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1
Peterson, Tim J., M. Saft, M. C. Peel, and A. John. "Watersheds may not recover from drought." Science 372, no. 6543 (May 13, 2021): 745–49. http://dx.doi.org/10.1126/science.abd5085.
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The Millennium Drought (southeastern Australia) provided a natural experiment to challenge the assumption that watershed streamflow always recovers from drought. Seven years after the drought, the runoff (as a fraction of precipitation) had not recovered in 37% of watersheds, and the number of recovered watersheds was not increasing. When recovery did occur, it was not explained by watershed wetness. For those watersheds not recovered, ~80% showed no evidence of recovering soon, suggesting persistence within a low-runoff state. The post-drought precipitation not going to runoff was found to be likely going to increased evapotranspiration per unit of precipitation. These findings show that watersheds can have a finite resilience to disturbances and suggest that hydrological droughts can persist indefinitely after meteorological droughts.
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Bernardino, Paulo N., Martin Brandt, Wanda De Keersmaecker, Stéphanie Horion, Rasmus Fensholt, Ilié Storms, Jean-Pierre Wigneron, Jan Verbesselt, and Ben Somers. "Uncovering Dryland Woody Dynamics Using Optical, Microwave, and Field Data—Prolonged Above-Average Rainfall Paradoxically Contributes to Woody Plant Die-Off in the Western Sahel." Remote Sensing 12, no. 14 (July 21, 2020): 2332. http://dx.doi.org/10.3390/rs12142332.
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Dryland ecosystems are frequently struck by droughts. Yet, woody vegetation is often able to recover from mortality events once precipitation returns to pre-drought conditions. Climate change, however, may impact woody vegetation resilience due to more extreme and frequent droughts. Thus, better understanding how woody vegetation responds to drought events is essential. We used a phenology-based remote sensing approach coupled with field data to estimate the severity and recovery rates of a large scale die-off event that occurred in 2014–2015 in Senegal. Novel low (L-band) and high-frequency (Ku-band) passive microwave vegetation optical depth (VOD), and optical MODIS data, were used to estimate woody vegetation dynamics. The relative importance of soil, human-pressure, and before-drought vegetation dynamics influencing the woody vegetation response to the drought were assessed. The die-off in 2014–2015 represented the highest dry season VOD drop for the studied period (1989–2017), even though the 2014 drought was not as severe as the droughts in the 1980s and 1990s. The spatially explicit Die-off Severity Index derived in this study, at 500 m resolution, highlights woody plants mortality in the study area. Soil physical characteristics highly affected die-off severity and post-disturbance recovery, but pre-drought biomass accumulation (i.e., in areas that benefited from above-normal rainfall conditions before the 2014 drought) was the most important variable in explaining die-off severity. This study provides new evidence supporting a better understanding of the “greening Sahel”, suggesting that a sudden increase in woody vegetation biomass does not necessarily imply a stable ecosystem recovery from the droughts in the 1980s. Instead, prolonged above-normal rainfall conditions prior to a drought may result in the accumulation of woody biomass, creating the basis for potentially large-scale woody vegetation die-off events due to even moderate dry spells.
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Zhang, Lingnan, Hui Li, Yilin Ran, Keyi Wang, Xiaomin Zeng, and Xiaohong Liu. "Regional and Local Moisture Gradients Drive the Resistance to and Recovery from Drought of Picea crassifolia Kom. in the Qilian Mountains, Northwest China." Forests 10, no. 9 (September 19, 2019): 817. http://dx.doi.org/10.3390/f10090817.
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Increasing evidence suggests that extreme droughts cause more frequent tree growth reduction. To understand the consequences of these droughts better, this study used tree-ring cores from nine sites to investigate how moisture and altitudinal gradients affect the radial growth of Picea crassifolia Kom., a common species in the Qilian Mountains in northwest China. The total annual precipitation and mean annual temperature in the eastern region were higher than those in the western region of the Qilian Mountains. The trees in the eastern region showed stronger resistance to drought than those in the west, as they had a smaller difference in radial growth between drought disturbance and pre-drought disturbance. At the same time, the trees in the east showed weaker ability to recover from drought, as they had a subtle difference in radial growth between post-drought disturbance and drought disturbance. Furthermore, the trees in the east also showed weaker relative resilience to drought, as they had a small difference in radial growth between post-drought and drought disturbance weighted by growth in pre-drought disturbance. For trees below 3000 m a.s.l., trees with high resistance capacity usually had low recovery capacity and low relative resilience capacity. Trees at higher altitudes also showed stronger resistance to drought and weaker ability to recover from drought after a drought event than those at lower altitudes in the middle of the Qilian Mountains. Trees at lower altitudes in the middle of the Qilian Mountains had more difficulties recovering from more severe and longer drought events. In the context of global warming, trees in the western region and at lower altitudes should be given special attention and protection in forest management to enhance their resistance to extreme droughts.
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Domenghini, Jacob C., Dale J. Bremer, Jack D. Fry, and Gregory L. Davis. "Prolonged Drought and Recovery Responses of Kentucky Bluegrass and Ornamental Groundcovers." HortScience 48, no. 9 (September 2013): 1209–15. http://dx.doi.org/10.21273/hortsci.48.9.1209.
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Municipalities often restrict irrigation of urban landscapes, causing plants to experience drought stress. Few data are available regarding drought resistance of non-turfgrass landscape species. This study evaluated the performance of one turfgrass (Poa pratensis L. ‘Apollo’) and eight herbaceous landscape species (Achillea millifolium L., Ajuga reptans L. ‘Bronze Beauty’, Liriope muscari Decne., Pachysandra terminalis Siebold and Zucc., Sedum album L., Thymus serpyllum L., Vinca major L., and Vinca minor L.) during a severe drydown and subsequent recovery. This greenhouse study was conducted in the spring/summer and again in the fall of 2010. S. album performed the best, averaging 254 days to decline to a drought rating of 1 (1 to 9 scale, 1 = dead/dormant and 9 = best quality). L. muscari and P. terminalis also performed well, averaging 86 days to a drought rating of 1. V. minor and V. major declined faster than the previous species, averaging 63 days. A. millifolium, A. reptans, P. pratensis, and T. serpyllum declined the fastest to a drought rating of 1 (mean 52 days). Thereafter, the only species to recover after 60 days of resuming irrigation were P. pratensis [46% pot cover (PC)], S. album (38% PC), and V. major (35% PC) in the spring/summer study; no species recovered during the fall study. Results indicate S. album, L. muscari, and P. terminalis are the most drought-resistant among the species evaluated in landscapes where severe drought may occur. V. minor and V. major are good selections in less severe droughts as is P. pratensis if periods of dormancy are acceptable.
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Abid, Muhammad, Zhongwei Tian, Syed Tahir Ata-Ul-Karim, Feng Wang, Yang Liu, Rizwan Zahoor, Dong Jiang, and Tingbo Dai. "Adaptation to and recovery from drought stress at vegetative stages in wheat (Triticum aestivum) cultivars." Functional Plant Biology 43, no. 12 (2016): 1159. http://dx.doi.org/10.1071/fp16150.
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Studying plants’ capability to adapt and recover from drought stress is essential because of the ever-changing nature of drought events. To evaluate the genotypically variable morpho-physiological adaptations to drought stress and recovery after re-watering, two wheat cultivars (Luhan-7 and Yangmai-16) were pot-cultured under three levels of water stress: severe (35–40% field capacity, FC) and moderate water deficits (55–60% FC) and well-watered conditions. Drought stress was applied at tillering (Feekes 2 stage) and jointing (Feekes 6 stage), respectively, followed by re-watering, and we observed changes in leaf characteristics, growth and physiological activities during water stress and rewatering periods as well as final grain yield traits at maturity. Results showed that drought stress adaptability associated with reduced leaf area, higher leaf thickness, chlorophyll, leaf dry matter and maintenance of leaf water potential were more strongly pronounced in Luhan-7 than in Yangmai-16. Under moderate stress both cultivars exhibited a small decrease in leaf gas-exchange and chlorophyll fluorescence activities, followed by rapid recovery. Under severe drought stress, Yangmai-16 displayed relatively less adaptability to drought, with a slower recovery after re-watering and a greater decrease in grain yield. It was concluded that even though crop growth rate completely recovered after re-watering, the final dry matter and grain yield outcomes were affected by pre-drought stress, and were dependant on the drought intensity, adaptability and recovery differences of the cultivars and growth stage. It was also concluded that genotypic variations in adaptability and recovery from drought stress are the indicators of drought tolerance and grain yield sustainability in wheat.
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De Faria, Bruno L., Gina Marano, Camille Piponiot, Carlos A. Silva, Vinícius de L. Dantas, Ludmila Rattis, Andre R. Rech, and Alessio Collalti. "Model-Based Estimation of Amazonian Forests Recovery Time after Drought and Fire Events." Forests 12, no. 1 (December 23, 2020): 8. http://dx.doi.org/10.3390/f12010008.
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In recent decades, droughts, deforestation and wildfires have become recurring phenomena that have heavily affected both human activities and natural ecosystems in Amazonia. The time needed for an ecosystem to recover from carbon losses is a crucial metric to evaluate disturbance impacts on forests. However, little is known about the impacts of these disturbances, alone and synergistically, on forest recovery time and the resulting spatiotemporal patterns at the regional scale. In this study, we combined the 3-PG forest growth model, remote sensing and field derived equations, to map the Amazonia-wide (3 km of spatial resolution) impact and recovery time of aboveground biomass (AGB) after drought, fire and a combination of logging and fire. Our results indicate that AGB decreases by 4%, 19% and 46% in forests affected by drought, fire and logging + fire, respectively, with an average AGB recovery time of 27 years for drought, 44 years for burned and 63 years for logged + burned areas and with maximum values reaching 184 years in areas of high fire intensity. Our findings provide two major insights in the spatial and temporal patterns of drought and wildfire in the Amazon: (1) the recovery time of the forests takes longer in the southeastern part of the basin, and, (2) as droughts and wildfires become more frequent—since the intervals between the disturbances are getting shorter than the rate of forest regeneration—the long lasting damage they cause potentially results in a permanent and increasing carbon losses from these fragile ecosystems.
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Gerdener, Helena, Olga Engels, and Jürgen Kusche. "A framework for deriving drought indicators from the Gravity Recovery and Climate Experiment (GRACE)." Hydrology and Earth System Sciences 24, no. 1 (January 16, 2020): 227–48. http://dx.doi.org/10.5194/hess-24-227-2020.
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Abstract. Identifying and quantifying drought in retrospective is a necessity for better understanding drought conditions and the propagation of drought through the hydrological cycle and eventually for developing forecast systems. Hydrological droughts refer to water deficits in surface and subsurface storage, and since these are difficult to monitor at larger scales, several studies have suggested exploiting total water storage data from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to analyze them. This has led to the development of GRACE-based drought indicators. However, it is unclear how the ubiquitous presence of climate-related or anthropogenic water storage trends found within GRACE analyses masks drought signals. Thus, this study aims to better understand how drought signals propagate through GRACE drought indicators in the presence of linear trends, constant accelerations, and GRACE-specific spatial noise. Synthetic data are constructed and existing indicators are modified to possibly improve drought detection. Our results indicate that while the choice of the indicator should be application-dependent, large differences in robustness can be observed. We found a modified, temporally accumulated version of the Zhao et al. (2017) indicator particularly robust under realistic simulations. We show that linear trends and constant accelerations seen in GRACE data tend to mask drought signals in indicators and that different spatial averaging methods required to suppress the spatially correlated GRACE noise affect the outcome. Finally, we identify and analyze two droughts in South Africa using real GRACE data and the modified indicators.
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Partelli-Feltrin, Raquel, Daniel M. Johnson, Aaron M. Sparks, Henry D. Adams, Crystal A. Kolden, Andrew S. Nelson, and Alistair M. S. Smith. "Drought Increases Vulnerability of Pinus ponderosa Saplings to Fire-Induced Mortality." Fire 3, no. 4 (September 28, 2020): 56. http://dx.doi.org/10.3390/fire3040056.
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The combination of drought and fire can cause drastic changes in forest composition and structure. Given the predictions of more frequent and severe droughts and forecasted increases in fire size and intensity in the western United States, we assessed the impact of drought and different fire intensities on Pinus ponderosa saplings. In a controlled combustion laboratory, we exposed saplings to surface fires at two different fire intensity levels (quantified via fire radiative energy; units: MJ m−2). The recovery (photosynthesis and bud development) and mortality of saplings were monitored during the first month, and at 200- and 370-days post-fire. All the saplings subjected to high intensity surface fires (1.4 MJ m−2), regardless of the pre-fire water status, died. Seventy percent of pre-fire well-watered saplings recovered after exposure to low intensity surface fire (0.7 MJ m−2). All of the pre-fire drought-stressed saplings died, even at the lower fire intensity. Regardless of the fire intensity and water status, photosynthesis was significantly reduced in all saplings exposed to fire. At 370 days post-fire, burned well-watered saplings that recovered had similar photosynthesis rates as unburned plants. In addition, all plants that recovered or attempted to recover produced new foliage within 35 days following the fire treatments. Our results demonstrate that the pre-fire water status of saplings is an important driver of Pinus ponderosa sapling recovery and mortality after fire.
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Mukeshimana, Gerardine, Amy L. Lasley, Wayne H. Loescher, and James D. Kelly. "Identification of Shoot Traits Related to Drought Tolerance in Common Bean Seedlings." Journal of the American Society for Horticultural Science 139, no. 3 (May 2014): 299–309. http://dx.doi.org/10.21273/jashs.139.3.299.
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Drought is an important abiotic stress that limits common bean (Phaseolus vulgaris) productivity. The objective of this study was to determine shoot traits that are associated with drought tolerance in common bean seedlings. Ten common bean genotypes consisting mainly of cultivars and breeding lines from the Mesoamerican race of the Middle American gene pool were first evaluated in the greenhouse. Genotypes were grown in a shallow soil profile to limit root growth and assess shoot phenotypes under stress. Water stress was imposed by withholding watering for 24 days after planting. Traits evaluated included wilting, unifoliate senescence, stem greenness, and recovery from drought. Biomass and number of pods/plant produced after drought recovery were evaluated to quantify the effect of early drought stress on bean growth and reproduction. A second group of 94 common bean genotypes from the Bean Coordinated Agricultural Project (BeanCAP) were evaluated using the same protocol to determine the genetic variability for the same traits in a wider range of genotypes. In general, genotypes known to possess drought avoidance in the field conferred by deep rooting traits performed poorly in these conditions suggesting that the assay could be used to identify seedling shoot traits that contribute to drought tolerance. Genotypes from race Mesoamerica showed the greatest range in wilting. Genotypes that showed a slow rate of wilting maintained a green stem and had a higher recovery rate after watering. Importantly, these genotypes demonstrated a smaller reduction in biomass and pod number under stress compared with non-stress treatments. A few genotypes recovered completely despite expressing severe wilting, whereas the majority of genotypes with high wilting rates did not recover. Among the BeanCAP materials, genotypes bred in the rainfed midwestern United States showed overall better recovery than those bred under the irrigated production system used in the western United States. Because recovery from drought is a prerequisite to plant regrowth, biomass, and pod production after drought stress, factors that contribute to recovery were studied. Stem greenness was highly positively correlated to the recovery, whereas wilting was negatively correlated to the recovery. In a regression analysis, stem greenness and slow wilting were found to be important contributors to the variability of recovery. In addition, photosynthetic rate and stomatal conductance (gS) explained variation in wilting and stem greenness. These results suggest that wilting and stem greenness might be useful traits to screen for drought tolerance in seedlings of common bean.
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Bassirirad, H., and MM Caldwell. "Root Growth, Osmotic Adjustment and NO3- Uptake During and After a Period of Drought in Artemisia tridentata." Functional Plant Biology 19, no. 5 (1992): 493. http://dx.doi.org/10.1071/pp9920493.
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Nitrate uptake in pot-grown, well watered and water-stressed Artemisia tridentata seedlings was determined both during drought and during recovery from drought using >15NO3-. Water deficit caused a 40% decrease in NO3- uptake compared to well watered plants and the restricted NO3- uptake persisted 4 days after rewatering. Between 4 and 14 days after rewatering, NO3- uptake in previously stressed plants was the same as that of the controls. Root relative growth rate (RGR) during the drying cycle was about one-fourth that of the control, but recovered to the control level within 4 days after rewatering. Between 4 and 14 days after rewatering, the previously droughted plant roots exhibited nearly three times greater RGR than the control plant roots. Estimates of root solute content indicated that at no time during the stress and recovery periods did the droughted roots exhibit osmotic adjustment. Changes in root growth properties were uncoupled from turgor. During the recovery period, drought-induced adjustments in cell wall yielding properties are thought to have increased root growth in previously stressed seedlings. Nevertheless, the greater root growth of previously droughted plants did not result in more NO3- acquisition than in control plants. The pattern of NO3- uptake upon rewatering was apparently more closely associated with root uptake capacity.
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Wang, Bin, Pengtao Yu, Yipeng Yu, Yanhui Wang, Lei Zhang, Yanfang Wan, Shunli Wang, and Xiande Liu. "Trees at a Moderately Arid Site Were More Sensitive to Long-Term Drought." Forests 12, no. 5 (May 6, 2021): 579. http://dx.doi.org/10.3390/f12050579.
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Climate change has dramatically altered the frequency and intensity of droughts, thereby altering tree growth. Understanding whether tree growth in semiarid areas in response to long-term drought and the post-drought recovery rate of tree growth vary along moisture gradients is crucial for predicting future forest change. Here, we assessed the spatial variation in both the growth resistance of Qinghai spruce (Picea crassifolia Kom.) to long-term drought and its post-drought recovery using a stand-total sampling strategy along a moisture gradient that covered three sites (with an annual precipitation of 330.4, 394.2, and 515.9 mm for the western, middle, and eastern sites, respectively) with six plots. Resistance and recovery were evaluated by analyzing the tree growth trends during a long-term drought period (1980–2001) and the subsequent post-drought period (2001–2013), respectively. Our results indicate that the trees with the highest temporal stability were those at the wetter eastern site; specifically, during the long-term drought period, the trees at the wetter eastern site showed the highest resistance (−0.015) and the lowest recovery (0.002). The trees in moderately arid conditions were much more sensitive to climate change than those at the relatively arid western site, showing the lowest resistance (−0.050) and highest recovery (0.020). Climate change had the strongest impact on tree growth at the moderately arid site, contributing 60.6% to the tree growth decreasing trend during the long-term drought period and 65.4% to the tree recovery during the post-drought period, respectively. Climate change had a lower impact on tree growth at the wet and dry sites, contributing less than 50% to the tree growth trends at these sites. The results indicate that a trade-off relationship exists between resistance and recovery at the different sites; that is, the highly resistant trees at the wetter eastern site tend to have lower recovery, whereas the weakly resistant trees at the moderately arid site tend to have higher recovery. These results have implications for predicting tree growth in response to future climate change.
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Phavaphutanon, L., F. T. Davies, and S. A. Duray. "Effect of Mycorrhiza on Growth Recovery of Neem Plants after Drought Exposure." HortScience 31, no. 4 (August 1996): 647d—647. http://dx.doi.org/10.21273/hortsci.31.4.647d.
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Growth recovery of mycorrhizal (VAM) and nonmycorrhizal (non-VAM) neem plants after drought exposure were followed under low phosphorus conditions. Drought significantly decreased plant growth regardless of mycorrhiza. Relative growth rate of droughted plants was greater than nondroughted plants during the growth recovery period, and compensated the loss of growth during the previous drought. VAM increased plant growth and improved regeneration of new roots outside the original root balls, particularly in plants previously exposed to drought. New roots of VAM plants were readily colonized by the VAM fungi, while those of non-VAM plants remained uncolonized. VAM growth enhancement after drought exposure was associated with greater uptake of phosphorus and other nutrients, and improved root regeneration.
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Zhang, Miao, and Xing Yuan. "Rapid reduction in ecosystem productivity caused by flash droughts based on decade-long FLUXNET observations." Hydrology and Earth System Sciences 24, no. 11 (November 24, 2020): 5579–93. http://dx.doi.org/10.5194/hess-24-5579-2020.
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Abstract. A flash drought is characterized by its rapid onset and arouses widespread concerns due to its devastating impacts on the environment and society without sufficient early warnings. The increasing frequency of soil moisture flash droughts in a warming climate highlights the importance of understanding its impact on terrestrial ecosystems. Previous studies investigated the vegetation dynamics during several extreme cases of flash drought, but there is no quantitative assessment on how fast the carbon fluxes respond to flash droughts based on decade-long records with different climates and vegetation conditions. Here we identify soil moisture flash drought events by considering decline rate of soil moisture and the drought persistency, and we detect the response of ecosystem carbon and water fluxes to a soil moisture flash drought during its onset and recovery stages based on observations at 29 FLUXNET stations from croplands to forests. Corresponding to the sharp decline in soil moisture and higher vapor pressure deficit (VPD), gross primary productivity (GPP) drops below its normal conditions in the first 16 d and decreases to its minimum within 24 d for more than 50 % of the 151 identified flash drought events, and savannas show highest sensitivity to flash drought. Water use efficiency increases for forests but decreases for cropland and savanna during the recovery stage of flash droughts. These results demonstrate the rapid responses of vegetation productivity and resistance of forest ecosystems to flash drought.
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Ahmadi, Behzad, Ali Ahmadalipour, Glenn Tootle, and Hamid Moradkhani. "Remote Sensing of Water Use Efficiency and Terrestrial Drought Recovery across the Contiguous United States." Remote Sensing 11, no. 6 (March 26, 2019): 731. http://dx.doi.org/10.3390/rs11060731.
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Ecosystem water-use efficiency (WUE) is defined as the ratio of carbon gain (i.e., gross primary productivity; GPP) to water consumption (i.e., evapotranspiration; ET). WUE is markedly influential on carbon and water cycles, both of which are fundamental for ecosystem state, climate and the environment. Drought can affect WUE, subsequently disturbing the composition and functionality of terrestrial ecosystems. In this study, the impacts of drought on WUE and its components (i.e., GPP and ET) are assessed across the Contiguous US (CONUS) at fine spatial and temporal resolutions. Soil moisture simulations from land surface modeling are utilized to detect and characterize agricultural drought episodes and remotely sensed GPP and ET are retrieved from the moderate resolution imaging spectroradiometer (MODIS). GPP, as the biome vitality indicator against drought stress, is employed to investigate drought recovery and the ecosystems’ required time to revert to pre-drought condition. Results show that drought recovery duration indicates a positive correlation with drought severity and duration, meaning that a protracted drought recovery is more likely to happen following severe droughts with prolonged duration. WUE is found to almost always increase in response to severe (or worse) drought episodes. Additionally, ET anomalies are negatively correlated with drought severity and ET is expected to decrease during severe (or worse) drought episodes. Lastly, the changes of WUE are decomposed in relation to its components and the cross-relation among the variables is revealed and a consistent changing pattern is detected.
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Subramanian, K. S., C. Charest, L. M. Dwyer, and R. I. Hamilton. "Effects of arbuscular mycorrhizae on leaf water potential, sugar content, and P content during drought and recovery of maize." Canadian Journal of Botany 75, no. 9 (September 1, 1997): 1582–91. http://dx.doi.org/10.1139/b97-870.
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The effect of colonization with the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) in maize (Zea mays L.) under drought or nondrought conditions, on leaf water potential and sugar and phosphorus status was examined in a greenhouse study. Seeds of selection-cycles 0 (C0, drought sensitive) and 8 (C8, drought resistant) of the tropical maize cultivar Tuxpeño sequía were used for this experiment. Maize plants were exposed to 3 weeks of drought (45–65 days after sowing) followed by 3 weeks of recovery (66 – 86 days) at preflowering stage. Daily midday leaf water potential during drought and recovery periods and daily soil moisture content and weekly leaf relative water content during drought were measured. Sugar concentrations, phosphorus contents, and dry masses of roots and shoots were determined at the end of drought and recovery periods. Mycorrhizal plants of C0 and C8 maintained higher (less negative) leaf water potential during 3 weeks of drought. During recovery, AM plants took less time (C0, 7 days; C8, 4 days) than non-AM plants (C0, 15 days; C8, 8 days) to attain leaf water potential comparable with well-watered plants. The AM plants had higher phosphorus contents at the end of drought and recovery periods. Drought reduced the sugars in shoots by 66 and 50% in non-AM plants and by only 30 and 32% in AM plants of C0 and C8, respectively. Root and shoot masses were higher in AM than non-AM plants under well-watered and drought-stressed conditions. Overall results suggest that AM colonization helped the host plant to sustain moderate drought stress and recover rapidly when the irrigation was restored. Key words: corn, drought, endomycorrhizae, recovery, water relations.
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Schwalm, Christopher R., William R. L. Anderegg, Anna M. Michalak, Joshua B. Fisher, Franco Biondi, George Koch, Marcy Litvak, et al. "Global patterns of drought recovery." Nature 548, no. 7666 (August 2017): 202–5. http://dx.doi.org/10.1038/nature23021.
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Nemati, Ahmad, Seyed Hossein Ghoreishi Najafabadi, Gholamreza Joodaki, and S. Saeid Mousavi Nadoushani. "Monitoring and Analysis of Drought Using Gravity Recovery and Climate Experiment (GRACE)." Hydrology 6, no. 3 (August 25, 2019): 75. http://dx.doi.org/10.3390/hydrology6030075.
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Drought monitoring needs comprehensive and integrated meteorological and hydrologic data. However, such data are generally not available in extensive catchments. The present study aimed to analyze drought in the central plateau catchment of Iran using the terrestrial water storage deficit index (TSDI). In this arid catchment, the meteorological and hydrologic observed data are scarce. First, the time series of terrestrial water storage changes (TWSC) obtained from the gravity recovery and climate experiment (GRACE) was calculated and validated by the water budget output. Then, the studied area was divided into semi-arid, arid, and hyper-arid zones and the common drought indices of SPI and RDIe within a timescale of 3, 6, and 12 months were calculated to compare the results obtained from the TSDI by using the meteorological data of 105 synoptic stations. Based on the results, the study area experienced a drought with extreme severity and expansion during 2007–2008. The drought spatial distribution map obtained from three indices indicated good conformity. Based on the maps, the severity, duration, and frequency of drought in the semi-arid zone were greater than that in other zones, while no significant drought occurred in the hyper-arid zone. Furthermore, the temporal distribution of drought in all three zones indicated that the TSDI could detect all short- and long-term droughts. The study results showed that the TSDI is a reliable, integrated, and comprehensive index. Using this index in arid areas with little field data led to some valuable results for planning and water resource management.
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Jia, Yuying, Wanxin Xiao, Yusheng Ye, Xiaolin Wang, Xiaoli Liu, Guohong Wang, Gang Li, and Yanbo Wang. "Response of Photosynthetic Performance to Drought Duration and Re-Watering in Maize." Agronomy 10, no. 4 (April 8, 2020): 533. http://dx.doi.org/10.3390/agronomy10040533.
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The drought tolerance and capacity to recover after drought are important for plant growth and yield. In this study, two maize lines with different drought resistance were used to investigate the effects of different drought durations and subsequent re-watering on photosynthetic capacity, electron transfer and energy distribution, and antioxidative defense mechanisms of maize. Under short drought, maize plants decreased stomatal conductance and photosynthetic electron transport rate, and increased NPQ (Non-photochemical quenching) to dissipate excess excitation energy in time and protect the photosynthetic apparatus. With the increased drought duration, NPQ, antioxidase activity, PItotal (total performance index), ∆I/Io, ψEo (quantum yield for electron transport), φEo (efficiency/probability that an electron moves further than QA−), δRo (efficiency/probability with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side) and φRo (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) were significantly reduced, while Y(NO) (quantum yield of nonregulated energy dissipation) and MDA (malondialdehyde) began to quickly increase. The photosynthetic rate and capacity of photosynthetic electron transport could not recover to the level of the plants subjected to normal water status after re-watering. These findings indicated that long drought damaged the PSI (photosystem I) and PSII (photosystem II) reaction center and decreased the electron transfer efficiency, and this damage could not be recovered by re-watering. Different drought resistance and recovery levels of photosynthetic performance were achieved by different maize lines. Compared with D340, D1798Z had higher NPQ and antioxidase activity, which was able to maintain functionality for longer in response to progressive drought, and it could also recover at more severe drought after re-watering, which indicated its higher tolerance to drought. It was concluded that the capacity of the energy dissipation and antioxidant enzyme system is crucial to mitigate the effects caused by drought, and the capacity to recover after re-watering was dependent on the severity and persistence of drought, adaptability, and recovery differences of the maize lines. The results provide a profound insight to understand the maize functional traits’ responses to drought stresses and re-watering.
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Fort, Kevin, Joaquin Fraga, Daniele Grossi, and M. Andrew Walker. "Early Measures of Drought Tolerance in Four Grape Rootstocks." Journal of the American Society for Horticultural Science 142, no. 1 (January 2017): 36–46. http://dx.doi.org/10.21273/jashs03919-16.
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Recent and severe droughts in major grape (Vitis)-growing regions of the United States and Australia underscore the importance of more efficient agricultural use of water. Grape rootstock breeding for increased drought tolerance could contribute to continued sustainable yields as fresh water supplies decline. Rhizotron containers were used in a greenhouse to investigate the predictive measures of drought tolerance in young grapevine rootstocks. Deeper rooting distributions were found for the drought-tolerant rootstocks ‘110R’ (Vitis berlandieri × Vitis rupestris) and ‘Ramsey’ (Vitis champinii, a natural hybrid of Vitis candicans × V. rupestris) as opposed to shallower distributions observed in the more drought-sensitive rootstocks ‘101-14Mgt’ (Vitis riparia × V. rupestris) and ‘Riparia Gloire’ (V. riparia). Production of new roots during a 6-day nonirrigated period declined 45% to 53% for ‘Riparia Gloire’ and ‘101-14Mgt’, respectively, but showed no change in ‘110R’ and ‘Ramsey’. Slow growth, a hallmark of abiotic stress tolerance, was evident in the drought-tolerant rootstocks in their relatively slow shoot growth before drought stress and their relatively slow new root growth during recovery, especially for ‘Ramsey’. High stomatal conductance (gS) corresponded with drought tolerance and distinguished rootstocks best during the first 3 days of recovery, with a mean value for ‘Ramsey’ 2.7 times higher than ‘101-14Mgt’. Stomatal conductance during recovery may serve as the most efficient means of predicting drought tolerance capacity in a breeding program.
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Lucas-Borja, Manuel Esteban, Arun K. Bose, Enrique Andivia, David Candel-Pérez, Pedro A. Plaza-Álvarez, and Juan C. Linares. "Assessing Tree Drought Resistance and Climate-Growth Relationships under Different Tree Age Classes in a Pinus nigra Arn. ssp. salzmannii Forest." Forests 12, no. 9 (August 27, 2021): 1161. http://dx.doi.org/10.3390/f12091161.
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The magnitude of drought impact in forest ecosystems depends on which group of trees are more severely affected; greater mortality of smaller trees can modulate the trajectories of succession, while the mortality of larger trees can disproportionately offset the ecosystem’s carbon balance. Several studies have documented a greater vulnerability of large trees to extreme droughts while some other studies reported a greater growth reduction in smaller trees during droughts. We tested these hypotheses by comparing tree basal area increment (BAI), drought resistance (i.e., magnitude of growth decline during drought), and resilience (i.e., magnitude of growth recovery after drought) across five different age-classes in black pine (Pinus nigra Arn. ssp. salzmannii) forests in Spain. Our results showed that the BAI patterns, drought resistance, and resilience were strongly influenced by tree age-classes. In addition, the effect of climatic water balance (precipitation minus potential evapotranspiration) on BAI significantly varied among age-classes. The effect of water balance on BAI was lower for younger age-classes (1–39 years of age) compared to older age-classes. We observed a greater growth reduction (i.e., lower resistance) in older trees (>40 years of age) during droughts compared to younger trees (<40 years of age). However, all trees, irrespective of their ages, were able to recover the growth rates after the drought. In general, younger trees showed a greater capacity in recovering the growth rate (i.e., more resilient) than older trees. We detected no significant effects of stand basal area and stand density on BAI, drought resistance, and resilience. Overall, our results indicated that growth of older trees was more negatively affected during drought. Therefore, these older/larger trees can be selected for commercial thinning, or can be released from competition, which can minimize the potential impacts of future droughts in black pine forests in Spain.
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Duan, Honglang, Defu Wang, Xiaohua Wei, Guomin Huang, Houbao Fan, Shuangxi Zhou, Jianping Wu, Wenfei Liu, David T. Tissue, and Songze Wan. "The decoupling between gas exchange and water potential of Cinnamomum camphora seedlings during drought recovery and its relation to ABA accumulation in leaves." Journal of Plant Ecology 13, no. 6 (August 26, 2020): 683–92. http://dx.doi.org/10.1093/jpe/rtaa056.
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Abstract Aims Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change, while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear. We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery. Methods Potted seedlings of Cinnamomum camphora were grown under well watered conditions prior to the experimental drought stress, which was initiated by withholding water. Seedlings were rewatered following attainment of two drought severities: mild drought (stomatal closure) and moderate drought (ψxylem = −1.5 MPa). We measured leaf-level water potential, gas exchange (photosynthesis and stomatal conductance), abscisic acid (ABA), proline and non-structural carbohydrates (NSCs) concentrations in seedlings of C. camphora during drought and a 4-day recovery. Important Findings We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery. Stomatal closure occurred at the mild drought stress, accompanied with ABA accumulation in leaves and decline in water potential, while leaf proline accumulation and variable NSC were evident at the moderate drought stress. More severe drought stress led to delayed recovery of gas exchange, but it did not have significant effect on water potential recovery. The relationships of water potential and gas exchange differed during drought stress and post-drought recovery. There was tight coupling between water potential and gas exchange during drought, but not during rewatering due to high ABA accumulation in leaves, thereby delaying recovery of stomatal conductance. Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C. camphora. Furthermore, greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.
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Hellwig, Jost, Michael Stoelzle, and Kerstin Stahl. "Groundwater and baseflow drought responses to synthetic recharge stress tests." Hydrology and Earth System Sciences 25, no. 2 (February 25, 2021): 1053–68. http://dx.doi.org/10.5194/hess-25-1053-2021.
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Abstract. Groundwater is the main source of freshwater and maintains streamflow during drought. Potential future groundwater and baseflow drought hazards depend on the systems' sensitivity to altered recharge conditions. We performed groundwater model experiments using three different generic stress tests to estimate the groundwater and baseflow drought sensitivity to changes in recharge. The stress tests stem from a stakeholder co-design process that specifically followed the idea of altering known drought events from the past, i.e. asking whether altered recharge could have made a particular event worse. Across Germany, groundwater responses to the stress tests are highly heterogeneous, with groundwater heads in the north more sensitive to long-term recharge and in the Central German Uplands to short-term recharge variations. Baseflow droughts are generally more sensitive to intra-annual dynamics, and baseflow responses to the stress tests are smaller compared to the groundwater heads. The groundwater drought recovery time is mainly driven by the hydrogeological conditions, with slow (fast) recovery in the porous (fractured rock) aquifers. In general, a seasonal shift of recharge (i.e. less summer recharge and more winter recharge) will have lesser effects on groundwater and baseflow drought severity. A lengthening of dry spells might cause much stronger responses, especially in regions with slow groundwater response to precipitation. Water management may need to consider the spatially different sensitivities of the groundwater system and the potential for more severe groundwater droughts in the large porous aquifers following prolonged meteorological droughts, particularly in the context of climate change projections indicating stronger seasonality and more severe drought events.
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Hong, Ilpyo, Joo-Heon Lee, and Hyo-Seob Cho. "National drought management framework for drought preparedness in Korea (lessons from the 2014–2015 drought)." Water Policy 18, S2 (December 1, 2016): 89–106. http://dx.doi.org/10.2166/wp.2016.015.
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The scale of damage caused by drought is on the rise in South Korea. The country has been experiencing a 4–6-year cycle of extreme droughts at a nationwide scale. From 2014–2015, South Korea suffered from its worst drought in the past 50 years. This study aims to provide an effective drought management policy by analyzing the Korean government's response to the 2014–2015 drought under the National Drought Management Framework, which is composed of four stages: prevention, preparedness, response, and recovery. The findings indicate that the Korean government effectively addressed the drought, yet there are no measures currently in place to cope with megadroughts that last for more than 5 consecutive years. Immediate attention is required to conduct research and introduce policies that will help in managing megadroughts. This paper takes an interdisciplinary approach to drought preparedness research in the context of megadroughts and proposes an efficient national drought management framework that involves engagement of relevant line ministries.
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Dreesen, F. E., H. J. De Boeck, I. A. Janssens, and I. Nijs. "Do successive climate extremes weaken the resistance of plant communities? An experimental study using plant assemblages." Biogeosciences 11, no. 1 (January 8, 2014): 109–21. http://dx.doi.org/10.5194/bg-11-109-2014.
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Abstract. The probability that plant communities undergo successive climate extremes increases under climate change. Exposure to an extreme event might elicit acclimatory responses and thereby greater resistance to a subsequent event, but might also reduce resistance if the recovery period is too short or resilience too low. Using experimental herbaceous plant assemblages, we compared the effects of two successive extremes occurring in one growing season (either two drought extremes, two heat extremes or two drought + heat extremes) to those of assemblages being exposed only to the second extreme. Additionally, the recovery period between the successive extremes was varied (2, 3.5 or 6 weeks). Among the different types of climate extremes, combined heat + drought extremes induced substantial leaf mortality and plant senescence, while the effects of drought and heat extremes were smaller. Preceding drought + heat extremes lowered the resistance in terms of leaf survival to a subsequent drought + heat extreme if the recovery period was two weeks, even though the leaves had completely recovered during that interval. No reduced resistance to subsequent extremes was recorded with longer recovery times or with drought or heat extremes. Despite the substantial mortality on the short term, the drought + heat and the heat extremes increased the end-of-season aboveground biomass independent of the number of extreme events or the duration of the recovery period. These results show that recurrent climate extremes with short time intervals can weaken the resistance of herbaceous plant assemblages. This negative effect in the short term can, however, be compensated in the longer term through rapid recovery and secondary positive effects.
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Dreesen, F. E., H. J. De Boeck, I. A. Janssens, and I. Nijs. "Do successive climate extremes weaken the resistance of plant communities? An experimental study using plant assemblages." Biogeosciences Discussions 10, no. 6 (June 10, 2013): 9149–77. http://dx.doi.org/10.5194/bgd-10-9149-2013.
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Abstract. The probability that plant communities undergo successive climate extremes increases under climate change. Exposure to an extreme event might elicit acclimatory responses and thereby greater resistance to a subsequent event, but might also reduce resistance if the recovery period is too short or resilience too low. Using experimental plant assemblages, we compared the effects of two successive extremes (either two drought extremes, two heat extremes or two drought + heat extremes) to those of assemblages being exposed only to the second extreme. Additionally, the recovery period between the successive extremes was varied (2, 3.5 or 6 weeks). Among the different types of climate extremes, combined drought + heat extremes induced substantial leaf and plant mortality, while the effects of drought and heat extremes were smaller. Preceding drought + heat extremes lowered the resistance in terms of leaf survival to a subsequent drought + heat extreme if the recovery period was 2 weeks, even though the leaves had completely recovered during that interval. No reduced resistance to subsequent extremes was recorded with longer recovery times or with drought or heat extremes. Despite mortality on the short term, the drought + heat and the heat extremes increased the end-of-season aboveground biomass, independent of the number of events or the recovery period. These results show that the effect of a preceding extreme event disappears quite quickly, but that recurrent climate extremes with short time intervals can weaken the resistance of herbaceous plant assemblages. This can however be compensated afterwards through rapid recovery and secondary, positive effects in the longer term.
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Stoelzle, Michael, Maria Staudinger, Kerstin Stahl, and Markus Weiler. "Stress testing as complement to climate scenarios: recharge scenarios to quantify streamflow drought sensitivity." Proceedings of the International Association of Hydrological Sciences 383 (September 16, 2020): 43–50. http://dx.doi.org/10.5194/piahs-383-43-2020.
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Abstract. Precipitation deficits and temperature anomalies are often the main cause for low flows and summer streamflow droughts. However, where groundwater is the main contribution to sustain water availability and ecological integrity during dry spells, the role of recharge and catchment storage is crucial to understand streamflow drought sensitivity. Here we introduce recharge stress tests as complement to climate scenarios to characterize and quantify the streamflow drought sensitivities of catchments. The stress tests are presented by applying them to six headwater catchments in Switzerland with various catchment and streamflow characteristics. The stress tests drive the bucket-type hydrological model HBV in a framework, in which pre-drought recharge conditions can be decreased to test how catchments respond to and recover from drought. We identified an upper limit of stress test durations around 12 months as indicator of maximum recharge- and storage-memory for the study catchments. Varying response on stress testing across the catchments suggests different storage properties and thus different recovery times from drought. From the stress test simulations, we found up to 200 d longer summer streamflow droughts with additional streamflow deficits which account for up to 40 d of median flow. Using a worst-case pre-drought recharge in stress test simulation leads to minimum flow reductions of 50 %–80 % compared with the reference simulation. Based on the results we conclude with recommendations for further stress test research in drought hydrology.
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Brunetti, Cecilia, Tadeja Savi, Andrea Nardini, Francesco Loreto, Antonella Gori, and Mauro Centritto. "Changes in abscisic acid content during and after drought are related to carbohydrate mobilization and hydraulic recovery in poplar stems." Tree Physiology 40, no. 8 (March 18, 2020): 1043–57. http://dx.doi.org/10.1093/treephys/tpaa032.
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Abstract Drought compromises plant's ability to replace transpired water vapor with water absorbed from the soil, leading to extensive xylem dysfunction and causing plant desiccation and death. Short-term plant responses to drought rely on stomatal closure, and on the plant's ability to recover hydraulic functioning after drought relief. We hypothesize a key role for abscisic acid (ABA) not only in the control of stomatal aperture, but also in hydraulic recovery. Young plants of Populus nigra L. were used to investigate possible relationships among ABA, non-structural carbohydrates (NSC) and xylem hydraulic function under drought and after re-watering. In Populus nigra L. plants subjected to drought, water transport efficiency and hydraulic recovery after re-watering were monitored by measuring the percentage loss of hydraulic conductivity (PLC) and stem specific hydraulic conductivity (Kstem). In the same plants ABA and NSC were quantified in wood and bark. Drought severely reduced stomatal conductance (gL) and markedly increased the PLC. Leaf and stem water potential, and stem hydraulic efficiency fully recovered within 24 h after re-watering, but gL values remained low. After re-watering, we found significant correlations between changes in ABA content and hexoses concentration both in wood and bark. Our findings suggest a role for ABA in the regulation of stem carbohydrate metabolism and starch mobilization upon drought relief, possibly promoting the restoration of xylem transport capacity.
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Severmutlu, Songul, Nedim Mutlu, Ercan Gurbuz, Osman Gulsen, Murat Hocagil, Osman Karaguzel, Tiffany Heng-Moss, Robert C. Shearman, and Rock E. Gaussoin. "Drought Resistance of Warm-season Turfgrasses Grown in Mediterranean Region of Turkey." HortTechnology 21, no. 6 (December 2011): 726–36. http://dx.doi.org/10.21273/horttech.21.6.726.
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There is a dearth of information about turfgrass drought resistance and adaptation in the Mediterranean region of Turkey. Turfgrass managers in this region need this information to help them make informed decisions regarding turfgrass selection and management. This research was conducted to assess the drought resistance of bermudagrass (Cynodon dactylon), buffalograss (Buchloe dactyloides), bahiagrass (Paspalum notatum), seashore paspalum (Paspalum vaginatum), zoysiagrass (Zoysia japonica), centipedegrass (Eremochloa ophiuroides), and tall fescue (Lolium arundinaceum) under Mediterranean conditions of Turkey. The study was conducted at two locations, Antalya and Mersin, and was repeated in 2006 and 2007 at both locations. One year after establishment, the turfs were subjected to drought stress for 90 days, which was followed by resumption of irrigation for recovery of the turf. Percentage leaf firing, turfgrass quality, and percent green shoot recovery were recorded. There were inter and intraspecies differences detected for percentage leaf firing and shoot recovery. Bermudagrass, bahiagrass, and buffalograss exhibited superior drought resistance as demonstrated by lower leaf firing and better shoot recovery values when compared with other species studied. Centipedegrass and zoysiagrass demonstrated a high leaf firing and very poor shoot recovery, whereas zoysiagrass and tall fescue were unable to recover from the drought stress in the sandy soil. Results showed that ‘SWI-1045’ (Contessa®) and ‘SWI-1044’ bermudagrass and ‘Cody’ buffalograss possessed superior drought resistance with acceptable turfgrass quality up to 30 days under drought stress that can be used for water-efficient turf management under the Mediterranean environment.
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Dosmann, Michael S., and Jeffery K. Iles. "Effects of Drought and Post-drought Recovery on Katsura Tree." HortScience 33, no. 3 (June 1998): 539e—540. http://dx.doi.org/10.21273/hortsci.33.3.539e.
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Katsura tree (Cercidiphyllum japonicum Sieb. & Zucc.) is appreciated because of its stately form and brilliant autumnal leaf color. One problem of the species, however, is its reputed intolerance to drought. While data either refuting or substantiating this claim are lacking, anecdotal references abound. To understand this issue better, a study was designed to measure the effect of drought and post-drought relief on growth and development of katsura. Two-year-old trees were container-grown in a greenhouse and subjected to one of three irrigation treatments (comprised of four irrigation phases) that simulated either drought or conditions where moisture was not limiting. In treatment one (control), plants in each phase were irrigated daily with the amount of water lost the previous 24 h. Plants in the second treatment experienced an initial drought phase (irrigation withheld until soil moisture content decreased to a predetermined level) followed by three non-drought phases. In the third treatment, plants were subjected to two drought phases, each followed by a non-drought phase. Destructive harvests were performed at the beginning of the study and at the conclusion of each phase. Due to abscission, trees subjected to one and two drought phases underwent a 38% and 63% reduction in lamina mass, respectively. Stem diameter in trees exposed to both drought phases was 16% less than that of controls. Net assimilation rates of trees within each treatment indicate that plants recovering from drought may be more efficient as assimilating systems than controls. Based upon our results, we find that katsura is a drought avoider, responding to drought by defoliating. Refoliation once water is available does occur and may lend itself to recovery.
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Hahn, Claudia, Andreas Lüscher, Sara Ernst-Hasler, Matthias Suter, and Ansgar Kahmen. "Timing of drought in the growing season and strong legacy effects determine the annual productivity of temperate grasses in a changing climate." Biogeosciences 18, no. 2 (January 27, 2021): 585–604. http://dx.doi.org/10.5194/bg-18-585-2021.
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Abstract. The frequency of extreme weather events, such as droughts, is assumed to increase and lead to alterations in ecosystem productivity and thus the terrestrial carbon cycle. Although grasslands typically show reduced productivity in response to drought, the effects of drought on grassland productivity have been shown to vary strongly. Here we tested, in a 2-year field experiment, if the resistance and the recovery of grasses to drought varies throughout a growing season and if the timing of the drought influences drought-induced reductions in annual aboveground net primary production (ANPP) of grasses. For the experiment we grew six temperate and perennial C3 grass species and cultivars in a field as pure stands. The grasses were cut six times during the growing season and subject to 10 week drought treatments that occurred either in the spring, the summer or the fall. Averaged across all grasses, drought-induced losses in productivity in spring were smaller (−20 % to −51 %) than in summer and fall (−77 % to −87 %). This suggests a higher resistance to drought in spring when plants are in their reproductive stage and their productivity is the highest. After the release from drought, we found no prolonged suppression in growth. In contrast, post-drought growth rates of formerly drought-stressed swards outperformed the growth rates of the control swards. The strong overcompensation in growth after the drought release resulted in relatively small overall drought-induced losses in annual ANPP that ranged from −4 % to −14 % and were not affected by the timing of the drought event. In summary, our results show that (i) the resistance in growth rates of grasses to drought varies across the season and is increased during the reproductive phenological stage when growth rates are highest; (ii) that the positive legacy effects of drought indicate a high recovery potential of temperate grasses to drought; and (iii) that the high recovery can compensate for immediate drought effects on total annual biomass production to a significant extent.
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Kam, Jonghun, Justin Sheffield, Xing Yuan, and Eric F. Wood. "The Influence of Atlantic Tropical Cyclones on Drought over the Eastern United States (1980–2007)." Journal of Climate 26, no. 10 (May 8, 2013): 3067–86. http://dx.doi.org/10.1175/jcli-d-12-00244.1.
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Abstract To assess the influence of Atlantic tropical cyclones (TCs) on the eastern U.S. drought regime, the Variable Infiltration Capacity (VIC) land surface hydrologic model was run over the eastern United States forced by the North American Land Data Assimilation System phase 2 (NLDAS-2) analysis with and without TC-related precipitation for the period 1980–2007. A drought was defined in terms of soil moisture as a prolonged period below a percentile threshold. Different duration droughts were analyzed—short term (longer than 30 days) and long term (longer than 90 days)—as well as different drought severities corresponding to the 10th, 15th, and 20th percentiles of soil moisture depth. With TCs, droughts are shorter in duration and of a lesser spatial extent. Tropical cyclones variously impact soil moisture droughts via late drought initiation, weakened drought intensity, and early drought recovery. At regional scales, TCs decreased the average duration of moderately severe short-term and long-term droughts by less than 4 (10% of average drought duration per year) and more than 5 (15%) days yr−1, respectively. Also, they removed at least two short-term and one long-term drought events over 50% of the study region. Despite the damage inflicted directly by TCs, they play a crucial role in the alleviation and removal of drought for some years and seasons, with important implications for water resources and agriculture.
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Hoyos, Natalia, Alexander Correa-Metrio, Steven M. Jepsen, Beverley Wemple, Santiago Valencia, Matthew Marsik, Rubén Doria, Jaime Escobar, Juan C. Restrepo, and Maria I. Velez. "Modeling Streamflow Response to Persistent Drought in a Coastal Tropical Mountainous Watershed, Sierra Nevada De Santa Marta, Colombia." Water 11, no. 1 (January 8, 2019): 94. http://dx.doi.org/10.3390/w11010094.
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Droughts constitute natural hazards that affect water supply for ecosystems and human livelihoods. In 2013–2016, the Caribbean experienced the worst drought since the 1950s, and climate projections for the southern Caribbean predict less rainfall by the end of the 21st century. We assessed streamflow response to drought for a watershed in the Colombian Caribbean by analyzing the effects of drought length and land cover on streamflow recovery. We generated a calibrated SWAT model and created annual and monthly drought scenarios from rainfall records. We used our model to predict water yield for selected land covers (wet forest, shade coffee, shrub, and dry forest) under drought conditions. Annual scenarios resulted in water yield reductions of ~15 mm month−1 (wet forest, coffee, and shrub) and 5 mm month−1 (dry forest) for the first month after a two-year drought. Maximum water yield reductions for monthly scenarios occurred after a 10-month drought and were ~100 mm month−1 (wet forest, coffee, and shrub) and 20 mm month−1 (dry forest). Streamflow recovered within nine months (annual scenarios), and two to eight months (monthly scenarios) after drought termination. Drought response seems to be conditioned by climatic factors (rainfall seasonality and spatial variability) and catchment properties.
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Wang, Wei, Yunzhong Shen, Fengwei Wang, and Weiwei Li. "Two Severe Prolonged Hydrological Droughts Analysis over Mainland Australia Using GRACE Satellite Data." Remote Sensing 13, no. 8 (April 8, 2021): 1432. http://dx.doi.org/10.3390/rs13081432.
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In recent years, many droughts have happened over mainland Australia, especially the two severe prolonged droughts, from 2006 to 2009 and 2018 to 2020, resulting in serious water scarcity. Therefore, using the Total Storage Deficit Index (TSDI) from the Gravity Recovery and Climate Experiment (GRACE), we analyzed the two severe prolonged droughts from the perspective of the affected area, spatial evolution, frequency, severity and drought driving factors. The results show that the affected area of Drought 2006–2009 ranged from 57% to 95%, and that of Drought 2018–2020 ranged from 45% to 95%. Drought 2006–2009 took its rise in southeastern Australia and gradually spread to the central part. Drought 2018–2020 originated in the southwest corner of the Northern Territory and northern New South Wales, and gradually expanded to Western Australia and the whole New South Wales respectively. During Drought 2006–2009, Victoria suffered drought all months, including 59% mild drought and 41% moderate drought, North Territory had the highest drought severity of 44.26 and Victoria ranked the second high with the severity of 35.51 (cm months). For Drought 2018–2020, Northern Territory was also dominated by drought all months, including 92% mild drought and 8% moderate drought, the drought severities were in North Territory and Western Australia with 52.19 and 31.44 (cm months), respectively. Finally, the correlation coefficients between the two droughts and Indo-Pacific climate variability including El Niño-Southern Oscillation and Indian Ocean Dipole (IOD) are computed. By comparing the correlation coefficients of Drought 2018–2020 with Drought 2006–2009, we find that the impact of the El Niño on the hydrological drought becomes weaker while IOD is stronger, and the role of Southern Oscillation on droughts is diverse with the quite different spatial patterns. The results from Fourier analysis confirm that the two hydrological droughts are all related to Indo-Pacific climate variability but with slightly different driving mechanisms.
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Zhang, Dan, Qi Zhang, Adrian D. Werner, and Xiaomang Liu. "GRACE-Based Hydrological Drought Evaluation of the Yangtze River Basin, China." Journal of Hydrometeorology 17, no. 3 (February 12, 2016): 811–28. http://dx.doi.org/10.1175/jhm-d-15-0084.1.
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Abstract In this study, hydrological drought in the Yangtze River basin (YRB) is characterized based on Gravity Recovery and Climate Experiment (GRACE) total water storage (TWS). An artificial neural network approach is applied to extend the GRACE TWS observations (2003–12) to a longer TWS time series (1979–2012), which is well matched (Nash–Sutcliff efficiency of 0.83) to the GRACE data. Hydrological drought is identified by water storage deficit (WSD; the shortfall in TWS from the average value) in three consecutive months. The method builds on previous research by considering potentially ineffective interdrought events and by characterizing drought recovery time from a multidecadal TWS time series. The results show that the YRB was in hydrological drought 29 times during 1979–2012, and the three subbasins of the YRB (upper, middle, and lower YRB) experienced between 21 and 28 hydrological drought events during the same period. The drought recovery time, defined as the time required for WSD to recover to average conditions, is evaluated by a simple statistical approach based on the empirical cumulative distribution function. The average drought recovery time is 3.3 months for the entire YRB and ranges from 2.3 to 3.4 months for the three subbasins. The severest YRB drought occurred during 2003–08 as a result of below-average precipitation, high temperatures, and intense human activities. The results demonstrate that GRACE data are useful for reconstructing the TWS time series for a large river basin, from which hydrological drought can be characterized, and for investigating spatial and temporal trends in water storage conditions.
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Đurić, Marija J., Angelina R. Subotić, Ljiljana T. Prokić, Milana M. Trifunović-Momčilov, Aleksandar D. Cingel, Milan B. Dragićević, Ana D. Simonović, and Snežana M. Milošević. "Molecular Characterization and Expression of Four Aquaporin Genes in Impatiens walleriana during Drought Stress and Recovery." Plants 10, no. 1 (January 14, 2021): 154. http://dx.doi.org/10.3390/plants10010154.
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Aquaporins comprise a large group of transmembrane proteins responsible for water transport, which is crucial for plant survival under stress conditions. Despite the vital role of aquaporins, nothing is known about this protein family in Impatiens walleriana, a commercially important horticultural plant, which is sensitive to drought stress. In the present study, attention is given to the molecular characterization of aquaporins in I. walleriana and their expression during drought stress and recovery. We identified four I. walleriana aquaporins: IwPIP1;4, IwPIP2;2, IwPIP2;7 and IwTIP4;1. All of them had conserved NPA motifs (Asparagine-Proline-Alanine), transmembrane helices (TMh), pore characteristics, stereochemical properties and tetrameric structure of holoprotein. Drought stress and recovery treatment affected the aquaporins expression in I. walleriana leaves, which was up- or downregulated depending on stress intensity. Expression of IwPIP2;7 was the most affected of all analyzed I. walleriana aquaporins. At 15% and 5% soil moisture and recovery from 15% and 5% soil moisture, IwPIP2;7 expression significantly decreased and increased, respectively. Aquaporins IwPIP1;4 and IwTIP4;1 had lower expression in comparison to IwPIP2;7, with moderate expression changes in response to drought and recovery, while IwPIP2;2 expression was of significance only in recovered plants. Insight into the molecular structure of I. walleriana aquaporins expanded knowledge about plant aquaporins, while its expression during drought and recovery contributed to I. walleriana drought tolerance mechanisms and re-acclimation.
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PARARAJASINGHAM, S., and D. P. KNIEVEL. "NITROGENASE ACTIVITY OF COWPEA (Vigna unguiculata (L.) Walp.) DURING AND AFTER DROUGHT STRESS." Canadian Journal of Plant Science 70, no. 1 (January 1, 1990): 163–71. http://dx.doi.org/10.4141/cjps90-018.
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Greenhouse experiments were conducted with the objectives (1) to investigate the nitrogenase activity (NA) of cowpea (Vigna unguiculata (L.) Walp.) root nodules during the development of and subsequent recovery from drought stress and (2) to determine whether the changes in NA during and following drought stress are related to nodule water potential. Nitrogenase activity of root nodules decreased by more than 80% within 6–8 d of withholding water and recovered 1 or 2 d after watering. Nodule water potential declined significantly from approximately −0.2 MPa to −0.48 MPa with 8 d of stress and recovered to prestress levels within 24 h after watering. Midday abaxial stomatal conductance decreased significantly with stress but recovered within 24 h following watering. Midday leaf water potential did not change significantly during the experimental period. Nodule NA declined 2 d before that of nodule water potential in apparent response to declining soil water content. This response and the lag in the recovery of NA following drought stress after nodule water potential had returned to prestress levels support the hypothesis that nodule water potential per se is not the primary cause for the decline in NA of cowpea root nodules during drought stress.Key words: Vigna unguiculata (L.) Walp., nitrogenase activity, drought stress, recovery, cowpea
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Vanková, Radomíra, Jana Dobrá, and Helena Štorchová. "Recovery from drought stress in tobacco." Plant Signaling & Behavior 7, no. 1 (January 2012): 19–21. http://dx.doi.org/10.4161/psb.7.1.18375.
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Liu, Laibao, Lukas Gudmundsson, Mathias Hauser, Dahe Qin, Shuangcheng Li, and Sonia I. Seneviratne. "Revisiting assessments of ecosystem drought recovery." Environmental Research Letters 14, no. 11 (November 8, 2019): 114028. http://dx.doi.org/10.1088/1748-9326/ab4c61.
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Seneviratne, Sonia I., and Philippe Ciais. "Trends in ecosystem recovery from drought." Nature 548, no. 7666 (August 2017): 164–65. http://dx.doi.org/10.1038/548164a.
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Crook, David A., Paul Reich, Nick R. Bond, Damien McMaster, John D. Koehn, and P. Sam Lake. "Using biological information to support proactive strategies for managing freshwater fish during drought." Marine and Freshwater Research 61, no. 3 (2010): 379. http://dx.doi.org/10.1071/mf09209.
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This paper provides an assessment of the biological attributes of fish species in south-eastern Australia and rates their potential risk from the impacts of drought. We used scientific literature and expert opinion to conduct a semiquantitative assessment of attributes considered to influence species resistance and resilience to drought for 15 freshwater fish species found in south-eastern Australia. We also present a conceptual framework to guide management of fish populations during drought. The framework focuses on (1) quantifying spatial variation in the severity of drought impacts on particular habitats (rivers, wetlands etc.), (2) assembling information on drought sensitivities of regionally important species, (3) identifying high risk areas (based on species sensitivity and drought severity), (4) determining and implementing appropriate management actions (pre-emptive, responsive), (5) monitoring outcomes and (6) disseminating information on outcomes. In many regions, historic population declines will serve to exacerbate the impacts of drought, and thus are a major threat to successful recovery from drought. Although we discuss both long-term, pre-emptive planning and short-term, responsive management actions, we contend that a long-term view is required to successfully address the threats posed by drought. Furthermore, although droughts clearly represent a severe disturbance to fish populations, ultimately it is anthropogenic factors that exacerbate drought and constrain recovery pathways (at global, regional and local scales), rather than drought per se. These factors must be addressed if we are to ensure the long-term viability of fish populations in inland aquatic ecosystems.
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Chakraborty, Tamalika, Albert Reif, Andreas Matzarakis, and Somidh Saha. "How Does Radial Growth of Water-Stressed Populations of European Beech (Fagus sylvatica L.) Trees Vary under Multiple Drought Events?" Forests 12, no. 2 (January 24, 2021): 129. http://dx.doi.org/10.3390/f12020129.
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European beech (Fagus sylvatica L.) trees are becoming vulnerable to drought, with a warming climate. Existing studies disagree on how radial growth varies in European beech in response to droughts. We aimed to find the impact of multiple droughts on beech trees’ annual radial growth at their ecological drought limit created by soil water availability in the forest. Besides, we quantified the influence of competition and canopy openness on the mean basal area growth of beech trees. We carried out this study in five near-natural temperate forests in three localities of Germany and Switzerland. We quantified available soil water storage capacity (AWC) in plots laid in the transition zone from oak to beech dominated forests. The plots were classified as ‘dry’ (AWC < 60 mL) and ‘less-dry’ (AWC > 60 mL). We performed dendroecological analyses starting from 1951 in continuous and discontinuous series to study the influence of climatic drought (i.e., precipitation-potential evapotranspiration) on the radial growth of beech trees in dry and less-dry plots. We used observed values for this analysis and did not use interpolated values from interpolated historical records in this study. We selected six drought events to study the resistance, recovery, and resilience of beech trees to drought at a discontinuous level. The radial growth was significantly higher in less-dry plots than dry plots. The increase in drought had reduced tree growth. Frequent climatic drought events resulted in more significant correlations, hence, increased the dependency of tree growth on AWC. We showed that the recovery and resilience to climatic drought were higher in trees in less-dry plots than dry plots, but it was the opposite for resistance. The resistance, recovery, and resilience of the trees were heterogeneous between the events of drought. Mean growth of beech trees (basal area increment) were negatively impacted by neighborhood competition and positively influenced by canopy openness. We emphasized that beech trees growing on soil with low AWC are at higher risk of growth decline. We concluded that changes in soil water conditions even at the microsite level could influence beech trees’ growth in their drought limit under the changing climate. Along with drought, neighborhood competition and lack of light can also reduce beech trees’ growth. This study will enrich the state of knowledge about the ongoing debate on the vulnerability of beech trees to drought in Europe.
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Casas-Gómez, Pablo, Raúl Sánchez-Salguero, Víctor Lechuga, Benjamín Viñegla, José Ignacio Seco Gordillo, José Antonio Carreira, and Juan Carlos Linares. "Adaptive Management in Relict Mediterranean Forests. Thinning Enhances Long-Term Growth but Short-Term Resilience to Drought in Abies pinsapo." Environmental Sciences Proceedings 3, no. 1 (November 11, 2020): 24. http://dx.doi.org/10.3390/iecf2020-07880.
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Current climate change in the Mediterranean basin is associated to increasing frequency and intensity of droughts. This climate dryness entails a serious impact on drought-sensitive forests, several of them considered as hot spots of biodiversity. Adaptive management, as experimental thinning for stand structural diversity enhancement, may increase tree-level resources availability. However, the long-term stand-level effectiveness of this approach at sustaining forest ecosystem functioning remains uncertain. Here, we attempt to place experimental thinning in a climate change adaptation context, using as experimental system the drought-sensitive fir Abies pinsapo. We conducted a long-term study (2004–2019), focused on tree basal area increment (BAI) and quantified to what extent thinning treatments improved drought resistance, recovery and resilience to drought in the remaining trees. The results support a post-thinning (after 2004) BAI increase in thinned stands (+104% if 30% thinning of basal area was applied; +141% for 60% thinning) compared to controls (+21%). Short-term growth resilience, estimated for an extreme drought occurred after thinning (2005), yielded higher resilience for thinned stands, throughout improved resistance, but similar recovery than control. However, extreme droughts observed thereafter (for instance in 2012) do not support a long-term increase in resilience. Growth resilience, estimated for wetter-than-average years showed similar short-term enhanced resilience in thinned stand, while these differences dispelled afterward.
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Singh, Alka, John Thomas Reager, and Ali Behrangi. "Estimation of hydrological drought recovery based on precipitation and Gravity Recovery and Climate Experiment (GRACE) water storage deficit." Hydrology and Earth System Sciences 25, no. 2 (February 2, 2021): 511–26. http://dx.doi.org/10.5194/hess-25-511-2021.
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Abstract. Drought is a natural extreme climate phenomenon that presents great challenges in forecasting and monitoring for water management purposes. Previous studies have examined the use of Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage anomalies to measure the amount of water missing from a drought-affected region, and other studies have attempted statistical approaches to drought recovery forecasting based on joint probabilities of precipitation and soil moisture. The goal of this study is to combine GRACE data and historical precipitation observations to quantify the amount of precipitation required to achieve normal storage conditions in order to estimate a likely drought recovery time. First, linear relationships between terrestrial water storage anomaly (TWSA) and cumulative precipitation anomaly are established across a range of conditions. Then, historical precipitation data are statistically modeled to develop simplistic precipitation forecast skill based on climatology and long-term trend. Two additional precipitation scenarios are simulated to predict the recovery period by using a standard deviation in climatology and long-term trend. Precipitation scenarios are convolved with water deficit estimates (from GRACE) to calculate the best estimate of a drought recovery period. The results show that, in the regions of strong seasonal amplitude (like a monsoon belt), drought continues even with above-normal precipitation until its wet season. The historical GRACE-observed drought recovery period is used to validate the approach. Estimated drought for an example month demonstrated an 80 % recovery period, as observed by the GRACE.
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Lee, Chan Wook, Sungjin Hong, Gihoon Moon, and Do Guen Yoo. "A Study on Resilience Analysis for Regional Drought Capacity Evaluation in South Korea." Journal of the Korean Society of Hazard Mitigation 21, no. 3 (June 30, 2021): 181–92. http://dx.doi.org/10.9798/kosham.2021.21.3.181.
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Increasing climate change is causing complex and diverse natural disasters that have never been experienced before. Recently, research and practical applications of the concept of resilience at the management level for these disasters have been presented. Drought is one of the disasters that lasts for a long time and takes a considerable amount of time for recovery, and resilience evaluations reflecting regional characteristics are needed. In this study, we aim to present the applicability of the resilience concept that reflects regional characteristics (whether or not drought has been experienced in the past) in droughts. To this end, 18 qualitative and quantitative indicators for the evaluation of drought resilience were proposed by judging overseas cases, data status, and domestic applicability. A methodology for calculating the proposed indicators through quantitative data analysis and surveys was presented, and detailed drought resilience evaluations were conducted based on two regions in Korea (Chungcheongnam-do and Chungcheongbuk-do). Through the resilience evaluation using this methodology, the drought response capacity of each local government could be comprehensively evaluated from various perspectives, and each determined factors for improving drought resilience. If a nationwide evaluation is conducted in the future based on these results, locally appropriate guidelines related to drought response and recovery can be established.
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Iñiguez, Vicente, Oscar Morales, Felipe Cisneros, Willy Bauwens, and Guido Wyseure. "Analysis of the drought recovery of Andosols on southern Ecuadorian Andean páramos." Hydrology and Earth System Sciences 20, no. 6 (June 22, 2016): 2421–35. http://dx.doi.org/10.5194/hess-20-2421-2016.
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Abstract. The Neotropical Andean grasslands above 3500 m a.s.l., known as páramo, offer remarkable ecological services for the Andean region. The most important of these is the water supply of excellent quality to many cities and villages in the inter-Andean valleys and along the coast. The páramo ecosystem and especially its soils are under constant and increased threat by human activities and climate change. In this study, the recovery speed of the páramo soils after drought periods are analysed. The observation period includes the droughts of 2009, 2010, 2011, and 2012 together with intermediate wet periods. Two experimental catchments – one with and one without páramo – were investigated. The Probability Distributed Moisture (PDM) model was calibrated and validated in both catchments. Drought periods and its characteristics were identified and quantified by a threshold level approach and complemented by means of a drought propagation analysis. At the plot scale in the páramo region, the soil water content measured by time domain reflectometry (TDR) probes dropped from a normal value of about 0.84 to ∼ 0.60 cm3 cm−3, while the recovery time was 2–3 months. This did not occur at lower altitudes (Cumbe) where the soils are mineral. Although the soil moisture depletion observed in these soils was similar to that of the Andosols (27 %), decreasing from a normal value of about 0.54 to ∼ 0.39 cm3 cm−3, the recovery was much slower and took about 8 months for the drought in 2010. At the catchment scale, however, the soil water storage simulated by the PDM model and the drought analysis was not as pronounced. Soil moisture droughts occurred mainly in the dry season in both catchments. The deficit for all cases is small and progressively reduced during the wet season. Vegetation stress periods correspond mainly to the months of September, October and November, which coincides with the dry season. The maximum number of consecutive dry days were reached during the drought of 2009 and 2010 (19 and 22 days), which can be considered to be a long period in the páramo. The main factor in the hydrological response of these experimental catchments is the precipitation relative to the potential evapotranspiration. As the soils never became extremely dry nor close to the wilting point, the soil water storage capacity had a secondary influence.
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Su, Lu, Qian Cao, Mu Xiao, David M. Mocko, Michael Barlage, Dongyue Li, Christa D. Peters-Lidard, and Dennis P. Lettenmaier. "Drought Variability over the Conterminous United States for the Past Century." Journal of Hydrometeorology 22, no. 5 (May 2021): 1153–68. http://dx.doi.org/10.1175/jhm-d-20-0158.1.
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AbstractWe examine the drought variability over the conterminous United States (CONUS) for 1915–2018 using the Noah-MP land surface model. We examine different model options on drought reconstruction, including optional representation of groundwater and dynamic vegetation phenology. Over our 104-yr reconstruction period, we identify 12 great droughts that each covered at least 36% of CONUS and lasted for at least 5 months. The great droughts tend to have smaller areas when groundwater and/or dynamic vegetation are included in the model configuration. We detect a small decreasing trend in dry area coverage over CONUS in all configurations. We identify 45 major droughts in the baseline (with a dry area coverage greater than 23.6% of CONUS) that are, on average, somewhat less severe than great droughts. We find that representation of groundwater tends to increase drought duration for both great and major droughts, primarily by leading to earlier drought onset (some due to short-lived recovery from a previous drought) or later demise (groundwater anomalies lag precipitation anomalies). In contrast, representation of dynamic vegetation tends to shorten major droughts duration, primarily due to earlier drought demise (closed stoma or dead vegetation reduces ET loss during droughts). On a regional basis, the U.S. Southwest (Southeast) has the longest (shortest) major drought durations. Consistent with earlier work, dry area coverage in all subregions except the Southwest has decreased. The effects of groundwater and dynamic vegetation vary regionally due to differences in groundwater depths (hence connectivity with the surface) and vegetation types.
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Chai, Qi, Fang Jin, Emily Merewitz, and Bingru Huang. "Growth and Physiological Traits Associated with Drought Survival and Post-drought Recovery in Perennial Turfgrass Species." Journal of the American Society for Horticultural Science 135, no. 2 (March 2010): 125–33. http://dx.doi.org/10.21273/jashs.135.2.125.
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The objective of this study was to determine physiological traits for drought survival and post-drought recovery upon re-watering in two C3 perennial grass species, kentucky bluegrass [KBG (Poa pratensis)] and perennial ryegrass [PRG (Lolium perenne)]. Plants were maintained well watered or exposed to drought stress by withholding irrigation and were then re-watered in a growth chamber. KBG had significantly higher grass quality and leaf photochemical efficiency, and lower electrolyte leakage than PRG during 20 days of drought. After 7 days of re-watering, drought-damaged leaves were rehydrated to the control level in KBG, but could not fully recover in PRG. KBG produced a greater number of new roots, while PRG had more rapid elongation of new roots after 16 days of re-watering. Superior drought tolerance in KBG was associated with osmotic adjustment, higher cell wall elasticity, and lower relative water content at zero turgor. Osmotic adjustment, cell wall elasticity, and cell membrane stability could play important roles in leaf desiccation tolerance and drought survival in perennial grass species. In addition, post-drought recovery of leaf hydration level and physiological activity could be associated with the accumulation of carbohydrates in leaves and rhizomes during drought stress and new root production after re-watering.
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Montagu, K. D., and K. C. Woo. "Recovery of tree photosynthetic capacity from seasonal drought in the wet - dry tropics: the role of phyllode and canopy processes in Acacia auriculiformis." Functional Plant Biology 26, no. 2 (1999): 135. http://dx.doi.org/10.1071/pp98034.
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Trees in the wet–dry tropics experience droughts of 4–5 months duration each year. We examined the phyllode and canopy responses to such drought and the subsequent recovery following rains, in 2-year-old field-grown Acacia auriculiformis A. Cunn. ex Benth., grown in Darwin, Australia. During the dry season, photosynthesis declined from 24 to 5 µmol m–2 s–1. Initially, decreases in phyllode chlorophyll and soluble protein content were paralleled by a decrease in stomatal conductance and the ratio of intercellular to ambient carbon dioxide concentrations (Ci:Ca) remained above 0.65. Only at the end of the dry season, when phyllode chlorophyll and soluble protein content had declined 73 and 52% respectively, did stomatal limitations predominated and the Ci:Ca ratio dropped to below 0.5. The first rains of the wet season, despite being small, removed stomatal limitations after 1–8 days. Within 4 weeks, photosynthetic rates in the phyllodes subjected to 5 months of drought, recovered to 70–95% of wet season values. Photosynthetic recovery appeared to be related to restoration of chlorophyll content and variations in the extent of recovery could be explained by the differing final chlorophyll contents. Both phyllode soluble protein content and stomatal conductance rates recovered to more than 90% of wet season values. These results indicate that during prolonged drought and recovery after rain, mesophyll limitations to photosynthesis predominated in this tree species. Shoot growth, to replace the 35–45% of foliage lost during the dry season, did not commence until more than 11 weeks after the first rains. Thus, the recovery of tree photosynthetic capacity in the early wet season was dependent on the recovery of foliage retained during the dry season, rather than the production of new foliage. Such a response may represent an important adaptive strategy that permits a rapid response to the first rains with a minimum outlay of new resource.
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Ye, Zhujia, Sasikiran Reddy Sangireddy, Chih-Li Yu, Dafeng Hui, Kevin Howe, Tara Fish, Theodore W. Thannhauser, and Suping Zhou. "Comparative Proteomics of Root Apex and Root Elongation Zones Provides Insights into Molecular Mechanisms for Drought Stress and Recovery Adjustment in Switchgrass." Proteomes 8, no. 1 (February 19, 2020): 3. http://dx.doi.org/10.3390/proteomes8010003.
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Switchgrass plants were grown in a Sandwich tube system to induce gradual drought stress by withholding watering. After 29 days, the leaf photosynthetic rate decreased significantly, compared to the control plants which were watered regularly. The drought-treated plants recovered to the same leaf water content after three days of re-watering. The root tip (1cm basal fragment, designated as RT1 hereafter) and the elongation/maturation zone (the next upper 1 cm tissue, designated as RT2 hereafter) tissues were collected at the 29th day of drought stress treatment, (named SDT for severe drought treated), after one (D1W) and three days (D3W) of re-watering. The tandem mass tags mass spectrometry-based quantitative proteomics analysis was performed to identify the proteomes, and drought-induced differentially accumulated proteins (DAPs). From RT1 tissues, 6156, 7687, and 7699 proteins were quantified, and 296, 535, and 384 DAPs were identified in the SDT, D1W, and D3W samples, respectively. From RT2 tissues, 7382, 7255, and 6883 proteins were quantified, and 393, 587, and 321 proteins DAPs were identified in the SDT, D1W, and D3W samples. Between RT1 and RT2 tissues, very few DAPs overlapped at SDT, but the number of such proteins increased during the recovery phase. A large number of hydrophilic proteins and stress-responsive proteins were induced during SDT and remained at a higher level during the recovery stages. A large number of DAPs in RT1 tissues maintained the same expression pattern throughout drought treatment and the recovery phases. The DAPs in RT1 tissues were classified in cell proliferation, mitotic cell division, and chromatin modification, and those in RT2 were placed in cell wall remodeling and cell expansion processes. This study provided information pertaining to root zone-specific proteome changes during drought and recover phases, which will allow us to select proteins (genes) as better defined targets for developing drought tolerant plants. The mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD017441.
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Gebauer, Roman, Roman Plichta, Josef Urban, Daniel Volařík, and Martina Hájíčková. "The resistance and resilience of European beech seedlings to drought stress during the period of leaf development." Tree Physiology 40, no. 9 (May 29, 2020): 1147–64. http://dx.doi.org/10.1093/treephys/tpaa066.
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Abstract Spring drought is becoming a frequently occurring stress factor in temperate forests. However, the understanding of tree resistance and resilience to the spring drought remains insufficient. In this study, European beech (Fagus sylvatica L.) seedlings at the early stage of leaf development were moderately and severely drought stressed for 1 month and then subjected to a 2-week recovery period after rewatering. The study aimed to disentangle the complex relationships between leaf gas exchange, vascular anatomy, tree morphology and patterns of biomass allocation. Stomatal conductance decreased by 80 and 85% upon moderate and severe drought stress, respectively, which brought about a decline in net photosynthesis. However, drought did not affect the indices of slow chlorophyll fluorescence, indicating no permanent damage to the light part of the photosynthetic apparatus. Stem hydraulic conductivity decreased by more than 92% at both drought levels. Consequently, the cambial activity of stressed seedlings declined, which led to lower stem biomass, reduced tree ring width and a lower number of vessels in the current tree ring, these latter also with smaller dimensions. In contrast, the petiole structure was not affected, but at the cost of reduced leaf biomass. Root biomass was reduced only by severe drought. After rewatering, the recovery of gas exchange and regrowth of the current tree ring were observed, all delayed by several days and by lower magnitudes in severely stressed seedlings. The reduced stem hydraulic conductivity inhibited the recovery of gas exchange, but xylem function started to recover by regrowth and refilling of embolized vessels. Despite the damage to conductive xylem, no mortality occurred. These results suggest the low resistance but high resilience of European beech to spring drought. Nevertheless, beech resilience could be weakened if the period between drought events is short, as the recovery of severely stressed seedlings took longer than 14 days.