Severe Drought Periods Research Articles

GWAS for Drought Resilience Traits in Red Clover (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is a well-appreciated grassland crop in temperate climates but suffers from increasingly frequent and severe drought periods. Molecular markers for drought resilience (DR) would benefit breeding initiatives for red clover, as would a better understanding of the genes involved in DR. Two previous studies, as follows, have: (1) identified phenotypic DR traits in a diverse set of red clover accessions; and (2) produced genotypic data using a pooled genotyping-by-sequencing (GBS) approach in the same collection. In the present study, we performed genome-wide association studies (GWAS) for DR using the available phenotypic and genotypic data. Single nucleotide polymorphism (SNP) calling was performed using GBS data and the following two red clover genome assemblies: the recent HEN-17 assembly and the Milvus assembly. SNP positions with significant associations were used to delineate flanking regions in both genome assemblies, while functional annotations were retrieved from Medicago truncatula orthologs. GWAS revealed 19 significant SNPs in the HEN-17-derived SNP set, explaining between 5.3 and 23.2% of the phenotypic variation per SNP–trait combination for DR traits. Among the genes in the SNP-flanking regions, we identified candidate genes related to cell wall structuring, genes encoding sugar-modifying proteins, an ureide permease gene, and other genes linked to stress metabolism pathways. GWAS revealed 29 SNPs in the Milvus-derived SNP set that explained substantially more phenotypic variation for DR traits, between 5.3 and 42.3% per SNP–trait combination. Candidate genes included a DEAD-box ATP-dependent RNA helicase gene, a P-loop nucleoside triphosphate hydrolase gene, a Myb/SANT-like DNA-binding domain protein, and an ubiquitin–protein ligase gene. Most accessions in this study are genetically more closely related to the Milvus genotype than to HEN-17, possibly explaining how the Milvus-derived SNP set yielded more robust associations. The Milvus-derived SNP set pinpointed 10 genomic regions that explained more than 25% of the phenotypic variation for DR traits. A possible next step could be the implementation of these SNP markers in practical breeding programs, which would help to improve DR in red clover. Candidate genes could be further characterized in future research to unravel drought stress resilience in red clover in more detail.

Subalpine fir response to drought in northern British Columbia, Canada

Abstract As global warming continues, drought severity and duration are expected to increase in many areas of the world, necessitating a thorough understanding of how trees react to severe drought periods. In this study, we used dendrochronological analyses to determine the response of subalpine fir [Abies lasiocarpa (Hook.) Nutt.] to historical drought events on sites along a latitudinal interval of 500 km in the Rocky Mountains in northern British Columbia, Canada. We used the ClimateBC Climate Moisture Deficit index to approximate drought conditions at the sites and to identify common drought years across sites. We then compared wood densities across the time series to temperature, precipitation, and climate moisture indices for the locations studied to determine relationships between subalpine fir wood densities and climate in this region. We demonstrated that subalpine fir wood density was often negatively correlated to spring and summer temperatures and that these stands are responsive to drought events in the short term. We found that the latitudinal difference between stands was not as pronounced as expected; however, northern sites had a stronger climate response and more frequent drought years than southern sites. This cautiously suggests that the impacts of climate change may be more intensely felt in forests at more northern latitudes. If droughts continue to become more frequent in northern British Columbia, as is predicted with changing climates, we might expect less carbon sequestration and lower wood strength in subalpine fir trees from this region.

Nitrogen facilitation was maintained in sown Mediterranean forage mixtures despite drought stress conditions with concurrent general benefits upon plant aboveground water status and yield

There is an urge to optimise the sustainability and resilience of grasslands, especially in light of the extreme weather risks posed by climate change. Plant sown diversity could contribute to mitigating these risks by improving resource use efficiency as well as reducing reliance on fertilisation. We established a field experiment to determine forage swards’ performance in terms of water use, nitrogen (N) use, and dry matter (DM) yield in a semi-arid Mediterranean area which faced a severe drought period. Most variables were tested over three growing seasons, whilst DM yield had an extra year of sampling in which two levels of N fertilisation were tested. Following the Generalised Diversity-Interactions modelling approach, we manipulated the composition and evenness of forage swards including a grass (Festuca arundinacea), a legume (Medicago sativa), and a non-legume forb (Cichorium intybus). Communities were grown as monocultures or mixtures of three species according to a simplex design, which allowed us to estimate separately the two components of the diversity effect: the individual species effects and that due to species interactions. Models were tested both with sown proportions (Pi0) and realised proportions (PiR). The Pi0 models indicated a major beneficial effect of mixtures in contrast to the average monoculture performance for all studied variables. In contrast, PiR models revealed that some of the effects in Pi0 models are indeed explained by the growing proportion of M. sativa over time. However, beneficial interaction effects are still found in PiR models, especially concerning N2 fixation (with δ15N as proxy), which was maintained regardless of the drought stress level experienced by the swards. All things considered, mixed swards merit attention as a valuable nature-based solution that can optimise N management (by boosting N2 input through fixation) as well as water use. This would result in well-nurtured swards with a better ability to cope with drought stress and maintain productivity.

Drought mitigation operation of water conservancy projects under severe droughts

ABSTRACT Severe droughts typically last for extended periods and result in substantial water shortages, posing challenges for water conservancy projects. This study proposed a framework for coordinating drought mitigation operations across projects of various scales. First, the regulation and drought mitigation capacities of each project were analyzed, and thus critical reservoirs was identified. Subsequently, a joint regulation model for water supply, prioritizing projects based on their regulatory capacity from weak to strong, was established. An optimization model is then developed to determine the drought-limited levels for critical reservoirs, aiming to minimize water shortages. This model facilitates temporal coordination of water resources to prevent severe water shortages with frequent mild water shortages. Results in the Chuxionglucheng District of Chuxiong, Yunnan Province, during the severe drought period from 2009 to 2013 demonstrate significant reductions in water shortage. Specifically, the maximum shortage ratio decreased from 59 to 45% for agriculture and from 52 to 8% for industry. Moreover, emergency measures for drought mitigation were compared and recommended for regions with weak projects regulation. Overall, this framework offers a systematic approach to enhancing drought resilience across diverse water conservancy projects in severe drought conditions.

Is snow drought a messenger for the upcoming severe drought period? A case study in the Upper Mississippi River Basin

The exacerbation of floods and the extension of droughts, attributed to climate change and human-induced factors, are posing a substantial risk to communities by causing water scarcity. The significance of safeguarding water resources and managing them is increasingly gaining prominence. Snow is an efficient source of water for recharging groundwater compared to rainfall. This is attributed to its gradual melting process and capacity to infiltrate the soil, thereby providing sustenance to the groundwater. Thus, snow drought can be considered a major contributing factor to the issue of water scarcity. The objective of this study was to investigate the evolution of snow drought over the period since 1980, as well as its impact on agricultural drought across the Upper Mississippi River Basin (UMRB). An analysis is conducted for comparison between the spatial estimations of snow drought in the UMRB and two drought indicators, namely the evaporative demand drought index (EDDI) and water deficit amounts. The effects of the El Niño and La Niña phenomena on the UMRB as well as the results of the summer agricultural drought conditions were investigated since 2000. The results point to two important findings: 1) the snow-drought-affected zones show an increasing trend since 1980 and 2) severe snow droughts in the winter (from October to April) of a water year trigger severe agricultural droughts in the summer months of the same water year since 2000. It is seen that monitoring snow droughts is as essential as following rainfall regimes in the planning of water resources, agricultural production, and irrigation methods.

Evidence for regional-scale declines in carabid beetles in old lowland beech forests following a period of severe drought

ContextEvidence for declines in insect populations is growing with climate change being one suspected driver. Forests, however, are still underrepresented in the relevant research. Recent droughts (2018–2020) have severely affected forests in Central Europe and have been linked to declines in carabid abundance, biomass as well as changes in species traits at the local scale.ObjectiveWe tested drought effects on forest carabids at regional scale. We additionally investigated whether variability in drought effects could be explained with the initial community composition and the local environmental context.MethodsWe used generalized linear mixed models to compare data from 1999 to 2001 and 2020 to 2022 across eleven old beech forest sites of high conservation interest in North-East Germany and investigated changes in carabid abundance, biomass, Hill numbers and selected species traits. We then tested additional community-related and environmental predictors to explain spatial variability in changes in biomass.ResultsWe found significant declines in biomass of 65% and in abundance of 51%. There were no significant changes in Hill numbers. We found consistent evidence that declines affected especially larger and less mobile species. Declines and changes in species traits also occurred in strictly protected old-growth beech forests. Among environmental predictors, landscape composition explained local variability in biomass declines best with stronger decline at forest sites with less forest area in their vicinity.ConclusionsOur findings reveal large-scale declines in forest carabids in the context of recent droughts and highlight the exceptional role of landscape composition in this regard. Future insect conservation strategies need to incorporate the landscape context and potential exposure to extreme weather.

Non-conservative behavior of organic matter and its interaction with metals in an equatorial estuary, Brazil.

Droughts are becoming more intense and frequent in the Brazilian semiarid because of El Niño and global climate changes. The Jaguaribe River estuary is a semiarid ecosystem that experiences a reduction in freshwater discharges due to droughts and river damming. The decrease in freshwater fluxes has increased metal availability through the water residence time increase in the Jaguaribe River estuary. Then, this study aimed to evaluate the dissolved organic matter quality and its interaction with metals in the Jaguaribe River estuary after a severe drought period. It was performed through carbon analyses, fluorescence spectroscopy, ultrafiltration technique, and determinations of metals by ICP-MS. Optical analysis showed that the dissolved organic carbon (DOC) was preponderantly composed of terrestrial-derived humic compounds, while the low ratio between the particulate organic carbon (POC) and chlorophyll-a indicated that POC was predominantly phytoplankton-derived. DOC and POC presented non-conservative removal during the estuarine mixing. DOM and dissolved elements were mostly distributed within the LMW fraction and presented a low percentage in the colloidal fraction. Li, Rb, Sr, Mo, and U showed conservative behavior, while Cu, Fe, Cr, and V had non-conservative behavior with a significant positive correlation with DOM, suggesting DOM as a relevant driver of metal availability at the Jaguaribe River estuary even during the rainy season.

Assessing Change Impacts on Flood and Drought hazard in Thua Thien Hue province using Standardized Precipitation Index (SPI)

The objective of this study is to comprehensively analyze short- and long-term drought and flood occurrences, providing valuable insights into the potential impact of climate change in the future. Our analysis, utilizing the SPI-6 and SPI-12 indices, focuses on historical data spanning from 1979 to 2019, revealing noteworthy patterns. Notable periods of severe drought include September 1982 to August 1983, September 2004 to August 2005, and October 2014 to August 2015. Conversely, instances of elevated humidity and extreme inundation were recorded from October 1980 to August 1981, October 1995 to June 1997, November 1999 to October 2000, November 2007 to October 2008, October 2011 to August 2012, and January 2017 to August 2018. These findings are consistent with historical records of drought and flood events in Thua Thien Hue Province over the past four decades. Incorporating the SPI-6 and SPI-12 indices alongside rainfall forecasts based on updated climate change and sea-level rise scenarios for 2020 in Vietnam, our study extends its projections to the period from 2020 to 2035. These projections indicate a significant departure from typical annual conditions, with both the severity and frequency of drought and flood events expected to increase. Specifically, Thua Thien Hue weather stations estimate a flood frequency of 14% (SPI-12) and 16% (SPI-6), equivalent to approximately one dry month every seven months. High humidity events are projected to occur at an 18% frequency, roughly once every 5-6 months. Analysis of future scenarios under RCP4.5 and RCP8.5 reveals varying levels of risk associated with drought and flood occurrences. Generally, the risk of flooding is slightly lower than that of drought, with only marginal differences observed in scenario RCP8.5. When considering seasonal rainfall patterns—where half of the year experiences a dry season and the other half is rainy—the incidence of drought surpasses that of high humidity in scenario RCP4.5. In contrast, in scenario RCP8.5, the likelihood of flooding outweighs that of drought. It’s noteworthy that historically, mountainous areas within Thua Thien Hue Province have experienced fewer droughts in comparison to coastal regions. Furthermore, the severity of drought and flood events is more pronounced in scenario RCP8.5, particularly concerning flood events. This underscores that despite higher total rainfall in RCP8.5, leading to more severe inundation events, the distribution exhibits unevenness marked by extreme conditions, including more severe drought events.

Liquid in vitro culture system allows gradual intensification of osmotic stress in Solanum tuberosum through sorbitol

Because of their shallow root system, drought stress is a major problem in potato cultivation. Due to climate change more severe drought periods are expected to occur in the vegetative growth phase of potato growth. Therefore, there is a great need for drought tolerant potato genotypes. Potato responds to drought stress in the field in various ways, including osmoregulation. Osmotic stress can be induced in vitro by adding an osmotic agent and thus lowering the osmotic potential of the medium. In this study, a new, cost-effective in vitro test system is presented, in which the osmotic agent can be gradually added after root formation to prevent an osmotic shock. This is achieved by using sieves as plant holders and liquid medium, which, allows an improved simulation of gradually drying soil. Responses to osmotic stress in four potato genotypes were analysed and an increase in proline under osmotic stress was detected. Moreover, genes of interest that were postulated to be linked to drought stress were shown by quantitative qRT-PCR to be regulated under osmotic stress. Furthermore, we showed that the content of sorbitol, which was used as osmotic agent, was 700- fold higher for ‘Eurostarch’ after seven days under osmotic stress and 1093- fold higher after 14 days, respectively, compared to control plants without sorbitol addition. Therefore, further investigations must show, whether it was taken up through the roots, is metabolised, stored or de novo synthesised by the potato plants.KeypointsThe established novel in vitro test system for potato allows gradually increasing stress exposition of rooted plants. Sorbitol seems not an ideal osmotic agent as it is likely taken up.

Comparing Remote Sensing and Geostatistical Techniques in Filling Gaps in Rain Gauge Records and Generating Multi-Return Period Isohyetal Maps in Arid Regions—Case Study: Kingdom of Saudi Arabia

Arid regions are susceptible to flash floods and severe drought periods, therefore there is a need for accurate and gap-free rainfall data for the design of flood mitigation measures and water resource management. Nevertheless, arid regions may suffer from a shortage of precipitation gauge data, whether due to improper gauge coverage or gaps in the recorded data. Several alternatives are available to compensate for deficiencies in terrestrial rain gauge records, such as satellite data or utilizing geostatistical interpolation. However, adequate assessment of these alternatives is mandatory to avoid the dramatic effect of using improper data in the design of flood protection works and water resource management. The current study covers 75% of the Kingdom of Saudi Arabia’s area and spans the period from 1967 to 2014. Seven satellite precipitation datasets with daily, 3-h, and 30-min temporal resolutions, along with 43 geostatistical interpolation techniques, are evaluated as supplementary data to address the gaps in terrestrial gauge records. The Normalized Root Mean Square Error by the mean value of observation (NRMSE) is selected as a ranking criterion for the evaluated datasets. The geostatistical techniques outperformed the satellite datasets with 0.69 and 0.8 NRMSE for the maximum and total annual records, respectively. The best performance was found in the areas with the highest gauge density. PERSIANN-CDR and GPM IMERG V7 satellite datasets performed better than other satellite datasets, with 0.8 and 0.82 NRMSE for the maximum and total annual records, respectively. The spatial distributions of maximum and total annual precipitation for every year from 1967 to 2014 are generated using geostatistical techniques. Eight Probability Density Functions (PDFs) belonging to the Gamma, Normal, and Extreme Value families are assessed to fit the gap-filled datasets. The PDFs are ranked according to the Chi-square test results and Akaike information criterion (AIC). The Gamma, Extreme Value, and Normal distribution families had the best fitting over 56%, 34%, and 10% of the study area gridded data, respectively. Finally, the selected PDF at each grid point is utilized to generate the maximum annual precipitation for 2, 5, 10, 25, 50, and 100-year rasters that can be used directly as a gridded precipitation input for hydrological studies.

A drought monitoring and early warning service for food security in South Africa

In this paper we present an operational system for drought monitoring and early warning over South Africa-Lesotho. The indicators used for the alert issuance are based on meteorological, agricultural and hydrological indices, assembled by satellite and reanalysis raw data, to cover for all aspects of drought. The service is operationally updated every 10 days and has a spatial resolution of 10 Km. A severe drought period for South Africa covering the time period 2017–2020 was used to test the performance of the drought system. Our analysis indicated that the service is useful, providing sufficient warning on the onsets of and duration of droughts. Comparison of our results with a South African national drought service indicates a very good agreement in early warning messaging. The service is particularly user friendly and easily transferable to any region worldwide.

An Overview of Mycorrhiza in Pines: Research, Species, and Applications.

In the latest literature, climate models show that the conditions for pines, spruces, larches, and birches will deteriorate significantly. In Poland, as well as in other European countries, there are already signs of the decline of these species. This review article deals with the symbiotic relationships between fungi and plants, which can hardly be overestimated, using the example of pine trees. These are the oldest known symbiotic relationships, which are of great benefit to both components and can help plants, in particular, survive periods of severe drought and the attack of pathogens on the roots. This article describes symbioses and their causal conditions, as well as the mycorrhizal components of pine trees and their properties; characterizes ectomycorrhizal fungi and their mushroom-forming properties; and provides examples of the cultivation of pure fungal cultures, with particular attention to the specificity of the mycorrhizal structure and its effects on the growth and development of Pinus species. Finally, the role of mycorrhiza in plant protection and pathogen control is described.

Multiomics analyses reveal the central role of the nucleolus and its machinery during heat stress acclimation in Pinus radiata.

Global warming is causing rapid changes in mean annual temperature and more severe drought periods. These are major contributors of forest dieback, which is becoming more frequent and widespread. In this work, we investigated how the transcriptome of Pinus radiata changed during initial heat stress response and acclimation. To this end, we generated a high-density dataset employing Illumina technology. This approach allowed us to reconstruct a needle transcriptome, defining 12 164 and 13 590 transcripts as down- and up-regulated, respectively, during a time course stress acclimation experiment. Additionally, the combination of transcriptome data with other available omics layers allowed us to determine the complex inter-related processes involved in the heat stress response from the molecular to the physiological level. Nucleolus and nucleoid activities seem to be a central core in the acclimating process, producing specific RNA isoforms and other essential elements for anterograde-retrograde stress signaling such as NAC proteins (Pra_vml_051671_1 and Pra_vml_055001_5) or helicase RVB. These mechanisms are connected by elements already known in heat stress response (redox, heat-shock proteins, or abscisic acid-related) and with others whose involvement is not so well defined such as shikimate-related, brassinosteriods, or proline proteases together with their potential regulatory elements. This work provides a first in-depth overview about molecular mechanisms underlying the heat stress response and acclimation in P. radiata.

A comprehensive drought index based on spatial principal component analysis and its application in northern China.

In the background of the greenhouse effect, drought events occurred more frequently. How to monitor drought events scientifically and efficiently is very urgent at present. In this study, we employed the Vegetation Water Supply Index (VSWI), Temperature Vegetation Drought Index (TVDI), and Crop Water Stress Index (CWSI) as individual variables to construct a composite drought index (CDI) using spatial principal component analysis (SPCA). The validity of CDI was assessed using gross primary productivity (GPP), soil moisture (SM), Standardized Precipitation Evapotranspiration Index (SPEI), and Vegetation Condition Index (VCI). CDI was subsequently used for drought monitoring in northern China from 2011 to 2020. The results showed that (1) at a 99% confidence level, the Pearson correlation coefficients between CDI and GPP was 0.72, while the value between CDI and SM was 0.69, which indicated the relationship between SM, GPP, and CDI was significant. (2) We compared CDI with other variables such as Standardized Precipitation Evapotranspiration Index (SPEI) and Crop Drought Index (CDI) and found that the monitoring result of CDI was more sensitive, which indicated that the proposed CDI had a better effect in local drought monitoring. (3) The results of CDI showed that the drought status in the northern region during 2011-2020 lasted from March to October, and the high severe drought period generally occurs in March-May and September-October, with low severe drought in June-August.

Meteorological Drought Assessment for Jhelum River Basin, Jammu and Kashmir\'s Sangam and Ram Munshi Bagh Stations

Abstract: Drought is a severe natural calamity that harms the global ecology. To examine drought conditions including intensity and duration, a variety of drought indicators (DIs) are commonly employed. This study assesses the occurrences of drought in Kashmir's Jhelum River Basin (JRB) at the Sangam and Ram Munshi Bagh stations. Several DI approaches, such as Deciles, Percent of Normal (PN), and Standardized Precipitation Index (Normal-, Log-, and Gamma-SPI), are used to analyse 20 years of monthly recorded precipitation data from 2002 to 2023. Every technique is used on the annual long-term precipitation data set. The findings indicate that nearly identical outcomes are obtained for the stations by the DI approaches. While the normalSPI indicates rainy and less droughty conditions, the log-SPI and gamma-SPI forecast moderate dry conditions. The results emphasize that the PN method predicts more moderate drought years in comparison with SPI method, however, Deciles method shows longer period of extreme and severe drought than other methods. As a result, the five methods indicate various drought intensities in 2017, 2018,2001, and 2002 with a peak moderate drought in 2017 in the Sangam station. The Ram Munshi Bagh station area experienced the less drought conditions from 2002 to 2023 with a moderate drought in 2017 and 2018 as well. Therefore, moderate drought conditions happened in 2017 -2018 in both stations confirm to the recorded drought reports for the same region.

Precipitation Assessment of Kabul City from 2006-2020

Assessment of precipitation conditions is a crucial factor in determining an area's current and future climatic conditions. This study investigates precipitation conditions in Kabul City from 2006 to 2020, covering the last 15 years. Research shows that 50% of precipitation occurs in the winter season in Kabul and varies from year to year. The trend line of precipitation has shown a minimal increase of 0.64mm/yr, which is insufficient due to the dense urban population's high-temperature increase and daily water usage. The study aims to assess the precipitation conditions in Kabul for the past 15 years. For this purpose, climatic data from the Afghanistan Meteorological Department (AMD) and daily precipitation data were analyzed. Standard deviation equations were applied to determine the dry and wet years from the average (normal) year. The analysis of the precipitation data demonstrated two periods of severe droughts and one moderate rainy period. The first severe drought occurred from 2007 to 2008, the second period of severe drought occurred from 2016 to 2018, and one moderate rainy period occurred from 2011 to 2014. The results indicate that Kabul City's precipitation is not enough due to the usage of groundwater by the dense urban population, car wash companies, public baths, and the recent establishment of too many greenhouses in the suburbs of Kabul City. Consequently, the water balance is negative, leading to a shortage. Understanding the precipitation condition of Kabul City and its trends over the past 15 years is crucial for policymakers and stakeholders when making decisions on water resources management, agriculture, food production, and environmental challenges incorporation projects. This research provides valuable information that can support evidence-based decision-making to address the challenges posed by the changing climate patterns in Afghanistan.

Spatiotemporal consistency and inconsistency of meteorological and agricultural drought identification: A case study of India

Drought identification is challenging because the severity, intensity and frequency of extreme drought events are heterogenous. Incorporating multiple datasets is to generate standardized drought indices for effective drought assessment, monitoring, and develop early warning systems. This study aims to explore the spatio–temporal relationship among drought indices of precipitation, soil moisture, vegetation condition and health based on standardizing multiple drought indices with trend detection. The indices were derived through standardized drought analysis from 2001 to 2020 over India and regional level. Moreover, time series decomposition was utilized to remove seasonal and random components for trend detection. This study enhanced the comprehension of meteorological and agricultural drought conditions in India by standardizing and analyzing trends in multiple drought indices. The results revealed that the most severe drought periods for subregions were consistent for all indices with trend analysis. All indices also reported a significant decline in trend for the 2009 drought event across the subregions in India. These findings contributed to a better understanding of drought dynamics in the subregion. However, vegetation-based indices were not always consistent to the indices of precipitation and soil moisture due to ecosystem resilience or heat stress. This study offered policymakers diverse information, including correlations and variations of multiple drought indices to assist in detecting the most severe periods of drought at a regional scale.

Spatiotemporal Variation in the Meteorological Drought Comprehensive Index in the Beijing–Tianjin–Hebei Region during 1961–2023

It is crucial to investigate the characteristics of meteorological drought in the Beijing–Tianjin–Hebei (BTH) region to improve the accuracy of agriculture and water resource monitoring and management. In this study, using instrumental observation data from 85 meteorological stations in the BTH region during 1961–2023 derived from the National Meteorological Information Center, we first calculated the meteorological drought comprehensive index (MCI) and analyzed the spatiotemporal characteristics of the MCI. In the BTH region, the MCI intensity from May to June was the most severe in the intraseasonal variation. The trend of the decreasing drought intensity in May–June has occurred for the past 60 years. The southern region in the BTH region was more likely to experience droughts. Next, the spatial patterns of the top two EOF modes of the May–June MCI were depicted. The primary spatial pattern of the BTH, which was characterized by consistent changes in the MCI throughout the entire BTH region, could be represented by the first mode’s R2 of 69.01%. Then, we compared the spatial pattern of the MCI intensity under different return periods. Using the May–June MCI of 1961–2023, the drought intensity gradually increased from northwest to southeast for the 10-, 20-, and 50-year return periods. However, the drought intensity decreased and then increased from northwest to southeast based on the 1991–2023 MCI. Notably, a 20-year return period of severe drought affected Beijing and northern Hebei in 2023. Finally, we discussed the linkages of drought in the BTH region and atmospheric circulation/sea surface temperature (SST) anomalies, which were calculated using the Pearson correlation coefficient and wavelet coherence. We suggest that the MCI variations in the BTH region may be related to the SST anomalies of the Indian Ocean in 1961–1990 and the Pacific Ocean in 1991–2023, respectively. The abovementioned studies have enlightened us to focus on predicting the Pacific SST for drought, which will facilitate agricultural production and water resource management in the BTH region.

Eccrine Hydration

A series of immersion experiments has indicated that humans are able to absorb sufficient fresh water from sea water by reverse osmosis through their eccrine sweat glands to remain fully hydrated without drinking anything at all. This unique facility would have enabled our ancestors to survive periods of severe drought.

Physiological response and drought resistance evaluation of Gleditsia sinensis seedlings under drought-rehydration state

G. sinensis is a crucial tree species in China, possessing important economic and ecological value, and having a wide geographical distribution. G. sinensis seedlings is highly vulnerable to the drought-rehydration-drought cycle during their growth, and there is a lack of quantitative and systematic research on the physiological mechanisms of drought resistance and rehydration in G. sinensis. There is also a lack of good drought-resistant families and reliable methods for evaluating drought resistance, which severely hinders the selection and promotion of drought-resistant G. sinensis families and the industry's development. Therefore, this study selection 58 families seedlings of G. sinensis to drought stress and rehydration using an artificial simulated water control method in potted seedlings. The aim was to compare the effects of different levels of drought and rehydration on the growth and physiological indices of seedlings from different families. Identification of drought-resistant families and dependable drought related indices and techniques, the explanation of divergence in drought stress effects on various drought-resistant seedlings and the mechanisms underpinning growth and physiological responses, and the provision of theoretical reference for G. sinensis drought-resistant variety selection and cultivation. The Drought Resistance Index (DRI) served as the primary indicator, supplemented by growth, leaf morphology, and photosynthetic physiological indicators, to thoroughly assess and identify five distinct drought tolerant taxa while also selecting five representative families. Soluble protein (SP), proline (Pro), and malondialdehyde (MDA) contents, as well as the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) in seedlings from the five families, increased as the degree of drought intensified. The highest values were appeared during periods of severe drought, and gradually decreased after subsequent rehydration. Principal component analysis (PCA) revealed MDA and soluble sugars (SS) as the primary predictors of drought and rehydration response in G. sinensis seedlings respectively. Changes in osmoregulatory substance content and increased antioxidant enzyme activity may be crucial for responding to drought tolerance mechanisms. Leaf morphological indicators, seedling height, soil plant analysis development (SPAD) value, photosynthetic indicators, and MDA are dependable parameters for assessing the drought tolerance of G. sinensis seedlings. When assessing the drought-resistance of seedlings using physiological indicators such as photosynthesis, a comprehensive analysis should incorporate multiple indicators and methods. This evaluation approach could serve as a reference for screening exceptional drought-resistant families of G. sinensis.