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Low soil fertility and drought are primary constraints for crop production and food security in many developing nations. Since smallholder farmers often collect seed for the next year's crop from plants grown with abiotic stress, it is important to understand how progeny from a stressed parental environment perform when they are grown under similar stresses. This study investigates the impact of a low phosphorus (P) or drought parental environment on progeny seed and root traits in common bean (Phaseolus vulgaris), with the intention of distinguishing impacts of reduced parental provisioning from adaptive responses. Greenhouse, field, and seedling experiments were used to evaluate seed, seedling, and mature root phenotypes in progeny from stressed and nonstressed parental conditions. In addition, progeny from different positions within the pod and pod developmental times were evaluated since they are expected to vary in parental provisioning. Seeds from the peduncular position in the pod had less individual seed weight, fewer basal roots, reduced root dry weight, and smaller taproot diameter than those from the stylar position. Progeny of some genotypes from drought‐stressed parents had smaller individual seed weight, fewer basal roots, less total seedling dry weight, shorter seedling basal roots, and smaller basal root diameters. Progeny of some genotypes from a low P parental environment had smaller individual seed P concentration, fewer shoot‐borne roots, and greater basal root whorl number. Progeny from drought‐stressed parents, progeny from a low P parental environment, and seeds from the peduncular position had root phenotypes that were likely to be related to less parental provisioning. Possible adaptive parental effects were found in both parental drought and parental low P studies. Adequate seed provision under stress merits consideration as a selection target in crop breeding for stressful environments. [ABSTRACT FROM AUTHOR]

Recent analyses on the length of drought recovery in forests have shown multi-year legacies, particularly in semi-arid, coniferous ecosystems. Such legacies are usually attributed to ecophysiological memory, although drought frequency itself, and its effect on overlapping recovery times, could also contribute. Here, we describe a multi-decadal study of drought legacies using tree-ring carbon-isotope ratios (δ13C) and ring-width index (RWI) in Pinus ponderosa at 13 montane sites traversing a winter–summer precipitation gradient in the Southwestern U.S. Sites and trees were selected to avoid collection biases that exist in archived tree-ring databanks. The spatial hydroclimate gradient and winter–summer seasonal patterns were well predicted by seasonal and inter-annual correlations between δ13C and atmospheric vapor pressure deficit (VPD). Using VPD, we found that the probability of extreme drought has increased up to 70% in this region during the past two decades. When the recent increase in drought frequency was not considered, multi-year legacies in both δ13C and RWI were observed at most sites. When the increase in drought frequency was detrended from tree-ring chronologies, some sites exhibited short legacies (1–2 years) in both δ13C and RWI, and there was a sight trend for longer legacies in RWI. However, when considered broadly across the region and multiple decades, no significant legacies were observed, which contrasts with past studies. Our results reveal that a contribution to observed multi-year legacies is related to shifts in the climate system itself, an exogenous factor, that must be considered along with physiological memory. [ABSTRACT FROM AUTHOR]

In this research, a socio-economic analysis of drought was conducted from the perspective of farmers in Isfahan Province. The research was based on an interpretive-constructive approach, and its method was qualitative. The data were collected through semi-structured interviews. The sample size was 35 farmers in the central and western parts of Isfahan Province who were selected based on the purposeful sampling of the maximum diversity. The basis for the completion of the interviews was theoretical saturation. To analyze the data obtained from the interviews, a systematic field theory analysis was done. The results of the study indicated that, from the farmers' point of view, drought is a multifactor phenomenon induced by multiple causes. In general, the farmers enumerated four main factors as the causes of drought, including ineffective water management, self-centered agriculture, climate change, and fatalistic causes. [ABSTRACT FROM AUTHOR]

This study analyses the drought events for the Gomti basin in Uttar Pradesh (UP), India using the standardized precipitation index (SPI) at the spatial and temporal scales. Daily precipitation data for 14 districts in the Gomti basin for 41 years (1971-2011) were used to calculate the SPI for 1-month, 4-month, 6-month and 12-month time scales. Results for the 6-month (June-November) and 12-month time scales were similar and drought years were observed in 1972, 1979, 1987, 1993, 1994, 2002 and 2010. The 4-month SPI was analysed for the main monsoon months in the Gomti basin, i.e. from June to September. Results showed that significant drought occurred during the monsoon months of 1979, 1987, 1993, 2002, 2009 and 2010. For drought analysis at the spatial scale, the Kriging interpolation method available in ArcMap was used. The 12-month SPI showed that the frequency of severe and extreme drought was more in the upper regions of the basin during 1971-2000 whereas drought frequency was more in the central and lower regions of the basin during 2001-2011. Further, the de Martonne aridity index was calculated for the period 1971-2007 and its correlation with the 1-month SPI for the period 1971-2007 was evaluated. [ABSTRACT FROM AUTHOR]

Recovery of plants after water stress events represents their high suitability for the urban condition areas. Reaction to drought and recovery of woody plants Cornus mas L., Lonicera caerulea L. and perennials Alchemilla mollis (Buser) Rothm., Geranium maculatum L., Geranium x magnificumwater stress, recovery performance, drought tolerant woody plants, drought tolerant perennials Hyl. ‘Rosemoor’ and Geranium ‘Philippe Vapelle’ were evaluate. Within a pot experiment the non‑destructive methods of monitoring: measurement of chlorophyll content using chlorophyll meter CL‑01, leaf stomatal conductance using Delta T Leaf porometer AP4 and modulated chlorophyll fluorescence using Hansatech FMS 1 were chosen. Based upon our results we may demonstrate different protective mechanisms of plants in water stress conditions. An increase in the chlorophyll concentration in stress‑exposed tissues and recovery of stomatal conductance in Cornus mas L. and in Alchemilla mollis (Buser) Rothm. were observed. In Cornus mas L. and Lonicera caerulea L. the early recovery of parameter ɸPSII (after 2 days of re‑watering) and the delayed recovery (after 6 days of re‑watering) in Geranium plants and Alchemilla mollis (Buser) Rothm.) were shown. [ABSTRACT FROM AUTHOR]

Highlights • Water deficits in Michigan asparagus production have increased linearly since 1997. • Irrigation reduced losses due to drought stress for one of two cultivars. • Cultivar differences in drought tolerance were likely due to differences in rooting depth. Abstract Increasing temperatures and rainfall variability in the Midwestern U.S. have spurred interest in strategies to reduce risks of heat and drought stress in traditionally rainfed crops including asparagus. A long-term field experiment was conducted on sandy soils in Western Michigan from 2010-17 to evaluate the effects of three levels of irrigation (none, overhead or sub-surface drip) and two asparagus cultivars (Guelph Millennium [GM] and Jersey Supreme [JS]) for reducing these risks. Overhead irrigation during the fern growth period resulted in cumulative yield improvements of 10% for GM during the 2012-17 growing seasons, with the largest yield benefits (21%) occurring in 2012, following hot, dry conditions the previous summer. In contrast, cumulative yields of JS were unaffected by irrigation, and yield reductions of 13% due to irrigation were observed in 2017, following wet conditions the previous late summer and fall. Estimates of cultivar water-use by depth suggest that JS was better able to tolerate drought due to a deeper root system compared to GM. However, our results suggest that JS may also be more sensitive than GM to excessive soil moisture during fall senescence. Yield response did not vary with delivery system, but sub-surface drip used less water than overhead irrigation. These results demonstrate the important role of both genetics and management practices in mitigating drought risk. [ABSTRACT FROM AUTHOR]

In this article, the Standardized Precipitation Index (SPI), at both the short- and long-time scale, has been evaluated to analyse drought in the Sardinia region (Italy). In fact, while the short-time scale SPI describes droughts that affect plant life and farming, the long-time scale SPI influences the way water supplies/reserves are managed. Initially, with the aim to detect the most important drought episodes that affected the region each month, the percentage of rain gauges showing severe or extreme drought values was evaluated. Then, in order to evaluate the temporal evolution of the SPI values, a trend analysis was performed. Results evidenced that, at the short-time scale, the observation period was characterized by several dry episodes while, at the long-time scale, the majority of the drought events were detected after 1980. Moreover, marked negative trends of the SPI values in winter, in the wet season and at the annual scale were detected. [ABSTRACT FROM AUTHOR]

The study aims at regional and probabilistic evaluation of bivariate drought characteristics to assess both the past and future drought duration and severity in Bangladesh. The procedures involve applying (1) standardized precipitation index to identify drought duration and severity, (2) regional frequency analysis to determine the appropriate marginal distributions for both duration and severity, (3) copula model to estimate the joint probability distribution of drought duration and severity, and (4) precipitation projections from multiple climate models to assess future drought trends. Since drought duration and severity in Bangladesh are often strongly correlated and do not follow same marginal distributions, the joint and conditional return periods of droughts are characterized using the copula-based joint distribution. The country is divided into three homogeneous regions using Fuzzy clustering and multivariate discordancy and homogeneity measures. For given severity and duration values, the joint return periods for a drought to exceed both values are on average 45% larger, while to exceed either value are 40% less than the return periods from the univariate frequency analysis, which treats drought duration and severity independently. These suggest that compared to the bivariate drought frequency analysis, the standard univariate frequency analysis under/overestimate the frequency and severity of droughts depending on how their duration and severity are related. Overall, more frequent and severe droughts are observed in the west side of the country. Future drought trend based on four climate models and two scenarios showed the possibility of less frequent drought in the future (2020–2100) than in the past (1961–2010). [ABSTRACT FROM AUTHOR]

Highlights • Differences exist between the performances of various drought indices used to identify drought impacts on crop yields. • Multiscalar drought indices outperform uniscalar drought indices for monitoring the impact of drought on crop yields. • Shorter drought time-scales are better at identifying drought impacts on crop yields. Abstract This article presents an analysis of the response of the annual crop yield in five main dryland cultivations in the United States to different time-scales of drought, and explores the environmental and climatic characteristics that determine the response. For this purpose we analysed barley, winter wheat, soybean, corn and cotton. Drought was quantified by means of the Standardized Precipitation Evapotranspiration Index (SPEI). The results demonstrate a strong response in the interannual variability of crop yields to the drought time-scales in the different cultivations. Moreover, the response is highly spatially variable. Crop types showed considerable differences in the month in which their yields are most strongly linked to drought conditions. Some crops (e.g. winter wheat) responded to drought at medium to long SPEI time-scales, while other crops (e.g. soybean and corn) responded to short or long drought time-scales. The study confirms that the differences in the patterns of crop yield response to drought time-scales are mostly controlled by average climate conditions, in general, and water availability (precipitation), in particular. Generally, we found that there is a weaker link between crop yield and drought severity in humid environments and also that the response tends to occur over longer time-scales. [ABSTRACT FROM AUTHOR]

We estimate the impacts of drought, as defined by the U.S. Drought Monitor (USDM), on crop yields and farm income in the United States during the 2001–2013 time period. Our empirical strategy relies on panel data models with fixed effects that exploit spatial and temporal variability in drought conditions and agricultural outcomes at the county level. We find negative and statistically significant effects of drought on crop yields equal to reductions in the range of 0.1% to 1.2% for corn and soybean yields for each additional week of drought in dryland counties, and 0.1% to 0.5% in irrigated counties. Region-specific results vary, with some regions experiencing no yield impacts from drought, while yield reductions as high as 8.0% are observed in dryland counties in the Midwest for every additional week of drought in the highest USDM severity category. Despite this impact on crop yields, we find that additional weeks of drought have little to no effect on measures of farm income. While precipitation and temperature explain most of the variability in crop yields, we find that the USDM captures additional negative impacts of drought on yields. [ABSTRACT FROM AUTHOR]

We describe a theoretically based framework (C-PMT+HAPA) for designing and evaluating collaborative processes to increase preparation for natural hazards in situations in which preparedness decisions are shared and actions must be taken jointly by more than one party. The framework combines two health behavior change theories from psychology, protection motivation theory (PMT) and the health action process approach (HAPA), with collaboration theory in natural resources management. The framework provides much needed guidance for designing the activities in which participants will collaborate and suggests theoretically supported intermediate outcomes that may indicate a successful trajectory toward the ultimate goal of increased preparation. We used this framework in a collaborative process, with participation by ranchers with grazing permits and U.S. Forest Service managers on the Tonto National Forest, to increase preparation for drought on public rangelands in the Southwestern U.S. Evaluation of intermediate outcomes indicated: (1) improved interactions and relations between parties; (2) improved ability to appraise drought risks; (3) improved understanding of the U.S. Forest Service process for approving practices that increase preparation for drought; and; (4) increased motivation to implement these practices. The strength of the intermediate outcomes suggests that the C-PMT+HAPA framework would be an effective, theoretically supported framework for designing and evaluating collaborative processes to encourage preparation for natural hazards. More generally, the framework could contribute to more transdisciplinary, system- and action-oriented research on disaster risk reduction that is coproduced with multiple stakeholders. [ABSTRACT FROM AUTHOR]

Climate change scenarios increase the frequency of combined episodes of drought, heat and high UV radiation, particularly in the Mediterranean region where dryland farming of olive (Olea europaea L.) orchards remains a common practice. Nonirrigated olive plants (drought treatment) were subjected to an episode of heat plus UV-B radiation shock (DH+UV-B treatment) for 2 days. After the treatments, plants were allowed to grow under irrigated conditions (recovery). Compared with irrigated plants, drought treatment induced lower relative water content but this status was not aggravated when DH+UV-B shock was applied. Additionally, the effective quantum yield of PSII was similar in the drought-stressed and DH+UV-B treatments. Interestingly, the DH+UV-B treatment produced higher photosynthetic pigment contents than drought-stressed plants. Concerning oxidative status, the DH+UV-B treatment induced similar lipid peroxidation levels and only cell membrane permeability was higher than in drought-stressed plants. On other hand, drought-stressed plants showed higher levels of anthocyanins and proline. Our data suggest that plants grown under dryland conditions modulated some tolerance mechanisms that may prevent cumulative damages by other stressors. Moreover, drought-stressed and DH+UV-B plants were able to recover their physiological performance in a similar way. These data represent an important contribution to understanding how dryland -grown olive plants will cope with climate change. Climate changes are increasing the frequency of crop stress events, particularly in the Mediterranean region where dryland olive farming remains a sustainable practice. We aimed to evaluate how olive plants under irrigated versus dryland farming regimes respond to heat plus high UV-B, and recover. The results suggest that plants pre-exposed to drought can modulate tolerance mechanisms towards coping with further multiple stress episodes and recovery. [ABSTRACT FROM AUTHOR]

Many recent studies on drought‐induced vegetation mortality have explored how plant functional traits, and classifications of such traits along axes of, for example, isohydry–anisohydry, might contribute to predicting drought survival and recovery. As these studies proliferate, the consistency and predictive value of such classifications need to be carefully examined. Here, we outline the basis for a systematic classification of plant drought responses that accounts for both environmental conditions and functional traits. We use non‐dimensional analysis to integrate plant traits and metrics of environmental variation into groups that can be associated with alternative drought stress pathways (hydraulic failure and carbon limitation), and demonstrate that these groupings predict physiological drought outcomes using both synthetic and measured data. In doing so, we aim to untangle some confounding effects of environment and trait variations that undermine current classification schemes, advocate for more careful treatment of the environmental context within which plants experience and respond to drought, and outline a pathway towards a general classification of drought vulnerability. [ABSTRACT FROM AUTHOR]

Climate change forecasts point to increased frequency of droughts which may affect plant growth. For protein crops such as lentil, genetic improvement of both water use and drought tolerance is necessary. Wild lentil species are known to have evolved in drought prone areas and can be introgressed into cultivated lentil, making them candidates for the evaluation of high transpiration efficiency (TE) and drought tolerance. We assessed TE, water use and drought tolerance at the plant level for five wild lentil species and in cultivated lentil. Under fully watered and moderate drought conditions, wild lentil genotypes consumed significantly less water to fix similar or more dry matter compared with their cultivated counterparts. Under severe drought conditions, the wild lentil genotype L. ervoides IG 72815 had significantly higher TE compared with L. culinaris Eston. Lens ervoides L-01-827A, had significantly higher yield compared with all other species in the presence or absence of drought and showed significantly higher (α = 5%) TE under moderate drought. Drought susceptibility index was identified as a tool to identify drought-tolerant lentil genotypes grown under severe drought. The numerous small seeds of wild lentil made it difficult to estimate drought indices that are weight based and require formulae that incorporate seed numbers. [ABSTRACT FROM AUTHOR]

Over the recent years, drought has been occurring with an ever increasing frequency in Poland. The longer the rainless period lasts, the more acute its impacts are. Agricultural drought manifests itself as a prolonged period of water shortage for agricultural crops during their growth season resulting in yield reduction. Extent of drought was evaluated by the climatic water balance (CWB). Climatic water balance is an indicator that determines the state of humidification of the environment using data measured at meteorological stations. It is defined as the difference between atmospheric precipitation and evapotranspiration (in millimeters) calculated by an empirical formula taking into account: temperature, sunshine, and length of the day. CWB was calculated using meteorological data from 294 weather stations and weather posts across Poland. Spatial data from point measurements were interpolated using the Geographic Information System (GIS) software. Yield forecasts were made for major crops in Poland using agro-meteorological yield models and weather indices (WI). Yield figures were based on data from the Central Statistical Office of Poland (GUS). The autumn of 2011 was the driest in several dozen years in many localities of southeastern Poland. For instance, at the weather station in Puawy, the lowest level of precipitation had been recorded since 1871. Weather conditions prevailing in the growing season of 2012 were very beneficial for winter cereals and winter rapeseed. As for sugar beet, the weather also favored high yields over most of the growing season, except the final stage of growth. Notwithstanding the extreme drought in the autumn of 2011, the good weather conditions in the remaining part of the growth period caused the yields of winter crops and sugar beet to be high. The very scant autumn precipitation, even though it had negative impact on the germination of cereals, seedling emergence, and seedling growth, did not cause any major losses to yields. Water supplies from September precipitation combined with frequent morning mists, fogs, and dew mitigated the impact of prolonged drought and were sufficient to sustain the yields at an acceptable level. [ABSTRACT FROM AUTHOR]

The Three-North Shelter Forest (TNSF) is a critical ecological barrier against sandstorms in northern China, but has shown extensive decline and death in Populus simonii Carr. in the last decade. We investigated the characteristics--tree-ring width, basal area increment (BAI), carbon isotope signature (13Ccor), and intrinsic water-use efficiency (iWUE)--of now-dead, dieback, and non-dieback trees in TNSF shelterbelts of Zhangbei County. Results from the three groups were compared to understand the long-term process of preceding drought-induced death and to identify potential early-warning proxies of drought-triggered damage. The diameter at breast height (DBH) was found to decrease with the severity of dieback, showing an inverse relationship. In all three groups, both tree-ring width and BAI showed quadratic relationships with age, and peaks earlier in the now-dead and dieback groups than in the non-dieback group. The tree-ring width and BAI became significantly lower in the now-dead and dieback groups than in the non-dieback group from 17 to 26 years before death, thus, these parameters can serve as early-warning signals for future drought-induced death. The now-dead and dieback groups had significantly higher δ13Ccor and iWUEs than the non-dieback group at 7-16 years prior to the mortality, indicating a more conservative water-use strategy under drought stress compared with non-dieback trees, possibly at the cost of canopy defoliation and long-term shoot dieback. The iWUE became significantly higher in the now-dead group than in the dieback group at 0-7 years before death, about 10 years later than the divergence of BAI. After the iWUE became significantly different among the groups, the now-dead trees showed lower growth and died over the next few years. This indicates that, for the TNSF shelterbelts studied, an abrupt iWUE increase can be used as a warning signal for acceleration of impending drought-induced tree death. In general, we found that long-term drought decreased growth and increased iWUE of poplar tree. Successive droughts could drive dieback and now-dead trees to their physiological limits of drought tolerance, potentially leading to decline and mortality episodes. [ABSTRACT FROM AUTHOR]

Despite a wealth of eco-physiological assessments of plant response to extreme drought, few studies have addressed the interactive effects of global change factors on traits driving mortality. To understand the interaction between hydraulic and carbon metabolic traits influencing tree mortality, which may be independently influenced by atmospheric [CO2] and temperature, we grew Eucalyptus sideroxylon A. Cunn. ex Woolls from seed in a full-factorial [CO2] (280, 400 and 640 μmol mol−1, C p, C a and C e, respectively) and temperature (ambient and ambient +4 °C, T a and T e, respectively) experiment. Prior to drought, growth across treatment combinations resulted in significant variation in physiological and morphological traits, including photosynthesis (A sat), respiration (R d), stomatal conductance, carbohydrate storage, biomass and leaf area (LA). C e increased A sat, LA and leaf carbohydrate concentration compared with C a, while C p generated the opposite response; T e reduced R d. However, upon imposition of drought, T e hastened mortality (9 days sooner compared with T a), while C e significantly exacerbated drought stress when combined with T e. Across treatments, earlier time-to-mortality was mainly associated with lower (more negative) leaf water potential (Ψl) during the initial drought phase, along with higher water loss across the first 3 weeks of water limitation. Among many variables, Ψl was more important than carbon status in predicting time-to-mortality across treatments, yet leaf starch was associated with residual variation within treatments. These results highlight the need to carefully consider the integration, interaction and hierarchy of traits contributing to mortality, along with their responses to environmental drivers. Both morphological traits, which influence soil resource extraction, and physiological traits, which affect water-for-carbon exchange to the atmosphere, must be considered to adequately predict plant response to drought. Researchers have struggled with assessing the relative importance of hydraulic and carbon metabolic traits in determining mortality, yet an integrated trait, time-dependent framework provides considerable insight into the risk of death from drought for trees. [ABSTRACT FROM AUTHOR]

Drought assessment of croplands and sylvo-pastoral areas is crucial in semi-arid regions. Satellite remote sensing offers an opportunity for such assessment. This study presents a method of spatial and temporal estimation of drought index in Medjerda basin (23,700 km2) using satellite data and its validation with in situ investigation of areas with crop damage realized by the ministry of agriculture. To estimate drought index, potential evapotranspiration (PET) is calculated using Penman-Monteith equation and modified FAO-56 crop coefficient (Kc) approach combined with remote-sensing data and actual evapotranspiration is derived from the Meteosat Second Generation platforms. The period of study is the 2010 water year. PET estimations show good accuracy with corrected pan evaporation observations up to 0.9. In comparison, the water stress coefficient (Ks) aggregated by land-cover type shows the coefficient of determination with the fraction of drought damage areas of 0.5 for the third decade of March and first decade of April in croplands areas and 0.8 for the second and third decades of May in croplands and sylvo-pastoral areas. This study showed that satellite data approaches could successfully be used to monitor drought in river basins in the Northern Africa and Mediterranean region. [ABSTRACT FROM AUTHOR]

California experienced an intense drought from 2012 to 2015, with southern California remaining in drought to the present. Widespread chaparral shrub mortality was observed during the peak of the drought in 2014. Some species were more impacted than others and shallowrooted shrub species were the most vulnerable to drought-associated mortality. This type of drought represents what is termed an ‘ecological drought’ during which an ecosystem is driven beyond thresholds of vulnerability, triggering impairment of ecosystem services and feedbacks thatmayresult in long-term type-conversion of natural communities. The ability of shrublands to recover will depend on the timing, intensity and seasonality of future extreme climate events, post-fire recruitment potential of species with obligate fire-associated recruitment, and interactions with other stresses. [ABSTRACT FROM AUTHOR]

The article offers information about the application of a tree-ring isotope based conceptual model to examine mechanisms and predispositions in relation to drought induced tree mortality, which is likely to increase in future as climate models forecast increased frequency of drought conditions. Other information about a strategy for dealing with drought as well as a tree’s predisposition to carbon starvation or to hydraulic failure is presented.

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]

Phosphatidic acid (PA) is an important lipid signaling molecule which interacts with Arabidopsis thaliana Sphingosine kinase1 (AtSPHK1) during several abiotic stresses particularly drought stress as a result of Abscisic acid (ABA) signaling in guard cells. PA molecules respond by generating lipid signal and/or by binding and translocating target proteins to membrane. However, site of interaction and role of PA binding to AtSPHK1 is not clear yet. Owing to the importance of AtSPHK1 during stress signaling it is imperative to decipher the site of PA interaction with AtSPHK1. To identify the PA binding region of AtSPHK1, various deletion fragments from N-terminal and C-terminal region were prepared. Results from protein lipid overlay assay using various truncated proteins of AtSPHK1 suggested the involvement of N-terminal region, between 110 and 205 amino acids, in binding with PA. In-silico analyses performed to build homologous structure of AtSPHK1 revealed that PA docking occurs in the hydrophobic cavity of DAG-Kinase domain. Deletion of amino acids 182 VSGDGI 187 perturbed PA-AtSPHK1 binding, indicating an essential role of these six amino acids in PA-AtSPHK1 binding. [ABSTRACT FROM AUTHOR]

Abstract: Aim: We investigate the effects of the environmental and geographical processes driving growth resilience and recovery in response to drought in Mediterranean Pinus pinaster forests. We explicitly consider how intraspecific variability modulates growth resilience to drought. Location: Western Mediterranean basin. Methods: We analysed tree rings from a large network of 48 forests (836 trees) encompassing wide ecological and climatic gradients, including six provenances. To characterize the major constraints of P. pinaster growth under extremely dry conditions, we simulated growth responses to temperature and soil moisture using a process‐based growth model coupled with the quantification of climate–growth relationships. Then, we related growth–resilience indices to provenance and site variables considering different drought events. Results: Pinus pinaster displayed strong variation in growth resilience across its distributional range, but common patterns were found within each provenance. Post‐drought resilience increased with elevation and drier conditions but decreased with spring precipitation. Trees from dry sites were less resistant to drought but recovered faster than trees from wet sites. Main conclusions: Resilience strategies differed among tree provenances: wet forests showed higher growth resistance to drought, while dry forests presented faster growth recovery, suggesting different impacts of climate warming on forest productivity. We detected geographically structured resilience patterns corresponding to different provenances, confirming high intraspecific variability in response to drought. This information should be included in species distribution models to simulate forest responses to climate warming and forecasted aridification. [ABSTRACT FROM AUTHOR]

Predicted increases in the frequency and severity of droughts have led to a renewed focus on how plants physiologically adjust to low water availability. A popular framework for understanding plant responses to drought characterizes species along a spectrum from isohydry to anisohydry based on their regulation of gas exchange and leaf water potential under drying conditions. One prediction that arises from this theory is that plant drought responses may hinge, in part, on their usage of non-structural carbohydrate (NSC) pools. For example, trees that respond to drought by closing stomates (i.e., isohydric) are predicted to deplete NSC reserves to maintain metabolism, whereas plants that keep stomata open during water stress (i.e., anisohydric), may show little change or even increases in NSC concentration. However, empirical tests of this theory largely rely on aboveground measurements of NSC, ignoring the potentially conflicting responses of root NSC pools. We sought to test these predictions by subjecting potted saplings of Quercus alba L. (an anisohydric species) and Liriodendron tulipifera L. (an isohydric species) to a 6 week experimental drought. We found that stem NSC concentrations were depleted in the isohydric L. tulipifera but maintained in the anisohydric Q. alba-as predicted. However, when scaled to whole-plant NSC content, the drought-induced decreases in stem NSCs in L. tulipifera were offset by increases in root NSCs (especially soluble sugars), resulting in no net change to whole-plant NSC content. Similarly, root sugars increased in Q. alba in response to drought. This increase was concurrent with declines in growth, suggesting a potential trade-off between allocation of photoassimilates to root sugars vs biomass during drought. Collectively, our results suggest that the responses of NSC in coarse roots can differ from stems, and indicate a prominent role of coarse roots in mitigating drought-induced declines in whole-tree NSC pools. [ABSTRACT FROM AUTHOR]

This study evaluated effects of drought stress on the concentrations of mineral elements in the leaves of different ecotypes of castor plant. The experimental design was a split-plot randomized complete block with three replications. It was carried out at Fozveh Agricultural Research Station located 20 km from Esfahan, Iran in 2014. The main plot was four levels of water stress (30%, 45%, 60%, and 75% moisture content) and the sub-plot was six castor plant ecotypes (Esfahan, Ardestan, Arak, Naein, Yazd, and Ahwaz). The potassium (K), magnesium (Mg), calcium (Ca), sodium (Na), iron (Fe), copper (Cu), and zinc (Zn) contents were measured and found to be significantly affected by drought stress. Drought stress increased K, Ca and Na contents and decreased Fe, Cu, Zn, and Mg contents of the plants. Various ecotypes of castor plant showed different reactions to drought stress and the Fe concentration varied significantly by the castor plant ecotypes. Interaction between water stress and ecotypes was significant only for Cu and Zn. Understanding the element concentrations under drought stress can be useful for predicting growth and development of castor plants. [ABSTRACT FROM PUBLISHER]

The article discusses the new global study of how shrubs and grasses respond to parched conditions. Topics include the deliberately blocking precipitation from falling at 100 research sites around the world, researchers found that a single year of drought can reduce the growth of vegetation by more than 80 percent, greatly diminishing its ability to absorb carbon dioxide, and procedure for creating artificial droughts in the field.

Green roofs are increasingly being used among the suite of tools designed to reduce the volume of surface water runoff generated by cities. Plants provide the primary mechanism for restoring the rainfall retention capacity of green roofs, but selecting plants with high water use is likely to increase drought stress. Using empirically-derived plant physiological parameters, we used a water balance model to assess the trade-off between rainfall retention and plant drought stress under a 30-year climate scenario. We compared high and low water users with either drought avoidance or drought tolerance strategies. Green roofs with low water-using, drought-avoiding species achieved high rainfall retention (66–81%) without experiencing significant drought stress. Roofs planted with other strategies showed high retention (72–90%), but they also experienced > 50 days of drought stress per year. However, not all species with the same strategy behaved similarly, therefore selecting plants based on water use and drought strategy alone does not guarantee survival in shallow substrates where drought stress can develop quickly. Despite this, it is more likely that green roofs will achieve high rainfall retention with minimal supplementary irrigation if planted with low water users with drought avoidance strategies. [ABSTRACT FROM AUTHOR]

Relating the changes of mangrove forests to spatially explicit reductions in rainfall amounts and increases in drought occurrences is a prerequisite for improving the effectiveness and success of mangrove forest conservation programs. To this end, we investigated the relationship between drought events (quantified using the Standardized Precipitation Index [SPI]) and changes in area and canopy cover of mangrove forests on the northern coast of the Persian Gulf and the Oman Sea using satellite imagery and long-term annual rainfall data over a period of 30 years (1986–2016). Statistical analyses revealed 1998 as the year marking the most significant change-point in the mean annual rainfall values in the catchments and mangroves, after which average SPI values consistently remained at lower levels. In the period of 1998–2016, decreases in the mean annual rainfall and increases in the severity of droughts differed spatially and were greater in the catchments and mangroves on the coasts of the Oman Sea than the coasts of the Persian Gulf. These spatially explicit results were closely mirrored by the mangrove response, with differential in reductions in mangrove areas and canopy cover that corresponded closely with the spatial distribution of drought intensities in the different parts of the coasts, with correlation coefficients ≥0.89 for the different coastal regions. [ABSTRACT FROM AUTHOR]

Drought is an event which affects a wide range from water resources to agriculture and vegetation. Drought is frequently experienced in Turkey and affects large areas. In this research, we studied the Seyhan Basin, which is one of the important water basins in Turkey. Previous studies show that the Mediterranean Region including the Seyhan Basin has been exposed to sever droughts in recent years. In this context, it is of great importance to monitor drought in the Seyhan Basin at regular intervals and study the impact of drought in this area on different environments. In this study, we examined the impact of drought in the year 2014, which affect the entire Seyhan Basin, on photosynthesis activity and distribution of vegetation. 2000-2014 EVI data from the MODIS TERRA platform were used for this purpose. Lastly, EVI data were classified according to the Equal Interval method. In this way, vegetation areas with high and low photosynthesis activity were detected. The findings obtained show that both agricultural and vegetation areas in the Seyhan Basin were significantly affected by drought conditions in 2014. Although drought conditions were present throughout the year in 2014, the vegetation was affected more severely by these conditions in spring and summer months. Results show that adverse affects of drought conditions on vegetation are particularly evident during the growth period. [ABSTRACT FROM AUTHOR]

Severe droughts in the Southern Great Plains (SGP: Kansas, Oklahoma, and Texas) in recent years have reduced the productivity of tallgrass prairie and resulted in substantial economic losses to the beef cattle industry in this region. Understanding spatial and temporal patterns of agricultural drought in the SGP can help ranchers to develop and implement drought mitigation strategies. In this study, the Land Surface Water Index (LSWI), calculated from the Moderate Resolution Imaging Spectroradiometer (MODIS) near infrared and shortwave infrared bands, was used to assess agricultural drought in the tallgrass prairie region of the SGP during 2000–2013. The number of consecutive days with LSWI < 0 (DNLSWI) during the growing season was defined as the drought duration, which, was then used to identify and analyze frequency of summer drought and whole growing season drought (WGSD). The spatial pattern of DNLSWI was consistent with the east-to-west decreasing precipitation gradient across the SGP region. Summer drought duration as depicted by the DNLSWI in the western portion of the study area was around one and a half month. The occurrence of WGSD increased from one year in the east to up to six years in the west, demonstrating the susceptibility of the tallgrass prairie region to drought. In addition to the total amount of precipitation, its intra-annual distribution also played an important role in drought development. A comparison with other widely used national drought products, namely the Evaporative Stress Index (ESI), the Vegetation Drought Response Index (VegDRI), and the United States Drought Monitor (USDM), shows that LSWI-based drought has good agreement with ESI and USDM. Quantitative analyses indicate that LSWI-based drought agreed better with ESI in severe drought conditions than in moderate or pre-drought conditions. Severe drought periods characterized by the USDM also had low LSWI values. The areas affected by drought derived from the LSWI-based drought index were significantly correlated with hay production. As an indicator of vegetation water stress at moderate spatial resolution (∼500 m), the LSWI has the potential to show drought conditions for an individual ranch and offer guidance for drought mitigation activities and livestock production. [ABSTRACT FROM AUTHOR]

Current methods of crop improvement are not keeping pace with projected increases in population growth. Breeding, focused around key traits of stem height and disease resistance, delivered the step-change yield improvements of the green revolution of the 1960s. However, subsequently, yield increases through conventional breeding have been below the projected requirement of 2.4% per year required by 2050. Genetic modification (GM) mainly for herbicide tolerance and insect resistance has been transformational, akin to a second green revolution, although GM has yet to make major inroads into intrinsic yield processes themselves. Drought imposes the major restriction on crop yields globally but, as yet, has not benefited substantially from genetic improvement and still presents a major challenge to agriculture. Much still has to be learnt about the complex process of how drought limits yield and what should be targeted. Mechanisms of drought adaptation from the natural environment cannot be taken into crops without significant modification for the agricultural environment because mechanisms of drought tolerance are often in contrast with mechanisms of high productivity required in agriculture. However, through convergence of fundamental and translational science, it would appear that a mechanism of sucrose allocation in crops can be modified for both productivity and resilience to drought and other stresses. Recent publications show how this mechanism can be targeted by GM, natural variation and a new chemical approach. Here, with an emphasis on drought, we highlight how understanding fundamental science about how crops grow, develop and what limits their growth and yield can be combined with targeted genetic selection and pioneering chemical intervention technology for transformational yield improvements. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Plant post-drought recovery performance is essential to predict shifts in ecosystem dynamics and production during frequent climate change-driven drought events. Yet, it is not clear how post-drought recovery is related to evolutionary and geographic variations in plants. In this study, we generated a global data set of post-drought recovery performance in 140 plant species from published studies. We quantified the plant post-drought recovery performance by calculating a recovery index for multiple plant physiological and hydraulic parameters, including leaf water potential, net photosynthetic rate, leaf hydraulic conductance and shoot biomass. The magnitude of recovery among four plant functional types (deciduous angiosperms, evergreen angiosperms, gymnosperms, and crops), two plant growth forms (shrubs and trees), two water management strategies (isohydric and anisohydric), four xylem porosity types (diffuse, ring, semi-ring and tracheid), and four major biomes (dry sclerophyll forest, boreal forest, temperate forest and tropical/subtropical forest) were compared. We found the inability to completely recover immediately after severe water stress is ubiquitous across all plant functional types and growth forms, while the rate and magnitude of post-drought recovery varied greatly across different plant taxonomic categories and geographic ranges. In general, plant hydraulic architecture, leaf anatomy and physiology affect plants' propensity towards recovery, and reflect evolutionary consequences of plant adaptation to their habitat. Due to the essential role of plant functional traits in regulating carbon storage in each biome, a better understanding plant post-drought recovery performance could improve our predictions on ecosystem productivity in a rapidly changing climate. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the potential of seed priming following terminal drought on tolerance against salt stress in bread wheat. Drought was imposed in field sown wheat at reproductive stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl 2 ) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz . 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4–18%), malondialdehyde (MDA) (27–35%) and tissue Na + contents (149–332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3–18%), osmolytes accumulation (21–33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na + contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation. [ABSTRACT FROM AUTHOR]

Climate warming is predicted to amplify drought stress. Thus, it is important to understand how coexisting plant species respond to severe droughts. Here we study how seven Mediterranean woody plant species with different evolutionary history and functional characteristics ( Pinus halepensis Mill., Juniperus phoenicea L. , Pistacia lentiscus L., Rhamnus lycioides L., Rosmarinus officinalis L., Genista scorpius (L.) DC., and Globularia alypum L.) responded to a severe winter drought during 2011-2012 in Spain. The study site is located in the Valcuerna valley, Monegros desert, northeastern Spain. We evaluated how the drought affected the annual growth-ring formation of the species by using dendrochronology and quantified the intensity of drought-induced defoliation and mortality and compared it between species and groups of species with different evolutionary history. Radial growth of all species was strongly reduced by the 2012 drought. The pre-Mediterranean species ( P. halepensis, J. phoenicea, P. lentiscus and R. lycioides) reduced growth more than the Mediterranean species ( R. officinalis, G. scorpius and G. alypum). Defoliation was significantly higher in pre-Mediterranean than in Mediterranean species. When species were analyzed separately we found that P. halepensis was the species with the highest growth reduction but J. phoenicea was defoliated more severely and showed higher mortality rates as a consequence of drought. In the case of the Mediterranean shrubs, drought-induced mortality was only noticeable in R. officinalis. Drought impacted growth of all species but this did not induce mortality in all of them. Growth reduction was dependent on evolutionary history. However, functional characteristics of the species such as leaf stomatal regulation and root architecture may be more important than evolutionary history on explaining drought-induced mortality. Indeed, species with shallow root systems such as J. phoenicea and R. officinalis were the most adversely affected by the drought. [ABSTRACT FROM AUTHOR]

Here, we conducted a meta-analysis of experimental drought manipulation studies using rainout shelters in five sites of natural grassland ecosystems of Europe. The single studies assess the effects of extreme drought on the intraspecific variation of the specific leaf area ( SLA), a proxy of plant growth. We evaluate and compare the effect size of the SLA response for the functional groups of forbs and grasses in temperate and sub-Mediterranean systems. We hypothesized that the functional groups of grasses and forbs from temperate grassland systems have different strategies in short-term drought response, measured as adjustment of SLA, with SLA-reduction in grasses and SLA-maintenance in forbs. Second, we hypothesized that grasses and forbs from sub-Mediterranean systems do not differ in their drought response as both groups maintain their SLA. We found a significant decrease of SLA in grasses of the temperate systems in response to drought while SLA of forbs showed no significant response. Lower SLA is associated with enhanced water-use efficiency under water stress and thus can be seen as a strategy of phenotypic adjustment. By contrast, in the sub-Mediterranean systems, grasses significantly increased their SLA in the drought treatment. This result points towards a better growth performance of these grasses, which is most likely related to their strategy to allocate resources to belowground parts. The observed SLA reduction of forbs is most likely a direct drought response given that competitive effect of grasses is unlikely due to the scanty vegetation cover. We point out that phenotypic adjustment is an important driver of short-term functional plant response to climatic extremes such as drought. Differential reactions of functional groups have to be interpreted against the background of the group's evolutionary configuration that can differ between climatic zones. [ABSTRACT FROM AUTHOR]

Drought is a typical disaster in the main soybean production area of northeast China. The spatiotemporal variations of drought related to soybean production based on a crop water deficit index (CWDI) and sensitivity to meteorological variables were investigated in northeast China using daily meteorological data from 87 weather stations from 1981 to 2010. Statistical analysis revealed that precipitation could not meet the water demands of soybeans during the seedling-branching, filling, and maturing stages, and excessive drought occurred more often in northeast China. The Mann-Kendall test indicated that the soybean CWDI significantly increased during the filling stage. Kriging spatial analysis showed that the most drought-prone area was located in the west of northeast China. Explanations for the spatiotemporal variations of the drought for soybean production were explored in terms of meteorological variables. Statistical analysis showed that the crop evapotranspiration, air temperature, wind speed, and number of sunshine hours were significantly higher and the precipitation and relative humidity were significantly lower in the drought-prone area than in the dry area less prone to droughts. An explored method of sensitive analysis quantitatively revealed that precipitation and humidity negatively affected the CWDI, whereas temperature, wind speed, and number of sunshine hours positively affected the CWDI. The CWDI was most sensitive to precipitation. These results not only provide valuable information for soybean planning and management but also produce important background and physical evidence for the influence of climate on the drought related to soybean production in northeast China. [ABSTRACT FROM AUTHOR]

Drought conditions in the western United States have limited water availability for the irrigation of agricultural products. This can have a dramatic impact on yield and quality of specialty perennial crops, such as juice grapes (Vitis labruscana Bailey). Washington State juice grape industry typically irrigates to 100% of crop-specific evapotranspiration (ETc) throughout the season to minimize yield loss. However, as conditions have limited water availability, growers need a new strategy to cope with the limited water supply. Regulated deficit irrigation (RDI) applies less water than plant ETc and has been shown to improve fruit quality in red wine grapes (Vitis vinifera). The objectives of this study were to evaluate the effects of RDI treatments on the yield and quality of 'Concord' juice grapes as compared with current commercial practice. The treatments reduced the amount of water applied between bloom and veraison by 25% (L25%), 33% (L33%), and 45% (L45%) from the control application. The results of this 4-year study initially indicated a dramatic decrease in yield in theL45% treatment (7.5 Mg/ha) as compared with the control treatment (19.2 Mg/ha); however, yield for the RDI treatments recovered in the subsequent seasons and was not statically different from the control. There were no statistical differences in fruit quality between treatments. This indicates that RDI has the potential to decrease water applied between bloom and veraison without impacting fruit quality; however, to avoid a sudden decrease in yield, it would be necessary to gradually reduce water applications over several years. [ABSTRACT FROM AUTHOR]

The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer of 2015 was characterized by exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C higher than the seasonal mean (1971-2000) over most of western Europe, and more than 3 °C higher in the east. It was the hottest and climatologically driest summer over the 1950-2015 study period for an area stretching from the eastern Czech Republic to Ukraine. For Europe, as a whole, it is among the six hottest and driest summers since 1950. High evapotranspiration rates combined with a lack of precipitation affected soil moisture and vegetation and led to record low river flows in several major rivers, even beyond the drought-hit region. The 2015 drought developed rather rapidly over the Iberian Peninsula, France, southern Benelux and central Germany in May and reached peak intensity and spatial extent by August, affecting especially the eastern part of Europe. Over the summer period, there were four heat wave episodes, all associated with persistent blocking events. Upper-level atmospheric circulation over Europe was characterized by positive 500 hPa geopotential height anomalies flanked by a large negative anomaly to the north and west (i.e., over the central North Atlantic Ocean extending to northern Fennoscandia) and another center of positive geopotential height anomalies over Greenland and northern Canada. Simultaneously, the summer sea surface temperatures (SSTs) were characterized by large negative anomalies in the central North Atlantic Ocean and large positive anomalies in the Mediterranean basin. Composite analysis shows that the western Mediterranean SST is strongly related to the occurrence of dry and hot summers over the last 66 years (especially over the eastern part of Europe). The lagged relationship between the Mediterranean SST and summer drought conditions established in this study can provide valuable skill for the prediction of drought conditions over Europe on interannual to decadal timescales. [ABSTRACT FROM AUTHOR]

Background: Plants are oftentimes exposed to many types of abiotic stresses. Drought is one of the main environmental stresses which limits plant growth, distribution and crop yield worldwide. Amygdalus mira (Koehne) Yü et Lu is an important wild peach, and it is considered an ideal wild peach germplasm for improving cultivated peach plants. Because of the loss of genetic variation, cultivated peach plants are sensitive to biotic and abiotic stresses. Wild peach germplasm can offer many useful genes for peach improvement. Responses to drought by withholding water have been studied in Amygdalus mira (Koehne) Yü et Lu roots. In this study, plants were divided into well-watered (control) and water-stressed (treatment) groups, and the treatment group did not receive water until the recovery period (day 16). Results: Several physiological parameters, including root water content and root length, were reduced by drought stress and recovered after rewatering. In addition, the relative conductivity, the levels of proline, MDA and H2O2, and the activities of ROS scavenging enzymes (POD, APX and CAT) were increased, and none of these factors, except the level of proline, recovered after rewatering. In total, 95 differentially expressed proteins were revealed after drought. The identified proteins refer to a extensive range of biological processes, molecular functions and cellular components, including cytoskeleton dynamics (3.16% of the total 95 proteins), carbohydrate and nitrogen metabolism (6.33% of the total 95 proteins), energy metabolism (7.37% of the total 95 proteins), transcription and translation (18.95% of the total 95 proteins), transport (4.21% of the total 95 proteins), inducers (3.16% of the total 95 proteins), stress and defense (26.31% of the total 95 proteins), molecular chaperones (9.47% of the total 95 proteins), protein degradation (3.16% of the total 95 proteins), signal transduction (7.37% of the total 95 proteins), other materials metabolism (5.26% of the total 95 proteins) and unknown functions (5.26% of the total 95 proteins). Proteins related to defense, stress, transcription and translation play an important role in drought response. In addition, we also examined the correlation between protein and transcript levels. Conclusions: The interaction between enzymatic and non-enzymatic antioxidants, the levels of proline, MDA, H2O2 and the relative conductivity, and the expression level of proteins in drought-treated plants all contribute to drought resistance in Amygdalus mira (Koehne) Yü et Lu. [ABSTRACT FROM AUTHOR]

Agricultural drought, a common phenomenon in most parts of the world, is one of the most challenging natural hazards to monitor effectively. Land surface water index (LSWI), calculated as a normalized ratio between near infrared (NIR) and short-wave infrared (SWIR), is sensitive to vegetation and soil water content. This study examined the potential of a LSWI-based, drought-monitoring algorithm to assess summer drought over 113 Oklahoma Mesonet stations comprising various land cover and soil types in Oklahoma. Drought duration in a year was determined by the number of days with LSWI <0 (DNLSWI) during summer months (June-August). Summer rainfall anomalies and LSWI anomalies followed a similar seasonal dynamics and showed strong correlations ( r = 0.62-0.73) during drought years (2001, 2006, 2011, and 2012). The DNLSWI tracked the east-west gradient of summer rainfall in Oklahoma. Drought intensity increased with increasing duration of DNLSWI, and the intensity increased rapidly when DNLSWI was more than 48 days. The comparison between LSWI and the US Drought Monitor (USDM) showed a strong linear negative relationship; i.e., higher drought intensity tends to have lower LSWI values and vice versa. However, the agreement between LSWI-based algorithm and USDM indicators varied substantially from 32 % ( D class, moderate drought) to 77 % (0 and D class, no drought) for different drought intensity classes and varied from ∼30 % (western Oklahoma) to >80 % (eastern Oklahoma) across regions. Our results illustrated that drought intensity thresholds can be established by counting DNLSWI (in days) and used as a simple complementary tool in several drought applications for semi-arid and semi-humid regions of Oklahoma. However, larger discrepancies between USDM and the LSWI-based algorithm in arid regions of western Oklahoma suggest the requirement of further adjustment in the algorithm for its application in arid regions. [ABSTRACT FROM AUTHOR]

The Standardized Precipitation Evapotranspiration Index (SPEI) based on three different potential evapotranspiration ( PET) estimation methods, including the Thornthwaite (TW) equation, the Penman-Monteith (PM) equation, and the Two-Source (2S) PET model were compared and evaluated by observed evidences over the Loess Plateau, which includes large area of sparse vegetation cover. The results show that the Loess Plateau has experienced substantial climate warming over the past four decades, which intensively raised the atmospheric water demand ( PET), thus the drought condition. The upward trends of PETTW were the most extensive, while the upward trends of PET2S and PETPM were similar to each other. The differences between SPEIPM and SPEITW were larger than the differences between SPEIPM and SPEI2S. The variability of SPEI2S and SPEIPM were more consistent with the observed streamflow and the normal difference vegetation index than that of SPEITW, and the SPEI2S even showed higher agreements than the SPEIPM. The 2S PET model considers radiation balances at the canopy level and soil surface separately, which helps this model more accurately estimate the PET in regions with sparse vegetation. The PM equation is a more physically based PET estimation method than the TW equation, which takes the other variables that effect atmospheric water demand into account. Therefore, the 2S PET model (first) and the PM equation (second) are recommended in calculating the SPEI over regions with large area of sparse vegetation cover, as a result of better physical mechanism and higher correlations with different types of observations. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: Soil salinity and drought are an enormous worldwide problem for agriculture, horticulture and silviculture. The initial responses of plants to drought and salinity are similar; both are attributed to water deficit which inhibits plant growth and development. Scope: In this review, an overview of the major physiological and biochemical changes that occur in plants as a consequence of salt and drought stress is presented. In addition, the role of beneficial plant growth-promoting bacteria in ameliorating many of the deleterious consequences of salt and drought stress is discussed. Mechanisms used by plant growth-promoting bacteria to ameliorate the effects of these stresses include the production of cytokinin, indoleacetic acid, ACC deaminase, abscisic acid, trehalose, volatile organic compounds, and exopolysaccharides. Conclusion: Given the fundamental understanding of many of the mechanisms operating in plant-bacterial interactions, it is expected that the practical use of beneficial bacteria in agriculture, horticulture and silviculture will grow dramatically in the coming years. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate Maize (Zea mays L.) elite lines currently available in CIMMYT's lowland tropical breeding program in Latin America under multiple abiotic stresses and identify lines with tolerance to drought, N deficiency, and combined heat and drought stress (HTDS). An incomplete line-by-tester design was used to evaluate 436 testcrosses under nonstressed conditions, 507 under N deficiency, 417 under drought stress (DS), and 368 under HTDS in 30 season-by-location combinations between 2012 and 2015. Elite lines CLRCY016, CML269, CML550, and CML551 performed well across all conditions, while CLQRCWQ118, CLWN306, and CML576 showed good performance under DS and N deficiency. CML574 was tolerant to DS and HTDS. Moreover, CML550 and CML574 are known for their partial tolerance to maize lethal necrosis. Grain yield measured under DS was to some extent predictive of attainable grain yield under N-deficient conditions (r = 0.65; P < 0.01) and HTDS (r = 0.54; P < 0.01) as indicated by the correlation across treatments. The fact that only a few lines were tolerant across treatments re-emphasizes the need to separately screen germplasm under each abiotic stress. Based on high best linear unbiased predicted general combining ability (BLUP GCA), it will be possible to develop hybrids tolerant to multiple abiotic stresses without incurring any yield penalty under nonstressed conditions using these inbred lines. [ABSTRACT FROM AUTHOR]

Scots pine (Pinus sylvestris L.) provenances cover broad ecological amplitudes. In a greenhouse study, we investigated the impact of drought stress and rewetting on gas exchange for three provenances (Italy: Emilia Romagna; Spain: Alto Ebro; Germany: East-German lowlands) of 2-year old Scots pine seedlings. CO2, water vapour and isoprenoid exchange of stressed and control trees were quantified with a four-chamber dynamic-enclosure system in the controlled environment of a climate chamber. The three provenances showed distinct isoprenoid emission patterns and were classified into a non-Δ3-carene, with either high α-/β-pinene or β-myrcene fraction, and a Δ3-carene dominated type. Isoprenoid emission rates, net-photosynthesis and transpiration were reduced during summer drought stress and significantly recovered after rewetting. A seasonal increase of isoprenoid emission rates towards autumn was observed for all control groups. Compared with the German provenance, the Spanish and Italian provenances revealed higher isoprenoid emission rates and more plastic responses to drought stress and seasonal development, which points to a local adaptation to climate. As a result of drought, net carbon uptake and transpiration of trees was reduced, but recovered after rewetting. We conclude from our study that Scots pine isoprenoid emission is more variable than expected and sensitive to drought periods, likely impacting regional air chemistry. Thus, a provenance-specific emission assessment accounting for reduced emission during prolonged (summer) drought is recommend for setting up biogenic volatile organic compound emission inventories used in air quality models. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO2 will make Earth warmer, and many studies have inferred that this warming will cause droughts to become more widespread and severe. However, rising atmospheric CO2 also modifies stomatal conductance and plant water use, processes that are often are overlooked in impact analysis. We find that plant physiological responses to CO2 reduce predictions of future drought stress, and that this reduction is captured by using plant-centric rather than atmosphere-centric metrics from Earth system models (ESMs). The atmosphere-centric Palmer Drought Severity Index predicts future increases in drought stress for more than 70% of global land area. This area drops to 37% with the use of precipitation minus evapo- transpiration (P-E), a measure that represents the water flux available to downstream ecosystems and humans. The two metrics yield consistent estimates of increasing stress in regions where precipitation decreases are more robust (southern North America, northeastern South America, and southern Europe). The metrics produce diverging estimates elsewhere, with P-E predicting decreasing stress across temperate Asia and central Africa. The differing sensitivity of drought metrics to radiative and physiological aspects of increasing CO2 partly explains the divergent estimates of future drought reported in recent studies. Further, use of ESM output in offline models may double-count plant feedbacks on relative humidity and other surface variables, leading to overestimates of future stress. The use of drought metrics that account for the response of plant transpiration to changing CO2, including direct use of P-E and soil moisture from ESMs, is needed to reduce uncertainties in future assessment. [ABSTRACT FROM AUTHOR]