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As we progress into the Anthropocene, rising temperatures have amplified evaporative demand and rendered heat-induced drought stress, or hotter drought, as the hallmark of climate change moving forward. It remains unknown, however, whether upper treeline environments have been affected. For this study, we grouped previously published and unpublished data from study sites within the southern Rocky Mountains by slope aspect to provide a possible baseline for what we expect for the Anthropocene. We returned to and resampled some of these study sites in the summer of 2019 after twelve years of sharply rising temperatures to measure patterns of seedling establishment. We also returned to a high-elevation site after seventeen years of warming to perform repeat photography in an attempt to capture visual evidence of threshold changes since 2002 in a location where little change had occurred during the twentieth century. Results from this research can be summarized into two main findings: (1) trends in recruitment over the past thirty years suggest that north-facing slopes are increasingly hospitable for successful seedling establishment compared to south-facing slopes at upper treeline and (2) spruce beetle–induced mortality is evident at upper treeline. Conceptually, this means that hotter drought could be progressively enveloping upper treeline along topoclimatic gradients. Unless ongoing trends in temperature deviate from expectations or unless precipitation increases considerably, there is little reason to justify the idea that upper treeline will continue to respond positively to hotter drought conditions during the Anthropocene, especially on south-facing slopes in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

This section offers science-related news briefs as of October 2021. Topics discussed include the degradation of water quality during periods of drought in the Central Valley region of California, the possibility of manufacturing commercial monomers without greenhouse gas emissions, and the symbiotic relationship between soybean root nodules and nitrogen-fixing bacteria.

Breeding drought tolerance in groundnuts cultivars would reduce yield losses due to drought stress in rain-fed growing areas. The mode of gene action governing the inheritance of drought tolerance and secondary traits was investigated by mating 30 lines according to North Carolina design II scheme. The parents and resulting 75 F2 progenies were grown in a split plot arrangement using an alpha lattice design, with two replications under drought and non-stressed environments for two seasons. The trials were conducted over two seasons, in 2017 A and 2017 B at the National Semi-Arid Resources Research Institute, located 27 km west of Soroti town in eastern Uganda. The results showed highly significant differences between families and parents for drought tolerance and agronomic traits. Traits including BIO, DTI(PY), DTI (BIO) and HI had the highest correlations with PY. HI was positively associated with no. of pods per plant under drought stressed and non-stressed environments. Under drought stressed environment, GCA was more important than SCA for traits such as SCMR2, and HI. However, SCA was more important than GCA for traits such as SCMR2, PY, BIO, DTI(PY), and DTI (BIO). The study identified parents with best GCA and combinations with best SCA effects for both agronomic and drought tolerance traits. The new population is shown to be a valuable genetic resource for variety selection and improvement of groundnut for adaptation to the drought prone areas of Uganda. [ABSTRACT FROM AUTHOR]

Reproductive stage drought stress is an important yield reducing factor in rainfed rice. Genetic mapping of morpho-physiological traits under the stress will help to develop cultivars suitable for drought prone environments through marker-assisted breeding (MAB). Though various yield QTLs under reproductive stage drought tolerance are available for MAB, but no robust markers controlling different morho-physiological traits are available for this stress tolerance. QTLs linked to morpho-physiological traits under drought stress were mapped by evaluating 190 F7 recombinant inbred lines (RIL) using bulk segregant analysis (BSA) strategy. Wide variations were observed in the RILs for eleven morpho-physiological traits involved during the stress. A total of 401 SSR primers were surveyed for parental polymorphism of which 77 were detected to be polymorphic. Inclusive composite interval mapping detected a total of five consistent QTLs controlling leaf rolling (qLR9.1), leaf drying (qLD9.1), harvest index (qHI9.1), spikelet fertility (qSF9.1) and relative water content (qRWC9.1) under reproductive stage drought stress. Another two non-allelic QTLs controlling leaf rolling (qLR8.1) and leaf drying (qLD12.1) were also detected to be linked and found to control the two traits. QTL controlling leaf rolling, qLR8.1 was validated in this mapping population and may be useful in MAB programs. Out of these five consistent QTLs, four (qLR9.1,qLD9.1,qHI9.1 and qRWC9.1) were detected to be novel QTLs and useful for MAB for improvement of reproductive stage drought tolerance in rice. [ABSTRACT FROM AUTHOR]

Possibility of using interspecific hybridization to increase genetic diversity of drought tolerance in safflower (Carthamus tinctorius L.) and effectiveness of different selection methods is poorly understood. The main objectives of this study were to evaluate the effectiveness of (a) interspecific hybridization to expand genetic diversity in safflower for agronomic traits and drought tolerance in advance generations and (b) different selection methods (direct vs. indirect) for improving seed yield. Interspecific hybridizations were performed between species of C. tinctorius × C. palaestinus (TP), C. palaestinus × C. oxyacantha (PO) and C. tinctorius × C. oxyacantha (TO). Based on the field screening of genotypes in F3 generation, four groups of selected genotypes (derived from combination of direct and indirect selection under both drought and normal environments along with selection based on drought tolerance index (STI)) were evaluated in F4 and F5 generations. Indirect selection for seed yield was significantly more efficient than direct selection. Selection in stress environment resulted to more efficiency than selection in normal environment. No significant difference was observed between direct selection and selection based on STI. The result showed that TP was the best population to combine high seed yield and drought tolerance in safflower. [ABSTRACT FROM AUTHOR]

Background and Aims The ability of wheat genotypes to save water by reducing their transpiration rate (TR) at times of the day with high vapour pressure deficit (VPD) has been linked to increasing yields in terminal drought environments. Further, recent evidence shows that reducing nocturnal transpiration (TRN) could amplify water saving. Previous research indicates that such traits involve a root-based hydraulic limitation, but the contribution of hormones, particularly auxin and abscisic acid (ABA), has not been explored to explain the shoot–root link. In this investigation, based on physiological, genetic and molecular evidence gathered on a mapping population, we hypothesized that root auxin accumulation regulates whole-plant water use during both times of the day. Methods Eight double-haploid lines were selected from a mapping population descending from two parents with contrasting water-saving strategies and root hydraulic properties. These spanned the entire range of slopes of TR responses to VPD and TRN encountered in the population. We examined daytime/night-time auxin and ABA contents in the roots and the leaves in relation to hydraulic traits that included whole-plant TR, plant hydraulic conductance (K Plant), slopes of TR responses to VPD and leaf-level anatomical traits. Key Results Root auxin levels were consistently genotype-dependent in this group irrespective of experiments and times of the day. Daytime root auxin concentrations were found to be strongly and negatively correlated with daytime TR, K Plant and the slope of TR response to VPD. Night-time root auxin levels significantly and negatively correlated with TRN. In addition, daytime and night-time leaf auxin and ABA concentrations did not correlate with any of the examined traits. Conclusions The above results indicate that accumulation of auxin in the root system reduces daytime and night-time water use and modulates plant hydraulic properties to enable the expression of water-saving traits that have been associated with enhanced yields under drought. [ABSTRACT FROM AUTHOR]

Aspergillus flavus colonization and aflatoxin contamination in peanut is one of the major problems of peanut production. The aflatoxin is carcinogenic and harmful to consumers. Drought resistant variety had low A. flavus infection and low aflatoxin contamination. The information on the association of root parameters and aflatoxin contamination in the end season drought is important for improvement of peanut cultivars for drought prone environments and reduction in pre-harvest aflatoxin contamination. This work aimed to investigate the association of root parameters and aflatoxin contamination of peanut in end of season drought. The split plot design was set up in the field. The two main plots were consisting of two water levels (field capacity (FC) and 1/3 available water (1/3 AW) from the R7 growth stage (R7) through harvest) and five subplots including five peanut varieties (ICGV 98308, ICGV 98324, ICGV 98348, Tainan 9 and Tifton 8). Data were recorded for Aspergillus flavus colonization, aflatoxin contamination, percent root length density, root surface, root diameter and root volume in the deeper soil layer (30-90 cm) at harvest. ICGV 98348 and ICGV 98324 were the best varieties for low aflatoxin contamination, low A. flavus colonization, and high roots traits (percent root length density, root surface, root diameter and root volume). Our studies demonstrated that roots traits may be important traits related to aflatoxin contamination and confirmed that colonization is related to aflatoxin contamination. Root traits may be useful alternative selection criteria for reduced aflatoxin contamination under terminal drought. [ABSTRACT FROM AUTHOR]

Drought represents a major constraint for agricultural productivity and food security worldwide. Plant growth promoting actinobacteria have attracted the attention as a promising approach to enhance plant growth and yield under stressful conditions. In this regard, bioprospecting in arid and semi-arid environments could reveal uncommon bacteria with improved biological activities. In the present study, the ability of actinobacteria isolated from a semi-arid environment (Saudi Arabia) to mitigate the negative impact of drought on growth and physiology of maize, a drought-sensitive crop, has been investigated. Among the different actinobacterial isolates screened for secondary metabolites production and biological activities, isolate Ac5 showed high ability of flavonoid, phytohormones and siderophores production. Moreover, Ac5 improved the growth and photosynthesis and induced a global metabolic change in the bacterized plants under water-deficit conditions. Interestingly, Ac5 treatment significantly mitigated the detrimental effects of drought stress on maize. Reduced H 2 O 2 accumulation and lipid peroxidation accompanied with higher levels of molecular antioxidants (total ascorbate, glutathione, tocopherols, phenolic acids and flavonoids) were observed in the bacterized plants. From the osmoregulation point of view, drought-stressed bacterized maize accumulated higher levels of compatible solutes, such as sucrose, total soluble sugars, proline, arginine and glycine betaine, as compared with the non-bacterized plants. Therefore, this study highlights the comprehensive impact of actinobacteria on the global plant metabolism and suggests the potential utilization of actinobacteria isolated from semi-arid environments to mitigate the negative impact of drought on crop plants. Image 1 • Biologically active actinobacteria were isolated from a semi-arid environment. • Actinobacteria improved the growth and photosynthesis of maize grown under drought. • Actinobacteria upregulated the osmoregulation and antioxidant defense metabolism. • Bacterized plants maintained proper redox homeostasis and showed lower cell damage. • Consequently, actinobacteria mitigated drought induced oxidative damage in maize. [ABSTRACT FROM AUTHOR]

Sixteen progeny lines of common beans obtained from single crosses made between two parents, GLP2 and KAT B1, were grown in randomized complete block design in a rainout shelter at the Agricultural and Mechanization Research Institute, Machakos, Kenya. The experiment was conducted to study inheritance of traits associated with drought stress adaptation and to establish if significant variation for those traits was existing in order to carry out selection for drought tolerance. The calculated mean values were used to estimate heritability, genetic advance, and correlation study for each trait. Water stress had a significant (p≤0.01) effect on the number of pods per plant, grains per plant, 100-seed weight, and yield per plant. The highest values for genotypic coefficient of variation (36.11%) and phenotypic coefficient of variation (36.70%) were recorded for pods plant-1 under stress condition. Highest broad-sense heritability estimates (96.54%, 94.97%, and 93.16%) coupled with high genetic advance as percent of the mean (22.32%, 34.97%, and 26.32%) were obtained for the number of pods plant−1, days to maturity, and yield plant−1, respectively, showing that selection of these traits together could lead to yield improvement under stressed conditions. Harvest index showed a significant and positive relationship with biomass aboveground (r=0.86) and the number of pods plant−1 (r=0.86) indicating the possibility of identifying high performing lines of common beans for drought stress environment for further studies on these traits. [ABSTRACT FROM AUTHOR]

Droughts are typical of the climate in Iran and have become more frequent over the last few decades. Iran's agriculture, water resources, and ecosystems are all vulnerable to drought. In this study, the monthly time series of precipitation, temperature, and potential evapotranspiration were obtained from the CRU TS 4.01 gridded dataset to calculate the Standardized Precipitation Index (SPI), the de Martonne Aridity Index (DMAI), and the Standardized Precipitation-Evapotranspiration Index (SPEI) during two 30-year periods (1957–1986 and 1987–2016). At the national scale, the annual SPI, DMAI, and SPEI have decreased by 0.02, 0.11, and 0.09 unit decade−1, respectively, since the beginning of the twentieth century. Over 1987–2016, these rates increased to 0.29, 0.70, and 0.36 unit decade−1. Over the period 1957–1986, 89.5% of the total area was classified by the DMAI as hyper-arid, arid, or semi-arid, increasing to 94.8% over 1987–2016. Over the period 1987–2016, around 42.1, 57.9, and 48.8% of the grid cells revealed significant (P < 0.1) decreasing trends in the annual SPI, DMAI, and SPEI, respectively (27.1, 45.5, and 35.6% at the 95% confidence level). Winter has made the largest contribution to the temporal variations of all indexes at the annual scale. Spatiotemporal variations of the SPEI were greater than the two other indexes since it considers the non-stationarity in potential evapotranspiration. It proved to be an appropriate climatic index for investigating the spatiotemporal variations of agricultural drought, as it considers the source and demand terms of the water balance equation. Analysis of the frequency of sever to moderate droughts during the two 30-year periods confirms that country's climate has significantly changed, especially in central, western, southwestern, southern, and eastern regions. [ABSTRACT FROM AUTHOR]

The genetic improvement of economically important production traits of dry bean (Phaseolus vulgaris L.), for geographic regions where production is threatened by drought and high temperature stress, is challenging because of the complex genetic nature of these traits. Large scale SNP data sets for the two major gene pools of bean, Andean and Middle American, were developed by mapping multiple pools of genotype-bysequencing reads and identifying over 200k SNPs for each gene pool against the most recent assembly of the P. vulgaris genome sequence. Moderately sized Bean Abiotic Stress Evaluation (BASE) panels, consisting of genotypes appropriate for production in Central America and Africa, were assembled. Phylogenetic analyses demonstrated the BASE populations represented broad genetic diversity for the appropriate races within the two gene pools. Joint mixed linear model genome-wide association studies with data from multiple locations discovered genetic factors associated with four production traits in both heat and drought stress environments using the BASE panels. Pleiotropic genetic factors were discovered using a multi-trait mixed model analysis. SNPs within or near candidate genes associated with hormone signaling, epigenetic regulation, and ROS detoxification under stress conditions were identified and can be used as genetic markers in dry bean breeding programs. [ABSTRACT FROM AUTHOR]

We have analyzed the record-breaking drought that affected western and central Europe from July 2016 to June 2017. It caused widespread impacts on water supplies, agriculture, and hydroelectric power production, and was associated with forest fires in Iberia. Unlike common continental-scale droughts, this event displayed a highly unusual spatial pattern affecting both northern and southern European regions. Drought conditions were observed over 90% of central-western Europe, hitting record-breaking values (with respect to 1979–2017) in 25% of the area. Therefore, the event can be considered as the most severe European drought at the continental scale since at least 1979. The main dynamical forcing of the drought was the consecutive occurrence of blocking and subtropical ridges, sometimes displaced from their typical locations. This led to latitudinal shifts of the jet stream and record-breaking positive geopotential height anomalies over most of the continent. The reduction in moisture transport from the Atlantic was relevant in the northern part of the region, where decreased precipitation and increased sunshine duration were the main contributors to the drought. On the other hand, thermodynamic processes, mostly associated with high temperatures and the resulting increase in atmospheric evaporative demand, were more important in the south. Finally, using flow circulation analogs we show that this drought was more severe than it would have been in the early past. [ABSTRACT FROM AUTHOR]

Plants have evolved different mechanisms to survive under stress conditions. This field study was conducted to evaluate the influence of nitrogen (N) application on dry biomass allocation and translocation in two maize varieties under short pre-anthesis and prolonged bracketing flowering period of drought. Two maize varieties, 'Pioneer 30B80ʹ and 'Suwan 4452ʹ receiving N at 0 (control), 160 (optimal) and 320 (supra-optimal) kg ha−1 were subjected to short pre-anthesis and prolonged bracketing flowering periods of drought. Prolonged bracketing flowering period of drought had more suppressive effect on anthesis-silking interval, dry matter allocation and translocation, leaf greenness, contribution of current assimilates to grain (CCAG), kernel number, kernel weight and kernel yield of two maize varieties than a short pre-anthesis drought. Nitrogen application at optimal level was the best for all traits, except CCAG. The maize variety 'Pioneer 30B80ʹ performed better under both drought types due to more root xylem vessels of large size and more accumulation of dry matter in leaves and roots than the variety 'Suwan 4452ʹ. Therefore, the variety 'Pioneer 30B80ʹ may be planted in drought prone environments and may be used in breeding program aimed at developing drought-tolerant cultivars. [ABSTRACT FROM AUTHOR]

Climate change projections for the western United States suggest that many regions will experience increasing frequency and severity of droughts. In summer 2015, the Pacific Northwest experienced a drought with early onset of stream low flows, reduced summer discharge, and elevated temperatures. We evaluated population responses of two dominant stream predators—coastal cutthroat trout (Oncorhynchus clarkii clarkii) and coastal giant salamander (Dicamptodon tenebrosus)—across nine Cascade Mountain streams. Drought conditions impacted both trout and salamanders, but their responses differed. Adult trout abundance and biomass were significantly lower in 2015 relative to 2014, a year with discharge and temperature closer to historical norms. Juvenile trout abundance did not differ between years but juveniles were significantly larger in 2015. Salamander abundance and biomass were not significantly different between years but body condition was lower in all nine streams in 2015. Differences in temperature among streams did not explain trout or salamander responses. Habitat was important for trout responses with trout abundance and biomass experiencing smaller declines in systems with more deep pool area. Despite notable short-term drought impacts to trout and salamanders in 2015, populations recovered to pre-drought conditions within two years in all but the smallest stream. [ABSTRACT FROM AUTHOR]

Abstract The Loess Plateau region of China is under increasing water shortage due to declining soil water content after reforestation. Thus, assessing the changes in soils properties in reforested lands is critical for sustainable restoration of vegetation. We conducted a continuous rainfall manipulation experiment from June 2015 to November 2016 using mature black locust (Robinia pseudoacacia) on southern Loess Plateau of China. The soil hydrological properties, aggregate distribution and aggregate organic carbon (OC) and total nitrogen (N) concentrations were measured. Two years of drought stress caused a significant decline in saturated hydraulic conductivity and total porosity, but an increase bulk density in the 0–10 cm soil layer. The short drought stress significantly decreased soil aggregate stability due to a decline in macro-aggregate mass. Drought stress significantly decreased total soil OC concentration and macro- and micro-OC or N concentrations, but had no significant effect on total N concentration after two years of drought. Furthermore, the influence of short drought on soil hydrological properties, aggregate distribution and aggregate OC and total N concentrations was mainly evident at the depth of 10 cm. Our results indicated that short drought has the potential to damage soil properties. The results of this study could provide more insight into the sustainability of afforestation in semi-humid areas of China's Loess Plateau. Highlights • Drought significantly changed soil physical properties in the topsoil layer. • Drought significantly decreased the soil aggregate stability. • Drought significantly decreased the soil-aggregated OC and N concentrations. • Drought has potential to worsen soil properties. [ABSTRACT FROM AUTHOR]

It has recently been reported that changing precipitation patterns increase tree mortality and reduce biomass accumulation in northern temperate and boreal forests. Functional diversity can mitigate the impacts of climate extremes in different types of ecosystems, but few studies have focused on tree functional diversity in forest ecosystems. It is critical to identify functional traits that could help anticipate the impact of drought on tree mortality, and how these affect above‐ground tree biomass productivity at the ecosystem level.We tested how three functional traits (ratio of dry leaf mass per unit area [LMA], xylem pressure at which 50% of stem xylem conductivity is lost through cavitation [Ψ50] and leaf area to sapwood ratio) influence severe drought impacts on stand mortality and productivity. We used structural equation modelling to compare the effect of a latent variable composed of these three traits between plots that had suffered drought and plots that had not, on the mortality and productivity of northern temperate and boreal forests of Québec, Canada.A latent variable composed of LMA and Ψ50 significantly explained drought‐induced tree mortality, but did not explain stand productivity response to severe drought. Therefore, even if these traits relate to the ability of species to survive drought (drought tolerance) at the tree level, they did not affect the maintenance of plant productivity during drought events (drought resistance) at the stand scale. We hypothesize that the effect of tree mortality on productivity was likely compensated by the formation of canopy openings that stimulate the growth of surviving trees.Synthesis and applications. Our results show that mitigation of water loss and xylem resistance to cavitation contribute similarly to severe drought tolerance in trees within northern temperate and boreal forests. Therefore, including drought‐resistant trees in fine‐scale mixtures might mitigate the impacts of drought on forest productivity due to the survivors' response to released resources. Our results show that mitigation of water loss and xylem resistance to cavitation contribute similarly to severe drought tolerance in trees within northern temperate and boreal forests. Therefore, including drought‐resistant trees in fine‐scale mixtures might mitigate the impacts of drought on forest productivity due to the survivors' response to released resources. [ABSTRACT FROM AUTHOR]

Highlights • Temperate trees strongly benefit from low-amount drought-intermitting rainfalls. • Trees with higher hydraulic conductivity use these rainfall events more efficiently. • Duration of the rainfall-facilitated recovery was between 2 and 9 days on average. Abstract Decreasing amounts of precipitation and more frequent dry periods will challenge temperate European forests in the future. During such dry periods, short drought-intermitting rainfall events might be the only renewing water source for trees. We investigated the effects of short drought-intermitting rainfall events on the water relations of mature individuals of six different tree species in a near-natural temperate forest during the exceptionally dry summer of 2015. We found the trees to strongly respond to short drought-intermitting rainfall events: maximum daily sap flow recovered already at precipitation amounts of 1.5 mm by up to 20%, and tree water deficit (TWD) and midday shoot water potential (Ψ midday) improved by up to 60% from rainfall amounts of >4.5 mm. We speculate that a mix of foliar and root water uptake as well as relaxation of canopy VPD and thus stomatal water control lead to the observed recoveries. Hydraulic conductivity was found to partly explain the differences in TWD recovery among species. Duration of the rainfall-facilitated recovery of tree water relations was on average 3 days in the coniferous species and Q. petraea but distinctly longer in C. betulus and F. sylvatica for which it reached 9 days. These results show that drought-intermitting short rainfall events strongly facilitate the relaxation of water stress in temperate tree species during drought events and possibly contribute as such to the ability of temperate trees to withstand longer periods of drought. [ABSTRACT FROM AUTHOR]

In the present study we performed a microcosm experiment to assess the effects of the insecticide lufenuron on zooplankton communities exposed to increased temperature and drought in (semi‐)arid regions. The experiment consisted of 3 environmental scenarios, assessed in 2 parts. Firstly, we assessed how water temperature (20 and 28 °C) affects the sensitivity and resilience of the zooplankton community to lufenuron. Secondly, we investigated the influence of drought on the structure of the zooplankton community at a high water temperature (28 °C) and evaluated its possible interaction with lufenuron. The results show that the community exposed to lufenuron at 28 °C had a faster lufenuron‐related response and recovery than the community at 20 °C. The combined effects of lufenuron and temperature resulted in a synergistic effect on some taxa (Daphnia sp., Cyclopoida, and Copepoda nauplii). The tested zooplankton community had a high resilience to drought, although some particular taxa were severely affected after desiccation (Calanoida). Interactions between drought and lufenuron were not statistically significant. However, rewetting after desiccation contributed to lufenuron remobilization from sediments and resulted in a slight Cyclopoida population decline at high exposure concentrations. The study shows how environmental conditions related to global change in (semi‐)arid regions may influence chemical fate and the vulnerability of zooplankton communities to chemical stress. Environ Toxicol Chem 2019;38:396–411. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Highlights • P. indica colonization readjusts plant metabolites and proteome to enhance adapt to stress. • P. indica colonization redistributes resources in the host plant to reduce negative effect imposed by the stress. • P. indica colonization sustains the presence of aquaporin water channels in drought-stressed plants. • P. indica colonization regulates proteins involved in autophagy in drought-stressed plants. Abstract The root fungal endophyte Piriformospora indica promotes the growth and survival of plants belonging to a number of species when exposed to various abiotic stresses, including drought, a major constraint of crop productivity. The application of 'omics technologies has revealed much of the molecular basis of the plant drought stress response. Here, the proteomic and metabolomic response of the leaves of moisture-stressed barley plants inoculated with P. indica was characterized. The abundance of 145 proteins was altered by the imposition of moderate drought on plants inoculated by P. indica, as was that of 104 in non-inoculated plants, while an episode of more severe stress altered the content of, respectively, 144 and 462 proteins. Many of these responsive proteins were involved in the plant's primary metabolism, in particular acting to mitigate the damage caused by oxidative stress. Colonization of the roots by P. indica enhanced the activity of both the photosystem and the electron transfer chain, and also promoted the accumulation of proteins protective of photorespiration, energy modulation, primary metabolism, transporters and autophagy. The beneficial effect of P. indica colonization on autophagy in plants exposed to stress may relate to alterations in the host's amino acid metabolism. [ABSTRACT FROM AUTHOR]

Highlights • Salicylic acid pretreatment alleviates drought-induced stress symptom. • Drought enhanced endogenous level of ABA and JA, as well as their signaling genes. • SA-mediated modulation coincided with antagonistic depression of ABA-signaling genes. • SA-mediated NPR1-dependent proline synthesis involves in redox control under drought. Abstract The goal of this study was to characterize hormonal regulation of drought stress-induced responses and salicylic acid (SA)-mediated stress responses, focusing on redox control. The responses of reactive oxygen species (ROS) and proline metabolism, antioxidant activity, and redox status to SA pretreatment and/or drought imposition were interpreted as being linked to those of endogenous hormonal levels and their signaling genes, especially in redox control processes. Drought enhanced the endogenous levels of abscisic acid (ABA) and jasmonic acid (JA) resulting in an increase of ABA/SA and (ABA + JA)/SA. The changes in endogenous hormonal balance were concomitant with an accumulation of ROS and proline, accompanied by a loss of reducing potential [NAD(P)H/NAD(P)+ and GSH/GSSG]. SA pretreatment scavenged drought-induced O 2 − accumulation (but not H 2 O 2) and led to an additional proline accumulation with enhanced expression of proline synthesis-related genes (P5CS1, P5CS2 and P5CR) and NADPH oxidase, and a reset of reducing potential with enhanced expression of redox regulating genes (TRXh5 and GRXC9). SA-mediated stress responses coincided with the enhanced expression of NPR1 and PR-1 , with an antagonistic depression of ABA- and JA-related genes (NCED3 , MYC2 , and PDF1.2). These results indicate that the SA-modulated NPR1-dependent signalling pathway and proline synthesis are an integrative process of redox control under drought. [ABSTRACT FROM AUTHOR]

The article offers information on the study on boosting the tree mortality with drought coupled with pathogens. Topics discussed include information on the impacts of pathogen diseases on the tree mortality; discussions on the effects of the timing of drought on physiological and structural responses of trees to pathogen infection; and the importance of timing of drought on changing tree biochemical, physiological and structural parameters.

Knowledge of tree-growth response to extreme climatic events, such as drought, is useful for forest managers to model the effects of future disturbances, and to develop management plans that mitigate the detrimental impacts. We analyzed the effects of an exceptional drought on Pinus palustris (Longleaf Pine) radial growth in the Alabama Fall Line Hills, based on site conditions and tree age. Results indicated that radial-growth response to drought was not influenced by site condition as we initially hypothesized, but was influenced by tree age. Management for resiliency to disturbance in Longleaf Pine ecosystems should consider the complexity of individual tree-growth response as a function of age and growing conditions. [ABSTRACT FROM AUTHOR]

Abstract Widespread environmental impacts of frequent drought episodes in Brazil have resulted in several drought-related diagnostics studies. However, the potential of many “opportunistic sensors”, such as the Global Positioning System (GPS), has not yet been considered in hydrological hazard monitoring in Brazil. In this study, the response of the Earth's crust to Brazil's 2012–2015 drought event in different structural provinces is analyzed by comparing GPS-observed vertical crustal deformations (VCDs) with the terrestrial water storage (TWS) derived from the Gravity Recovery and Climate Experiment (GRACE). The results indicate that there is no spatial correlation between annual amplitudes of the TWS and VCDs in different structural provinces apart from the purely elastic response of the crust to TWS dynamics, at almost all the 39 GPS stations that were analyzed. However, approximately 15% of the monitoring stations show that VCD leads TWS with a phase lag of 2–4 months. Errors associated with VCD and TWS are within the accepted range for space geodetic techniques (i.e., GPS and GRACE) and despite the need for further investigation, the phase lead seems to be associated with rainfall, which impacts the TWS through the hydrographs. Overall, the GPS-based drought index (DI VCD) reflects the water depletion in many regions of Brazil, which agrees with the GRACE-based DI TWS in terms of the Spearman correlation coefficient (ranging from 0.4 to 0.9) in the Amazon, Tocantins, La Plata, and São Francisco river basins. This agreement confirms the drought persistence during the study period and that DI VCD can be used to monitor hydrological droughts. In regions in which DI TWS sufficiently agrees with DI VCD (48% of the sites), near real-time drought monitoring is feasible. This could be useful in the optimization of models for the forward prediction of drought events in other regions worldwide, where GPS vertical displacements strongly correlate with hydrological GRACE signals. Graphical Abstract Highlights • Crustal bending due to loading isn’t correlated with structural provinces in Brazil. • GPS-based crustal deflection can be used as indicator to depict drought over Brazil. • Drought index using crustal deflection is feasible and dispenses inverse modeling. • Few sites present phase lag between driven force (loading) and response (bending). • GPS and GRACE show that the Brazil's 2012–2015 drought was unprecedented. [ABSTRACT FROM AUTHOR]

Since the industrial revolution, temperature averages have been changing both in local and global scale. These variations are related with the climate and global warming changes. Such typical changes (i.e., increasing heavy precipitation, and declined light or total precipitation) are also observed in Turkey. As expected, decreased precipitation usually promotes drought conditions, and can cause extended dry days or periods. Thus, strong relationship can be considered between precipitation scarcity and drought conditions. In this study, changes in precipitation (i.e., total, bottom/lowest and extreme 10%), dry days length, dry spells (>6 days) and drought severity risk based on Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) were evaluated quantitatively over Turkey from 1971 to 2000 with regards to climate changes. Trend analysis is performed by using Innovative-Şen analysis (ITA) method to evaluate trend behavior of precipitation, lengths of dry days and spells. Results show that changes in dry days (ΔDD/ΔT) converge to (-2% ±3%)/°C, while changes in prolonged dry spells change (ΔDS/ΔT) are comparatively higher (3% ±5%)/°C. For precipitations, mean values of ΔP/ΔT converges to constant value as (-6% ±8%)/°C, (0% ±2%)/°C and (-1% ±4%)/°C for total, top 10% heavy and lowest 10% precipitations, respectively. These changes are supported by ITA outputs. All results support and point out that prolonged drought risk frequency and severity has been increasing. [ABSTRACT FROM AUTHOR]

Central America has suffered the impact of several extreme hydrometeorological events, among which drought stands out. This has had adverse effects of different kinds in the region known as the Central American Dry Corridor (CSC, in Spanish). The objective of this work was to describe the impacts that agriculture, livestock and economy of the CSC countries have suffered due to droughts: agricultural, hydrological and socioeconomic. A review of primary and secondary sources was carried out, such as scientific articles, press reports and studies reports from national and international institutions. The most recurrent impacts are at the level of basic grains and cattle, also due in part to the ENSO (El Niño-Southern Oscillation) phenomenon. Because the CSC is a region with high vulnerability to drought and other extreme hydrometeorological events, it is necessary to carry out an adequate characterization of the CSC taking as a baseline similar studies like this one, that orginate a discussion process for the design and implementation of strategies and anticipated public policies of adaptation and mitigation of the drought in the CSC and therefore, lead to improve the quality of life of its population. [ABSTRACT FROM AUTHOR]

More frequent and severe El Niño Southern Oscillations (ENSO) are causing episodic periods of decreased rainfall. Although the effects of these ENSO‐induced droughts on tree growth and mortality have been well studied, the impacts on other demographic rates such as reproduction are less well known. We use a four‐year seed rain dataset encompassing the most severe ENSO‐induced drought in more than 30 years to assess the resilience (i.e., resistance and recovery) of the seed composition and abundance of three forest types in a tropical dry forest. We found that forest types showed distinct differences in the timing, duration, and intensity of drought during the ENSO event, which likely mediated seed composition shifts and resilience. Drought‐deciduous species were particularly sensitive to the drought with overall poor resilience of seed production, whereby seed abundance of this functional group failed to recover to predrought levels even two years after the drought. Liana and wind‐dispersed species were able to maintain seed production both during and after drought, suggesting that ENSO events promote early successional species or species with a colonization strategy. Combined, these results suggest that ENSO‐induced drought mediates the establishment of functional groups and dispersal types suited for early successional conditions with more open canopies and reduced competition among plants. The effects of the ENSO‐induced drought on seed composition and abundance were still evident two years after the event suggesting the recovery of seed production requires multiple years that may lead to shifts in forest composition and structure in the long term, with potential consequences for higher trophic levels like frugivores. In 2015/16, the most intense and prolonged El Nino‐induced drought in the last 30 years affected tropical forests across the globe. We used a 4‐year dataset of monthly seed fall to assess the effects of this severe event on seed production across different functional groups and dispersal types. We found this drought has prolonged effects on seed production even after typical rainfall returns. [ABSTRACT FROM AUTHOR]

Blooms of cyanobacteria are a current threat to global water security that is expected to increase in the future because of increasing nutrient enrichment, increasing temperature and extreme precipitation in combination with prolonged drought. However, the responses to multiple stressors, such as those above, are often complex and there is contradictory evidence as to how they may interact. Here we used broad scale data from 494 lakes in central and northern Europe, to assess how cyanobacteria respond to nutrients (phosphorus), temperature and water retention time in different types of lakes. Eight lake types were examined based on factorial combinations of major factors that determine phytoplankton composition and sensitivity to nutrients: alkalinity (low and medium‐high), colour (clear and humic) and mixing intensity (polymictic and stratified). In line with expectations, cyanobacteria increased with temperature and retention time in five of the eight lake types. Temperature effects were greatest in lake types situated at higher latitudes, suggesting that lakes currently not at risk could be affected by warming in the future. However, the sensitivity of cyanobacteria to temperature, retention time and phosphorus varied among lake types highlighting the complex responses of lakes to multiple stressors. For example, in polymictic, medium‐high alkalinity, humic lakes cyanobacteria biovolume was positively explained by retention time and a synergy between TP and temperature, while in polymictic, medium‐high alkalinity, clear lakes only retention time was identified as an explanatory variable. These results show that, although climate change will need to be accounted for when managing the risk of cyanobacteria in lakes, a "one‐size fits‐all" approach is not appropriate. When forecasting the response of cyanobacteria to future environmental change, including changes caused by climate and local management, it will be important to take this differential sensitivity of lakes into account. Biological responses to multiple stressors are often complex and are not easily generalizable. We used data from 494 European lakes, categorized into eight types to test the generality of the widely hypothesized synergistic effect of temperature and eutrophication on cyanobacterial abundance and the effect of prolonged periods of drought as an additional stressor. The abundance of cyanobacteria was explained by different combinations of stressors in each lake type and the hypothesized synergy was only detected in two lake types, indicating that a one‐size fits‐all approach is not appropriate for effectively managing the future risk of cyanobacterial blooms to climate change. [ABSTRACT FROM AUTHOR]

Drought severity in regions North and Northwest of Rio de Janeiro state (SRJ) was evaluated using the Standardized Precipitation Index (SPI) for the monthly (SPI-1) and annual (SPI-12) scales, as well as its relationship with El Niño - Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Data of 14 rainfall stations from a time series considering the period of 1967–2013 was used. The SPI calculation was based on the SCI package available at R software version 3.4.2 library. SPI categories used are Very Dry, Moderately Dry and Extremely Dry associated with the hot and cold phases of the PDO, followed by ENSO events according to the Oceanic Niño index (ONI) in El Niño region 3.4 using an interaction matrix. The matrix was evaluated by the coefficients of Kendall ( τ ), Sperman ( ρ ), Pearson ( r ) and R 2 determination, followed by Willmott's concordance index ( d ), Standard Error of Estimation ( SEE ) and Student's t- test. The intense activity of La Niña in the cold 1st phase of the PDO increased rainfall with greater intensity in the Northwest region compared to the North. In the 2nd cold phase of the PDO, the events of El Niño, La Niña and Neutral years of the ENSO mutually contribute to the changes in rainfall regime of both regions. The most frequent SPI categories are Moderately Dry and Extremely Dry. SPI-1 was efficient in perceiving extreme droughts, while SPI-12 results were not significant in the revealing of extreme droughts. In addition, there was no relational pattern through statistical indexes between droughts detected by SPI, ENSO and PDO. Nevertheless, when ENSO cycles were persistent within both phases of the PDO, droughts occurred, mainly on the monthly scale. [ABSTRACT FROM AUTHOR]

Both the dominance and the mass ratio hypotheses predict that plant internal nutrient cycling in ecosystems is determined by the dominant species within plant communities. We tested this hypothesis under conditions of extreme drought by assessing plant nutrient (N, P and K) uptake and resorption in response to experimentally imposed precipitation reductions in two semiarid grasslands of northern China. These two communities shared similar environmental conditions, but had different dominant species—one was dominated by a rhizomatous grass (Leymus chinensis) and the other by a bunchgrass (Stipa grandis). Results showed that responses of N to drought differed between the two communities with drought decreasing green leaf N concentration and resorption in the community dominated by the rhizomatous grass, but not in the bunchgrass-dominated community. In contrast, negative effects of drought on green leaf P and K concentrations and their resorption efficiencies were consistent across the two communities. Additionally, in each community, the effects of extreme drought on soil N, P and K supply did not change synchronously with that on green leaf N, P and K concentrations, and senesced leaf N, P and K concentrations showed no response to extreme drought. Consistent with the dominance/mass ratio hypothesis, our findings suggest that differences in dominant species and their growth form (i.e., rhizomatous vs bunch grass) play an important nutrient-specific role in mediating plant internal nutrient cycling across communities within a single region. [ABSTRACT FROM AUTHOR]

In Northeast Brazil (NEB), severe droughts have high socioeconomic impacts. In this study, the spatial–temporal characteristics of drought were evaluated based on a new drought index at 4‐km spatial resolution, derived from regional empirical relationships between a remote sensing‐based index and rain‐gauge‐based standardized precipitation index (SPI), a well‐known drought meteorological index. This index was used to compare the spatial pattern of severe drought events (1982–1983, 1992–1993, 1997–1998, and 2012–2013) of the last 30 years. Strong El Niño related droughts were found to be generally spatially limited, affecting around 30% of NEB and concentrated in the northern part of the region, while 2012 drought, which was not El Niño related, was widespread, reaching 46% of NEB. These results stressed the importance of analyzing droughts at the subregion scale using data with higher spatial resolution. Statistically significant trends (p < 0.05) toward drier conditions detected in the SPI time‐series were linked to the tropical Atlantic Ocean warming trend, which result in an increased drought risk and social vulnerability in the region. [ABSTRACT FROM AUTHOR]

A significantly negative interannual relationship is identified between the ground surface temperature (GTS) over the Tibetan Plateau (TP) and the rainfall over northwestern China and western Mongolia (NWC-WM) through analyzing the Chinese weather station data, GPCP precipitation, and ERA-Interim reanalysis in July during 1980-2012. This relationship is verified by the model sensitivity experiments carried out by using RegCM4.1 during 1982-2011. The positive/negative GTS forcing of three different magnitudes is added in two key regions over the TP in RegCM4.1. One of the key regions covers the central and eastern TP (denoted as TPC). The other covers the northern and north slope of the TP (denoted as TPN). The model results suggest that when the GTS anomalies in either of the two key regions are negative (positive), the rainfall anomalies over NWC-WM are positive (negative), which is consistent with observations. Furthermore, rainfall anomalies over NWC-WM are more sensitive to the GTS anomalies over the TPN region than those over the southern TP. The model results also reveal that the negative (positive) GTS anomalies over region TPN mainly cause the decrease (increase) of the latent heat release related to rainfall (surface sensible heat) and descent (ascent) over the TPN region but ascent (descent) to the north of the TP between 40° and 50° N. In addition, the specific humidity between 40° and 50° N is increased (decreased). Therefore, the increase (decrease) in specific humidity and the ascent (descent) between 40° and 50° N cause the increase (decrease) in the rainfall over NWC-WM. [ABSTRACT FROM AUTHOR]

Hydrological extremes are changing under the impacts of environmental change, i.e., climate variation and human activity, which can substantially influence ecosystems and the living environment of humans in affected region. This study investigates the impacts of environmental change on hydrological drought in the middle reaches of the Yangtze River in China based on hydrological modelling. Change points for streamflow into two major lakes and a reservoir in the study area were detected in the late 1980s using the Mann-Kendall test. Streamflow simulation by a water balance model was performed, and the resulting Kling-Gupta efficiency value was >0.90. Hydrological drought events were identified based on the simulated streamflow under different scenarios. The results show that the hydrological drought occurrence was increased by precipitation, whereas the drought peak value was increased by potential evapotranspiration. The impacts of precipitation and potential evapotranspiration on drought severity and duration varied in the study area. However, hydrological drought was intensified by the influence of human activity, which increased the severity, duration and peak value of droughts. The dominant factor for hydrological drought severity is precipitation, followed by potential evapotranspiration and human activity. The impacts of climate variation and human activity on drought severity are larger than on drought duration. In addition, environmental change is shown to have an “accumulation effect” on hydrological drought, demonstrating that the indirect impacts of environmental change on hydrological drought are much larger than the direct impacts on streamflow. This study improves our understanding of the responses of hydrological extremes to environmental change, which is useful for the management of water resources and the prediction of hydrological disasters. [ABSTRACT FROM AUTHOR]

We used the lesser prairie‐chicken (Tympanuchus pallidicinctus), an iconic grouse species that exhibits a boom–bust life history strategy, on the Southern High Plains, USA, as a bioindicator of main and interactive effects of severe drought and grazing. This region experienced the worst drought on record in 2011. We surveyed lesser prairie‐chicken leks (i.e., communal breeding grounds) across 12 years that represented 7 years before the 2011 drought (predrought) and 4 years during and following the 2011 drought (postdrought). Grazing was annually managed with the objective of achieving ≤50% utilization of aboveground vegetation biomass. We used lek (n = 49) count data and covariates of weather and managed grazing to: (a) estimate long‐term lesser prairie‐chicken abundance and compare abundance predrought and postdrought; (b) examine the influence of annual and seasonal drought (modified Palmer drought index), temperature, and precipitation on long‐term lesser prairie‐chicken survival and recruitment; and (c) assess and compare the influence of grazing on lesser prairie‐chicken population predrought and postdrought. Lesser prairie‐chicken abundance was nearly seven times greater predrought than postdrought, and population declines were attributed to decreased survival and recruitment. The number of days with temperature >90th percentile had the greatest effect, particularly on recruitment. The population exhibited a substantial bust during 2011 and 2012 without a boom to recover in four postdrought years. Adaptive grazing positively influenced the population predrought, but had no effects postdrought. Results suggest that the severe drought in 2011 may have been beyond the range of environmental conditions to which lesser prairie‐chickens, and likely other species, have adapted. Land management practices, such as grazing, should remain adaptive to ensure potential negative influences to all species are avoided. Increasing habitat quantity and quality by reducing habitat loss and fragmentation likely will increase resiliency of the ecosystem and individual species. We used the lesser prairie‐chicken (Tympanuchus pallidicinctus), an iconic grouse species that exhibits a boom–bust life history strategy, on the Southern High Plains, USA, as a bioindicator of main and interactive effects of severe drought and grazing. The population exhibited a substantial bust during 2011–2012, primarily through reduced recruitment due to excessive heat, without a boom to recover in four postdrought years. Adaptive grazing positively influenced the population predrought, but had no effects postdrought. [ABSTRACT FROM AUTHOR]

Drought is a natural disaster that significantly affects human life; therefore, precise monitoring and prediction is necessary to minimize drought damage. Conventional drought monitoring is based predominantly on ground observation stations; however, satellite imagery can be used to overcome the disadvantages of existing monitoring methods and has the advantage of monitoring wide areas. In this research, we assess the applicability of drought monitoring based on satellite imagery, focusing on historic droughts in 2001 and 2014, which caused major agricultural and hydrological issues in South Korea. To assess the applicability and accuracy of the drought index, drought impact areas in the study years were investigated, and spatiotemporal comparative analyses between the calculated drought index and previously affected areas were conducted. For drought monitoring based on satellite imagery, we used hydro-meteorological factors such as precipitation, land surface temperature, vegetation, and evapotranspiration, and applied remote sensing data from various sensors. We verified the effectiveness of using precipitation data for meteorological drought monitoring, vegetation and land surface temperature data for agricultural drought monitoring, and evapotranspiration data for hydrological drought monitoring. Moreover, we confirmed that the Standard Precipitation Index (SPI) can be indirectly applied to agricultural or hydrological drought monitoring by determining the temporal correlation between SPI, calculated for various time scales, and satellite-based drought indices. [ABSTRACT FROM AUTHOR]

This study proposes a quantitative approach for extreme drought hotspot assessment related to climate change, the hotspot drought risk index (HDRI), and evaluates the response of extreme drought to climate change in the five major river basins of the Korean Peninsula. According to an analysis of seasonal and regional drought characteristics on the Korean Peninsula, drought occurs most frequently in spring, and the central and southern areas are generally more vulnerable to drought. Drought risk analysis under various climate change scenarios indicates significant drought risk over the entire Korean Peninsula excepting some parts of the Han and Nakdong river basins from 2011 to 2040. Extreme drought may be particularly severe in the mid‐west area as these basins lack available water resources. Drought risk decreases in the southern Korean Peninsula in the 2011–2040 and 2071–2099 periods, during which the area vulnerable to drought also decreases. However, some parts of central Korea and the western and eastern coastlines remain susceptible to drought. The drought risk evaluation method suggested herein may be useful for predicting drought and establishing realistic coping strategies for extreme drought in a changing climate. [ABSTRACT FROM AUTHOR]

The article discusses the impacts of tropical forest droughts. Topics discussed include regulation of the Earth's climate due to their influence over the carbon, water, and energy cycles; changes in the environment; and the scientific challenges to improving our understanding of ecosystem responses to drought.

Xinjiang is an important maize cultivation area in Northwest China. Investigating the relationship between meteorological drought and climate-driven maize yield can help to mitigate the negative impacts of drought on agricultural production in Xinjiang. In this study, multi-source data, including meteorological, agricultural, and socio-economic data, are collected to analyze the spatiotemporal patterns of drought and assess drought disaster risk. The standardized precipitation evapotranspiration index is calculated to classify different drought grades in the study area. The main results are as follows: (1) the relationship between drought and climate-driven maize yield is determined using a stepwise regression analysis, which indicates that drought conditions occurring from May to July are crucial for the yield in Xinjiang; (2) the modified Mann-Kendall test detects that the frequency-intensity-coverage of drought from May to July shows a decreasing tendency as a whole in the study area; (3) the correlation analysis shows that the multivariate ENSO index may be the dominant force in regional drought evolution; and (4) a drought disaster risk assessment system is constructed based on principles of natural disaster management. The drought disaster risk is higher in southwestern and northwestern Xinjiang, areas that should deserve more attention. [ABSTRACT FROM AUTHOR]

The article reports on a warning from scientists that the Great Salt Lake in Utah is at risk of collapse due to its low water level and salt concentrations exceeding a threshold at which essential microorganisms begin to die. Driven by drought and water diversion, the trends are said to threaten the base of the lake's food web. Actions taken to address the impending crisis include the signing of a landmark series of bills aimed at rescuing the lake and addressing the drought.

Summary: Spatial differences in environmental selective pressures interact with the genomes of organisms, ultimately leading to local adaptation. Landscape genomics is an emergent research area that uncovers genome–environment associations, thus allowing researchers to identify candidate loci for adaptation to specific environmental variables. In the present study, we used latent factor mixed models (LFMMs) and Moran spectral outlier detection/randomization (MSOD‐MSR) to identify candidate loci for adaptation to 10 environmental variables (climatic, soil and atmospheric) among 43 515 single nucleotide polymorphisms (SNPs) from 202 accessions of the model legume Medicago truncatula. Soil variables were associated with a large number of candidate loci identified through both LFMMs and MSOD‐MSR. Genes tagged by candidate loci associated with drought and salinity are involved in the response to biotic and abiotic stresses, while those tagged by candidates associated with soil nitrogen and atmospheric nitrogen, participate in the legume‐rhizobia symbiosis. Candidate SNPs identified through both LFMMs and MSOD‐MSR explained up to 56% of variance in flowering traits. Our findings highlight the importance of soil in driving adaptation in the system and elucidate the basis of evolutionary potential of M. truncatula to respond to global climate change and anthropogenic disruption of the nitrogen cycle. [ABSTRACT FROM AUTHOR]

In order to define the spatial temporal distribution of drought characteristics and its response to climate change in the Beijing-Tianjin- Hebei region at different time scales, daily climatic data of 24 meteorological stations from 1961 to 2016 were selected in this study. The standardized precipitation evapotranspiration index ( SPEI) was established by using precipitation and reference crop evapotranspiration (ET0) data at different time scales, in which ET0 was calculated by FAO Penman Monteith equation. In order to find out the drought characteristics, Mann Kendall test, drought indices, climate tendency rate and rotated empirical orthogonal function (REOF) analysis were carried out on the SPEI. The results show that from the inter annual changes, there is a humid trend in Beijing-Tianjin-Hebei region; from the seasonal perspective, it is getting wet in spring, autumn (P<0. 05) and winter, and there is a drought trend in summer. The drought coverage appears as the features of the domain drought at the annual scale and the intensity of drought is light and moderate mainly. Viewing form spatial distribution, the western region has a humid trend, while it is dry in the eastern part of Beijing-Tianjin-Hebei region. According to spatial abnormal distribution of loading vectors in the Beijing Tianjin Hebei region, it can be divided into 4 sub regions: central area in the north region (sub-regionⅠ), east area in the north region (sub-region II), west area in the north region (sub-region III) and southern region (subregion IV). Drought in Ⅲ and Ⅳ sub regions gradually alleviates, while Ⅰ and Ⅱ sub regions shows a trend of getting dry. [ABSTRACT FROM AUTHOR]

Drought is occurring with increased frequency under climate warming. To understand the behavior of drought and its variation in the future, current and future drought in the twenty-first century over China is discussed. The drought frequency and trend of drought intensity are assessed using the Palmer Drought Severity Index (PDSI), which is calculated based on historical meteorological observations and outputs of the fifth Coupled Model Intercomparison Project (CMIP5) under three representative concentration pathway (RCP) scenarios. The simulation results of drought period, defined by PDSI class, could capture more than 90% of historical drought events. Projection results indicate that drought frequency will increase over China in the twenty-first century under the RCP4.5 and RCP8.5 scenarios. In the mid-twenty-first century (2021-2050), similar patterns of drought frequency are found under the three emission scenarios, and annual drought duration would last 3.5-4 months. At the end of the twenty-first century (2071-2100), annual drought duration could exceed 5 months in northwestern China as well as coastal areas of eastern and southern China under the RCP8.5 scenario. Drought is slightly reduced over the entire twenty-first century under the RCP2.6 scenario, whereas drought hazards will be more serious in most regions of China under the RCP8.5 scenario. [ABSTRACT FROM AUTHOR]

Droughts are natural disasters that pose significant threats to agricultural production as well as living conditions, and a spatial-temporal difference analysis of agricultural drought risk can help determine the spatial distribution and temporal variation of the drought risk within a region. Moreover, this type of analysis can provide a theoretical basis for the identification, prevention, and mitigation of drought disasters. In this study, the overall dispersion and local aggregation of projection points were based on research by Friedman and Tukey (IEEE Trans on Computer 23:881-890, 1974). In this work, high-dimensional samples were clustered by cluster analysis. The clustering results were represented by the clustering matrix, which determined the local density in the projection index. This method avoids the problem of determining a cutoff radius. An improved projection pursuit model is proposed that combines cluster analysis and the projection pursuit model, which offer advantages for classification and assessment, respectively. The improved model was applied to analyze the agricultural drought risk of 13 cities in Heilongjiang Province over 6 years (2004, 2006, 2008, 2010, 2012, and 2014). The risk of an agricultural drought disaster was characterized by 14 indicators and the following four aspects: hazard, exposure, sensitivity, and resistance capacity. The spatial distribution and temporal variation characteristics of the agricultural drought risk in Heilongjiang Province were analyzed. The spatial distribution results indicated that Suihua, Qigihar, Daqing, Harbin, and Jiamusi are located in high-risk areas, Daxing’anling and Yichun are located in low-risk areas, and the differences among the regions were primarily caused by the aspects exposure and resistance capacity. The temporal variation results indicated that the risk of agricultural drought in most areas presented an initially increasing and then decreasing trend. A higher value for the exposure aspect increased the risk of drought, whereas a higher value for the resistance capacity aspect reduced the risk of drought. Over the long term, the exposure level of the region presented limited increases, whereas the resistance capacity presented considerable increases. Therefore, the risk of agricultural drought in Heilongjiang Province will continue to exhibit a decreasing trend. [ABSTRACT FROM AUTHOR]

Cowpea ( Vigna unguiculata L. Walp.) is an important African food legume suitable for dry regions. It is the main legume in two contrasting agro-ecological regions of Kenya as an important component of crop rotations because of its relative tolerance to unpredictable drought events. This study was carried out in an effort to establish a collection of bacterial root nodule symbionts and determine their relationship to physicochemical soil parameters as well as any geographical distributional patterns. Bradyrhizobium spp. were found to be widespread in this study and several different types could be identified at each site. Unique but rare symbionts were recovered from the nodules of plants sampled in a drier in-land region, where there were also overall more different bradyrhizobia found. Plants raised in soil from uncultivated sites with a natural vegetation cover tended to also associate with more different bradyrizobia. The occurrence and abundance of different bradyrhizobia correlated with differences in soil texture and pH, but did neither with the agro-ecological origin, nor the origin from cultivated (n = 15) or uncultivated (n = 5) sites. The analytical method, protein profiling of isolated strains by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), provided higher resolution than 16S rRNA gene sequencing and was applied in this study for the first time to isolates recovered directly from field-collected cowpea root nodules. The method thus seems suitable for screening isolate collections on the presence of different groups, which, provided an appropriate reference database, can also be assigned to known species. [ABSTRACT FROM AUTHOR]

Droughts are extremely widespread natural disasters, which cause the most severe losses among natural disasters. The comprehensive drought risk in Northwest China (NWC) was evaluated based on the self-calibrating (SC) Palmer Drought Severity Index (PDSI) and copula method. The major conclusions are the following: (1) based on the rotated empirical orthogonal function (REOF), a significant consistency in the spatial distribution of the monthly averaged SC-PDSI was observed in NWC, especially in the subregions Inner Mongolia Plateau (IM), Hexi Corridor (HX), and Qiangtang Plateau (QT); (2) the largest frequency was obtained for slight drought and slight wet conditions, while extreme drought and extreme wet showed the lowest values; (3) with respect to the PDSI-th, the Clayton, Arch12, Arch12, Arch12, Arch12, and Frank played the major roles in the copula weight in the subregions IM, HX, Qinghai River Basin (QH), QT, North Xinjiang (NXJ), and South Xinjiang (SXJ), respectively. In terms of PDSI-pm, Arch12, Clayton, Gaussian, Arch12, Clayton, and Clayton dominated the weights of multi-copula functions in the regions IM, HX, QH, QT, NXJ, and SXJ, respectively; and (4) the frequency and probability of droughts in each area differed. The least drought events occurred in the QT and the most emerged in the HX for SC-PDSI. [ABSTRACT FROM AUTHOR]

The features of hydro-climate anomalies in China in 2015–2016 were analyzed in great detail, together with possible responses to the super 2015–16 El Niño event. The 2015–16 El Niño is characterized as a “strong” event in terms of the duration, intensity, and coverage of warming sea surface temperature (SST) in the central and east-central equatorial Pacific in comparison to the 1982–83 and 1997–98 events. The floods and droughts frequency were incidence of floods and droughts per year, respectively. The results show several significant anomalies in China: 1) About 9%–173% of precipitation variance in 2015–16 can be attributed to this El Niño; 2) There was significant inconformity between hydro-climate anomalies and the occurrence of floods and droughts; 3) Flood frequency has increased, especially over Southeast China and the Yangtze River in the summer of 2016; 4) Drought frequency has also increased, especially over Northeast China in summer of 2015, Northwest China in spring of 2016, and most parts in winter of 2015. The response of China hydro-climate anomalies to the 2015–16 El Niño was significant via El Niño and warm Indian Ocean induced circulation anomalies, which were characterized by stronger and more westward-extending western Pacific subtropical high and anomalous water vapor transport. Knowledge of the response of hydro-climate extremes to El Niño can provide valuable information to improve flood and drought forecasting in China. [ABSTRACT FROM AUTHOR]

Guizhou Province, China, experienced several severe drought events over the period from 1960 to 2013, causing great economic loss and intractable conflicts over water. In this study, the spatial and temporal characteristics of droughts are analyzed with the standard precipitation index (SPI), comprehensive meteorological drought index (CI), and reconnaissance drought index (RDI). Meanwhile, historical drought records are used to test the performance of each index at identifying droughts. All three indices show decreasing annual and autumn trends, with the latter particularly prominent. 29, 30, and 32 drought events were identified during 1960–2013 by the SPI, CI, and RDI, respectively. Continuous drought is more frequent in winter–spring and summer–autumn. There is a significant increasing trend in drought event frequency, peak, and strength since the start of the 21st century. Drought duration indicated by CI shows longer durations in the higher-elevation region of central and western Guizhou. The corresponding drought severity is high in these regions. SPI and RDI indicate longer drought durations in the lower elevation central and eastern regions of Guizhou Province, where the corresponding drought severity is also very strong. SPI shows an increasing trend in drought duration and drought severity across most of the regions of Guizhou. In general, SPI and RDI show an increasing trend in the western Guizhou Province and a decreasing trend in central and eastern Guizhou. Comparing these three drought indices with historical records, the RDI is found to be more objective and reliable than the SPI and CI when identifying the periods of drought in Guizhou. [ABSTRACT FROM AUTHOR]