also experienced a decline during exposure to both waterlogging and drought during 8 d; yet, SPAD and LRWC able to recover completely at 7 d after waterlogging and drought treatment were terminated. [ABSTRACT FROM AUTHOR]

Drought is a significant abiotic constraint in Salvia miltiorrhiza production, particularly during seedling cultivation. Therefore, researching drought resistance is crucial. This study aimed to investigate the effects of drought stress on the agronomic and physiological characteristics of S. miltiorrhiza at the seedling stage, evaluate drought resistance of various germplasms, and identify drought resistance markers. To simulate drought stress, five different concentrations of polyethylene glycol (PEG) (0%, 5%, 10%, 15%, and 20%) were applied to four S. miltiorrhiza germplasms at the seedling stage. Agronomic traits, root morphology, and physiological and biochemical indicators were measured. The data were then analyzed using the membership function method, correlation analysis, and stepwise regression analysis. The results revealed that as the PEG concentration increased, the aboveground agronomic traits and underground root morphology of the four S. miltiorrhiza germplasms showed a decline. The activities of catalase and peroxidase initially increased and then decreased, while the contents of soluble sugar (SS), soluble protein, and proline increased compared to the control. Based on the membership function values of 16 morphological and physiological indicators, the drought resistance order of the four S. miltiorrhiza germplasms was as follows: Yudanshen VD > Yudanshen VA > Yudanshen VB > Yudanshen VC. Additionally, an optimal regression equation (D = 0.887X1 - 0.003X2 + 0.142X3) was developed through stepwise regression analysis, indicating that X1, X2, and X3 represent the maximum root length, root surface area, and SS content, respectively. Consequently, this study presents a comprehensive and reliable method for evaluating drought resistance in S. miltiorrhiza germplasm resources. [ABSTRACT FROM AUTHOR]

Climate anomalies are increasing and posing strong selection, which can lead to rapid evolution. This is occurring on a backdrop of interannual variability that might weaken or even reverse selection. However, the effect of interannual climatic variability on rapid evolution is rarely considered. We study the climatic differences that contribute to rapid evolution throughout a 7-year period, encompassing a severe drought across 12 populations of Mimulus cardinalis (scarlet monkeyflower). Plants were grown in a common greenhouse environment under wet and dry treatments, where specific leaf area and date of flowering were measured. We examine the association between trait values and different climate metrics at different time periods, including the collection year, prior years, and cumulative metrics across sequential years. Of the climatic variables we assessed, we find that anomalies in mean annual precipitation best describe trait differences over our study period. Past climates, of 1–2 years prior, are often related to trait values in a conflicting direction to collection-year climate. Uncovering these complex climatic impacts on evolution is critical to better predict and interpret the impacts of climate change. [ABSTRACT FROM AUTHOR]

Here we address the combined impact of multiple stressors that are becoming more common with climate change. To study the combined effects of a lower water table (WT) and increased frequency of drought periods on the resistance and resilience of peatlands, we conducted a mesocosm experiment. This study evaluated how the photosynthesis of lawn Sphagnum mosses responds to and recovers from an experimental periodic drought after exposure to the stresses of a deep or deepened WT (naturally dry and 17‐year‐long water level drawdown [WLD] in fen and bog environments).We aimed to quantify if deep WTs (1) support acclimation to drought, or (2) increase the base‐level physiological stress of mosses or (3) exacerbate the impact of periodic drought.There was no evidence of acclimation in mosses from drier environments; periodic drought decreased the photosynthesis of all Sphagnum species studied. WLDdecreased the photosynthesis of bog‐originating mosses prior to periodic drought, indicating that these mosses were stressed by the hydrological change. Deep WTs exacerbated Sphagnum vulnerability to periodic drought, indicating that the combination of drying habitats and increasing frequency of periodic drought could lead to a rapid transition in lawn vegetation. Water‐retaining traits may increase Sphagnum resilience to periodic drought. Large capitula size was associated with a higher resistance; the bog originating species studied here lacked large capitula or dense carpet structure and were more vulnerable to drought than the larger fen originating species. Consequently, lawns in bogs may become threatened.Recovery after rewetting was significant for all mosses, but none completely recovered within 3 weeks. The most drought‐resilient species had fen origin, indicating that fens are less likely to undergo a sudden transition due to periodic drought.Synthesis: Water level drawdown associated with climate change increases the sensitivity of Sphagnum mosses to periods of drought and moves them closer to their tipping point as species on the edge of their ecological envelope rapidly shut down photosynthesis and recover poorly. [ABSTRACT FROM AUTHOR]

Understanding relationships among warming climate, increased drought severity, and the genetic architecture of hybrid drought resilience is necessary for forest conservation and management. We calculated three drought-related tree-ring-growth indices (dendrophenotypes) using tree-ring data from hybrid Pinus strobiformis–Pinus flexilis study trees at nine sites across Colorado, New Mexico, Arizona, and Texas. Along with hybrid index (percentage of P. strobiformis ancestry inherited by a single tree) and climate variables, we used dendrophenotypes to (Q1) examine relationships among climate and hybrid index, (Q2) examine relationships between dendrophenotypes and hybrid index, and (Q3) conduct a genotype–phenotype analysis. We observed a significant correlation between hybrid index and dendrophenotypes resulting from high-temperature drought in addition to a significant correlation between those dendrophenotypes and our dataset of single-nucleotide polymorphisms. We conclude that P. strobiformis–P. flexilis trees exhibiting higher hybrid indices are more resilient to high-temperature drought events and encourage future research that identifies a genetic linkage between relevant loci and their conferred physiological benefits. [ABSTRACT FROM AUTHOR]

Mediterranean Europe is experiencing a rise in severe wildfires, resulting in growing socioeconomic and ecological impacts. Postfire restoration has become a crucial approach to mitigate these impacts and promote ecosystem recovery. However, the ecological effects of such interventions are still not well understood. We employed remote sensing techniques to evaluate the impact of postfire emergency stabilization on the recovery of deciduous oak forests in Portugal. Our study encompassed 3013 sampling points located in areas with and without postfire interventions. We chose the Normalized Difference Vegetation Index (NDVI) as an indicator of oak forest recovery over a four-year period following wildfires that took place in 2016 and 2017. We used a Generalized Additive Mixed Model (GAMM) to assess how NDVI changed over time as a function of postfire restoration, fire characteristics, topography, and postfire drought events. We found that postfire restoration had a significant positive effect on NDVI recovery over time, although this effect was small. Severe drought and fire recurrence up to six fires had a negative effect on the recovery of NDVI. Conversely, severe wetness and either low or high burn severities had a positive effect on recovery. Our study emphasizes the importance of monitoring postfire restoration effects on forest recovery to guide restoration planning and improve forest management in burned areas. This becomes even more relevant under increased wildfire severity predicted for the Mediterranean region interacting with other climate-driven disturbances, which will further negatively affect forest recovery. [ABSTRACT FROM AUTHOR]

This study examined the drought preparedness of drought-prone communities in the Sudano-Sahelian zone of Cameroon. The study employed a mixed-method approach, using qualitative and quantitative data collection methods, including interviews, household surveys, focus group discussions, and field observations. The data were then analysed using SPSS for quantitative data and content analysis for qualitative data. The results reveal that the respondents primarily rely on their personal and community abilities to prepare for droughts. A significant proportion (χ2 = 11.676, P = 0.020) of the respondents depend on community leaders for drought information, while others rely on family and friends. They also use indigenous knowledge and construct boreholes/wells to prepare for droughts. However, limited government support, inadequate extension/scientific support services, and insufficient formal training limited drought preparedness. Age, household size, and income significantly influenced perceived preparedness for drought. Based on the findings, the study concludes that informal/locally-driven strategies are important in drought preparedness and should be strengthened. The study recommends the establishment of drought management committees at the grassroots level and the effective use of indigenous knowledge in combination with scientific knowledge for drought planning and adaptation. Given the geographical variation in climatic stressors, a focus on a specific event such as drought has enhanced the understanding of drought disaster preparedness at the community level for effective planning and policy interventions. This study contributes to the literature in the disaster preparedness discipline with a lens on community drought preparedness. [ABSTRACT FROM AUTHOR]

Inherent biases in numerical simulation models of global climate models (GCMs) reduce the scope for accurately assessing future droughts under multimodel ensemble. The aim of this research is to increase the efficiency of multimodel ensembles. Consequently, this paper introduces a two-way hybrid weighting scheme for ensembling multiple GCMs. The proposed weighting scheme enhances the coherence of the multimodel ensemble of climate model simulations with real observed data and minimizes the impact of non-identical seasonal behavior in climate simulations within the multimodel ensemble. In the application, we consider precipitation data from 18 GCMs of CMIP6 from the Tibet Plateau region. To evaluate the effectiveness of the proposed scheme, we compared the proposed ensemble data with simple model averaged (SMA) ensemble using the Pearson product-moment correlation coefficient (r), root mean squared error (RMSE), and mean absolute error (MAE). Furthermore, we assessed the future characteristics of various drought categories using the steady-state probabilities of a Markov Chain. Small values of errors metircs and high correlation indicate that the proposed hybrid weighting scheme exhibits better performance than the SMA. Under the proposed index, the long term probabilities of various drought classe show variations across different time scales of drought. These results provide perspectives on how the the long term probabilities of various drought categories evolve over time. [ABSTRACT FROM AUTHOR]

Droughts lead to reduced biomass production and unfavourable nutrient composition in grassland. As an alleviation, yet unexploited strategy, mixed ensiling of grass with agro‐industrial by‐products may improve the ensilability and nutritive value of drought‐impaired grassland. This study investigated first whether mixed ensiling of drought‐impaired grass with either sugar beet pulp (SBP), wheat gluten feed (WGF) or brewers' grains (BG) has a beneficial impact on chemical composition, fermentation characteristics, in vitro gas production (GP) and physically effective neutral detergent fibre (peNDF) of silages. Secondly, it was tested whether the application of anaerobic fungi culture supernatant (AF), mixed ruminal fluid (RF) or lactic acid bacteria (LAB) provides further advantages. Additionally, the microbial community composition was evaluated in selected silages. All silages showed satisfying conservation characteristics with high lactic acid levels and low dry matter losses, and peNDF values typically found for conserved forages. Mixed ensiling with BG substantially increased the crude protein concentration, whereas SBP increased the total degradability and WGF enhanced both. The further addition of fresh AF resulted in the overall highest lactic acid levels, especially in SBP‐based silages, but without changes in in vitro GP. The in vitro GP was higher with RF, particularly in mixed silages, suggesting an improved degradability. The LAB‐treated silages showed lower pH compared to controls, but had no impact on in vitro GP kinetics. Concluding, mixed ensiling holds potential to produce high‐quality silages from drought‐impaired grassland. The further addition of silage additives can be useful for certain substrates, but appeared not mandatory. [ABSTRACT FROM AUTHOR]

Mental and behavioral disorders are an important public health problem and constitute a priority for the WHO, whose recommendations include the surveillance of their risk factors. On the other hand, drought episodes have been increasing in frequency and severity in Europe since 1980. Therefore, to review the present knowledge about the impact of drought on mental and behavioral disorders, in the present climate change context, and to underline potential research gaps, could be of major interest. Thus, we performed a narrative review using online academic databases with the aim of identifying relevant literature about the impact of drought on mental and behavioral disorders. To the best of our knowledge, no study in Europe quantifies the potential association between drought and mental disorders. A limited number of studies have found significant associations between droughts (with different temporal ranges) and various measures of mental health. However, according to our review, only three of them quantified the association between drought and objective mental health outcomes, such as number of emergencies due to clinically diagnosed mental disorders or suicides. Additionally, few studies used specific indices as a measure of drought; and finally, as far as authors are aware, none of them has analyzed this relationship adjusting for various other potential environmental confounders. Moreover, the eventual association could vary between different geographical areas within the same country. Therefore, national and regional studies would be especially necessary. Thus, there is a need for specific national and regional studies, in Europe and globally, that assess the impact of specific indices of drought (with different temporal ranges) on objective mental health outcomes controlling for potential environmental confounders. Moreover, the quantification of its cost would be necessary for health prioritization, evidence-based policies and strategic health planning. [ABSTRACT FROM AUTHOR]

This paper studies the past and future annual droughts in the five agro-ecological zones (AEZs) of Cameroon. Station data and model outputs from the Coupled Model Intercomparison Project Phase 5 were used to compute areal datasets for each AEZ. Six statistical metrics and compromise programming method were used to evaluate and rank the models, respectively. The top three models were used to build multi-model ensemble (MME) and deduce bias-corrected MME data. They were then used to compute the Standardized Precipitation Index (SPI) used as drought indicator. As a result, the performance of the models depends on the AEZ and decreases with the increase in drought intensity. The 1980s was the most marked by severe-extreme droughts and a significant increase in drought intensity was observed in the entire domain during the past period, the years 1974, 1985 and 1988 showing the highest drought intensities. The MME tends to overestimate and underestimate the frequencies and the magnitude of these events, respectively. Bias-corrected MME data improve the results in most cases. As for the period 2071–2099, all the AEZs are likely to experience severe-extreme droughts which are expected to be more frequent before 2083 in the North (AEZs 1 and 2) and after this year in the South (AEZs 3, 4 and 5). It is also expected a slight increasing trend of the mean spatial SPIs showing a slight decrease in drought intensity. The RCPs 8.5 and 2.6 project the lowest and the highest decrease in drought intensity, respectively, while the RCP4.5 shows an average decrease. This study highlights future periods and areas at potential risk of severe-extreme droughts and can guide decision-makers in mitigation and adaptation measures. [ABSTRACT FROM AUTHOR]

The evaluation and monitoring of drought, a complex disaster, are essential issues for the planning of agricultural activities and the operation and management of water resources. In this study, the meteorological drought of the Black Sea region in northern Turkey is evaluated with the Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) methods at 3-, 6-, and 12-month time scales. Meteorological parameters obtained between 1965 and 2019 from 28 meteorological observation stations are used to analyze the drought. Drought-wet period percentages, percentages of occurrence of drought classes, critical period, and negative peak index values are investigated. As a result of the study, it is observed that the percentage of drought occurrence at all time scales is higher than 50% at two stations in the study region, which received precipitation above the average of Turkey. The sum of the extreme drought (ED) and severe drought (SD) values throughout the region is approximately 15% for the whole area. There is a high correlation coefficient, 97.8, 97.6, and 97.3 for the 3-, 6-, and 12-month time scales, respectively, between the SPI and RDIst methods in the evaluation of meteorological drought in the Black Sea region, which is generally a rainy region. It is determined that with the increase in the time scale, the percentage of ED occurrence increased and the risk level of the region around RDI and 17089 station is the highest. It has been determined that the correlation between oscillation indices and meteorological drought indices for the Black Sea region is almost non-existent. The highest correlation value between the oscillation and meteorological drought indices in the region is obtained with the Atlantic Multidecadal Oscillation (AMO). [ABSTRACT FROM AUTHOR]

CircRNAs (circular RNAs) reduce the abundance of miRNAs through ceRNA (competing endogenous RNA), to regulate many physiological processes and stress responses in plants. However, the role of circRNA in drought stress is poorly understood.Through ring identification and sequencing verification of ath‐circ032768, bioinformatics analysis predicted the interaction of ath‐circ032768–miR472‐RPS5, and further obtained transgenic plants overexpressing ath‐circ032768 and silencing STTM‐miR472. The change in drought stress was analysed using biochemical and molecular biological methods.Sequencing and biological analysis confirmed that ath‐circ032768, miR472 and RPS5 were responsive to drought stress, and changes in gene expression were consistent with the prediction of ceRNA. The silencing vectors ath‐circ032768 and STTM‐miR472 were constructed using molecular biology techniques, and stable transgenic plants with drought tolerance obtained. Further physiological and biochemical studies showed that ath‐circ032768 could bind to miR472, and that miR472 could bind to the RPS5 gene, resulting in decreased expression of RPS5. Hence, ath‐circ032768 can competitively inhibit degradation of RPS5 by miR472 through ceRNA. This process is accompanied by increased expression of DREB2A, RD29A and RD29B genes.Through the ath‐circ032768–miR472‐RPS5 pathway, the RPS5 stress resistance protein interacts with DREB2A protein to enhance expression of downstream drought resistance genes, RD29A and RD29B, and participate in the regulation mechanism of plant drought resistance, thereby improving drought tolerance of plants. [ABSTRACT FROM AUTHOR]

Despite the abundant evidence of impairments to plant performance and survival under hotter‐drought conditions, little is known about the vulnerability of reproductive organs to climate extremes. Here, by conducting a comparative analysis between flowers and leaves, we investigated how variations in key morphophysiological traits related to carbon and water economics can explain the differential vulnerabilities to heat and drought among these functionally diverse organs. Due to their lower construction costs, despite having a higher water storage capacity, flowers were more prone to turgor loss (higher turgor loss point; ΨTLP) than leaves, thus evidencing a trade‐off between carbon investment and drought tolerance in reproductive organs. Importantly, the higher ΨTLP of flowers also resulted in narrow turgor safety margins (TSM). Moreover, compared to leaves, the cuticle of flowers had an overall higher thermal vulnerability, which also resulted in low leakage safety margins (LSM). As a result, the combination of low TSMs and LSMs may have negative impacts on reproduction success since they strongly influenced the time to turgor loss under simulated hotter‐drought conditions. Overall, our results improve the knowledge of unexplored aspects of flower structure and function and highlight likely threats to successful plant reproduction in a warmer and drier world. Summary statement: By conducting a comparative morphophysiological analysis between flowers and leaves, we showed that, due to their lower construction costs, flowers were more vulnerable to hotter‐drought events than leaves, thus evidencing possible threats to successful plant reproduction in a warmer and drier world [ABSTRACT FROM AUTHOR]

Background: The cuticular wax serves as a primary barrier that protects plants from environmental stresses. The Eceriferum (CER) gene family is associated with wax production and stress resistance. Results: In a genome-wide identification study, a total of 52 members of the CER family were discovered in four Gossypium species: G. arboreum, G. barbadense, G. raimondii, and G. hirsutum. There were variations in the physicochemical characteristics of the Gossypium CER (GCER) proteins. Evolutionary analysis classified the identified GCERs into five groups, with purifying selection emerging as the primary evolutionary force. Gene structure analysis revealed that the number of conserved motifs ranged from 1 to 15, and the number of exons varied from 3 to 13. Closely related GCERs exhibited similar conserved motifs and gene structures. Analyses of chromosomal positions, selection pressure, and collinearity revealed numerous fragment duplications in the GCER genes. Additionally, nine putative ghr-miRNAs targeting seven G. hirsutum CER (GhCER) genes were identified. Among them, three miRNAs, including ghr-miR394, ghr-miR414d, and ghr-miR414f, targeted GhCER09A, representing the most targeted gene. The prediction of transcription factors (TFs) and the visualization of the regulatory TF network revealed interactions with GhCER genes involving ERF, MYB, Dof, bHLH, and bZIP. Analysis of cis-regulatory elements suggests potential associations between the CER gene family of cotton and responses to abiotic stress, light, and other biological processes. Enrichment analysis demonstrated a robust correlation between GhCER genes and pathways associated with cutin biosynthesis, fatty acid biosynthesis, wax production, and stress response. Localization analysis showed that most GCER proteins are localized in the plasma membrane. Transcriptome and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) expression assessments demonstrated that several GhCER genes, including GhCER15D, GhCER04A, GhCER06A, and GhCER12D, exhibited elevated expression levels in response to water deficiency stress compared to control conditions. The functional identification through virus-induced gene silencing (VIGS) highlighted the pivotal role of the GhCER04A gene in enhancing drought resistance by promoting increased tissue water retention. Conclusions: This investigation not only provides valuable evidence but also offers novel insights that contribute to a deeper understanding of the roles of GhCER genes in cotton, their role in adaptation to drought and other abiotic stress and their potential applications for cotton improvement. [ABSTRACT FROM AUTHOR]

Salvia miltiorrhiza is commonly used as a Chinese herbal medicine to treat different cardiovascular and cerebrovascular illnesses due to its active ingredients. Environmental conditions, especially drought stress, can affect the yield and quality of S. miltiorrhiza. However, moderate drought stress could improve the quality of S. miltiorrhiza without significantly reducing the yield, and the mechanism of this initial drought resistance is still unclear. In our study, transcriptome and metabolome analyses of S. miltiorrhiza under different drought treatment groups (CK, A, B, and C groups) were conducted to reveal the basis for its drought tolerance. We discovered that the leaves of S. miltiorrhiza under different drought treatment groups had no obvious shrinkage, and the malondialdehyde (MDA) contents as well as superoxide dismutase (SOD) and peroxidase (POD) activities dramatically increased, indicating that our drought treatment methods were moderate, and the leaves of S. miltiorrhiza began to initiate drought resistance. The morphology of root tissue had no significant change under different drought treatment groups, and the contents of four tanshinones significantly enhanced. In all, 5213, 6611, and 5241 differentially expressed genes (DEGs) were shared in the A, B, and C groups compared with the CK group, respectively. The results of KEGG and co-expression analysis showed that the DEGs involved in plant-pathogen interactions, the MAPK signaling pathway, phenylpropanoid biosynthesis, flavonoid biosynthesis, and plant hormone signal transduction responded to drought stress and were strongly correlated with tanshinone biosynthesis. Furthermore, the results of metabolism analysis indicated that 67, 72, and 92 differentially accumulated metabolites (DAMs), including fumarate, ferulic acid, xanthohumol, and phytocassanes, which were primarily involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, and diterpenoid biosynthesis pathways, were detected in these groups. These discoveries provide valuable information on the molecular mechanisms by which S. miltiorrhiza responds to drought stress and will facilitate the development of drought-resistant and high-quality S. miltiorrhiza production. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum spp.), a leading sugar and energy crop, is seriously impacted by drought stress. However, the molecular mechanisms underlying sugarcane drought resistance, especially the functions of epigenetic regulators, remain elusive. Here, we show that a S. spontaneum KDM4/JHDM3 group JmjC protein, SsJMJ4, negatively regulates drought-stress responses through its H3K27me3 demethylase activity. Ectopic overexpression of SsJMJ4 in Arabidopsis reduced drought resistance possibly by promoting expression of AtWRKY54 and AtWRKY70 , encoding two negative regulators of drought stress. SsJMJ4 directly bound to AtWRKY54 and AtWRKY70 , and reduced H3K27me3 levels at these loci to ensure their proper transcription under normal conditions. Drought stress down-regulated both transcription and protein abundance of SsJMJ4, which was correlated with the reduced occupancy of SsJMJ4 at AtWRKY54 and AtWRKY70 chromatin, increased H3K27me3 levels at these loci, as well as reduced transcription levels of these genes. In S. spontaneum , drought stress-repressed transcription of SsWRKY122 , an ortholog of AtWRKY54 and AtWRKY70 , was associated with increased H3K27me3 levels at these loci. Transient overexpression of SsJMJ4 in S. spontaneum protoplasts raised transcription of SsWRKY122 , paralleled with reduced H3K27me3 levels at its loci. These results suggest that the SsJMJ4-mediated dynamic deposition of H3K27me3 is required for an appropriate response to drought stress. [ABSTRACT FROM AUTHOR]

Background: The number of globally food-insecure people is increasing since 2017. Sub-Saharan Africa has the highest proportion of severely food-insecure people in the world. Tigray region of Ethiopia is one of the food-insecure regions, which, over the past many decades has been affected by recurrent food insecurities. In the drought–prone rural areas of Tigray, many people are living under the condition of chronic hunger. Proper food security studies are vital for proper intervention mechanisms. Yet, previous food security studies have rarely addressed the four pillars of food security: availability, access, utilization, and stability. In this study, all components are duly considered to assess the food insecurity status in the drought–prone rural areas of Tigray, Ethiopia. Of the 34 rural districts in Tigray, 363 households from three drought–prone rural districts were studied. Results: Household Food Insecurity Access Scale and Food Insecurity Experience Scale were adapted to measure the food availability, access to food, and stability components of food security; and, Household Dietary Diversity Score (HDDS), Food Consumption Score (FCS), mid-upper arm circumference, and Bitot's spot were used to analyze the food utilization aspect. Findings show that 68% of the studied community frequently ate less food than they felt they needed and 82.1% of the households have experienced hunger because of lack of food. The study rural districts were unconnected to road networks; hence, 87.9% of the elderly and 20.4% of the women and girls had no access to food markets. Regarding the food utilization, 81.5% of the studied households had poor FCS; and the average HDDS and FCS for the study areas were 2.47 and 18.9, respectively. The prevalence of Global acute malnutrition, severe acute malnutrition (SAM), and moderate acute malnutrition (MAM) for 6–59 months of age children in the study areas were 50.3, 4.2, and 46.1%, respectively. More notably, the prevalence of SAM for children from the food-insecure households was 21.2%. The prevalence of MAM for pregnant and lactating women (PLW) in the study areas was 59.5. Further, the prevalence of Bitot's spot among 6–59 months of age children was 1.9%. On the other hand, all the rural households had anxiety about their future food demands. Conclusion: The rural households living in the studied areas were critically food-insecure. All the measurements implied that the food insecurity situation in the study areas was unacceptably worrisome and life-threatening. This calls for an instant action to avert the occurrence of famine and starvation in the drought–prone rural areas of Tigray region. Thus, interventions should primarily target the vulnerable rural people and need to be planned based on attaining food availability first rather than concurrently addressing all components of food security. Further, due emphasis should be given to diversifying livelihood strategies of the vulnerable villagers. [ABSTRACT FROM AUTHOR]

Globally, drought stress poses a significant threat to crop productivity. Improving the drought tolerance of crops with microbial biostimulants is a sustainable strategy to meet a growing population's demands. This research aimed to elucidate microbial biostimulants' (Plant Growth Promoting Rhizobacteria) role in alleviating drought stress in oil-seed crops. In total, 15 bacterial isolates were selected for drought tolerance and screened for plant growth-promoting (PGP) attributes like phosphate solubilization and production of indole-3-acetic acid, siderophore, hydrogen cyanide, ammonia, and exopolysaccharide. This research describes two PGPR strains: Acinetobacter calcoaceticus AC06 and Bacillus amyloliquefaciens BA01. The present study demonstrated that these strains (AC06 and BA01) produced abundant osmolytes under osmotic stress, including proline (2.21 and 1.75 µg ml− 1), salicylic acid (18.59 and 14.21 µg ml− 1), trehalose (28.35 and 22.74 µg mg− 1 FW) and glycine betaine (11.35 and 7.74 mg g− 1) respectively. AC06 and BA01 strains were further evaluated for their multifunctional performance by inoculating in Arachis hypogaea L. (Groundnut) under mild and severe drought regimes (60 and 40% Field Capacity). Inoculation with microbial biostimulants displayed distinct osmotic-adjustment abilities of the groundnut, such as growth parameters, plant biomass, photosynthetic pigments, relative water content, proline, and soluble sugar in respective to control during drought. On the other hand, plant sensitivity indexes such as electrolyte leakage and malondialdehyde (MDA) contents were decreased as well as cooperatively conferred plant drought tolerance by induced alterations in stress indicators such as catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD). Thus, Acinetobacter sp. AC06 and Bacillus sp. BA01 can be considered as osmolyte producing microbial biostimulants to simultaneously induce osmotic tolerance and metabolic changes in groundnuts under drought stress. [ABSTRACT FROM AUTHOR]

Efficient methods for predicting weather-related hazards are crucial for stakeholders managing environmental risks. Many environmental hazards depend on the evolution of meteorological conditions over protracted periods, requiring assessments that account for evolving conditions. The TAMSAT-ALERT approach addresses this challenge by combining observational monitoring with a weighted climatological ensemble. As such, it enhances the utility of existing systems by enabling users to combine multiple streams of monitoring and forecasting data into holistic hazard assessments. TAMSAT-ALERT forecasts are now used in a number of regions in the Global South for soil moisture forecasting, drought early warning and agricultural decision support. The model presented here, General TAMSAT-ALERT, represents a significant scientific and functional advance on previous implementations. Notably, General TAMSAT-ALERT is applicable to any variable for which time series data are available. In addition, functionality has been introduced to account for climatological non-stationarity (for example due to climate change); large-scale modes of variability (for example El Nino), and persistence (for example of land-surface condition). In this paper, we present a full description of the model, along with case studies of its application to prediction of Central England Temperature, Pakistan vegetation condition and African precipitation. [ABSTRACT FROM AUTHOR]

Canopy temperature provides valuable information for efficient irrigation management and for detecting drought injury in a fast and non-destructive way. It also helps quantify the trade-offs between water conservation and the cooling benefit of the irrigated urban landscape, a critical issue in semiarid inland southern California with limited available water resources. Two adjacent hybrid bermudagrass and tall fescue irrigation trials were conducted to determine canopy temperature changes under a wide range of irrigation treatments from 2017 to 2019 in Riverside, California, USA. The canopy temperature data were also used to develop an empirical crop water stress index (CWSI) for each species. The CWSI values ranged from -0.15 to 0.71 for tall fescue and from -0.28 to 0.54 for hybrid bermudagrass. We observed a moderate correlation between visual rating scores (VR) and CWSI values for tall fescue (r = -0.68) and hybrid bermudagrass (r = -0.61). The fitted linear regression between VR and CWSI data suggested CWSI thresholds close to zero for both species to maintain their acceptable visual quality. The irrigation level consistently showed a significant effect on canopy temperature for both species. On average, a 10% decrease in irrigation application increased the canopy temperature of tall fescue and hybrid bermudagrass by 1.3°C and 0.9°C, respectively. Therefore, deficit irrigation might reduce the cooling benefits of irrigated urban lawns in the semiarid climate of inland southern California. [ABSTRACT FROM AUTHOR]

To adapt forest ecosystems and forest management to climate change, it is essential to know which forest regions and which tree species are resilient to climate variability and which ones are possibly affected most by past and anticipated future changes. In this contribution, for the main forest regions of Türkiye and six tree species, recent climate variability and trends were quantified and statistically correlated to record tree defoliation and vitality. Climate variables considered are maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tmean), and total precipitation (Prcp), which are compared to forest health responses recorded as part of the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) on 277 plots across forests along the Black Sea and Mediterranean regions. In addition, long-term data on satellite measurements of the normalized difference vegetation index (NDVI) were extracted for the same 277 plots for the period 2008–2020. Firstly, 30 years (1991–2020) of reanalysis of climate variables from ECMWF were extracted for all plots; secondly, individual correlations and cross-correlations of climate variables and tree health and vitality were computed for the period 2008–2020 (significance level of 95%) for the four most dominant species from the Black Sea forests (F. orientalis, Q. cerris, P. sylvestris, P. orientalis) and two species from Mediterranean forests (P. brutia and C. libani). Temperature showed a stronger effect on most species than precipitation. Finally, time-lagged correlations were analyzed for seven-time lags (significance level of 95%) to evaluate legacy effect. The analysis revealed that different tree species from the two regions show different responses to climate variables. Species in the Mediterranean region are more resistant to droughts and climatic variations. Legacy effects of defoliation and NDVI have lasted for at least 2 years. [ABSTRACT FROM AUTHOR]

Drought events have become increasingly frequent and intensive due to the combined influence of climate change and anthropogenic activities. However, it remains unclear how meteorological drought characteristics (duration, severity, and intensity) respond to the changing environment and what are the dominant factors determining the drought evolution in different climate regions. Here, we divide mainland China into four sub-climatic regions, namely the Humid region (HR), Transition region (TR), Arid region (AR), and Tibetan Plateau (TP), based on the aridity index and geomorphology. Then systematically investigate the spatiotemporal patterns of drought characteristics in different climate regions over China (during 2000–2019) based on the SPEI and run theory. And the contribution of precipitation (Pre) and potential evapotranspiration (PET) to drought characteristics are quantitatively analyzed using a detrended numerical experiment method. We find that (1) a pattern of "dry gets drier, wet gets wetter" was found in China. (2) Meteorological drought characteristics exhibit apparent regional heterogeneity: droughts in AR are of long duration and high severity, while droughts in HR and TR show a pattern of high frequency. (3) An increase in the annual Pre (PET) resulted in increases (decreases) in average SPEI in China of 45.18% (31.62%). Therefore, Pre is the dominant factor determining the increase of SPEI over China. For the four sub-climatic regions, Pre is the dominant factor in the increase of SPEI in TR and HR, with the contribution of 41.64% and 60.16%. PET is the dominant factor in the decrease of SPEI in AR, with the contribution of 50.11%. The contributions of Pre (45.09%) and PET (44.09%) in TP are roughly equivalent. These findings provide valuable insights for policymakers in shaping climate change adaptation and mitigation strategies. By understanding the leading meteorological factors influencing drought, policymakers can implement effective measures to minimize the influence of disasters. [ABSTRACT FROM AUTHOR]

Over the past decades, drought has been considered as one of the most catastrophic natural disasters due to the devastating implications associated with this phenomenon. This research examines drought characteristics, severity, intensity, and duration in Sudan from 1980 to 2017 using meteorological observations and remote sensing datasets. According to analyses of the standardized precipitation index (SPI) provided by 29 sites, 72% of all dry occurrences appear to have occurred during the 1980s. The wettest occurrences, on the other hand, occurred after the mid-1990s timeframe and accounted for 82% of the total. SPI-3 research over Sudan revealed dry conditions during the 1980s. Early datasets indicate extreme drought periods occurred between 1982 and 1987, while fewer occurrences were observed during the 1990s and 2000s. SPI-3 shows that rainfall increased dramatically in the 1990s. Among the understudied time scales, 1982, 1983, 1984, 1987, 1990, 1992, and 2004 regimes recorded the driest events, whereas 1988, 1998, 1999, 2000, 2003, 2005, 2006, 2007, and 2016 had the wettest. Recent seasonal vegetation conditions from the normalized difference vegetation index (NDVI) and soil moisture were examined. The intensity of severe droughts declined for 2000, 2005, 2010, 2015, and 2020 periods. Conversely, a discernible upward trend in wet conditions with corresponding increases can be observed. Findings depict a graphical illustration of changes in the vegetation condition index (VCI), both geographically and chronologically in Sudan between 2000 and 2020. Generally, a positive correlation between the SPI-12 and AMO was obtained across Sudan's different regions. Significant power association peaked between 1 and 2 and 6 and 10 years from 1980 to 1990 and 6 and 8 years from 2005 to 2017. This study lays the groundwork for future drought studies, which further provides the technical basis for policymakers to address the consequences of drought on agriculture and the economy. [ABSTRACT FROM AUTHOR]

In the two decades, since the advent of the term "flash drought," considerable research has been directed toward the topic. Within the scientific community, we have actively forged a new paradigm that has avoided a chaotic evolution of conventional drought but instead recognizes that flash droughts have distinct dynamics and, particularly, impacts. We have moved beyond the initial debate over the definition of flash drought to a centralized focus on the triad of rapid onset, drought development, and associated impacts. The refinement toward this general set of principles has led to significant progress in determining key variables for monitoring flash drought development, identifying notable case studies, and compiling fundamental physical characteristics of flash drought. However, critical focus areas still remain, including advancing our knowledge on the atmospheric and oceanic drivers of flash drought; developing flash drought‐specific detection indices and monitoring systems tailored to practitioners; improving subseasonal‐to‐seasonal prediction of these events; constraining uncertainty in flash drought and impact projections; and using social science to further our understanding of impacts, particularly with regard to sectors that lie outside of our traditional hydroclimatological focus, such as wildfire management and food‐security monitoring. Researchers and stakeholders working together on these critical topics will assure society is resilient to flash drought in a changing climate. This article is categorized under:Science of Water > Water Extremes [ABSTRACT FROM AUTHOR]

Assessments of future droughts are essential tools due to the potential for serious damage to the environment, economy, and society, particularly under climate change. This study proposes a framework for assessing drought characteristics at different scales, periods, and emission scenarios modeled by phase 6 of the Coupled Model Intercomparison Project. The four drought characteristics were determined by applying the Run theory to a standardized precipitation index time series, and the severe drought areas were detected by the Jenks Natural Breaks and Kriging methods. The study produced four main findings. (1) A stochastic weather generator, AWE-GEN, captures the variability of precipitation with inter- and intra-annual stochastic properties, and presents naturally occurring variability as an ensemble. (2) According to the ensemble average of drought characteristics, future droughts are projected to become less frequent with similar durations and intensity due to future rise in precipitation. However, the ensemble (stochastic or natural) and spatial variabilities are expected to increase, making drought management difficult (e.g., future decrease of 18% in DE max for END585). (3) Different temporal scales can affect the detection and characterization of drought events. Smaller temporal scales identify mild drought events of short duration and low severity, while larger scales merge and extend drought events, resulting in more prolonged and severe droughts. (4) Severe drought areas can expand compared with a control period for drought duration and severity, but may decrease for drought interval and frequency especially for the END period (e.g., 24% and 17% increase for DD max and D S max , and 85% and 78% decrease for DI mean and DE max for SPI3 and END585). The framework proposed in this study is expected to provide important information for the building of strategies required to adapt to and mitigate the potential impacts of drought in the future. [ABSTRACT FROM AUTHOR]

Understanding the relationship between hydrological and meteorological drought in drought-prone regions is critical for proper reservoir management. This study presents a novel multiscale framework for investigating the associations between hydrological and meteorological drought based on the Time-Dependent Intrinsic Correlation (TDIC) method. Firstly, the characteristics of short, medium and long term standardized precipitation index (SPI) and the standardized runoff index (SRI) of the Wadi Mina basin (Algeria) have been analyzed based on data from 6 rainfall and hydrometric stations. Then an Improved Complete Ensemble Empirical Mode Decomposition with adaptive noise (ICEEMDAN) method is used to decompose the most correlated SPI and SRI series to different scales. A stronger association between the two types of droughts is evident in the low-frequency trend component regardless of the station, but their evolution pattern does not remain the same. Subsequently, a TDIC based running correlation analysis is performed between the modes to examine the SPI–SRI associations over the time domain and across the time scales. TDIC analysis has proven the dynamic behavior in the SPI–SRI associations bearing frequent alterations in nature and strength across the process scales and along the time domain. In general, at the intra-annual scales the SPI–SRI correlations are mostly weak positive with localized alterations to negative along the time domain, whereas the relationship is dominantly strong positive and long range at inter-annual scales up to 4 years. This dynamic behavior in the SPI–SRI association and the evolution pattern of trend decipher that the rainfall processes are not directly transferred to streamflow drought, but it also gets controlled by many other local meteorological processes. [ABSTRACT FROM AUTHOR]

Water availability is a limiting factor to plant development and productivity. Many drought‐induced physiological processes that affect patterns of growth, biomass allocation, and ultimately, yield, are also regulated by the red/far‐red photoreceptor phytochromes (PHYs). However, as the mechanisms and responses to drought stress vary among plant developmental phases, it is reasonable to conjecture that PHY‐dependent morphophysiological responses to drought may be different according to the plant growth stage. In this study, we submitted tomato phyB1 mutant plants to water deficit in two distinct growth stages, during vegetative and flower‐bearing reproductive phases, comparing the morphophysiological development, fruit yield and quality to wild‐type (WT). In general, phyB1 plants overcome growth limitations imposed by water availability limitations during vegetative phase, being taller and leafier than WT. Restrictions to growth are less acute for both genotypes when water deficit occurs during reproductive phase compared to vegetative phase. phyB1 yield is lower when water is limited during reproductive phase, but its fruits accumulate more soluble solids, associated with better quality. These results highlight that drought‐induced modulations in tomato growth and yield are dependent upon PHYB1 regulation and the developmental phase when water deficit is applied. [ABSTRACT FROM AUTHOR]

Summary: Plenty of rainfall but unevenly seasonal distribution happens regularly in southern China. Seasonal drought from summer to early autumn leads to citrus fruit acidification, but how seasonal drought regulates citrate accumulation remains unknown.Herein, we employed a set of physiological, biochemical, and molecular approaches to reveal that CsABF3 responds to seasonal drought stress and modulates citrate accumulation in citrus fruits by directly regulating CsAN1 and CsPH8.Here, we demonstrated that irreversible acidification of citrus fruits is caused by drought lasting for > 30 d during the fruit enlargement stage. We investigated the transcriptome characteristics of fruits affected by drought and corroborated the pivotal roles of a bHLH transcription factor (CsAN1) and a P3A‐ATPase gene (CsPH8) in regulating citrate accumulation in response to drought. Abscisic acid (ABA)‐responsive element binding factor 3 (CsABF3) was upregulated by drought in an ABA‐dependent manner. CsABF3 activated CsAN1 and CsPH8 expression by directly and specifically binding to the ABA‐responsive elements (ABREs) in the promoters and positively regulated citrate accumulation.Taken together, this study sheds new light on the regulatory module ABA‐CsABF3‐CsAN1‐CsPH8 responsible for citrate accumulation under drought stress, which advances our understanding of quality formation of citrus fruit. [ABSTRACT FROM AUTHOR]

SUMMARY: Drought is one of the major and growing threats to agriculture productivity and food security. Metabolites are involved in the regulation of plant responses to various environmental stresses, including drought stress. The complex drought tolerance can be ascribed to several simple metabolic traits. These traits could then be used for detecting the genetic architecture of drought tolerance. Plant metabolomes show dynamic differences when drought occurs during different developmental stages or upon different levels of drought stress. Here, we reviewed the major and most recent findings regarding the metabolite‐mediated plant drought response. Recent progress in the development of drought‐tolerant agents is also discussed. We provide an updated schematic overview of metabolome‐driven solutions for increasing crop drought tolerance and thereby addressing an impending agricultural challenge. Significance Statement: Metabolites bridge the gene product and the ultimate phenotypes. We summarized the recent advances in metabolite‐mediated plant drought reponse, which will be beneficial for basic and application research of plant drought tolerance. [ABSTRACT FROM AUTHOR]

Mulberries are vital for the silk industry as the sole natural food for silkworms, but their quality and quantity can be greatly impacted by environmental factors, notably water shortages or droughts. In this study, the proline content and expression levels of the Pyrroline-5-carboxylate reductase (P5CR) gene in four recommended Thai mulberry varieties (Sakhonnakorn, Sakhonnakorn 85, Burirum 60, and Srisaket 84) and one standard drought tolerant variety (SRCM9809-34) were measured under drought stress. Additionally, physiological data and antioxidative enzymatic activities were also examined. The findings revealed that SRCM9809-34, a drought-tolerant variety, had the lowest proline content, followed by Sakhonnakorn 85, Burirum 60, while the highest proline content was observed in Srisaket 84. Although there was no correlation between the expression level of the P5CR gene and proline content, the overall trend in all varieties was the same: proline content increased after drought conditions. Regarding physiological responses, the wilting score showed similar results to proline content, with SRCM9809-34 having the lowest proline content and wilting score. Moreover, SRCM9809-34 exhibited the highest RWC, Pn and WUE values, as well as the lowest level of MDA and H2O2. Our results validated and indicated that SRCM9809-34 is a drought-tolerant variety. From this finding, among the four Thai mulberry varieties, Sakhonnakorn 85 exhibited the highest potential for drought tolerance, and this potential can be enhanced through crossbreeding with SRCM9809-34. [ABSTRACT FROM AUTHOR]

Aim: As climate change increases the frequency and severity of droughts in many regions, conservation during drought is becoming a major challenge for ecologists. Droughts are multidimensional climate events whose impacts may be moderated by changes in temperature, water availability or food availability, or some combination of these. Simultaneously, other stressors such as extensive anthropogenic landscape modification may synergize with drought. Useful observational models for guiding conservation decision‐making during drought require multidimensional, dynamic representations to disentangle possible drought impacts, and consequently, they will require large, highly resolved data sets. In this paper, we develop a two‐stage predictive framework for assessing how drought impacts vary with species, habitats and climate pathways. Location: Central Valley, California, USA. Methods: We used a two‐stage counterfactual analysis combining predictive linear mixed models and N‐mixture models to characterize the multidimensional impacts of drought on 66 bird species. We analysed counts from the eBird participatory science data set between 2010 and 2019 and produced species‐ and habitat‐specific estimates of the impact of drought on relative abundance. Results: We found that while fewer than a quarter (16/66) of species experienced abundance declines during drought, nearly half of all species (27/66) changed their habitat associations during drought. Among species that shifted their habitat associations, the use of natural habitats declined during drought while use of developed habitat and perennial agricultural habitat increased. Main Conclusions: Our findings suggest that birds take advantage of agricultural and developed land with artificial irrigation and heat‐buffering microhabitat structure, such as in orchards or parks, to buffer drought impacts. A working lands approach that promotes biodiversity and mitigates stressors across a human‐induced water gradient will be critical for conserving birds during drought. [ABSTRACT FROM AUTHOR]

Flash droughts tend to cause severe damage to agriculture due to their characteristics of sudden onset and rapid intensification. Early detection of the response of vegetation to flash droughts is of utmost importance in mitigating the effects of flash droughts, as it can provide a scientific basis for establishing an early warning system. The commonly used method of determining the response time of vegetation to flash drought, based on the response time index or the correlation between the precipitation anomaly and vegetation growth anomaly, leads to the late detection of irreversible drought effects on vegetation, which may not be sufficient for use in analyzing the response of vegetation to flash drought for early earning. The evapotranspiration-based (ET-based) drought indices are an effective indicator for identifying and monitoring flash drought. This study proposes a novel approach that applies cross-spectral analysis to an ET-based drought index, i.e., Evaporative Stress Anomaly Index (ESAI), as the forcing and a vegetation-based drought index, i.e., Normalized Vegetation Anomaly Index (NVAI), as the response, both from medium-resolution remote sensing data, to estimate the time lag of the response of vegetation vitality status to flash drought. An experiment on the novel method was carried out in North China during March–September for the period of 2001–2020 using remote sensing products at 1 km spatial resolution. The results show that the average time lag of the response of vegetation to water availability during flash droughts estimated by the cross-spectral analysis over North China in 2001–2020 was 5.9 days, which is shorter than the results measured by the widely used response time index (26.5 days). The main difference between the phase lag from the cross-spectral analysis method and the response time from the response time index method lies in the fundamental processes behind the definitions of the vegetation response in the two methods, i.e., a subtle and dynamic fluctuation signature in the response signal (vegetation-based drought index) that correlates with the fluctuation in the forcing signal (ET-based drought index) versus an irreversible impact indicated by a negative NDVI anomaly. The time lag of the response of vegetation to flash droughts varied with vegetation types and irrigation conditions. The average time lag for rainfed cropland, irrigated cropland, grassland, and forest in North China was 5.4, 5.8, 6.1, and 6.9 days, respectively. Forests have a longer response time to flash droughts than grasses and crops due to their deeper root systems, and irrigation can mitigate the impacts of flash droughts. Our method, based on cross-spectral analysis and the ET-based drought index, is innovative and can provide an earlier warning of impending drought impacts, rather than waiting for the irreversible impacts to occur. The information detected at an earlier stage of flash droughts can help decision makers in developing more effective and timely strategies to mitigate the impact of flash droughts on ecosystems. [ABSTRACT FROM AUTHOR]

Fires occurring over the peatlands in Indonesian Borneo accompanied by droughts have posed devastating impacts on human health, livelihoods, economy and the natural environment, and their prevention requires comprehensive understanding of climate‐associated risk. Although it is widely known that the droughts are associated with El Niño events, the onset process of El Niño and thus the drought precursors and their possible changes under the future climate are not clearly understood. Here, we use a causal network approach to quantify the strength of teleconnections to droughts at a seasonal timescale shown in observations and climate models. We portray two drivers of June‐July‐August (JJA) droughts identified through literature review and causal analysis, namely Niño 3.4 sea surface temperature (SST) in JJA (El Niño Southern Oscillation [abbreviated as ENSO]) and SST anomaly over the eastern North Pacific to the east of the Hawaiian Islands (abbreviated as Pacific SST) in March‐April‐May (MAM) period. We argue that the droughts are strongly linked to ENSO variability, with drier years corresponding to El Niño conditions. The droughts can be predicted with a lead time of 3 months based on their associations with Pacific SST, with higher SST preceding drier conditions. We find that under the SSP585 scenario, the Coupled Model Intercomparison Phase 6 (CMIP6) multi‐model ensembles show significant increase in both the maximum number of consecutive dry days in the Indonesian Borneo region in JJA (p = 0.006) and its linear association with Pacific SST in MAM (p = 0.001) from year 2061 to 2100 compared with the historical baseline. Some models are showing unrealistic amounts of JJA rainfall and underestimate drought risks in Indonesian Borneo and their teleconnections, owing to the underestimation of ENSO amplitude and overestimation of local convections. Our study strengthens the possibility of early warning triggers of fires and stresses the need for taking enhanced climate risk into consideration when formulating long‐term policies to eliminate fires. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S), a novel gas signaling molecule, has been shown to enhance plant resistance to various abiotic stresses. Here, we investigated the effect of sodium hydrosulfide (NaHS, a H2S donor) on the growth, photosynthetic parameters, and enzyme activities related to carbon and nitrogen metabolism, as well as the levels of carbohydrates and nitrogen metabolites in foxtail millet seedlings subjected to drought stress conditions in pots. The findings revealed that drought stress led to a significant 41.2% decline in the total dry weight (DW) after 12 days of treatment, whereas plants treated with NaHS showed a lesser reduction of 18.7% in total DW. Under drought stress, exogenous NaHS was found to enhance carbon metabolism in foxtail millet seedlings by significantly enhancing photosynthetic capacity, starch, and sucrose content. Additionally, exogenous NaHS was observed to improve nitrogen metabolism by substantially increasing soluble protein content, nitrogen assimilate activity, and synthesis of nitrogen-containing compounds in foxtail millet seedlings. In summary, the exogenous application of NaHS stimulated seedling growth and enhanced drought resistance in foxtail millet by modulating carbon and nitrogen metabolism processes affected by drought stress. [ABSTRACT FROM AUTHOR]

Adaptive characteristics of plants, such as those associated with photosynthesis and resource use efficiency, are usually affected by synthesis costs and resource availability. The impact of extreme climate events such as long-term drought on plant physiological functions needs to be examined, particularly as it concerns the internal management of water and nitrogen (N) resources. In this study, we evaluated the resource management strategies for water and N by xerophytic shrubs, Artemisia ordosica and Salix psammophila, under extreme summer drought. This was carried out by comparing the plants' physiological status during periods of wet and dry summer conditions in 2019 and 2021. Compared with the wet period, A. ordosica and S. psammophila both decreased their light-saturated net carbon (C) assimilation rate (Asat), stomatal conductance (gs), transpiration rate (E), leaf N content per leaf area (Narea), and photosynthetic N use efficiency (PNUE) during the summer drought. Whether in wet or dry summers, the gas-exchange parameters and PNUE of A. ordosica were generally greater than those associated with S. psammophila. The instantaneous water use efficiency (IWUE) response to drought varied with species. As a drought-tolerant species, the A. ordosica shrubs increased their IWUE during drought, whereas the S. psammophila shrubs (less drought-tolerant) decreased theirs. The divergent responses to drought by the two species were largely related to differences in the sensitivity of gs, and as a result, E. Compared with A. ordosica, S. psammophila's inferior plasticity regarding gs response affected its ability to conserve water during drought. Our research illustrates the need for assessing plasticity in gs when addressing plant adaptation to long-term drought. A high dry-season IWUE in xerophytic shrubs can benefit the plants by augmenting their C gain. [ABSTRACT FROM AUTHOR]

The main production area of Camellia vietnamensis (C. vietnamensis) is in the low mountain and hilly areas of southern China. The low survival rate of seedlings caused by drought is one of the main obstacles restricting the development of the C. vietnamensis industry. An exploration of the key adaptation mechanism of C. vietnamensis to drought stress is important in order to improve its drought resistance. We conducted a study on the morphological, physiological, biochemical, and drought resistance-related genes of five C. vietnamensis cultivars grown in Hainan province under varying degrees of drought stress. The results indicate that drought stress can lead to a decrease in the relative water content and photosynthetic capacity of C. vietnamensis leaves. Compared with the control, the drought damage index, malondialdehyde, relative electrical conductivity, soluble protein, soluble sugar and proline contents of the five C. vietnamensis cultivars increased with drought-stress duration and degree. With increasing drought-stress intensity, the activity of antioxidant enzymes and the content of related metabolites (total polyphenols, total flavonoids, tea saponins) gradually increased, and the expression levels of phenylpropanoid pathway-related genes (Cv4CL1, CvCAD1, CvCAD2, CvPOX1, CvPOX2, CvPOX3) were upregulated. Based on the results of the drought tolerance coefficients, principal component analysis, and hierarchical cluster analysis, we classified five C. vietnamensis cultivars into drought-tolerant cultivars ('Haida 1'); moderately drought-tolerant cultivars ('Haida 4' and 'Wanhai 4'); and drought-sensitive cultivars ('Wanhai 3' and 'Wanhai 1'). The results of this study provide a theoretical basis for the promotion and cultivation of C. vietnamensis and the selection of drought-resistant cultivars. [ABSTRACT FROM AUTHOR]

Subtropical forests, recognized for their intricate vertical canopy stratification, exhibit high resistance to extreme drought. However, the response of leaf phenology to drought in the species‐rich understory remains poorly understood. In this study, we constructed a digital camera system, amassing over 360,000 images through a 70% throughfall exclusion experiment, to explore the drought response of understory leaf phenology. The results revealed a significant advancement in understory leaf senescence phenology under drought, with 11.75 and 15.76 days for the start and end of the leaf‐falling event, respectively. Pre‐season temperature primarily regulated leaf development phenology, whereas soil water dominated the variability in leaf senescence phenology. Under drought conditions, temperature sensitivities for the end of leaf emergence decreased from −13.72 to −11.06 days °C−1, with insignificance observed for the start of leaf emergence. Consequently, drought treatment shortened both the length of the growing season (15.69 days) and the peak growth season (9.80 days) for understory plants. Moreover, this study identified diverse responses among intraspecies and interspecies to drought, particularly during the leaf development phase. These findings underscore the pivotal role of water availability in shaping understory phenology patterns, especially in subtropical forests. [ABSTRACT FROM AUTHOR]