Persistent Drought Research Articles

Identifying the origin, recharge, and salinity sources of the Romqan saline spring, causing intense salinization of the Shirinrud River in southern Iran

Salinization of originally freshwater rivers by saline springs is a growing threat to availability of water resources in the semiarid region of southern Iran. The problem is further complicated by persistent drought of recent years, which has resulted in prolonged periods of reduced streamflow. This issue has prompted research on possibility of finding practical techniques for flow stoppage of saline springs by investigating their recharge and salinization mechanisms as well as emergence time. To this end, the Shirinrud river in southern Iran is selected as a case study. While this river contains freshwater flow, it is intensively salinized due to annual discharge of ∼110000 tons salt from the Romqan saline spring. Study area streamflow gauges, water sampling, plus field observations and measurements have been used to provide the required data and information. Data analyses included evaluation of temperature variations of study area groundwaters, long-term salinity of the Shirinrud River, and isotopic and hydrochemical compositions of water samples. Results of thermal, isotopic, and hydrochemical tracing methods together with hydrogeological evidences in the Romqan spring site indicated that although the Romqan saline spring is recharging from a fresh groundwater flow, it becomes intensely salinized due to passage of ∼1.7 km of its recharging water pass inside the Romqan salt diapir. Furthermore, sudden drying of a freshwater spring at border of Romqan salt diapir just after the 1999 earthquake in spring site area, resulted in redirection of the fresh groundwater flow of the dried spring into the Romqan salt diapir, followed by emergence of the Romqan saline spring in the Shirinrud River bed. For flow stoppage of the Romqan saline spring, an interceptor drainage system is suggested, which would divert the spring fresh recharging groundwater flow at border of Romqan salt diapir and finally desalinize the Shirinrud River from Romqan saline spring.

Exploring the Spatially Compounding Multi‐Sectoral Drought Vulnerabilities in Colorado's West Slope River Basins

AbstractThe state of Colorado's West Slope Basins are critical headwaters of the Colorado River and play a vital role in supporting Colorado's local economy and natural environment. However, balancing the multi‐sectoral water demands in the West Slope Basins while maintaining crucial downstream deliveries to Lake Powell is an increasing challenge for water managers. Internal variability of the hydroclimatic system and climate change complicate future vulnerability assessments. This work contributes a detailed accounting of multi‐sectoral drought vulnerability in the West Slope Basins and the impacts of drought on downstream deliveries. We first introduce a novel multi‐site Hidden Markov Model (HMM)‐based synthetic streamflow generator to create an ensemble of streamflows for all West Slope basins that better characterizes the region's drought extremes. We capture the effects of climate change by perturbing the HMM to generate an ensemble of streamflows reflecting plausible changes in climate. We then route both ensembles through StateMod, Colorado's water allocation model, to evaluate spatially compounding drought impacts across the West Slope Basins. Our results illustrate how drought events emerging from the system's stationary internal variability in the absence of climate change can significantly impact local water uses and deliveries to Lake Powell, exceeding extreme conditions in the historical record. Further, we find that even modest climate change can cause a regime shift where historically low downstream delivery volumes and extreme drought impacts become routine. These results can inform future Colorado River planning efforts, and our methodology can be expanded to other snow‐dominated regions that face persistent droughts.

Attribution analysis of the persistent and extreme drought in southwest China during 2022–2023

Abstract Southwest China experienced a severe drought during winter 2022–spring 2023. This drought mainly struck Yunnan Province and surrounding regions (21°–30° N, 97°–106° E), with precipitation deficit lasting for about 8 months from Oct 2022 to May 2023. The area-mean precipitation and surface soil moisture in the study region during the drought were both the lowest recorded for the same period since 1950. The Standardized Precipitation Evapotranspiration Index (SPEI) also reached its lowest level since 1950 at −2.76. Quantitative analysis shows that precipitation deficit and potential evapotranspiration (PET) increase contributed 71.36%, and 28.64% to the SPEI, respectively. Of the raw contribution of PET, 7.05% can in turn be attributed to the changes in precipitation. Using data from the CMIP6 Detection and Attribution Model Intercomparison Project (DAMIP), we found that anthropogenic forcing increased the likelihood of a PET anomaly such as the one during the drought by about 133 times, with a fraction of attributable risk (FAR) of 0.99 [0.98, 1.00]. For the precipitation anomaly, we obtained a FAR of 0.26 [−1.12, 0.70], suggesting that anthropogenic forcings may have little impact. The extreme drought also increased the risk of fires, with the Fire Weather Index reaching its second-highest value since 1950 and abnormally high burned areas observed by satellites.

Drought Quantification in Africa Using Remote Sensing, Gaussian Kernel, and Machine Learning

Effective drought management requires precise measurement, but this is challenging due to the variety of drought indices and indicators, each with unique methods and specific uses, and limited ground data availability. This study utilizes remote sensing data from 2001 to 2020 to compute drought indices categorized as meteorological, agricultural, and hydrological. A Gaussian kernel convolves these indices into a denoised, multi-band composite image. Further refinement with a Gaussian kernel enhances a single drought index from each category: Reconnaissance Drought Index (RDI), Soil Moisture Agricultural Drought Index (SMADI), and Streamflow Drought Index (SDI). The enhanced index, encompassing all bands, serves as a predictor for classification and regression tree (CART), support vector machine (SVM), and random forest (RF) machine learning models, further improving the three indices. CART demonstrated the highest accuracy and error minimization across all drought categories, with root mean square error (RMSE) and mean absolute error (MAE) values between 0 and 0.4. RF ranked second, while SVM, though less reliable, achieved values below 0.7. The results show persistent drought in the Sahel, North Africa, and southwestern Africa, with meteorological drought affecting 30% of Africa, agricultural drought affecting 22%, and hydrological drought affecting 21%.

Drought assessment in Kabul River basin using machine learnings

Droughts significantly impact water resources and agriculture, leading to economic losses and potential human fatalities. This study aims to predict droughts by analysing changes in the Standardised Precipitation Evapotranspiration Index (SPEI) for the Kabul River basin using data from 1981 to 2022. The research is divided into three phases: calculating SPEI, splitting the dataset into training (80%) and testing (20%) subsets, and evaluating model performance. Various machine learning algorithms, including XGBoost, Decision tree, AdaBoost, and KNN, were employed alongside different climatic variables. The models were assessed using statistical metrics such as R², RMSE, MAE, MSE for regression, and confusion matrix, accuracy, precision, recall, F1 score, ROC AUC, and Log loss for classification. Results showed strong performance, with R² values of 0.97, 0.86, 0.92, and 0.96 for XGBoost, KNN, Decision tree, and AdaBoost, respectively. SPEI demonstrated significant potential for drought forecasting, and spatial distribution mapping revealed persistent moderate drought occurrences.

Accelerated Atmospheric to Hydrological Spread of Drought in the Yangtze River Basin under Climate

Persistent droughts pose a threat to agricultural production, and the changing environment worsens the risk of drought exposure. Understanding the propagation of drought in changing environments and assessing possible impact factors can help in the early detection of drought, guiding agricultural production practices. The current study cannot reflect the propagation status of drought to the total terrestrial hydrological drought, so this work creatively investigated the atmospheric to hydrological drought propagation time in the Yangtze River Basin under the dynamic and static perspectives based on the Standardized Precipitation Evapotranspiration Index and the Terrestrial Water Storage Anomalous Drought Index, fine-tuned the time scale to the seasonal scale, and explored the contributing capacity of the variable interactions. The results show that: (1) under the dynamic perspective, while the propagation time is decreasing in the annual scale, the spring season shows the opposite trend; and (2) large variability exists in the timing of drought propagation at spatial scales, with elevation playing the most important influential role, and bivariate interactions contributing stronger explanations compared to single variables. This study highlights the importance of considering the impact of variable interactions and contributes to our understanding of the response of secondary droughts to upper-level droughts, providing valuable insights into the propagation of droughts to total terrestrial hydrologic drought.

Iron Toxicity in Plants: A Review

Iron (Fe) is an essential micronutrient for plant growth and development. However, increased absorption of iron leads to iron toxicity. This leads to damage to plant cell membranes, decreased growth, productivity, and thus general health. The presence of free iron in cells can lead to an imbalance Redox in cells Pro-oxidant state, thus generating oxidative stress. In plants, iron is involved in chlorophyll synthesis, and is therefore essential for maintaining the structure and function of chloroplasts. Micronutrients in the soil can limit plant growth, even if all other nutrients are available in sufficient quantities. Micronutrient deficiencies are widespread due to the nature of the soil, high pH, low organic matter, salt stress, and persistent drought. High levels of bicarbonate in irrigation water, as well as unbalanced use of fertilizers. Iron (Fe) toxicity is a widespread nutritional disorder. It grows in acidic, sulphurous soils, as well as low sandy soils (i.e. iron is easily reducible) that contain a high percentage of organic matter. Iron toxicity can be reduced by using rice that is tolerant to high levels of iron.

Drought shocks and labour reallocation in rural Africa: evidence from Ethiopia

Abstract We study how rural households in Ethiopia adapt to droughts through labour reallocation. Using three waves of panel data and exploiting spatio-temporal variations in drought exposure, we find that households reduce on-farm work and increase off-farm self-employment in response to both short-term and persistent droughts, without abandoning family farming. Diversification into off-farm activities is driven by drought-related productivity declines in agriculture and contributes to consumption smoothing and food security. Households with better access to financial services are more likely to reallocate labour off-farm. Our results highlight the importance of strengthening the rural non-farm economy to enhance rural households’ climate resilience.

Integrated remote sensing and geographic information system overlay analysis for groundwater potential evaluation using AHP and fuzzy AHP: Southern sections of the western Afar rift margin and associated rift floor

A persistent drought commonly affects the southern sections of the western Afar rift margin and the associated rift floor, leaving the populace concerned about their access to food. A comprehensive assessment and usage of the local groundwater resource is therefore essential to overcoming the ongoing drought and meeting the area's increasing demand for sustainable water. With the aid of RS, GIS, AHP, and Fuzzy AHP methods, this study aims to assess the area's groundwater potential. Lineament density, Geology,Topographic Wetness Index (TWI), Recharge, Slope, Land Use and Land Cover, Soil, and Drainage Density were created using GIS and RS techniques and are the thematic layers taken into consideration for this purpose. The weight of these themes for their relative significance to groundwater occurrence was determined using AHP and Fuzzy AHP (FAHP). Lineament density is the primary factor influencing the presence of groundwater, followed by geology, TWI, and recharge. The Very low (221.48 km2), Low (9084.46 km2), Moderate (8281.96 km2), High (1441.65 km2), and Very High (102.45 km2) groundwater potential zones (GWPZs) were delineated using the GIS-overlay analysis technique. The validation of the groundwater potential zone map was completed using the well discharge, transmissivity, and specific capacity, and the scatter plot demonstrated a strong connection with R2 values of 0.81, 0.79, and 0.80, respectively. The sensitivity index (SI) shows that lineament density and geology, which have SI values of 2.08% and 1.74%, respectively, have the greatest influence on the distributions of groundwater potentiality in the catchment, while drainage density has the least influence, with a SI value of −0.89%. By ensuring sustainable management and development, the study's findings will help with decision-making for the long-term supply of groundwater. Additionally, the approach utilized in the study can be applied to other comparable arid to semiarid regions.

Understanding Salinity Intrusion and Residence Times in a Small-Scale Bar-Built Estuary under Drought Scenarios: The Maipo River Estuary, Central Chile

The Maipo River estuary is a low-inflow bar-built estuary that includes a protected wetland, which harbors a rich ecosystem. The estuary and wetland have been threatened by a persistent drought for more than a decade, which has resulted in greater salinity intrusion and increased residence times. Previous studies have described salinity and pollutants in estuaries; however, almost all have focused on deeper and/or wider estuaries with dimensions much larger than those of the small-scale Maipo River estuary. In this study, we used the numerical model FVCOM to simulate the dynamics of the Maipo River estuary under drought scenarios and explored the interactions between river discharge and tides in terms of saline intrusion and particle dispersal. The model was validated against observations collected during a field campaign near the river mouth. The simulations successfully reproduced the water surface elevation but underestimated salinity values, such that the vertical salinity structure observed in the field was not captured by the model in this shallow and morphologically complex estuary. Consequently, our model results provide qualitative insight related to salinity and baroclinic dynamics. Results of maximum saline intrusion showed an exponential decay with increasing river discharge, and the analysis of salinity intrusion time series revealed that droughts may cause permanent non-zero salinity levels in the estuary, potentially affecting ecological cycles. The incorporation of passive tracers showed that decreasing river discharge increases the residence time of particles by allowing the tracers to re-enter the estuary. Model results showed the formation of accumulation zones (hotspots) in the shallower zones of the estuary.

Exotic tree plantations in the Chilean Coastal Range: balancing the effects of discrete disturbances, connectivity, and a persistent drought on catchment erosion

Exotic tree plantations in the Chilean Coastal Range: balancing the effects of discrete disturbances, connectivity, and a persistent drought on catchment erosion

Drought stimulus enhanced stress tolerance in winter wheat (Triticum aestivum L.) by improving physiological characteristics, growth, and water productivity

The impact of drought events on the growth and yield of wheat plants has been extensively reported; however, limited information is available on the changes in physiological characteristics and their effects on the growth and water productivity of wheat after repeated drought stimuli. Moreover, whether appropriate drought stimulus can improve stress resistance in plants by improving physiological traits remains to be explored. Thus, in this study, a pot experiment was conducted to investigate the effects of intermittent and persistent mild [65%–75% soil water-holding capacity (SWHC)], moderate (55%–65% SWHC), and severe drought (45%–55% SWHC) stress on the growth, physiological characteristics, yield, and water-use efficiency (WUE) of winter wheat. After the second stress stimulus, persistent severe drought stress resulted in 30.98%, 234.62%, 53.80%, and 31.00% reduction in leaf relative water content, leaf water potential, photosynthetic rate (Pn), and indole-3-acetic acid content (IAA), respectively, compared to the control plants. However, abscisic acid content, antioxidant enzyme activities, and osmoregulatory substance contents increased significantly under drought stress, especially under persistent drought stress. After the second rehydration stimulus (ASRR), the actual and maximum efficiency of PSII and leaf water status in the plants exposed to intermittent moderate drought (IS2) stress were restored to the control levels, resulting in Pn being 102.56% of the control values; instantaneous WUE of the plants exposed to persistent severe drought stress was 1.79 times that of the control plants. In addition, the activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase, as well as the content of proline, under persistent mild drought stress increased by 52.98%, 33.47%, 51.95%, 52.35%, and 17.07% at ASRR, respectively, compared to the control plants, which provided continuous antioxidant protection to wheat plants. This was also demonstrated by the lower H2O2 and MDA contents after rehydration. At ASRR, the IAA content in the IS2 and persistent moderate drought treatments increased by 36.23% and 19.61%, respectively, compared to the control plants, which favored increased aboveground dry mass and plant height. Compared to the control plants, IS2 significantly increased wheat yield, WUE for grain yield, and WUE for biomass, by 10.15%, 32.94%, and 33.16%, respectively. Collectively, IS2 increased grain growth, yield, and WUE, which could be mainly attributed to improved physiological characteristics after drought-stimulated rehydration.

Exploring the variability of root system architecture under drought stress in heat-tolerant spring-wheat lines

Background and aimsGlobal wheat production is under threat due to climate change, specifically heat and drought and their combination. This study aims to address the root trait responses of heat-tolerant wheat genotypes to drought.MethodsThe variability in root traits of CIMMYT wheat lines, which were previously developed for heat stress tolerance (HTWL), was evaluated alongside 10 Pakistani-approved varieties under three cultivation conditions and soil moisture levels.ResultsOur findings revealed that the plasticity of the wheat root system is highly pronounced, with rhizosphere conditions exerting a more substantial influence (5–49%) than the genotypic response (1–14%). Furthermore, in the hydroponic and pot system, we noted higher maximum-root length (1.5–1.8 fold) and root-to-shoot ratio (3.4–10.6 fold) as compared to field condition, while the root biomass was substantially higher in the field trial (3-57 fold). Nonetheless, persistent drought conditions exerted contrasting impact with reduction in most of the traits except specific root length and harvest index which were increased under drought.ConclusionsThe variation in root traits against drought indicates the potential for the development of improved genotypes that can withstand multiple stresses. Furthermore, it is crucial to consider rhizosphere conditions when selecting genotypes, as the plasticity of wheat roots may lead to misinterpretations if rhizosphere conditions are disregarded. Root dry weight and root-to-shoot ratio are more stable traits as compared to maximum root length and specific root length. It is recommended to evaluate a broader range of rhizosphere conditions to select tolerant genotypes.

Drought, water management, and agricultural livelihoods: Understanding human-ecological system management and livelihood strategies of farmer's in rural California

Mitigating impact between agricultural livelihoods and water conservation efforts in the face of significant drought requires a sophisticated understanding of policy efforts enacted to manage water supply and the logic of human livelihood decision-making. This case study extends literature on human-water decision-making in agricultural areas by using a political ecology framework to understand how and why farmers facing significant water shortages make livelihood decisions, and how such decisions are affected by broader socio-political contexts. Specifically, we focus on farmers' livelihood strategies in the Central San Joaquin Valley of California. Here, the effects of extreme and persistent drought have resulted in a resource management governance structure that forces farmer decision-making within the narrow bounds of the newly emerging California water policy. We argue that government public policy intervention has created a potential system of “big winners and big losers,” leading to three divergent strategies farmers adopt: Nimbility, Abandonment, and Policy Engagement. These findings raise questions about how policy interventions shape livelihood strategies of farmers in the Tulare Lake Basin and by extension other areas where public policy intervention is emerging to respond to decreased water supply resources.

Exploring household water conservation methods in rural South Africa: a case of the Mbhashe and Mnquma local municipalities

Amidst the persistent drought disaster declared in 2015, the Amathole District Municipality grapples with severe water scarcity issues, particularly affecting local municipalities such as Mbhashe and Mnquma. Consequently, households in these areas confront the challenges of unreliable and contaminated water sources, prompting them to adopt water conservation measures to mitigate shortages. This study investigates the efficacy of water conservation methods among rural households in these drought-affected regions. It identifies associated challenges and potential interventions to ensure access to clean and dependable water. Employing a mixed methods approach, the study examines household water conservation practices through narrative analysis and descriptive statistics of survey data. Findings reveal that storing water in drums, containers, and tanks is the most prevalent conservation method, alongside measures like greywater reuse, lifestyle adjustments, and rainwater harvesting. With financial constraints and infrastructural limitations hindering broader adoption, the study found water conservation to be a challenge among the households as a minority (7.8%) of respondents adopted multiple water conservation strategies. In comparison, most respondents (73.6%) could only afford to practice one water conservation strategy at a time, and others (18.6%) had no conservation strategies. Drought conditions, lack of infrastructure, poverty, and attitudinal factors are primary barriers to effective water conservation. The study underscores the need for municipal-level initiatives to enhance water sources and advocates for increased investment in education, awareness campaigns, and policy interventions to address rural communities’ water scarcity challenges.

Developing a Multivariate Agro‐Meteorological Index to Improve Capturing Onset and Persistence of Droughts Utilizing Vapor Pressure Deficit and Soil Moisture

AbstractDrought is associated with adverse environmental and societal impacts across various regions. Therefore, drought monitoring based on a single variable may lead to unreliable information, especially about the onset and persistence of drought. Previous studies show vapor pressure deficit (VPD) data can detect drought onset earlier than other drought indicators such as precipitation. On the other hand, soil moisture (SM) is a robust indicator for assessing drought persistence. This study introduces a nonparametric multivariate drought index Vapor Pressure Deficit Soil moisture standardized Drought Index (VPDSDI) which is developed by combining VPD with SM information. The performance of the multivariate index in terms of drought onset detection is compared with the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI) for six major drought events across the United States including three rapidly developing drought events (this term refers to flash droughts that develop on monthly scales) and three conventional drought events. Additionally, the performance of the proposed index in detecting drought persistence is compared with the Standardized Soil moisture Index (SSI), which is an agricultural drought index. Results indicate the multivariate index detects drought onset always earlier than SPI for conventional events, but VPDSDI detects drought onset earlier than or about the same time as SPEI for rapidly developing droughts. In terms of persistence, VPDSDI detects persistence almost identical to SSI for both rapidly developing and conventional drought events. The results also show that combining VPD with SM reduces the high variability of VPD and produces a smoother index which improves the onset and persistence detection of drought events leveraging VPD and SM information.

Centennial-scale cooling-induced megadroughts in Myanmar's tropical arid region over the past 8000 years

The future impact of global warming on tropical arid regions is unclear due to uncertainties about the correlation between rising temperatures and changes in precipitation patterns. A critical factor is the reliability of the sedimentary chronologies. Hence, to better understand the potential long-term consequences of climatic warming or cooling for tropical arid regions we compared a pollen record from the annually-laminated sediments of a crater lake in Myanmar with ice core records of the Siberian High, both of which have an annual resolution. Our findings reveal that over the past 8000 years, the Myanmar region experienced six significant drought events, three of which coincided precisely with intensifications of the Siberian High-pressure system. Furthermore, five out of these six events were synchronous with the North Atlantic Bond events within the limit of the dating uncertainties. Conversely, warm periods were associated with increased precipitation along with relatively short-lived drought events. Our findings suggest that regardless of the El Niño intensity, a cooling trend in the Northern Hemisphere may result in persistent extreme drought conditions in arid tropical regions. Therefore, as well as the environmental implications of global warming, it is also important to address the potential hazards associated with cooling, especially in arid tropical regions. To facilitate effective disaster management and to develop strategies for climate change mitigation, it is crucial to better understand the complex relationship between temperature fluctuations and drought. Overall, our findings are a reminder of the importance of not ignoring the potential disasters that may arise from cooling trends while focusing exclusively on warming.

Does biochar combined with cover crops improve health and productivity of sandy, sloping, and semi‐arid soils?

AbstractBiochar may improve the health of environmentally sensitive soils (i.e., low C, sandy, sloping) especially if combined with cover crops (CCs), but research is scant. We assessed how wood biochar (836 g C kg−1) applied at 0, 6.25, 12.5, 25, and 50 Mg ha−1 to sandy, sloping, and semi‐arid soils with and without CCs affects soils and crop yields in the central US Great Plains for 3 years. We measured crop yields and CC biomass each year, and most soil properties in Years 1 and 3. Biochar did not interact with CCs, suggesting the combination was no better than biochar or CC alone. In the semi‐arid soil, crop and CC did not establish due to persistent droughts. Biochar benefits were highly site‐specific. Biochar improved some soil properties but only in the sandy and sloping soils and at the biochar application depth (0‐ to 15‐cm soil depth). The 50 Mg biochar ha−1 improved the soil's ability to sorb water (0.08 cm s−1/2). Also, in the sandy soil, it increased soil organic matter concentration (2.5 g kg−1), soil pH (0.65 units), and available water (0.07 m3 m−3) only in Year 1, suggesting a biochar benefit in sandy soils is short‐lived. In the sloping soil, >25 Mg biochar ha−1 reduced bulk density (0.16 Mg m−3) and increased soil mean weight diameter of water‐stable aggregates (0.58 mm), organic matter concentration (11.42 g kg−1), infiltration (9.35 cm), CC biomass production (0.27 Mg ha−1), and some microbial biomass groups. Biochar did not affect crop yields. Overall, >25 Mg biochar ha−1 improved properties in some soils without interacting with CCs.

Potential for historically unprecedented Australian droughts from natural variability and climate change

Abstract. In drought-prone Australia, multi-year droughts have detrimental impacts on both the natural environment and human societies. For responsible water management, we need a thorough understanding of the full range of variability in multi-year droughts and how this might change in a warming world. But research into the long-term frequency, persistence, and severity of Australian droughts is limited. This is partly due to the length of the observational record, which is short relative to the timescales of hydroclimatic variability and hence may not capture the range of possible variability. Using simulations of Australian precipitation over the full past millennium (850–2000), we characterise the nature of multi-year meteorological droughts across Australia and include a particular focus on the Murray–Darling Basin (MDB), the largest agricultural region in Australia. We find that simulated Australian droughts in the 20th century (1900–2000) are within the bounds of pre-industrial natural variability in terms of drought intensity, severity, and frequency. A tendency for droughts to last longer in southwestern and eastern Australia (including the MDB) in the 20th century, compared with the pre-industrial period, suggests an emerging anthropogenic influence, consistent with projected rainfall changes in these regions. Large volcanic eruptions tend to promote drought-free intervals in the MDB. Model simulations of droughts over the last millennium suggest that future droughts across Australia could be much longer than what was experienced in the 20th century, even without any human influence. With the addition of anthropogenic climate change, which favours drought conditions across much of southern Australia due to reduced cool-season rainfall, it is likely that future droughts in Australia will exceed recent historical experience.

Regulatory effects of non-growing season precipitation on the community structure, biomass allocation, and water-carbon utilization in a temperate desert steppe

Under the influence of global change, precipitation amounts and extreme precipitation frequency during non-growing seasons in mid-high latitude grasslands have been increasing. However, the ecological effects of non-growing season precipitation in the desert steppe have long been overlooked due to an insufficient understanding of the correlative mechanisms linking non-growing season precipitation to plant growth. Therefore, a 3-year non-growing season precipitation manipulation experiment was conducted to reveal the response of desert steppe plants to non-growing season precipitation changes. Our study indicates that, by influencing water budget and availability, non-growing season precipitation directly or indirectly impacted community structure, plant biomass allocation, and water-carbon utilization intensity. Adaptive strategies of communities and plants included: ① Dominant species enhanced their dominance in the community to adapt to non-growing season precipitation changes. ② Stipa krylovii exhibited different biomass allocation strategies in response to non-growing season precipitation variations. Plants in the precipitation shading plots tended to allocate biomass to the roots, while those in the precipitation increase plots favored aboveground development. ③ Persistent drought during the growing season intensified early insufficient development of plants in the precipitation shading plots. Upon entering the wet period, plants in the precipitation shading plots shifted into a compensatory growth mode with high water-carbon activity intensity, while those in the precipitation increase plots entered a moderate growth mode with relatively low water-carbon activity intensity. Additionally, our study found that the regulatory effects of non-growing season precipitation were more pronounced in the growing seasons with less precipitation in the early to middle stage. Moreover, increased non-growing season precipitation enhanced plant water use efficiency (WUE) and strengthened their resilience to drought conditions. Our study suggests that the ecological role of non-growing season precipitation may be further highlighted in the future climate change pattern. Given the worldwide increase in frequency of extreme precipitation events, particular vigilance should be paid to the underlying long-term adverse effects of severe droughts during the non-growing season. Our findings provide new insights and valuable experimental observational evidence for the climate change impact assessment and response in xerophytic grassland ecosystems.