Seasonal Drought Research Articles

Soil CO2 efflux response to two decades of altered carbon inputs in a temperate coniferous forest

Global soils play a critical role in carbon (C) cycling and storage, and even minor disturbances to soil C flux can cause CO2 release to the atmosphere, exacerbating the greenhouse effect. This study investigates the long-term effects of forest detrital manipulation on soil CO2 efflux at a temperate forest site in Oregon’s western Cascade Mountains. We assessed the variation in seasonal and diurnal autotrophic and heterotrophic contributions to in situ soil CO2 efflux after 25 + years of detritus additions and removals and found slight increases in soil CO2 efflux rates concurrent with slight increases in soil C stocks, relative to C input rates, that may reflect underlying changes to C cycling in this system resulting from sustained detritus manipulation coupled with environmental change. Total CO2 efflux experienced increased contributions from functionally autotrophic root and rhizosphere respiration relative to the heterotrophic component. Seasonal and diurnal differences between soil respiration rates by treatment suggest a soil moisture buffering effect provided by the extra woody detritus that may support vegetative growth at times when seasonal drought would ordinarily slow plant and soil microbial metabolic activity. Overall, this research highlights the long-term effects of sustained litter additions and removals on soil CO2 efflux, which can help illuminate the response of C cycling in forests to current and future global change.

Rare Earth Elements Induce Drought Tolerance in Dicranopteris pedata from Ion-Adsorbed Rare Earth Mining Area in Southern China

The ion adsorption rare earth (IARE) mining areas in southern China frequently experience severe seasonal drought, posing significant challenges to plant growth. This study investigates the hypothesis that rare earth elements (REEs) present in these mining areas induce drought resistance in Dicranopteris pedata (D. pedata). An experiment was designed with three drought stress intensities (0%, 5%, and 10% PEG6000) and three levels of rare earth element (REE) addition (none, low, and high). After 72 h of drought stress, physiological indices and metabolomic profiles of D. pedata were examined. The results showed that under drought conditions, the REE additions increased the catalase and peroxidase activities of D. pedata by 99.04% and 81.25%, respectively, and the contents of proline, soluble proteins, and soluble sugars by 97.52%, 71.24%, and 61.81%, respectively. Metabolomic analysis revealed up-regulation of lipid and lipid-like molecules, as well as flavonoid metabolism, which contribute to improved drought resistance in D. pedata under stress. Furthermore, REE addition further up-regulated flavonoid and anthocyanin synthesis compared to drought stress alone, enhancing the plant’s resilience to drought. These findings suggest that D. pedata responds to drought stress by modulating enzyme activities, osmoregulatory substances, and metabolic pathways upon REE exposure. This study underscores the dual role of REEs in enhancing both the drought tolerance and enrichment capacity of D. pedata in IARE mining areas, which is crucial for sustaining plant growth amidst drought stress, and provides new ideas for the ecological restoration and sustainable development of IARE mining areas.

Effects of tillage practices on water storage and soil conservation in red soil slope farmland in Southern China

Under the current conditions of global climate change, many unreasonable tillage practices exacerbate soil erosion and seasonal drought in agriculture. The red soil slope farmland makes up a significant portion of agricultural land in southern China. It is crucial to enhance the water storage and soil conservation effects (WSE) by adopting appropriate agronomic practices on the red soil slope farmland, which ensures regional agriculture’s sustainable development. Therefore, this study employed a combination of experimental plot positioning observations and artificially simulated rainfall experiments to analyze the WSE of four tillage practices: Conventional tillage (CT), Downslope ridge tillage (DT), Cross-slope ridge tillage (RT), and Plastic Mulching (PM). This study proposed the optimal tillage practices based on a comprehensive evaluation of their effects. The results indicate that there is a significant interaction (p < 0.05) between tillage practices and growth stages on soil water retention and infiltration characteristics. Under the same growth stage conditions, PM can reduce soil bulk density by 0.03–14.29% (p < 0.05) and increase temperature, soil moisture content, and total porosity by 4.00–6.67%, 0.68–18.23%, and 1.30–13.47% (p < 0.05), respectively, demonstrating the best water retention capabilities among the four tillage practices. However, during the rainfall-runoff process, the surface runoff amount (SRA) generated by PM and DT accounts for 68.15% and 90.83% of the total runoff, respectively, which is detrimental to soil water infiltration during rainfall. Both practices exhibit poor resistance to soil erosion and demonstrate low water storage and soil conservation effect index (WSEI) values of 0.38 and 0.33, respectively. Secondly, RT’s SRA constitutes only 9.42% of the total runoff, which is beneficial for increasing the cumulative soil water infiltration amount (CIA) during rainfall. Among the three tillage practices, namely RT, DT, and CT, RT demonstrates strong soil water retention capabilities. It can significantly reduce the kinetic energy of soil erosion, enhance soil erosion resistance, and exhibit the highest WSEI of 0.84. Furthermore, CT exhibits a moderate WSEI of 0.75. In summary, from the perspective of WSEI, RT is the tillage practice that should be prioritized for promotion in the cultivation process of red soil slope farmland. Our research results can provide a scientific basis for constructing optimal tillage mode and improving the WSE of southern China’s red soil slope farmland.

Different wetting states in riparian sediment ecosystems: Response to microplastics exposure

Climate change alters the wetting state of riparian sediments, impacting microbial community response and biogeochemical processes. Microplastics (MPs) invade nearly all ecosystems on earth, posing a significant environmental risk. However, little is known about the response mechanism of MP exposure in sediment ecosystems with different wetting states under alternating seasonal rain and drought conditions. In this study, sediments with three different wetting states were selected to explore the differential response of ecosystems to PLA MP exposure. We observed that PLA MP exposure directly affected biogeochemical processes in sediment ecosystems and induced significant changes in microbial communities. PLA MP exposure was found to alter the composition of key species and microbial functional groups in the ecosystem, resulting in a more complex, interconnected, but less stable microbial network. Our findings showed that PLA MP exposure enhances the contribution of stochastic processes, for example the dispersal limitation increasing from 7.41 % to 54.32 %, indicating that sediment ecosystems strive to buffer disturbances from PLA MP exposure. In addition, 87 pathogenic species were detected in our samples, with PLA MPs acting as vectors for their transmission, potentially amplifying ecosystem disturbance. Importantly, we revealed that submerged sediments may present a greater environmental risk, while alternating wet and dry sediments demonstrate greater resistance and resilience to PLA MPs pollution. Overall, this study sheds light on how sediment ecosystems respond to MP exposure, and highlights differences in sediment response mechanisms across wetting states.

Seasonal drought drives sugarcane borer outbreaks.

Sugarcane borers (SCB) pose a major threat to sugarcane production. Effective pest management requires detailed knowledge of SCB phenology and population dynamics in responses to environmental changes. This study tested the hypothesis that drought drives SCB outbreaks and identified season-specific effects by investigating large-scale field data of these pests in 4 key sugarcane-growing provinces in south subtropical and tropical China (Guangxi, Guangdong, Yunnan, and Hainan) from 1987 to 2018. The standardized precipitation evapotranspiration index was used as a drought indicator at various time scales. We found that drought during a specific month can result in significant changes in the annual SCB outbreak status, such as November in Guangxi, June in Yunnan, and September in Hainan. By summarizing seasonal effects of drought across study locations, we found a general pattern that SCB outbreaks increased with drier conditions in summer, whereas they were promoted by wetter conditions in fall. This research provides crucial knowledge for predicting SCB outbreaks under seasonal and climate changes. This information is also highly critical for increasing the efficiency and accuracy of integrated pest management strategies.

Critical radicle length window governing loss of dehydration tolerance in germinated Perilla seeds: insights from physiological and transcriptomic analyses

BackgroundPerilla (Perilla frutescens L. Britt.) is an important oilseed and medicinal crop that frequently faces seasonal drought stress during seed germination, leading to a loss of dehydration tolerance (DT), which affects seed emergence and significantly reduces yield. DT has been successfully re-established for many species seeds. However, the physiological mechanisms and gene networks that regulate Perilla’s response to DT loss remain unclear.ResultsPhenotypic analysis determined that the window for DT in Perilla seeds occurs at radicle lengths of 0–4 mm. Integrating physiological and transcriptomic analyses revealed that the loss of DT promotes the production of reactive oxygen species (ROS) and regulates oxidase activity and gene expression. This implies that DT may influence seed germination by modulating ROS activity. Four radicle length (i.e., 0, 1, 3, and 4 mm) stages were analyzed, and 262 differentially expressed genes (DEGs) were identified that responded to DT. The majority of these genes were associated with epigenetics, cell function, and transport mechanisms. Analysis of expression data shows that desiccation inhibits the signaling network of genes encoding small secreted peptides (SSPs) and receptor-like protein kinases (RLKs). Finally, a relevant network diagram of DT response was proposed. Based on this information, we have revealed the metabolism regulation maps of the four main pathways involving these DEGs (i.e., metabolic pathways, cell cycle, plant hormone signal transduction, and motor proteins).ConclusionsIn conclusion, these findings deepen our understanding of gene network responses to DT during Perilla seed germination and provide potential target genes for the genetic improvement of drought resistance in this crop.

Field survey for assessing seawater reverse osmosis (SWRO) applications on very small islands in Indonesia

Very small islands in Indonesia face challenges in accessing clean water due to limited space for building water resource facilities, such as reservoirs. Most of the time, the inhabitants of these islands rely on rainwater and wells, which are not sustainable sources due to drought seasons and seawater intrusion. To address this issue, Seawater Reverse Osmosis (SWRO) can be implemented in these areas where seawater is abundant. However, there may be obstacles when applying SWRO systems in such environments. This study aimed to assess the capabilities of SWRO facilities, and the obstacles involved in evaluating clean water access on very small islands. We used a combination of structured questionnaires, interviews, and direct observations on two small islands in Indonesia, Belakang Padang Island and Labu Island. On Belakang Padang Island, we interviewed the water resource manager in October 2022 and March 2023 and surveyed 61 households in the Tanjung Sari subdistrict in October 2022. On Labu Island, we interviewed the staff of the SWRO system and surveyed 35 coastal households in September 2023. On both islands, the government improved residents’ access to clean water by constructing SWRO facilities in 2016 on Belakang Padang Island and in 2021 on Labu Island. However, on Belakang Padang Island, the system was not operational when we visited on March 15, 2023. The main obstacles were slow bureaucratic processes for repairs and maintaining the operation of SWRO facilities. These problems need to be addressed before expanding the implementation of this system to other very small islands in Indonesia.

Application of the Standardized Precipitation Index for Forecasting Seasonal Drought in Vietnam

Drought is a natural disaster that causes significant damages to the economy, society and environment. Forecasting droughts is crucial for disaster risk management and water security. This study introduces a new method for forecasting seasonal droughts in Vietnam using the Standardized Precipitation Index (SPI) which is based on a combination of dynamic modeling and statistical methods. The precipitation forecast products from regional climate models (RegCM, clWRF) with inputs from Climate Forecast System (CFSv2) were used to calculate the SPI index after statistical calibration. Results show that calibrating model precipitation with statistical methods such as Artificial Neural Networks (ANN) and Multivariate Linear Regression (MLR) significantly improves the precipitation forecast accuracy. Evaluation indices indicate that the SPI calculated with the post-calibration model precipitation has a good reproducibility for drought events, particularly mild droughts. However, there remains some limitations on accurate forecast of the intensity and spatial distribution of moderate drought events in certain regions such as Central Vietnam.

Underestimation of meteorological drought intensity due to lengthening of the drought season with climate change

Abstract Meteorological drought may lead to water shortages, which has negative impacts on water-dependent sectors. Whilst there is a wealth of studies on changing drought intensity or frequency due to climate change, much less is known regarding potential shifts in the timing of drought. The purpose of this study is to analyze the timing of the drought season in the Netherlands and climatic changes therein, with a special focus on the onset of the drought season. Based on an analysis of meteorological observations in the Netherlands over the period 1965–2023, we conclude that the Dutch meteorological drought season has extended forward in time. On average, the drought season starts 16 d earlier in the period 1994–2023 compared to 1965–1993. This is mostly the result of an increase in potential evapotranspiration, while the amount of precipitation does not show a clear change at the start of the growing season. Using three climate model ensembles, we show that a forced climate change signal exists, but that natural variability also plays a role. Following this assessment of trends in meteorological variables, we analyze the consequences for the operational monitoring of meteorological drought. In the Netherlands, this is done by means of the ‘precipitation deficit’-indicator, based on a fixed-in-time starting point (1 April) of the drought season. The combination of this fixed starting point and the observed earlier onset of the drought season, means that in some years the indicator underestimates drought intensity, and that climatic trends are underestimated. We therefore advocate for an update of the operational drought indicator, such that meteorological drought occurring before 1 April will not be missed.

Disentangling the Complex Effects of Seasonal Drought, Floor Mass, and Roots on Soil Microbial Biomass in a Subtropical Moist Forest

Severe seasonal droughts driven by global climate change significantly alter the cycling of carbon and nutrients in forest ecosystems, while the investigation into the impacts of floor mass and plant roots on soil microbial biomass within the context of recurrent seasonal droughts is still rare. To investigate the environmental determinants governing soil microbial biomass with the escalating severity of seasonal droughts, we conducted a study in a montane subtropical moist evergreen broad-leaved forest in southwestern China from June 2019 to May 2023. The study results revealed that soil microbial biomass, as well as soil moisture, floor mass, and plant roots, showed an apparent single-hump modal within one year. In the comparative analysis of the soil microbial biomass fluctuation amplitudes across control and watered plots, a discernible disparity was observed, indicating significant differences in microbial biomass dynamics between the respective experimental conditions. The pooled data revealed a statistically significant influence of seasonal drought, floor mass, plant roots, and their reciprocal interactions on the soil microbial biomass, highlighting these factors as pivotal determinants of microbial community dynamics. This study elucidates the interactive regulatory mechanisms by which seasonal drought, floor mass, and plant roots collectively modulate soil microbial biomass within tropical and subtropical forests, offering insights into the complex ecological processes governing microbial community dynamics. This interactive regulation might influence the trajectory of plant species and soil microbial communities, facilitating their adaptive development and evolutionary responses.

Liana versus tree seedling responses to spatial and temporal variation in dry season severity

AbstractLianas are key components of tropical forests, particularly at sites with more severe dry seasons. In contrast, trees are more abundant and speciose in wetter areas. The seasonal growth advantage (SGA) hypothesis postulates that such contrasting distributions are produced by higher liana growth relative to trees during seasonal droughts. The SGA has been investigated for larger size classes (e.g., ≥5 cm diameter at 1.3 m, dbh), but rarely for seedlings. Using eight annual censuses of &gt;12,000 seedlings of 483 tree and liana species conducted at eight 1‐ha plots spanning a strong rainfall gradient in central Panama, we evaluated whether liana seedlings had higher growth and/or survival rates than tree seedlings at sites with stronger droughts. We also tested whether an extreme El Niño drought during the study period had a more negative effect on tree compared to liana seedlings. The absolute density of liana seedlings was similar across the rainfall gradient, ranging from 0.32 individuals/m2 (0.20–0.49, 95% credible interval [CI]) at the driest end of the gradient and 0.27 individuals/m2 (0.13–0.51 95% CI) at the wettest end of the gradient. The relative density of liana seedlings compared to tree seedlings was higher at sites with stronger dry seasons (0.27, 0.21–0.33, 95% CI), compared to wetter sites (0.12, 0.04–0.20 95% CI), due to lower tree seedling densities at drier sites. However, liana seedlings did not grow or survive better than tree seedlings in drier sites compared to wetter sites. Tree seedlings were more negatively impacted in terms of mortality by the extreme El Niño drought than liana seedlings, with an increase in annual mortality rate of 0.013 (0.003–0.025 95% CI) compared to lianas of −0.009 (−0.028 to 0.008 95% CI), but not growth. Our results indicate that lianas do not have a SGA over trees at the seedling stage. Instead, higher survival of liana versus tree seedlings during severe droughts or differences in liana versus tree fecundity or germination across the rainfall gradient likely explain why liana seedlings have higher relative densities at drier sites.

Early field performance of three planted Inland Northwest conifer species: Effects of root growth potential, morphology, and environmental conditions

A common concern to planting for reforestation is seedling failure that is directly measurable by seedling early field performance of growth and survival. Root growth potential (RGP) is a commonly used metric of seedling quality and has been considered indicative of seedling field performance. The effect of RGP is thought to be dependent on planting site and underlining environmental conditions. Moisture stress often is considered the primary cause of seedling failure in addition to other environmental factors such as soil physicochemical properties in regions such as the Inland Northwest of the United States that is prone to growing season drought. In addition, it is interesting to test whether seedling early field performance is related to their morphological attributes and whether the morphological attributes are related to RGP. A comprehensive evaluation on early field performance of three planted conifer species of interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco), grand fir (Abies grandis (Douglas ex D. Don) Lindl.), and western larch (Larix occidentalis Nutt.) was conducted in this study. It was found that RGP did not show clear correlation with early field performance across species. RGP also was not significantly correlated with seedling morphological measures such as below- and above-ground biomass and root-to-shoot ratio (R:S, by mass). Early field performance of growth and survival varied greatly across individuals of seedlings. The most influential predictors of early seedling growth and survival were their initial size (indicative of energy reserve) and soil temperature that likely interacted with soil moisture. Our findings suggest that seed stock selection for reforestation probably should favor species and genotypes with greatest heat tolerance that may be better adapted to future conditions in the region.

Spatio-temporal variation of meteorological, hydrological and agricultural drought vulnerability: Insights from statistical, machine learning and wavelet analysis

The study of how agricultural drought (AD) is responsible for meteorological drought (MD) and hydrological drought (HD) is crucial for drought prevention and the socio-economic development of a nation. This is due to AD constitutes a significant threat to the nation's food productivity and security. In depth comprehension and mitigation of drought incidents depend on understanding their frequency and propagation patterns. In this study, spatio-temporal variation of three types of droughts have been assessed in the sub-tropical environment of eastern India. In this perspective, seasonal i.e., pre-monsoon, monsoon, post-monsoon, and winter MD, HD, and AD were assessed considering Standardized Precipitation Index (SPI), Standardized Water Level Index (SWI), and Standardized Soil Moisture Index (SSMI) statistical tool respectively in sub-tropical agro-climatic zone of eastern India. In addition to this, spatial drought vulnerability of MD, HD and AD was assessed using Analytic Hierarchy Process (AHP) considering suitable factors for each drought type, and overall drought vulnerability was assessed using “Random Forest (RF)” and “Artificial Neural Network (ANN)” methods. Furthermore, drought periodicity has been measured using a wavelet power spectrum analysis. The result of seasonal drought revealed that pre-monsoon season has more frequent drought occurrences than other seasons among the applied three types of droughts. The outcomes of overall drought vulnerability revealed that RF gives the optimum result followed by ANN i.e., 0.841 and 0.828, respectively, for validation purposes. The periodicity of drought ranges from 0.25 to 4 as obtained from wavelet analysis. In general, this research on how AD spreads from MD and HD is crucial for drought resilience, drought management, and food security among the stakeholders and policymakers for achieving the SDGs.

METEOROLOGICAL DROUGHT DEVELOPMENTS IN THAI BINH PROVINCE IN THE CONTEXT OF CLIMATE CHANGE

This article presents the frequency and trends of meteorological drought in Thai Binh province for the period 1991-2021 and forecasts drought trends for the period 2025-2065 based on climate change scenarios. The PED drought index is calculated using the corresponding daily temperature and rainfall data for each of these periods. The results indicate that meteorological drought in Thai Binh can occur in both the dry and rainy seasons. During the period from 1991 to 2021, medium drought occurred in the dry season nearly once every ten years. Drought occurrences in both the rainy and dry seasons show an increasing trend in intensity and the number of drought months. In the future, during the period from 2025 to 2065, dry season drought will fluctuate less under the RCP4.5 scenario but will sharply increase in frequency and intensity under the RCP8.5 scenario. In the rainy season, drought is projected to increase in both scenarios. The number of drought months is relatively high and will rise significantly in both RCP4.5 and RCP8.5 scenarios. A notable aspect of this study is the analysis of meteorological drought trends for the period 2025-2065, based on climate change scenarios.

Temporal-spatial characteristics of climate drought and its effects on grain yield in Hunan Province, China

The examination of the spatiotemporal characteristics and developmental trends of drought is crucial for enhancing water resource management, bolstering drought resistance, and improving disaster prevention capabilities. This study employs the Standardized Precipitation Evapotranspiration Index (SPEI) and grain yield data across various time scales, in conjunction with methodologies such as Run Theory, Mann-Kendall, and Standardized Yield Residual Series, to conduct an in-depth investigation into the spatiotemporal variation characteristics of meteorological drought in Hunan Province and its impact on grain yield. The findings suggest that: (1) Since 1960, the likelihood of seasonal drought occurrence in Hunan Province has been ranked as autumn &amp;gt; winter &amp;gt; spring &amp;gt; summer, with mild drought occurring most frequently, followed by moderate drought, while the frequency of severe and extreme drought remains low. (2) Meteorological drought in Hunan Province exhibits spatial differences at the seasonal scale, with the overall drought changes in spring and summer displaying a non-significant upward trend; the western and southern regions exhibit a trend of aridification in autumn; and in winter, the Zhangjiajie and Xiangxi regions show an insignificant downward trend. (3) From 1960 to 2022, grain production in Hunan Province has demonstrated a pattern of fluctuation and increase. The meteorological yield of grain crops displays a high-low-high spatial distribution from south to north. Concurrently, there is a positive correlation between short-term climate change and meteorological output, while long-term climate change is not evident. (4) El Niño Southern Oscillation (ENSO) is a significant circulation factor affecting meteorological drought in Hunan Province, and the meteorological drought in autumn and winter in Hunan Province is significantly influenced by ENSO. The research findings can provide reference significance and a scientific basis for drought research and comprehensive management in Hunan Province, and offer data and theoretical support for promoting economic development.

Seasonal shifts in depth-to-water uptake by young thinned and overstocked lodgepole pine (Pinus contorta) forests under drought conditions in the Okanagan Valley, British Columbia, Canada

Abstract. As drought and prolonged water stress become more prevalent in dry regions under climate change, preserving water resources becomes a focal point for maintaining forest health. Forest regeneration after forest loss or disturbance can lead to overstocked juvenile stands with high water demands and low water-use efficiency. Forest thinning is a common practice with the goal of improving tree health, carbon storage, and water use while decreasing stand demands in arid and semi-arid regions. However, little is known about the impacts of stand density on seasonal variation in depth-to-water uptake or the magnitude of the effect of growing season drought conditions on water availability. Existing reports are highly variable by climatic region, species, and thinning intensity. In this study, stable isotope ratios of deuterium (δ2H) and oxygen (δ18O) in water collected from various soil depths and from branches of lodgepole pine (Pinus contorta) under different degrees of thinning (control: 27 000 stems per hectare; moderately thinned: 4500 stems per hectare; heavily thinned: 1100 stems per hectare) over the growing season were analyzed using the MixSIAR Bayesian mixing model to calculate the relative contributions of different water sources in the Okanagan Valley in the interior of British Columbia, Canada. We found that under drought conditions the lodgepole pine trees shifted their depth-to-water uptake through the growing season (June to October) to rely more heavily on older precipitation events that percolated through the soil profile when shallow soil water became less accessible. Decreased forest density subsequent to forest thinning did not cause a significant difference in the isotopic composition of branch water but did cause changes in the timing and relative proportion of water utilized from different depths. Thinned lodgepole pine stands were able to maintain water uptake from 35 cm below the soil profile, whereas the overstocked stands relied on a larger proportion of deep soil water and groundwater towards the end of the growing season. Our results support other findings by indicating that, although lodgepole pines are drought-tolerant and have dimorphic root systems, they do not shift back from deep water sources to shallow soil water when soil water availability increases following precipitation events at the end of the growing season.

A Multiscalar Standardized Vapor Pressure Deficit Index for Drought Monitoring and Impacts

ABSTRACTVapour pressure deficit (VPD) is a critical measure of the atmospheric demand for water and can be used to assess short‐term and seasonal drought. To provide for probabilistic comparisons of VPD across space and time, we develop a Standardized Vapor Pressure Deficit Index (SVPDI). Similar to the way that other standardised drought indices are used, SVPDI allows for the analysis and comparison of changes in VPD across regions with different base level VPD values. It also should be useful for analysing impacts on vegetation that has varying levels of adaptation to high VPD. We use 1‐, 3‐, 6‐ and 12‐month timescales for the development of SVPDI and show that the gamma distribution is superior to other zero‐limited probability distributions for analysing VPD and, therefore, for calculating SVPDI. Then, focusing on the short‐term variations at the 1‐ and 3‐month timescales, we show how SVPDI has changed globally from 1958 to 2023 and how those changes differ from those of the commonly used Standardized Precipitation Evaporation Index (SPEI). We find that SVPDI shows more widespread drying conditions that also are larger in magnitude compared to those of SPEI. Although the two indices are moderately well correlated across the terrestrial surface, we discover that they are more decoupled in humid and arid regions compared to dry sub‐humid and semi‐arid regions. Using four locations that have recently experienced severe drought, we find that SVPDI generally showed longer drought duration and more severe drought events in the last decade when compared to SPEI.

Transgressive segregation and generation mean analysis reveal the gene action underlying the inheritance of drought tolerance in rice

Climate change, an effective driver of unprecedented seasonal droughts, is greatly affecting rice production in Africa by threatening food security and safety. Rice, one of the major staple crops on the continent, can save the situation through the development of drought-tolerant cultivars, presenting a major challenge for future rice improvement programs as drought is regarded as a critical limitation in rain-fed ecosystems. This study sought to understand the genetic basis and inheritance behind the expression of tolerance of rice breeding lines to drought-stress through generation mean analysis. To achieve these objectives, two drought-sensitive genotypes (Jasmine 85 and CRI-Agrarice) were crossed with a drought-tolerant genotype (APO) to develop six populations (F1, F2, BC1, BC2, P1 and P2) under screenhouse drought-stress and non-stress evaluation. Data were collected on grain yield and yield-related traits among which the generation mean analysis was conducted. At least one transgressive phenotype was produced in the F2 population for each trait whether there is a significant difference or not among the parental lines under drought-stress. Under non-stress conditions, there was a significance for all six types of gene action for days to flowering in both crosses. Among both crosses and water-regimes, additive x additive gene interaction was significant for most of the traits even though the scaling tests were not significant indicating the effectiveness of selection in early generations. Therefore, either forward breeding or backcross breeding can be adopted as breeding strategies for rapid improvement for these lines to drought tolerance.

Drought-Induced Alterations in Carbon and Water Dynamics of Chinese Fir Plantations at the Trunk Wood Stage.

Over the past three decades, China has implemented extensive reforestation programs, primarily utilizing Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) in southern China, to mitigate greenhouse gas emissions and counter extreme climate events. However, the effects of drought on the carbon sequestration capacity of these forests, particularly during the trunk wood stage, remain unclear. This study, conducted in Huitong, Hunan, China, from 2008 to 2013, employed the eddy covariance method to measure carbon dioxide (CO2) and water fluxes in Chinese fir forests, covering a severe drought year in 2011. The purpose was to elucidate the dynamics of carbon and water fluxes during a drought year and across multi-normal year averages. The results showed that changes in soil water content (-8.00%), precipitation (-18.45%), and relative humidity (-5.10%), decreases in air temperature (-0.09 °C) and soil temperature (-0.79 °C), and increases in vapor pressure deficit (19.18%) and net radiation (8.39%) were found in the drought year compared to the normal years. These changes in environmental factors led to considerable decreases in net ecosystem exchange (-40.00%), ecosystem respiration (-13.09%), and gross ecosystem productivity (-18.52%), evapotranspiration (-12.50%), and water use efficiency (-5.83%) in the studied forests in the drought year. In this study, the occurrence of seasonal drought due to uneven precipitation distribution led to a decrease in gross ecosystem productivity (GEP) and evapotranspiration (ET). However, the impact of drought on GEP was greater than its effect on ET, resulting in a reduced water use efficiency (WUE). This study emphasized the crucial role of water availability in determining forest productivity and suggested the need for adjusting vegetation management strategies under severe drought conditions. Our results contributed to improving management practices for Chinese fir plantations in response to changing climate conditions.

Plastic mulching enhances maize yield and water productivity by improving root characteristics, green leaf area, and photosynthesis for different cultivars in dryland regions

Uneven precipitation during the growing season and frequent seasonal droughts on the Loess Plateau in Northwest China adversely affect crop production and water use efficiency. While plastic mulching (PM) has been used to alleviate water stress, few studies have examined the traits maize cultivars need to adapt to the altered water environment under PM and achieve high yields. A two-year field experiment was conducted to assess the root characteristics and aboveground growth traits of three widely used high-yielding maize cultivars—Zhengdan 958 (ZD), Huanong 138 (HN), Heboshi 122 (HBS)—under no mulching (NM) and PM conditions. Among the three cultivars, HBS had the highest root system indices—root length density (RLD), root surface area density (RSD), and root biomass—in the topsoil (0–40 cm), followed by ZD and HN under both NM and PM conditions. Under NM, HBS_NM treatment exhibited strong water absorption, improving photosynthesis and yield, making it suitable for drought conditions. Under PM, topsoil moisture increased significantly, with root system indices increasing by 22.5–36.1 % for RLD, 30.2–36.1 % for RSD, and 25.2–36.5 % for root biomass across the cultivars compared to NM. While ZD_PM did not have the highest root system indices under PM, it exhibited higher green leaf area index (4.5–7.5 %), chlorophyll content (2.8–8.6 %), and photosynthetic rate (6.0–14.5 %), resulting in the highest aboveground biomass and yield among the treatments. These findings suggest ZD is better adapted to the enhanced soil moisture under PM. Future research should focus on breeding genotypes that thrive under PM conditions, emphasizing traits such as larger leaf areas and higher photosynthetic rates to boost crop productivity in rainfed areas.