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It is of great practical significance to thoroughly study the environmental changes and conduct desertification assessments of sandy lands to elucidate the formation and recovery mechanism of desertification. The purpose of this study is to evaluate the desertification process and its driving factors accurately and objectively, and compare the differences of desertification process in different areas. We used Moderate Resolution Imaging Spectroradiometer (MODIS) surface albedo (MCD43A3) and leaf area index (LAI) (MCD15A2H) products to calculate the desertification divided index (DDI) to reveal the spatial-temporal variation regularity of the four sandy lands in northern China during 2000–2017 as well as the correlation between desertification and precipitation. The results showed that the total desertification degree of sandy lands in northern China showed a downward trend during the study period. By grading the desertification level, it was found the decline trend of severe desertification and high desertification was relatively significant (p < 0.05). The spatial trend of the desertification level in sandy lands was significantly different, and the decreased area of severe desertification and high desertification in Mu Us sandy land was the largest (−0.042 × 104 km2 yr−1 and −0.052 × 104 km2 yr−1), while the interannual variation of the various desertification levels in Hulun Buir sandy land was small (±0.003 × 104 km2 yr−1). The precipitation and DDI were positively correlated in most areas (p < 0.05). Especially in Mu Us sandy land and Hunshandake sandy land, the proportional area of positive correlation between the precipitation and DDI was more prominent, accounting for 72.9% and 63.7%, respectively. This study had important decision-making significance for the effective management of sandy lands in arid/semiarid areas. [ABSTRACT FROM AUTHOR]

Understanding the impact of water availability on vegetation growth in the context of climate change is crucial for assessing the resilience of vegetation to environmental shifts. In this study, the relationship between vegetation growth and water availability was studied using a variety of indicators. The Normalized Difference Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), and Solar-Induced Chlorophyll Fluorescence (SIF) were utilized as vegetation growth indicators, while the standardized precipitation evapotranspiration index (SPEI) and soil moisture indicators served as water use indices. To investigate the vegetation response to water deficit in the Loess Plateau during the growing season from 2000 to 2020, Spearman's rank correlation coefficients were calculated using a 5-year sliding window approach. The spatial and temporal heterogeneity of vegetation response to water deficit during the growing seasons were also explored. The results showed that: (1) with the improvement of moisture conditions, vegetation growth recovered significantly, and there was no expansion trend for vegetation water deficit. (2) The most sensitive timescale of vegetation to water deficit was 6–8 months; the response degree and sensitivity of vegetation to water surplus and deficit were the highest from June to August; and broadleaved forest was the vegetation type most sensitive to water deficit in the early growing season, while grass was the vegetation type most sensitive to water deficit during the mid and late growing seasons. (3) Soil moisture emerged as the dominant factor influencing vegetation growth in the Loess Plateau, followed by precipitation, albeit to a lesser extent. These findings contribute to understanding the mechanism and characteristics of the response of vegetation to climate fluctuations induced by global climate change. [ABSTRACT FROM AUTHOR]

Reference evapotranspiration (ET0) is a vital component in hydrometeorological research and is widely applied to various aspects, such as water resource management, hydrological modeling, irrigation deployment, and understanding and predicting the influence of hydrologic cycle variations on future climate and land use changes. Quantifying the influence of various meteorological variables on ET0 is not only helpful for predicting actual evapotranspiration but also has important implications for understanding the impact of global climate change on regional water resources. Based on daily data from 69 meteorological stations, the present study analyzed the spatiotemporal pattern of ET0 and major contributing meteorological variables to ET0 from 1960 to 2017 by the segmented regression model, Mann-Kendall test, wavelet analysis, generalized linear model, and detrending method. The results showed that the annual ET0 declined slightly because of the combined effects of the reduction in solar radiation and wind speed and the increase in vapor pressure deficit (VPD) and average air temperature in the Loess Plateau (LP) during the past 58 yr. Four change points were detected in 1972, 1990, 1999, and 2010, and the annual ET0 showed a zigzag change trend of 'increasing-decreasing-increasing-decreasing-increasing'. Wind speed and VPD played a leading role in the ET0 changes from 1960 to 1990 and from 1991 to 2017, respectively. This study confirms that the dominant meteorological factors affecting ET0 had undergone significant changes due to global climate change and vegetation greening in the past 58 years, and VPD had become the major factor controlling the ET0 changes on the LP. The data presented herein will contribute to increasing the accuracy of predictions on future changes in ET0. [ABSTRACT FROM AUTHOR]

Abstract Reliable attribution of changes in streamflow is fundamental to our understanding of the hydrological cycle and is needed to enable decision makers to manage water resources in a sustainable way. Here, we used a new attribution method based on the Budyko framework (complementary method) to quantify the contributions of climate change and human activities to the changes in annual streamflow in 22 catchments on China's Loess Plateau during the past three decades. Our results showed that after the Grain-for-Green (GFG) project, the annual streamflow decreased by 36% on average (3–72%), with reductions being more intense in northern catchments. The sensitivity of streamflow to precipitation and potential evapotranspiration also decreased, with a mean rate of −0.7 mm yr−1/mm yr−1 and −0.2 mm yr−1/mm yr−1, respectively. Using the upper and lower bounds of the human effects on streamflow from the complementary method as a reference, we found that these effects at half of the stations were under- or over-estimated by the total differential method. The contribution analysis from the complementary method showed that although human activities decreased streamflow by 26% (or 54% as a relative value) on average, the contribution of potential evapotranspiration alone to the decrease in streamflow was 9% (42%), highlighting the important role of increasing atmospheric moisture demand in the water cycle. In addition, the 5-year incremental analysis showed that the impacts of climate and human activities on streamflow had strong spatiotemporal variability. Graphical abstract Unlabelled Image Highlights • Annual streamflow significantly decreased by 36% on average after the GFG project. • Half of the stations in estimating human effect are underestimated or overestimated by the total differential method. • Potential evapotranspiration alone decreased streamflow by 9% (or 42% as relative value). [ABSTRACT FROM AUTHOR]