Reference crop evapotranspiration (ET₀) is essential for determining crop water requirements and developing irrigation strategies. In this study, ET₀ was calculated via the FAO-56 Penman‒Monteith model, and the spatiotemporal variations in ET₀ over China from 1960 to 2019 were analyzed. We then quantified the contributions of five driving factors (air temperature, wind speed, relative humidity, sunshine hours, and CO₂ concentration) to the ET₀ trends via a detrending experiment. The results revealed that nationwide ET₀ showed no significant (p>0.05) decreasing trend from 1960 to 2019, with a trend of -8.56×10^-2 mm a^-2. The average temperature and wind speed were identified as the dominant factors affecting ET₀ trends at the national scale. The contributions of the driving factors to the ET₀ trends were ranked in the following order: average temperature (21.3%) > wind speed (-15.63%) > sunshine hours (-11.99%) > CO₂ concentration (6.36%) > relative humidity (3.58%). Spatially, the dominant factors influencing the ET₀ trends varied widely. In the southeastern region, average temperature and sunshine hours dominated the trends of ET₀, whereas wind speed and average temperature were the dominant factors in the northwestern region. The findings provide valuable insights into the dominant factors affecting ET₀ trends in China and highlight the importance of considering different driving factors in calculating crop water requirements.

The Qinba Mountains are climatically and ecologically recognized as the north- south transitional zone of China. Analysis of its phenology is critical for comprehending the response of vegetation to climatic change. We retrieved the start of spring phenology (SOS) of eight forest communities from the MODIS products and adopted it as an indicator for spring phenology. Trend analysis, partial correlation analysis, and GeoDetector were employed to reveal the spatio-temporal patterns and climatic drivers of SOS. The results indicated that the SOS presented an advance trend from 2001 to 2020, with a mean rate of -0.473 d yr^-1. The SOS of most forests correlated negatively with air temperature (TEMP) and positively with precipitation (PRE), suggesting that rising TEMP and increasing PRE in spring would forward and delay SOS, respectively. The dominant factors influencing the sensitivity of SOS to climatic variables were altitude, forest type, and latitude, while the effects of slope and aspect were relatively minor. The response of SOS to climatic factors varied significantly in space and among forest communities, partly due to the influence of altitude, slope, and aspect.

Water use efficiency (WUE), as a pivotal indicator of the coupling degree within the carbon-water cycle of ecosystems, holds considerable importance in assessment of the carbon-water balance within terrestrial ecosystems. However, in the context of global warming, WUE evolution and its primary drivers on the Tibetan Plateau remain unclear. This study employed the ensemble empirical mode decomposition method and the random forest algorithm to decipher the nonlinear trends and drivers of WUE on the Tibetan Plateau in 2001- 2020. Results indicated an annual mean WUE of 0.8088 gC/mm∙m² across the plateau, with a spatial gradient reflecting decrease from the southeast toward the northwest. Areas manifesting monotonous trends of increase or decrease in WUE accounted for 23.64% and 9.69% of the total, respectively. Remarkably, 66.67% of the region exhibited trend reversals, i.e., 39.94% of the area of the Tibetan Plateau showed transition from a trend of increase to a trend of decrease, and 26.73% of the area demonstrated a shift from a trend of decrease to a trend of increase. Environmental factors accounted for 70.79% of the variability in WUE. The leaf area index and temperature served as the major driving forces of WUE variation.

Terrestrial ecosystems heavily depend on vegetation, which responds to carbon dioxide (CO₂) fertilization in hot and humid regions. The subtropical humid karst region is a hot and humid region; whether and to what extent CO₂ fertilization affects vegetation changes in such regions remains unclear. In this study, we investigated the degree to which CO₂ fertilization influences vegetation changes, along with their spatial and temporal differences, in the subtropical humid karst region using time-lag effect analysis, a random forest model, and multiple regression analysis. Results showed that CO₂ fertilization plays an important role in vegetation changes, exhibiting clear spatial variations across different geomorphological zones, with its degree of influence ranging mainly between 11% and 25%. The highest contribution of CO₂ fertilization was observed in the karst basin and non-karstic region, whereas the lowest contribution was found in the karst plateau region. Previous studies have primarily attributed vegetation changes in subtropical humid karst region to ecological engineering, leading to an overestimation of its contribution to these changes. The findings of this study enhance the understanding of the mechanism of vegetation changes in humid karst region and provide theoretical and practical insights for ecological and environmental protection in these regions.

Wetlands play a critical role in the global environment. The Middle Yangtze River Basin (MYRB), known for its abundant wetland resources, has experienced notable changes resulting from the complex interplay of environmental factors. Therefore, we investigated the spatiotemporal characteristics of wetland ecological quality in the MYRB from 2001 to 2020. Utilizing the random forest (RF) regression algorithm and patch-generated land-use simulation (PLUS) model, we forecasted variations in wetland habitat quality and their determinants under the Shared Socioeconomic Pathway-Representative Concentration Pathway (SSP- RCP) framework from 2035 to 2095. The main findings are as follows: (1) The RF algorithm was optimal for land-use and land-cover (LULC) classification in the MYRB from 2001 to 2020, when notable changes were observed in water bodies and buildings. However, the forested area exhibited an increase and decrease of 3.9% and 1.2% under the SSP1-2.6 and SSP5-8.5 scenarios, respectively, whereas farmland exhibited a diminishing trend. (2) Wetlands were primarily concentrated in the central and eastern MYRB, with counties in the southwest exhibiting superior ecological-environmental quality from 2001 to 2020. Notably, wetland coverage revealed significantly high level, significant changes, frequent but relatively minor changes under the SSP1-2.6, SSP2-4.5, and SSP 5-8.5 scenarios, respectively. (3) Regions with lower habitat quality were primarily concentrated in urbanized areas characterized by frequent human activities, indicating a clear degradation in habitat quality across different scenarios. In conclusion, we established a foundational framework for future investigations into the eco-hydrological processes and ecosystem quality of watersheds.

Due to water conflicts and allocation in the Lancang-Mekong River Basin (LMRB), the spatio-temporal differentiation of total water resources and the natural-human influence need to be clarified. This work investigated LMRB’s terrestrial water storage anomaly (TWSA) and its spatio-temporal dynamics during 2002-2020. Considering the effects of natural factors and human activities, the respective contributions of climate variability and human activities to terrestrial water storage change (TWSC) were separated. Results showed that: (1) LMRB’s TWSA decreased by 0.3158 cm/a. (2) TWSA showed a gradual increase in distribution from southwest of MRB to middle LMRB and from northeast of LRB to middle LMRB. TWSA positively changed in Myanmar while slightly changed in Laos and China. It negatively changed in Vietnam, Thailand and Cambodia. (3) TWSA components decreased in a descending order of soil moisture, groundwater and precipitation. (4) Natural factors had a substantial and spatial differentiated influence on TWSA over the LMRB. (5) Climate variability contributed 79% of TWSC in the LMRB while human activities contributed 21% with an increasing impact after 2008. The TWSC of upstream basin countries was found to be controlled by climate variability while Vietnam and Cambodia’s TWSC has been controlled by human activities since 2012.

Emphasis on future environmental changes grows due to climate change, with simulations predicting rising river temperatures globally. For Poland, which has a long history of thermal studies of rivers, such an approach has not been implemented to date. This study used 9 Global Climate Models and tested three machine-learning techniques to predict river temperature changes. Random Forest performed best, with R²=0.88 and lowest error (RMSE: 2.25, MAE:1.72). The range of future water temperature changes by the end of the 21st century was based on the Shared Socioeconomic Pathway scenarios SSP2-4.5 and SSP5-8.5. It was determined that by the end of the 21st century, the average temperature will increase by 2.1°C (SSP2-4.5) and 3.7°C (SSP5-8.5). A more detailed analysis, divided by two major basins Vistula and Odra, covered about 90% of Poland’s territory. The average temperature increase, according to scenarios SSP2-4.5 and SSP5-8.5 for the Odra basin rivers, is 1.6°C and 3.2°C and for the Vistula basin rivers 2.3°C and 3.8°C, respectively. The Vistula basin’s higher warming is due to less groundwater input and continental climate influence. These findings provide a crucial basis for water management to mitigate warming effects in Poland.

To explore water level variations and their dynamic influence on the water quality of Huayang Lakes, the water level from 1967 to 2023 and water quality from 2015 to 2023 were analyzed using the Mann-Kendall trend test, box plots, and violin plots. The results show a notable hydrological rhythm of water level alternation between dry and flood seasons in Huayang Lakes, with an average water level of 12.82 m and a monthly range of 11.21-17.24 m. Since 2017, the water level of Huayang Rivers has shown a decreasing trend of -0.02 m/a. Total phosphorus (TP) has become the primary pollutant. The TP concentrations in Longgan Lake (the largest lake) during the dry, rising, flood, and retreating seasons from 2015 to 2023 were 0.083, 0.061, 0.050, and 0.059 mg/L, respectively. The effect of water level on TP was mainly observed during the low-water period. When the water level in the dry season rose to 12.25 and 13.00 m, the percentage of TP exceeding 0.1 mg/L in Longgan Lake decreased to 55.8% and 33.3%, respectively. During the dry season, wind and wave disturbances caused the release of endogenous phosphorus in Huayang Lakes. This led to drastic fluctuations in TP concentration, reducing the correlation between water level and TP. When external control is limited, the water level during the dry season should be maintained between 12.25 and 13.0 m. Additionally, it is necessary to accelerate the restoration of submerged macrophyte species (such as Hydrilla verticillata and Vallisneria natans) in the Huayang Rivers.

Nitrate (NO₃⁻) accumulation and transport processes in the thick vadose zone affect the evolution of the groundwater NO₃⁻ content in intensive agricultural regions. Agricultural land-use change (ALUC), typically accompanied by substantial alterations in nitrogen fertilizer application and irrigation practices, is an important influencing factor. This study evaluated the changes in NO₃⁻ accumulation and transport in the deep vadose zone (DVZ, below the root zone), and the groundwater NO₃⁻ content associated with ALUC from grain to vegetable fields in the North China Plain (NCP). The ALUC from grain to vegetable resulted in nitrate- nitrogen (NO₃⁻-N) accumulation in DVZ increased by 235.5 kg ha⁻¹ m⁻¹ (163.2%) in the piedmont plain and 224.9 kg ha⁻¹ m⁻¹ (102.7%) in the central plain, respectively. This change accelerated downward transport velocity in the DVZ (from 0.81±0.47 to 0.89±0.55 m yr⁻¹ in the piedmont plain, and from 0.24±0.12 to 0.92±0.12 m yr⁻¹ in the central plain) and increased NO₃⁻ leaching fluxes. High transport velocity and leaching fluxes resulted in chemical N-fertilizer entering the aquifer in several areas in the piedmont plain. The impact of the agricultural activity intensity changes, accompanied by the ALUC, on groundwater quantity and quality should be considered in similar regions.

Dune barrier systems represent highly sought-after coastal landscapes for tourism and urban development around the world. However, a century ago, they were considered hazardous environments due to their great dynamic nature. As a result, stabilization practices were considered necessary. The systematic introduction of fast-growing exotic trees helped stabilize the sand, making it easier for tourism urbanization to take place, but also leading to erosion processes. This paper aims to assess long-term changes in vegetation cover over a large temperate barrier in Argentina. This complex region includes urban resorts, afforestation zones, and protected areas. A GIS-based geospatial analysis was conducted using a large satellite database (> 350 images), and the future evolution of the vegetation was modeled. The results revealed two primary spatiotemporal patterns associated with a gradual expansion of vegetation cover, accompanied by a concurrent reduction in sandy areas. In 1986, the dune area comprised 75% more surface than vegetation, whereas in 2021, it represented 60% less than vegetation. Furthermore, the 2050 scenario suggests a potential 40% reduction of dunes in certain areas. It is necessary to enhance management actions aimed at maintaining dune mobility and ensuring local and regional sediment balance. Long-term management strategies must focus on restoring native plant communities and controlling invasive species, and avoiding new dune fixation initiatives based on the introduction of exotic species.