Drylands with fragile ecosystems and severe water shortages are particularly vulnerable to climatic change. Northwestern China (NWC), a typical arid region, faces uncertainty regarding future wetting or drying trends. A comprehensive assessment and projection of these conditions are crucial for water resource management. In this study, we employ a Lagrangian trajectory model, optimal fingerprint analysis, and a maximum covariance technique to evaluate wetting and/or drying trends in NWC over the historical (1981–2023) and future (2024–2099) periods. Our results show that over 80% of NWC experienced increases in air temperature, precipitation, and evaporation during the historical period. External and internal water vapor sources contribute 92% and 8%, respectively, to precipitation changes. Incoming water vapor predominantly originated from the North Atlantic (31.9%) and the South China Sea ‐ Bay of Bengal region (39.3%), with a strong positive correlation (r = 0.71) between Atlantic sea surface temperatures and precipitation minus evaporation in NWC. Water vapor enters NWC from the southern, northern, and western boundaries, while 83.4% escapes through the eastern boundary. The precipitation trend is strongly influenced by the combined effects of anthropogenic and natural forcings, accounting for 36.8% to the observed increase. Under a 1.5°C warming scenario, warming‐wetting regions shift northward, whereas higher warming levels (2°C, 3°C, 4°C) cause these regions to shift southeastward and shrink. Our findings underscore NWC's high sensitivity to climate warming and highlight the pressing challenge of water security in a warming world.

The double-ring infiltrometer is widely used to measure soil unsaturated hydraulic conductivity in the field. The scale effect of the inner and outer ring size (especially the inner one) affects the measurement results. In the semi-arid steppe, where water is scarce and transportation is inadequate, studying the scale effect caused by the inner-ring diameter of the infiltrometer can reduce the test consumption on the premise of ensuring the test accuracy. In this paper, a total of 190 double-ring infiltration tests with different inner-ring diameters (15, 20, 25, 30, and 40 cm) and 0.33 times outer buffer index were carried out at 38 sites with five soil types in the Xilin river basin, China. Results showed that: (1) When comparing the simulated parameters of six infiltration models, parameters increased with the increase of the infiltrometer inner diameter, but the trend gradually slowed down, indicating that the increase of the infiltrometer inner diameter would weaken the influence of the infiltrometer scale effect. However, the infiltrometer with an inner diameter of 40 cm is not enough to completely overcome the scale effect. (2) Through principal component analysis, the infiltration process is mainly affected by the particle size and the initial moisture content. (3) The soil infiltration map based on infiltration tests was more practical than the soil type map, which can provide a theoretical basis for ecological and soil restoration in the future.

Natural ecosystems of the West Liao River basin (WLRB) in northeast China have been damaged by both natural and human factors from the 1990s. Since 2000, China’s Grain-for-Green Program (GFGP) has been widely adopted with the aim of improving ecosystem services. An accurate evaluation of the eco-hydrological effects for policy implementation is essential to provide references for further restoration of ecosystem services. This study quantified and characterized the ecosystem services and their trade-offs/synergies using models and statistical methods in the WLRB from 1990 to 2020. Moreover, the impact of key drivers on ecosystem services was evaluated by the difference-in-differences model. Among them, the study mainly investigated how GFGP affects ecosystem services. The results confirmed that the water yield, carbon sequestration, habitat quality, and total ecosystem service of the WLRB decreased in the pre-GFGP period (1990–2000). However, this tendency was reversed in the regions where the GFGP was implemented during the period of 2001–2020. Furthermore, a synergistic relationship was shown among carbon sequestration, soil conservation, and habitat quality. Additionally, there were tradeoffs between water yield and the other three ecosystem services, especially in mountain areas. The GFGP could restore carbon sequestration, habitat quality, and total ecosystem services by 1.3%, 2.1%, and 0.6%, respectively. Nevertheless, GFCP may enlarge the tradeoff and imbalance between water yield and habitat quality. Results highlight the need for the governance of ecosystem protection and suggest natural restoration in the mountain area for maintaining water yield and helping ecosystem restoration. Timely adjustment of the policy implementation areas is the key to improving and balancing multiple ecosystem services in the future.

Based on monthly precipitation (P), temperature (T) data, and remote sensing images collected from March 2000 to February 2019, this article was constructed to reveal the synergistic effect between P and T for the NDVI in northern China qualitatively and quantitatively by using a one-variable linear regression, the coefficient of variation, multivariate correlation coefficients, and a geodetector. The results show that the NDVI in the study area decreased from 2000 to 2012, increased from 2013 to 2018, decreased in the west, and increased in the east of Northern China. Overall, the NDVI, P, and the average maximum temperature (Tmax) had the strongest multivariate correlations (approximately 43.4% of the total study area passed the 95% confidence level significance test), followed by the average temperature (Tave) and average minimum temperature (Tmin). The explanatory power of the synergistic effect between P and Tmax for the NDVI was the strongest, with the value of explanatory power varying from 0.41 to 0.81, followed by Tave and Tmin. Spatially, the explanatory power of the synergistic effect between P and T for the NDVI was strengthened overall in the study area from northwest to southeast. The annual change rate of the explanatory power showed that the overall explanatory power between P and T for the NDVI in the study area was weakened in the central area and strengthened in the east and the west. Specifically, the synergistic effect between P and T on the NDVI was weakened in both Shaanxi and Ningxia Huizu Zizhiqu, while the opposite occurred in Xinjiang Uygul Zizhiqu, Qinghai, and another five provinces in the eastern part of the study area.

Desertification is a major environmental problem facing the world today, and climate change is an important factor influencing desertification. This study investigates the impact of changes in key climate factors on desertification based on normalized difference vegetation index data, precipitation data and evaporation data from Inner Mongolia between 1982 and 2020 using correlation analysis, regression modelling, and residual analysis. The results show that precipitation and evaporation are significantly correlated with mild desertification and severe desertification, respectively, with correlation coefficients reaching 0.98 and −0.96, respectively. In severely desertified areas in central-eastern Inner Mongolia, there is a high correlation between desertification and temperature, the characteristics of the correlation of average maximum and minimum temperatures with desertification are similar to those of the correlation of average temperature with desertification, and the average maximum and minimum temperatures are well correlated with mild desertification, with correlation coefficients as high as 0.98 and 0.978, respectively. Climate contribution accounts for 97% of desertification in severely desertified areas, indicating that climate change has increased desertification in these areas. In regions with improved desertification, approximately 75% are primarily influenced by climate change (with a relative contribution greater than 50%), with climate factors exhibiting a relative contribution greater than 75% to desertification in 30% of these regions.

HIGHLIGHTS. Qualitative analysis of the relationship between precipitation and climate factors.Quantitative analysis of climate factors on precipitation.