Rainfall and vapor pressure deficit (VPD) are well-studied hydrological variables that largely determine aboveground net primary production (ANPP) in most ecosystems. Meanwhile, the impacts of another important part of the hydrologic cycle, non-rainfall water from fog and dew, remain poorly understood at the ecosystem level. To fill this gap, we used meteorological variables measured at weather stations along with satellite-derived vegetation greenness data from surrounding areas to examine how fog and dew frequency affect summer plant growth across the contiguous United States. Our analysis shows that, even after accounting for precipitation, VPD, and land-cover type, fog and, more so, dew enhanced vegetation productivity in water-limited regions. In contrast, non-rainfall water had a neutral or negative impact on plant growth in humid regions, with fog showing the strongest and most widespread negative effects. Taken together, our findings reveal that summertime non-rainfall water has differential effects on vegetation that are largely determined by ecosystem-level water availability. These aridity-dependent effects of fog and dew should be considered in future ecological and agricultural studies and in assessments of projected climate impacts on vegetation.
Climate change is increasing the frequency and intensity of extreme rainfall events, profoundly affecting vegetation–atmosphere–soil interactions and ecosystem stability. Northeast China (NEC), a major ecological region, is highly sensitive to precipitation variability. However, the annual mechanisms underlying vegetation responses to rainfall extremes, the mediating roles of soil moisture (SM) and vapor pressure deficit (VPD), and the ecosystem-specific differences remain insufficiently understood. This study investigates these processes during 2000–2022 by integrating precipitation extremes, normalized difference vegetation index (NDVI), SM, VPD, and land cover data. Ten rainfall extreme indices were evaluated using the Mann–Kendall (MK) test and Sen’s slope estimator, while NDVI responses were examined through correlation analysis, mixed-effects models, and structural equation modeling (SEM). Results show strong spatial heterogeneity in precipitation extremes, with intensified heavy rainfall in southern NEC and prolonged drought conditions in northern areas. Vegetation exhibited significant greening trends (NDVI slope = 0.0026 yr−1, R2 = 0.718, p < 0.001), accompanied by increasing SM (slope = 0.0478 yr−1, p = 0.003) and mild warming (slope = 0.0005 yr−1, p = 0.045). NDVI showed a strong correlation with SM (ρ = 0.65, p < 0.01) but a weak relationship with temperature (ρ = 0.04, p > 0.05), highlighting SM as the dominant driver of regional greening. Grasslands and cultivated lands were more sensitive to rainfall fluctuations, whereas forests showed greater resilience. SEM results indicate that extreme rainfall affects NDVI mainly through indirect pathways mediated by SM and VPD, with mediation effects exceeding 97%. These findings improve understanding of nonlinear vegetation–atmosphere–land interactions and provide scientific insights for climate adaptation, ecosystem management, and ecological restoration under future climate change.
Climate-induced changes in rainfall patterns, particularly increases in event intensity and altered seasonal distribution, pose significant challenges for groundwater recharge and water resource management, especially in semi-arid Mediterranean environments. This study was motivated by the pronounced scarcity of long-term field data quantifying how rainfall intensity and vegetation cover interact to shape the soil water budget and diffuse recharge under natural conditions. To address this gap, a 3-year lysimeter experiment was conducted in the aeolian dune system of Doñana National Park (SW Spain), utilizing four precision weighable lysimeters of different sizes and vegetation covers (bare soil, pine canopy, and shrubland). Meteorological and hydrological variables were continuously monitored, allowing detailed partitioning of precipitation, evaporation, and drainage at high temporal resolution. The results show that a small number of high-intensity storms (> 20 mm/day) dominated annual rainfall input and were responsible for most groundwater recharge, whereas low-intensity rainfall contributed negligibly to recharge. Bare-soil lysimeters exhibited consistently high and stable recharge rates (50–55% of rainfall), while vegetated lysimeters showed much lower and more variable recharge (11–60%), with intense storms effectively bypassing interception and transpiration limits. These findings illustrate that vegetation cover critically modulates the effect of rainfall intensity on recharge, with groundwater input under vegetation potentially matching bare soil recharge when intense events are frequent. This insight has important implications for understanding and managing groundwater resources in sandy, semi-arid regions undergoing climate-driven changes in rainfall regime.
C. Kohfahl, F. R. Bermudo· Hydrogeology Journal· 0 citations
Understanding how desert riparian vegetation responds to managed flow releases is essential for ecological restoration in arid inland river basins. This study examines vegetation dynamics and hydrological responses in the desert reach of the Hotan River, a seasonal river crossing the Taklimakan Desert. To avoid temporal inconsistency, two data windows were explicitly separated: Landsat-derived vegetation information was used to describe long-term vegetation changes from 1985 to 2020, while environmental flow release, river-section water consumption, and groundwater-depth analyses were limited to the period with available hydrological observations, 2006–2020. NDVI and vegetation-cover classes were derived from cloud-screened and atmospherically corrected Landsat imagery, and the response of vegetation indicators to cumulative environmental flow release and groundwater depth was evaluated using transparent regression models with diagnostic statistics. Results indicate that vegetation cover improved overall during the study period, although the response was spatially heterogeneous. Vegetation conditions were generally better near the upper and terminal parts of the desert reach, whereas a relatively vulnerable zone occurred approximately 15–115 km downstream of the river confluence. During 2006–2020, NDVI and grassland area generally increased with cumulative environmental flow release, whereas annual grassland-area change showed large interannual fluctuations and was not significantly explained by cumulative release alone. The revised analysis clarifies that the study contributes a reach-scale synthesis linking long-term vegetation mapping with monitored environmental flow releases and groundwater response in the Hotan River desert reach, rather than a full 40-year ecohydrological attribution. These findings provide a basis for improving environmental flow scheduling and monitoring design in arid desert rivers.
Biao Cao, Minjie Liu, Caihong Hu et al.· Water· 0 citations
Soil moisture is a key indicator of agricultural and hydrological drought, but its meteorological controls vary across temporal scales. Using ESA CCI soil moisture products from 2010 to 2022, this study investigated soil moisture variability in the Yangtze River Basin at weekly, monthly, and annual scales. The product was first validated using ground observations and ERA5 reanalysis data, and a generalized additive model (GAM) was then applied to quantify the relative contributions of precipitation, temperature, wind speed, and VPD under normal conditions and during three extreme drought events. The validation showed that ESA CCI soil moisture captured basin-scale variations well, with mean absolute deviations of 0.0460, 0.0434, and 0.0072 m3/m3 in the upper, middle, and lower reaches, respectively, and a basin-wide RMSE of 0.0127 m3/m3 against ERA5. The attribution results revealed a clear scale-dependent shift in soil moisture controls. At the weekly scale, VPD dominated soil moisture variability, with a basin-wide average contribution of 47.04% and a maximum contribution of 55.92% in the lower reaches, indicating that short-term soil drying is mainly driven by VPD. At the monthly scale, precipitation became the primary control, with a basin-wide average contribution of 36.62% and a maximum contribution of 44.65% in the upper reaches, reflecting the role of accumulated rainfall recharge in maintaining soil moisture storage. During extreme drought events, the monthly-scale dominance of precipitation weakened, and precipitation, VPD, temperature, and wind speed each contributed approximately 20–30%, suggesting that drought development results from the combined effects of reduced water input and enhanced atmospheric water loss. These findings indicate that precipitation-based drought monitoring may underestimate rapid soil drying risks, whereas incorporating atmospheric demand indicators such as VPD can improve drought early warning and water resource management under a warming climate.
Yucheng Liu, Ran Huo, Bowen Zhu et al.· Atmosphere· 0 citations
This study investigates hydroclimatic variability and water balance dynamics in the Akmola region during 2003–2023 using observations from 16 meteorological stations. The study evaluates changes in air temperature, precipitation, reference evapotranspiration (ET0), climatic water balance, and drought conditions. Reference evapotranspiration was calculated using the FAO-56 Penman–Monteith method, while drought variability was assessed using the 12-month Standardized Precipitation–Evapotranspiration Index (SPEI-12). Temporal trends were analyzed using the Mann–Kendall test and Sen’s slope estimator. The results revealed significant spatial heterogeneity in hydroclimatic conditions across the region. Air temperature showed a consistent increasing trend at most stations, accompanied by increasing atmospheric evaporative demand. All stations were characterized by a persistently negative climatic water balance, with mean annual values of approximately −750 mm, indicating a regional moisture deficit. Reference evapotranspiration exhibited significant spatial variability, with the highest values observed in the southern and central parts of the region. Precipitation remained the dominant control of water balance variability (r = 0.79–0.96), while increasing temperature intensified moisture deficits through increased evapotranspiration. SPEI-12 indicated recurrent drought episodes and increasing drought vulnerability associated with warming-induced atmospheric water demand. The study demonstrates that increasing evapotranspiration is becoming a major driver of water stress in the Akmola region and highlights the importance of integrating climatic water balance and SPEI indicators for drought monitoring and climate adaptation in semi-arid steppe regions.
Raikhan Beisenova, Ainur Orkeyeva, A. Rakhmetova et al.· Resources· 0 citations
Evapotranspiration (ET) links climate, the terrestrial water cycle and ecosystem functioning, yet its variability before the satellite era remains poorly constrained. We developed a random forest (RF) model that combines flux-tower observations with meteorological variables, atmospheric carbon dioxide concentration, leaf area index (LAI), aridity index and rooting depth to reconstruct monthly ET at 5267 weather stations from 1688 to 2020. Station coverage was concentrated in Western Europe before 1850 and expanded more widely thereafter. Record-level validation produced coefficient of determination = 0.74 and Kling–Gupta efficiency = 0.77, whereas site-grouped and temporal hold-out tests indicated lower transferability and greater uncertainty for early estimates. ET across the available stations generally increased, particularly during 1900–1950, but trends were regionally heterogeneous. Humid mid- to high-latitude regions commonly showed increases, whereas parts of Australia and the southwestern United States declined. Model interpretation indicated that temperature contributed most strongly to RF-predicted ET, while LAI became more influential after the mid-twentieth century. These are model-learned associations, not independent causal effects. Climatic water availability (P-ET), treated as a simplified climatic water-balance indicator rather than runoff or managed water availability, remained positive in many humid mid-latitude regions and negative in arid and semi-arid regions. Since 1930, P-ET defined wet extremes increased in several moisture-rich mid- to high-latitude regions, while dry extremes intensified in semi-arid transition zones. The P-ET-based population exposure proxy improved in many humid regions but worsened in drylands. This study substantially extends the temporal range of ET reconstruction and provides critical evidence for understanding how climate variability and human influences have shaped the water cycle over the past three centuries.
Yang Ao, Haiyang Shi, Geping Luo· Environmental Research Lette...· 0 citations
