PICO
This session invites contributions that explore how ecosystems and hydrological processes respond to droughts (hereafter referred to as drought responses), aiming to uncover both underlying mechanisms and broader consequences. We welcome studies based on observational, modeling, and conceptual approaches. Topics of interest include, but are not limited to:
1. New insights into drought responses based on emerging in-situ and satellite observations of soil moisture, evapotranspiration, and vegetation dynamics.
2. Process-based understanding of ecohydrological responses to droughts of varying severity under changing climate and land surface conditions.
3. Long-term trends and resilience of ecohydrological systems under recurrent droughts, with a focus on resistance, recovery, and key environmental drivers.
4. Advances in modeling frameworks (process-based or AI-based) and observation-constrained approaches for improving the representation of drought responses.
5. Social and ecological impacts of evolving droughts, including implications for ecosystems, agriculture, water resources, and human well-being.
By integrating hydrology, ecology, and remote sensing, this session seeks to advance our understanding of ecohydrological drought responses and to inform sustainable adaptation strategies in a changing environment.
Vapor pressure deficit (VPD) is widely used as a measure of atmospheric dryness and evaporative demand in drought studies, yet its interpretation as an independent drought driver remains unclear because of its close coupling to soil-moisture and radiation. Disentangling the atmospheric forcing from land-surface controls on VPD is essential for correctly diagnosing the drought responses, attributing ecohydrological impacts, and interpreting land–atmosphere feedbacks under water-limited conditions. Here, we present an analytical thermodynamic framework that mechanistically describes VPD as a function of observed radiative and surface-evaporative conditions, requiring no additional parameters. This formulation links VPD to variations in lower-atmospheric heat storage reflected in diurnal air temperature range (DTR) and saturation vapor pressure. The resulting analytical expression is decomposable and helps to disentangle the atmospheric and land-surface drivers of VPD. When applied over global land, the approach reproduces observed spatial and temporal variability in VPD with R2 of 0.9 and 0.8 respectively. It captures observed responses of VPD to solar radiation, clouds, and evapotranspiration across diverse climate and moisture regimes. Our results demonstrate that much of the variability in VPD during dry periods emerges as a thermodynamic response to surface water limitation rather than purely atmospheric forcing. This coupling provides a mechanistic basis for interpreting VPD as both a driver and an indicator of ecohydrological drought responses, with important implications for diagnosing drought stress, understanding land–atmosphere feedbacks, and improving projections of ecosystem vulnerability under climate change.
How to cite: Ghausi, S., Chauhan, T., and Kleidon, A.: Thermodynamic controls on vapor pressure deficit during droughts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3487, https://doi.org/10.5194/egusphere-egu26-3487, 2026.
The recent megadrought in the southwestern U.S. is the most severe in over a millennium, intensifying pressure on water resources and compromising ecosystem function. However, this megadrought is often diagnosed using indirect methods such as tree-ring reconstructions, which can be spatially biased and imperfect proxies of climatic conditions. Direct measurements of soil moisture provide quantitative records of soil water storage in the land surface, but it is only recently that the spatial and temporal scopes of these measurements have become large enough to diagnose the megadrought. By leveraging a dense network of in situ soil moisture measurements across depths, we quantified the trends in soil moisture during the megadrought and assessed its underlying drivers. The southwestern U.S. exhibited a pervasive drying trend of soil moisture during the megadrought, though there was significant spatial heterogeneity across basins. Reductions in mid-to-late season precipitation, along with widespread increases in VPD – vapor pressure deficit, were associated with long-term declines in soil moisture across all depths. Hydroclimate teleconnections were associated with soil moisture trends at larger spatiotemporal scales. Observed declines in soil moisture were not captured by a common microwave-based product but were better captured by gravimetry-based measurements. Our study highlights the importance of cool-season water inputs in the southwestern U.S., along with the future risks to water resources caused by rising VPD.
How to cite: Hu, J., Barnes, M., Pervin, R., and Kannenberg, S.: Hydroclimate-driven soil moisture declines during the North American megadrought, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15961, https://doi.org/10.5194/egusphere-egu26-15961, 2026.
Soil moisture is a key variable in land surface water and energy cycles, and passive microwave remote sensing inversion is one of the primary approaches for large-scale soil moisture monitoring. Although physically based models for passive microwave soil moisture retrieval have been well established, the inversion process still faces challenges due to the large number of model parameters, some of which are difficult to obtain. In particular, soil surface roughness and vegetation single-scattering albedo, which characterize soil and vegetation effects, cannot be directly measured. As a result, most existing retrieval methods adopt empirically fixed parameter values, neglecting their temporal variability. In this study, a simulated brightness temperature dataset combined with a probability density approach is used to estimate monthly soil roughness and vegetation single-scattering albedo over the Shandian River Basin based on multi-temporal brightness temperature observations. These time-varying parameters are then incorporated into passive microwave soil moisture retrieval and evaluated against in situ soil moisture measurements and the MCCA soil moisture product. The results indicate that (1) soil roughness and vegetation single-scattering albedo exhibit pronounced intra-annual variability; (2) when the temporal variability of these parameters is considered, the overall accuracy of the retrieved soil moisture is comparable to that of the MCCA product, with good agreement in summer and improved stability in winter, and the temporal variations are more consistent with ground-based observations; and (3) introducing time-varying parameters reduces the intra-annual differences in monthly mean soil moisture, primarily because part of the brightness temperature variability is explained by parameter changes rather than being entirely attributed to soil moisture variations. Overall, incorporating the time-varying characteristics of soil and vegetation parameters enhances the temporal performance of passive microwave soil moisture retrieval, and furnishes new insights for the refinement of associated inversion methods.
How to cite: Pang, Z., Qin, X., Jiang, W., and Lu, J.: Impact of Time-Varying Soil and Vegetation Parameters on Passive Microwave Soil Moisture Retrieval, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15928, https://doi.org/10.5194/egusphere-egu26-15928, 2026.
The Himalayan region is experiencing rapid hydroclimatic shifts, yet the physiological resilience of its dominant forest species remains poorly understood. Although Pinus roxburghii (Chir pine), one of the dominant species of the central Himalaya, covers 16% of the forest area, our understanding of its water-use strategies under compounding stress conditions such as low soil moisture (SM) and high vapor pressure deficit (VPD) is limited. Here, we investigated the hydro-physiological response of a Chir pine-dominated forest in the Kumaun Himalayas (Almora, India) using continuous Thermal Dissipation Probe (TDP) measurements over 304 days. By integrating sap-flux-derived transpiration with daily environmental data, we quantified tree water regulation across dormant and growing seasons. Efforts are also made to enhance our knowledge of the behavior of Chir-pine under water stress conditions, which was quantified by isolating 50th percentile thresholds (SM < 0.13 m³ m⁻³; VPD > 0.76 kPa) of the stress conditions. Our analysis reveals a significant seasonal variation in hydraulic sensitivity. During the growing season, mean sap flow (812.4 cm³ h⁻¹) was notably higher than during the dormant season (513.9 cm³ h⁻¹) driven by peak photosynthetic demand. We also found that SM emerged as the key determinant of Himalayan Chir-pine transpiration, while VPD did not have any such signatures. However, trees maintained high flux under isolated atmospheric drought (high VPD, high SM); the transition to combined stress triggered a sharp, non-linear decline in sap flow. This indicates an isohydric strategy of Chir-pine, where strong stomatal regulation prioritizes the prevention of xylem embolism over carbon gain during the environmental stress. This study provides the first mechanistic baseline for scaling tree-level hydraulics to forest-stand water balances in the Central Himalayas, offering critical insights for predicting regional forest water security under a changing climate.
How to cite: Bohra, K., Lohani, P., and Mukherjee, S.: Seasonal Sap Flow Dynamics Under Variable Water Stress in a Himalayan Chir Pine (Pinus roxburghii) Forest, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18809, https://doi.org/10.5194/egusphere-egu26-18809, 2026.
In arid regions, precipitation is scarce and predominantly occurs as pulsed rainfall events. These events alter both atmospheric and soil moisture conditions, thereby obscuring the dominant controls on plant water transport and making their role in replenishing vegetation water use unclear. We isolated the direct atmospheric pathway by excluding infiltration beneath canopies and quantified organ-level sap flow responses of Haloxylon ammodendron and Tamarix ramosissima to controlled rainfall applied in the morning, afternoon and at night (2, 6 and 10 mm) in the Ulan Buh Desert (June–August). Sap flow of primary branches, main trunks and root system was measured with heat-balance sensors and analysed against meteorological drivers using partial correlations and random-forest models. Responses were strongly time dependent: nighttime rainfall events most readily induced reverse flow, with larger magnitudes in H. ammodendron (e.g. −29.7 g·h-1 in stems; −5.2 g·h-1 in roots). Optimum rainfall amount differed by species: by day, reversals required ≈6 mm in H. ammodendron but ≈10 mm in T. ramosissima; at night, ≈2 mm versus ≈6 mm, respectively. Aboveground organs of T. ramosissima responded sooner (trunk 19 min; branch 21 min) than those of H. ammodendron (≈23 min), whereas root system of H. ammodendron responded earlier (38 min vs. 43 min). Photosynthetically active radiation was the dominant meteorological driver of sap flow in both species and exerted a stronger overall effect in T. ramosissima. Our results demonstrate that small, well-timed nighttime pulses can transiently reverse xylem flow via the atmospheric pathway, with species-specific optimum rainfall amount. This insight carries practical implications for the scheduling of restoration efforts in desert oases, particularly when incorporating considerations of water resource carrying capacity and planting density.
How to cite: Yuan, Z., Cheng, Y., and Chu, L.: Dissecting reverse sap flow in desert shrubs: effects of event timing, rainfall thresholds and species, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4391, https://doi.org/10.5194/egusphere-egu26-4391, 2026.
Saline lakes on the Qinghai–Tibet Plateau (QTP) affect the regional climate and water cycle through water loss (E, evaporation under ice–free and sublimation under ice–covered conditions). Due to the observation difficulty over lakes, E and its underlying driving forces are seldom studied targeting saline lakes on the QTP, particularly during the ice–covered periods (ICP). In this study, The E of Qinghai Lake (QHL) and its influencing factors during the ice–free periods (IFP) and ICP were first quantified based on six years of observations. Subsequently, three models were calibrated and compared in simulating E during the IFP and ICP from 2003 to 2017. The annual E sum of QHL is 768.58 ± 28.73 mm, and the E sum during the ICP reaches 175.22 ± 45.98 mm, accounting for 23% of the annual E sum. E is mainly controlled by the wind speed, vapor pressure difference, and air pressure during the IFP, but is driven by the net radiation, the difference between the air and lake surface temperatures, wind speed, and ice coverage during the ICP. The mass transfer model simulates lake E well during the IFP, and the model based on energy achieves a good simulation during the ICP. Moreover, wind speed weakening resulted in an 7.56% decrease in E during the ICP of 2003~2017. Our results highlight the importance of E in ICP, provide new insights into saline lake E in alpine regions, and can be used as a reference to further improve hydrological models of alpine lakes.
How to cite: Shi, F.: Evaporation and sublimation measurement and modelling of an alpine saline lake influenced by freeze–thaw on the Qinghai–Tibet Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10423, https://doi.org/10.5194/egusphere-egu26-10423, 2026.
Drought depletes water resources and can trigger substantial productivity losses and plant mortality. However, predicting drought impacts on water resources and ecosystem functioning remains difficult because evapotranspiration (ET) responses are highly uncertain. The sign and magnitude of drought-induced ET anomalies affect not only the water balance, but also land-atmosphere interactions and drought progression. Atmospheric drying (high vapor pressure deficit, VPD) can enhance ET, whereas soil moisture (SM) depletion suppresses soil evaporation and plant transpiration via stomatal regulation. Therefore, drought ET responses emerge from competing constraints imposed by atmospheric demand and moisture supply. Here we quantify how VPD and SM jointly control growing-season drought ET anomalies across hydroclimatic regimes in China using satellite remote sensing, physics-constrained machine learning ET estimations, and hydro-meteorological reanalysis data. ET is derived by coupling the Penman–Monteith framework with machine learning, yielding estimates that have been extensively validated and shown to perform robustly under data-limited conditions and during drought events. We then characterize the sign and magnitude of ET anomalies during drought by jointly considering meteorological, hydrological, and ecological drought metrics. Then, we disentangle the contribution of atmospheric demand and moisture supply constraints on ET anomalies based on the percentile binning method (assuming weak VPD and SM dependence in their short intervals), thereby distinguishing water demand-limited from water supply-limited regimes. The enhancement driven by atmospheric drying dominates in water demand-limited regions, while the suppression driven by soil moisture deficit prevails in water supply-limited regions, and both vary along dry-wet gradients. Finally, using an explainable machine learning approach (SHAP), we diagnose multiyear changes in these controls. We find regime-dependent trends with opposite signs: the positive VPD effect on drought ET anomalies declines in demand-limited regions, whereas the negative SM effect becomes less negative in supply-limited regions. These opposite-sign trends are primarily associated with evolving air-temperature and soil-moisture anomaly patterns, highlighting non-stationary drought controls on ET across China’s hydroclimatic regimes.
How to cite: Zhang, C., Shi, Z., Wang, S., and Zheng, Z.: Opposite shifts in drought-season evapotranspiration controls across hydroclimatic regimes in China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16585, https://doi.org/10.5194/egusphere-egu26-16585, 2026.
Evapotranspiration (ET) is a key variable in both the global carbon and water cycles, and its response to land use and land cover change (LUCC) remains a critical issue for climate modeling and sustainable water resource management. Existing studies have largely focused on the combined impacts of vegetation parameters—such as leaf area index (LAI), land cover type, reflectance, and emissivity—on ET, while the independent contributions of individual vegetation structural and physiological parameters have received limited attention. In this study, we employed a scenario-controlled experiment using the coupled carbon–water process model PML-V2 to disentangle and quantify the effects of different vegetation parameters on interannual ET variability across China from 2001 to 2020. Results demonstrate that PML-V2 effectively captures the independent driving effects of vegetation parameters on ET dynamics. Among these, LAI emerged as the dominant biophysical driver, increasing ET at a national average rate of 0.68 mm yr⁻¹, whereas land cover type changes exerted a minor negative effect (-0.04 mm yr⁻¹). Spatially, LAI-driven increases in ET were pronounced in northern China but slightly declined in the south. Other vegetation parameters exhibited negligible effects. In terms of contributions to ET variability, LAI explained the largest fraction (36%), followed by climate forcing (35%) and atmospheric CO₂ concentration (26%). These findings underscore the importance of accounting for the differentiated roles of vegetation parameters in future LUCC and ecological restoration strategies, particularly in water-limited northern China, to achieve a balance between ecological restoration and long-term water sustainability.
How to cite: Li, C. and Zhang, Y.: Vegetation change impact on the actual Evapotranspiration in China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15686, https://doi.org/10.5194/egusphere-egu26-15686, 2026.
Soil-atmosphere compound drought, characterized by concurrent low soil moisture (SM) and high vapor pressure deficit (VPD), poses an increasingly severe threat to terrestrial carbon sinks. Although vegetation can tolerate mild drought through physiological responses, extreme drought could still cause irreversible damage, leading to significant declines in ecological functions. However, the critical tipping points triggering ecosystem transitions from resistance to vulnerability remain poorly quantified. Here, we developed a data-driven framework to identify nonlinear response thresholds of vegetation to compound drought across China and assessed associated impacts on gross primary production (GPP) under CMIP6 scenarios. Using observations from 2001 to 2020, we found that vegetation response was not linearly related to drought occurrence; instead, a distinct drought threshold exists (mean compound drought index percentile of approximately 14.1%). Dropping below this threshold triggers a transition from resistance to vulnerability (termed ecological drought), causing a precipitous collapse in photosynthetic function where average GPP anomalies plummeted from -0.84 to -4.57 gC m⁻² mon⁻¹. Future projections (2081–2100) confirm that this threshold-driven vulnerability persists, with ecological droughts projected to occur more frequently across over 56% and 61% of vegetated areas under the two respective emission scenarios. Critically, our cross-scenario comparison reveals that the magnitude of GPP losses is governed by drought intensity rather than frequency alone. Under the high-emission SSP5-8.5 scenario, drought intensity dominates in 55.9% of the vegetated area, accelerating at a relative rate 2.32 times that of frequency. This rapid intensification drives greater average GPP losses (-28.17 ± 23.48 gC m⁻² mon⁻¹) compared to the lower-emission path (-24.59 ± 18.23 gC m⁻² mon⁻¹), resulting in higher total GPP losses (-236.53 ± 198.56 versus -199.05 ± 162.59 gC m⁻²). These findings demonstrate that drought intensity overrides frequency as the primary driver constraining terrestrial carbon uptake.
How to cite: Cheng, Y. and Liu, L.: Soil-atmosphere compound drought intensity overrides frequency in constraining future carbon uptake across China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17713, https://doi.org/10.5194/egusphere-egu26-17713, 2026.
Rivers, as an important source of CO2 emissions, release substantial amounts of CO2 into the atmosphere through gas exchange at the water-air interface, profoundly influencing the global carbon cycle. In recent years, frequent drought events driven by global climate change have markedly impacted aquatic ecosystems. Hydrological drought, identified by prolonged low river discharge, can disrupt the transport and decomposition of organic matter, leading to pronounced effects on riverine CO2 emissions. Nonetheless, the magnitude of this drought-induced alteration in CO2 emission fluxes is still not fully understood. In this study, we investigated riverine CO2 emissions in the Yangtze River networks, China, from 1979 to 2019 using the boundary layer method. We quantified the impact of hydrological droughts on riverine CO2 emissions from the perspective of river classification. Results showed that hydrological droughts reduced CO2 evasion by approximately 33% compared to non-drought periods. Specifically, CO2 emission flux declined by 18.91%, 25.06%, 31.43%, and 43.22% under mild, moderate, severe, and extreme drought, respectively. River width contraction was identified as the dominant mechanism driving drought-induced reductions in CO2 emissions. Our results showed that lower-order rivers exhibited larger CO2 emission declines, while higher-order rivers showed smaller reductions. This study contributes to a more comprehensive understanding of the impact of hydrological droughts on riverine CO2 emissions, while also providing useful insights for riverine carbon flux dynamics.
How to cite: Wang, Z., She, D., and Liu, S.: Quantify the impact of hydrological droughts on carbon dioxide emission from the Yangtze River networks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6872, https://doi.org/10.5194/egusphere-egu26-6872, 2026.
Flash droughts, characterized by rapid onset and increasing frequency, pose significant threats to ecosystem stability and function. However, there remains no global consensus regarding forest responses to flash droughts. Here, using a reconstructed global high spatiotemporal resolution Standardized Precipitation-Evapotranspiration Index dataset and an interpretable machine learning framework, we find that global forests have experienced increasingly rapid, intense, and prolonged flash droughts over the past four decades. Managed forests are more prone to browning from flash droughts than intact forests due to their limited capacity to acclimate to rapid drought stress driven by extreme heat. Notably, our meta-analysis confirms that current forest management practices, designed to maximize ecosystem services, exacerbate the vulnerability of managed forests to flash droughts globally. Our findings highlight the escalating risks posed by increasingly frequent and prolonged flash droughts to managed forests, underscoring the urgent need to integrate resistance and resilience to extreme climatic events into forest management strategies.
How to cite: Xu, H., Zhang, Z., Xu, Y., and Pang, J.: Flash droughts threaten global managed forests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15920, https://doi.org/10.5194/egusphere-egu26-15920, 2026.
In recent decades, compound drought and heat-extreme (CDHE) events have garnered attention due to their amplified impacts on the food-energy-water nexus. In comparison to individual extremes, these short-duration compound events severely impede the terrestrial ecosystem, leading to perpetual damage, yield loss, and mortalities. During these events, plants experience xylem embolism, resulting in a reduced water transport capacity. Alongside, elevated heating intensifies the hydric stress resulting from soil dryness through cascading land-atmosphere interactions. This results in rising leaf-level evaporative demand and canopy temperature, driving stomatal closure, which in turn reduces carbon uptake and increases desiccation. However, the impact of these extreme events varies across plant-functional-types (PFTs), primarily due to differences in hydraulic and carbon-economy traits. On the other hand, plants can adjust their thermal tolerance, structure, and stomatal sensitivity by experiencing frequent perturbances; such acclimation alters their later responses. Therefore, there is not only a need to understand how terrestrial ecosystems varyingly respond to CDHE events, but it is also essential to investigate whether there are any temporal changes in their response.
In this study, we use rootzone soil moisture from GLEAM and near-surface air temperature from ERA-5 to identify CDHE events that persist for at least 5 consecutive days during the growing season during 2001-2021 globally. Then, we estimate the resistance and resilience of four distinct PFTs in the context of CDHE. These are: forests (woody), shrublands (non-forest-woody), grasslands (non-woody and natural), and croplands (non-woody and managed). We estimated resistance as the ratio between normalised loss (maximum perturbation in vegetation) and tolerance period (the time taken to reach maximum perturbation from its onset). Resilience is articulated as the recovery rate up to the pre-drought level following the tolerance period. For this purpose, we have acquired daily gridded datasets of gross primary productivity (GPP) and evapotranspiration (ET) from X-BASE and estimated the ecosystem water-use efficiency (WUE). It represents the coupled carbon-water exchange of vegetation at ecosystem-level. Since it is a flux ratio rather than a structural or radiometric index, it captures changes in plant function under environmental stress in ways that greenness metrics cannot. Under drought or heatwaves, ET declines faster than GPP in water-limited regions, resulting in momentary increases in WUE, followed by sharp decline as stress continues to increase. This bidirectional sensitivity is beneficial for analysing stomatal behaviour. Earlier studies have reported that WUE spontaneously responds to stomatal regulation and is also able to capture stress signals across woody and non-woody vegetation.
Outcomes of this study exhibit significant changes in ecosystem resistance and resilience during the last two decades; however, the magnitude of alterations varies across PFTs. During the period of tolerance and recovery, changes in WUE can result from physiological adjustments that alter photosynthesis per unit water loss, and changes in surface partitioning that alter the fraction of ET attributable to plants. Thus, we also evaluate the contribution of physiological coupling and hydrological partitioning (between vegetation and non-vegetative evaporation) in WUE alterations during tolerance and recovery periods, and found that these contributions also exhibit significant temporal changes.
How to cite: Gupta, A. and Lanka, K.: Temporal changes in Ecosystem Resistance and Resilience to Compound Drought and Heat Extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-903, https://doi.org/10.5194/egusphere-egu26-903, 2026.
Compound heat and drought events pose severe challenges to crop growth and development through antagonistic and additive effects. In the Huang-Huai-Hai Plain, summer maize specifically encounters "dual water-heat stress" as its growing season overlaps with peak hazard periods. However, while the spatial patterns of compound events are evolving, existing studies predominantly adopt a static perspective and rely on meteorological indices, thereby overlooking direct root-zone water constraints and lacking the analysis of dynamic migration trajectories over long-term sequences. To address this, our study focuses on the core summer maize production region of China—the Huang-Huai-Hai Plain. Based on daily root-zone soil moisture and air temperature data during the growing seasons from 1980 to 2020, we constructed a Compound Heat and Drought Event (CHDE) index by substituting traditional meteorological indices with the Soil Moisture Deficit Index (SMDI)—which better reflects root-zone water stress—combined with the Temperature Condition Index (TCI). This study targets daily-scale compound events and analyzes their spatiotemporal characteristics. Building upon static analysis, we introduced a Barycenter Migration to establish a dynamic spatiotemporal analysis framework, tracking evolutionary trajectories across three dimensions: Frequency, Duration, and Severity. Results indicate that the negative correlation between root-zone soil moisture and high temperature follows a "weak-strong-weak" evolution throughout the growing season; the jointing-tasseling (V6-VT) stage exhibits the strongest negative correlation, highest hazard severity, and most frequent occurrence, thus being identified as the critical phenological stage. Spatially, hazard hotspots demonstrate a distinct "central-to-south" migration during crop development, shifting from the central plains during the vegetative growth stage to the southern regions during the reproductive growth stage, with the timing of occurrence expanding toward earlier growth stages. The exposure to compound events experienced a trough in the 1990s, reversed from a decreasing to an increasing trend around 2000, and underwent a abrupt change in 2011–2012. Notably, approximately 60% of the region showed an increase in frequency over the last two decades, exhibiting a distinct spatial asymmetry: increases were primarily concentrated in the southern plains (e.g., Henan, northern Anhui), whereas the northern regions (e.g., Hebei, northern Shandong) were characterized mainly by decreases or stability .Through the spatiotemporal analysis of compound events, this study reveals the evolutionary patterns and regional heterogeneity of compound stress during the summer maize growing stage in the Huang-Huai-Hai Plain, providing a scientific basis for formulating maize irrigation strategies.
How to cite: Mi, L., Zhang, C., and Huo, Z.: Spatiotemporal Evolution and Migration of Compound Heat and Drought Events during the Summer Maize Growing Season in the Huang-Huai-Hai Plain, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8633, https://doi.org/10.5194/egusphere-egu26-8633, 2026.
Droughts are Europe’s costliest natural disasters, with damages estimated at 621 million Euros per event. Changing precipitation patterns and rising atmospheric water demand are increasingly affecting terrestrial ecosystem functioning in Europe, with profound implications for sustainable water resources management and ecosystem carbon uptake. However, responses are driven not only by drought type and severity but also by diverse land surface properties, including soil texture and vegetation functional traits. A clear understanding of how water deficits propagate to inhibit ecosystem functioning is needed to assess drought risk for specific ecosystems under a warming climate. This study uses Community Land Model v5 (CLM5) simulations over Europe from 1960 to 2024 to identify drought events as spatiotemporal clusters and to systematically determine their propagation across hydrological compartments (e.g., from precipitation to root-zone soil moisture) and their impacts on gross primary production (GPP) and transpiration (T). We find that precipitation droughts often propagate into soil moisture droughts, especially during large-scale droughts, such as in the years 1995, 2003, and 2018. However, soil moisture droughts can also emerge even when precipitation deficits are not typically classified as drought events, for example, when vapor pressure droughts increase evaporation over a prolonged period. Further, we compare trends of drought characteristics and show increasing dynamics in the propagation of vapor pressure droughts and increasing severity of soil moisture droughts. These anomalies interact across multiple time scales to drive a wide, though predominantly negative, range of GPP and T responses: Short-term anomalies can already cause significant impacts on dry ecosystems and grasslands, while having only minor effects in humid ecosystems. These results are essential for understanding ecosystem-specific impacts during discrete drought events and for identifying ecosystems whose functioning is under increased risk as drought frequency and severity increase under climate change in Europe, essentially supporting EU Adaptation Strategy and the Water Framework Directive.
How to cite: Poppe Terán, C., Naz, B. S., Belleflamme, A., Shrestha, P. K., Rahmati, M., Vereecken, H., and Hendricks-Franssen, H.-J.: Drivers of propagation and impacts of meteorological and agricultural droughts across Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12460, https://doi.org/10.5194/egusphere-egu26-12460, 2026.
The response mechanisms of vegetation to drought vary significantly depending on both drought and vegetation types. Clarifying the propagation process from meteorological drought (MD) to agricultural drought (AD) and its impact on vegetation is of great significance for ecological barrier protection in China. Focusing on the sub-humid and semi-arid regions of Northern China, this study analyzes the time effect and driving factors of vegetation response to MD and AD, while quantifying the drought propagation time (DPT) during 1982–2020. The results indicate that: (1) Across the study area, MD response follows a "short lag-short cum" pattern, while AD exhibits "long lag-short cum" pattern. Compared to sub-humid regions, all vegetation types and forest sub-types in semi-arid regions show a "high sensitivity-high tolerance" pattern toward MD, while exhibiting a "delayed response-low tolerance" pattern toward AD. (2) Regarding MD, shrubland is the most sensitive, while grassland exhibits the highest tolerance; additionally, the drought tolerance of needleleaf forests exceeds that of broadleaf forests. Regarding AD, forests show the highest sensitivity and the strongest tolerance, with broadleaf forests responding more rapidly than needleleaf forests. (3) Significant soil hydrological buffering exists, with 51.8% of vegetation and 53.4% of forest regions exhibiting an 8–9 month DPT. Semi-arid response patterns align with the whole study area (grassland < forest < cropland < shrubland). Broadleaf is consistently shorter than needleleaf across the entire study area, as well as in sub-humid and semi-arid regions. (4) Among the driving factors of vegetation response to drought, temperature (TMP), precipitation (PRE), potential evapotranspiration (PET), and vapor pressure deficit (VPD) rank as the top three in importance. TMP dominates the lagged effects of vegetation response to both MD and AD, whereas PRE determines the cumulative effects for both drought types.
How to cite: Liu, J., Wang, P., Guo, R., Zhang, Z., Cao, W., Liu, Y., and Yuan, Y.: Vegetation Response to Meteorological and Agricultural Drought and Drought Propagation Characteristics in the Sub-Humid and Semi-Arid Regions of Northern China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4805, https://doi.org/10.5194/egusphere-egu26-4805, 2026.
Assessing water conservation functions is critical for sustainable water resource utilization under the changing climate. Spatiotemporal variations of water conservation capacity, driven by climate change and human activities, cause regional socio-economic disparities, yet existing methods fail to accurately characterize factor interactions and are limited to single underlying surfaces, reducing global applicability. To address this, this study integrates the Water Conservation Index (WCI) and geographic detector to evaluate 1985–2022 long-term dynamic changes of water conservation capacity and its driving factors in China's Yellow River Water Conservation Area with complex underlying surface and severe climate change, improving large-scale research reliability. Results show an abrupt 2000 shift in capacity, decline then rise, consistent with climate change; it displays a south-high-north-low pattern, consistent with soil water content (SWC). SWC dominates spatial distribution, followed by ET, LST, and LAI yet precipitation drives SWC. Two-factor interactions between SWC and ET exceed single-factor effects. Post-2000, land use change, urban expansion, and GDP growth boosted FVC and thereafter capacity. These findings provide a theoretical and methodological foundation for water conservation protection under complex conditions, and scientific support for water resource allocation and climate change adaptation policies, facilitating global sustainable development.
How to cite: Zhao, C.: Spatiotemporal Dynamics and Driving Factors of Water Conservation Capacity in China's Yellow River Water Conservation Area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4719, https://doi.org/10.5194/egusphere-egu26-4719, 2026.
The Yellow River Basin (YRB) is an important ecological corridor in northern China, which has undergone substantial changes in multiple eco-hydrological processes. Such changes may decouple carbon, water and energy within ecosystem and cause substantial eco-hydrological risks. In this study, changes in key eco-hydrological variables are investigated and general associtions of evolution trends are revealed by correlation-based networks. Causal networks are then used with physical constraints, to quantitatively portray the directions and magnitudes of eco-hydrological feedbacks. A new index called the Standardized Compound Drought-Vegetation Loss Index (SCDVI) is proposed and used to quantify EHS risk based on stability (derived from resistance and resilience). The results show that the upper reaches of the basin, particularly the source and nearby subregion, show synergistic evolutions between ecological and hydrological subsystems while in the middle and lower reaches eco- and hydro-subsystems show poor synergistic changes. EHS stability was relatively low in the southeastern YRB, where the risk of experiencing compound drought and vegetation loss event (CDVE) was high. The study also found that regions with high vegetation productivity were more prone to a high resistance–low resilience trade-off, while areas with low vegetation productivity exhibited the opposite trade-off.
How to cite: Xu, Y.-P., wang, L., Chen, X., and Du, C.: Quantifying Eco-hydrological risks in the Yellow River Basin, China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4388, https://doi.org/10.5194/egusphere-egu26-4388, 2026.
The central Chilean Andes present a unique and precious habitat for vegetation and animal species. However, that habitat is perceived to be under threat from both pastoral grazing and climate change. High-altitude summer grazing is a common pastoral management practice in the region. At the same time Central Chile has experienced a prolonged drought since 2010, with winter precipitation down by approximately 40% over the preceding decade, while average monthly temperatures have increased by about 1°C over the last 20 years.
This study investigates the temporal evolution of vegetation cover, over the period 2003-2022, in three neighbouring Andean catchments in Central Chile. The three catchments have experienced different pastoral grazing regimes during this period, which allows an assessment of the impact of pastoral grazing. Vegetation cover is analysed through a sequence of annual NDVI snapshots (MODIS imagery) over the period 2003-2022, taken towards the end of the grazing period in late summer. Data is represented as annual spatial maps, and as time-series of catchment vegetation cover.
Results indicate that all three study sites experienced a continual long-term decline in vegetation cover. Since the decline is similar in all three catchments, it cannot be unequivocally attributed to the pastoral grazing. Instead, the results suggest a strong correlation between temporal trends in key climate indicators (temperature, rainfall, evaporation soil moisture) and the declining NDVI, especially for seasonally-averaged temperature (R = - 0.75) and soil moisture (R = 0.76). The projected continuation of recent climatic trends suggests that the region’s high-altitude vegetation cover will continue to deteriorate in the coming years.
How to cite: Van De Wiel, M. and Larraín, R.: Impacts of pastoral grazing and climate change on vegetation cover in the central Chilean Andes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12072, https://doi.org/10.5194/egusphere-egu26-12072, 2026.
Vegetation responses to drought play a central role in regulating land–atmosphere interactions, carbon cycling, and ecosystem stability, yet large-scale differences in vegetation resilience across river basins and climate regimes remain insufficiently characterized. This study examines drought-driven changes in vegetation stability and recovery at the global river-basin scale, combining historical observations from 2000–2023 with future projections for 2024–2099 under two climate scenarios (SSP245 and SSP585). Vegetation dynamics are assessed using satellite-derived leaf area index as an indicator of ecosystem condition, while meteorological drought, irrigation, and environmental controls are evaluated within a regression-based attribution framework. Results indicate that many major river basins exhibit weak precipitation control on vegetation dynamics, increasing exposure to drought stress, particularly in arid and semi-arid regions. Irrigation emerges as a key buffering mechanism, contributing between roughly one-fifth and one-half of vegetation resilience during pre-drought and drought phases. Short-term drought projections using machine-learning regression highlight pronounced sensitivity in evergreen and deciduous needleleaf forests, with wetlands and grasslands also showing elevated vulnerability under increasing water limitations. Differences in vegetation response are strongly ecosystem-dependent, reflecting contrasting elasticities to both climatic forcing and human water management. The findings reveal substantial spatial heterogeneity in vegetation resilience across global river basins and emphasize the growing importance of irrigation in moderating drought impacts under future climate conditions. These results offer new insights into ecosystem-specific drought responses and provide a basin-scale perspective relevant for climate adaptation, water management, and ecosystem sustainability assessments.
How to cite: Baig, F. and Faiz, M. A.: Linking Drought Stress to Vegetation Stability and Recovery at the Global River-Basin Scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5253, https://doi.org/10.5194/egusphere-egu26-5253, 2026.
Drought is one of the most widespread and complex natural hazards, with the potential to inflict significant socioeconomic damage. However, current research still falls short in addressing catastrophic droughts, particularly in predicting the socioeconomic consequences of extreme drought scenarios. This study developed a socioeconomic drought classification model based on drought-affected population during extreme drought events, integrating both natural climatic factors and human activity factors to systematically evaluate the spatial patterns and driving mechanisms of socioeconomic drought. The results demonstrate the model exhibits excellent predictive performance (0.85±0.015) for different levels of socioeconomic disaster events. Additionally, SHAP-based feature importance analysis revealed that precipitation, spatial distribution of water sources, and human water consumption constitute the three key driving factors of socioeconomic drought, with the first two factors showing particularly prominent contributions. Notably, the impact of human water consumption on socioeconomic drought exhibits a significant time-lag effect (approximately 4-9months), indicating that longer temporal scales should be considered when assessing anthropogenic influences on drought. These findings highlight the necessity of incorporating both climatic variability and anthropogenic factors in future drought impact assessments, offering new insights for adaptive water resource management under changing environments.
How to cite: Cao, Y.: Understanding Driving Mechanisms and Socioeconomic Impacts during Extreme Drought Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8970, https://doi.org/10.5194/egusphere-egu26-8970, 2026.
