Search

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]

Abstract: To reveal the regional climate changes in Xinjiang, China, precipitation and air temperature datasets from 54 meteorological stations and multiple model simulation results from CMIP5 were analyzed. The analytical results revealed an increasing trend of the air temperature in Xinjiang over the last 50 years (i.e., 1962–2011). An increasing trend of the precipitation replaced the decreasing trend since early 1980s and the climate was thus transited from warm–dry to warm–wet in early 1980s. To evaluate the effects of climate change on the ecosystems in Xinjiang, the correlation analyses between climatic parameters (i.e., precipitation and air temperature) and ecological indicators (i.e., GPP, NPP and LAI) were conducted using the 1-km annual GPP and NPP datasets from the MODIS products from 2000 to 2010 and the AVHRR BU LAI products from 1981 to 2011. The correlation analyses demonstrated that the trends of total GPP and NPP during the growing season closely followed the trend of the precipitation from 2000 to 2010. The annual mean LAI of the areas covered with vegetation was also positively correlated with the annual precipitation over the past 30 years. However, the NPP was negatively correlated with the air temperature while the GPP having no correlation with the air temperature. The results further confirm the proposition that water resource availability is the limiting factor with regard to the primary production of the ecosystem in Xinjiang. [Copyright &y& Elsevier]

By controlling the sputtering power, rotational speed of the substrate and sputtering time, Ni–Cr thin films with appropriate composition were fabricated by double-target magnetron co-sputtering techniques. The homogeneity and oxidation of Ni–Cr thin film has been studied by Auger electron spectroscopy (AES). The structures of Ni–Cr thin films were determined by an X-ray diffractometer (XRD). The oxidation and the resistance stability of the Ni–Cr thin film after rapid thermal process (RTP) have been studied. The relations between TCR and RTP techniques of Ni–Cr thin films were discussed. [ABSTRACT FROM AUTHOR]

The electromechanical properties of nichrome (Ni–Cr 80/20 wt.%) used as a common material for application in thin film strain gauges have been studied. The surface topography and chemical composition of Ni–Cr thin films grown on the glass substrate by magnetron sputtering have been analyzed by atomic force microscope (AFM) and energy dispersive spectroscopy (EDS), respectively. The temperature coefficient of resistance (TCR) has been determined by a Nano-volt/Micro ohm meter. The gauge factor (FG) has been determined by the cantilever method. Low stable TCR values (22 ppm to 46 ppm in the 50–150°C temperature range) have been obtained. Resistance stability is achieved by rapid thermal annealing (RTA) at 300°C for 10 min combined with a 24 h thermal annealing (TA) at 150°C. The desired 45 Ω/m sheet resistance and a gauge factor of 2.6 have been attained for 40-nm-thickness films. The films have very small roughness of 2.1~4.4 nm. [ABSTRACT FROM AUTHOR]

By controlling the sputtering power, rotated speed of substrate and sputtering time, Ni–Cr films with appropriate composition were fabricated by double-target magnetron co-sputtering techniques. The cross-sectional micrograph and element diffusion of Ni–Cr films deposited on stainless steel substrates by magnetron sputtering have been analyzed by scanning electron microscope (SEM) and energy dispersive spectroscope (EDS). The results indicate that the according compositions of Ni–Cr films are 58 wt.% Ni and 42 wt.% Cr when the sputtering powers of Ni and Cr targets are 288 W and 280 W, respectively. In the same time, the diffusions of Ni, Fe and Cr were revealed and the diffusion distances of Ni and Cr are calculated by Fick's second law with a Pile-Up law model. The largest diffusion distance is about 885 nm, beyond which the content of Ni and Cr detected by EDS is the same as the substrate. [ABSTRACT FROM AUTHOR]

The occurrence of drought is related to complicated interactions between many factors, such as precipitation, temperature, evapotranspiration and vegetation. In this study, the relationships between drought and precipitation, temperature, vegetation and evapotranspiration were investigated with a random forest (RF), and a new combined drought monitoring index (CDMI) was constructed. The effectiveness of the CDMI in monitoring drought in Shaanxi Province was verified by the in situ 1 ∼ 12-month standardized precipitation index (SPI); relative soil moisture (RSM) and four other commonly used remote sensing drought monitoring indices. The results show that CDMI is more correlated with the SPI and RSM than the four indices. Moreover, the spatial distributions of drought for the CDMI and RSM are similar. Therefore, the CDMI can be used to monitor droughts in Shaanxi Province, and machine learning can explore the relationships between various factors and establish a drought index without knowledge of the causal mechanisms of these factors. [ABSTRACT FROM AUTHOR]

Magnetostrictive bioinspired whisker is a new kind of sensor that can realize tactile and flow sensing by utilizing magnetoelastic effect. The sensitivity is a key technical indicator of whisker sensor. The paper presented a new magnetostrictive whisker based on Galfenol cantilever beam, as well as its operation principle. Then, the static and dynamic sensitivity of the whisker sensor was investigated by using a self-made experimental system. The results illustrated that the proposed sensor has a high sensitivity. Its static sensitivity is 2.2 mV/mN. However, its dynamic sensitivity depends on the vibration frequency. When working at the natural frequency of the cantilever beam, the dynamic sensitivity performs an obvious increase—1.3 mV/mN at 3.5 Hz (the first-order natural frequency) and 2.1 mV/mN at 40 Hz (the second-order natural frequency), respectively. [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]

With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a significant impact on net primary productivity (NPP) and affect the global carbon cycle. Currently, the seasonal response characteristics of NPP to phenological changes in dryland ecosystems are still not well defined. This article calibrated and analyzed the normalized difference vegetation index (NDVI) time series of Advanced Very-High-Resolution Radiometer (AVHRR) data from 1982 to 2015 in the Loess Plateau, China. The spatial and temporal distributions of vegetation phenology and NPP in the Loess Plateau under semihumid and semiarid conditions were investigated. The seasonal variation in the NPP response to vegetation phenology under the climate change was also analyzed. The results showed that, different from the northern forest, there was distinct spatial heterogeneity in the effect of climate change on the dynamic change in vegetation growth in the Loess Plateau: 1) an advance of the start of the growing season (SOS) and a delay of the end of the growing season (EOS) significantly increased the NPP in spring and autumn, respectively, in the humid southeast; 2) in the arid northwest, the NPP did not significantly increase in spring and autumn but significantly decreased in summer. [ABSTRACT FROM AUTHOR]

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]

Ni–Al intermetallic compounds nanocrystalline thin films were deposited by direct current magnetron co-sputtering from elemental Ni and Al targets. The integrity of the thin films and their elemental compositions were assessed using a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope analyzer. The morphologies of thin alloy films are density and smoothing characterized by atomic force microscope and SEM. The preferred (111) orientation in both as-deposited and annealed films are identified using X-ray diffractometer (XRD). The electrical properties of the alloy films were studied, and show good metallic conduction characteristics. From room temperature to 200°C, the resistance of the thin films are assumed to be linear as a function of varying temperature. All the thin films show a positive temperature coefficient of resistance (TCR). As 1% O2 was introduced into the vacuum chamber during sputtering, the root mean square roughness of the films increased, grain size turned out to be smaller, and the crystallization process was blocked. The amorphous Al2O3 phase was found in XRD patterns. The results of TCR measurement show a different electric conduction mechanism compared with alloy films. [ABSTRACT FROM AUTHOR]

Soil organic carbon stocks (SOCS) are critical for both maintaining many ecosystem functions and regulating global climate. To address the serious soil erosion and land degradation problems on the Loess Plateau (LP), the Chinese government launched the famous "Grain for Green Program" (GGP) in 1999. However, how the SOCS change under the impacts of both GGP and climate change remains unclear. Here, we investigated the impacts of climate change and the GGP on SOCS of the top 1 m soil on the LP during 1980–2015, using a data-driven model and a multi-period land use/cover dataset. Our SOCS estimates showed that SOCS of grasslands and forestlands on the LP ranged from approximately 1400 ± 75 to 1700 ± 77 Tg C during 1980–2015. The SOCS of grasslands ranged from approximately 1000 ± 56 to 1200 ± 58 Tg C, which were roughly twice those of forestlands. Our analyses suggested that SOCS of grasslands and forestlands on the LP varied in the years before the GGP was launched in 1999, due to the continued warming and frequent drought. Unexpectedly, the SOCS did not significantly enhance after the GGP was implemented. Compared to 1995, the SOCS of grasslands and forestlands on the LP only increased on average by approximately 3.7% during 2000–2015, due mainly the adverse impact of climate change, as well as the limited effect of vegetation restoration on SOC at the early stage of the vegetation restoration programs. The study highlights the noticeably adverse effects of climate change on SOCS in the LP, providing valuable scientific support for the implementation of large-scale ecological restoration initiatives in the region. [Display omitted] • Soil organic carbon stocks (SOCS) of grasslands and forestlands on the LP varied significantly over 1980–2015. • Climate changes had important influences on soil organic carbon stocks on the LP. • Management of grasslands and forests are crucial for enhancing carbon storage on the LP. [ABSTRACT FROM AUTHOR]

Highlights • We analyze the spatiotemporal pattern of the ECC on the Loess Plateau. • The average annual ECC is 577 ± 124 g C m−2 yr−1 during 1982–2012. • Due to revegetation, 26 counties have exceeded the ECC threshold. • 138 counties have water competition between ecosystems and socio-economic systems. • Under future climate change and growing water demand, ECC will increase by 6–36%. Abstract Revegetation, especially afforestation, has served as an important tool for controlling desertification. However, revegetation in water-limited regions will inevitably reduce the water available for socio-economic systems, which is poorly considered in decision-making on sustainable ecosystem management. This paper proposed a framework to determine the threshold of vegetation productivity (i.e., ecosystem carrying capacity), corresponding to available water resources for ecosystems (i.e., annual precipitation minus water demand for socio-economic systems) on the Loess Plateau. The average annual ecosystem carrying capacity (ECC) during 1982–2012 is 577 ± 124 g C m−2 yr−1, with spatial gradients increasing from northwest to southeast. Vegetation in rocky mountain areas has the largest value of 833 ± 200 g C m−2 yr−1. Factorial analysis suggests that changes in precipitation and human water use contributed to 55% and 45% of the multi-decadal changes in regional ECC, respectively. Meanwhile, due to revegetation, 26 counties on the Loess Plateau, mainly in the southeast and eastern parts, have exceeded the ECC threshold during the study period. An additional 138 counties have a high potential for water competition between the ecosystems and socio-economic systems. At the regional scale, there are 9 years (∼30% of the study period) during which the ECC threshold has been exceeded, especially after 1997. Considering the climate change in the future and the growing demand for water in socio-economic systems, the corresponding ECC threshold will increase by 6–36%. We believe that these findings can provide reference for policy-makers to make decisions towards ecosystem sustainability while meeting human needs for water resources. [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]

Abstract Remote sensing based vegetation index provides a practical method for the monitoring of vegetation dynamics at regional and global scales. Here, using a long-term remotely sensed normalized difference vegetation index (NDVI) dataset, we quantified the vegetation changes in the Loess Plateau (LP) over the last three decades (1982–2015), which includes the period before the Chinese"Grain for Green Program"(GGP) was launched (1982–1999), and the period after the GGP (1999–2015). The correlations between the NDVI and four climate related variables, i.e., precipitation, temperature, root-soil moisture (RSM), and a drought proxy-standardized evapotranspiration deficit index (SEDI), were also examined. The results indicated that, (i) the GGP strongly changed the vegetation in the LP. The growing-season mean NDVI (GSM-NDVI) and the annual mean NDVI (AM-NDVI) decreased slightly before the GGP launched in 1999, with slopes of −3.38 × 10−3 and − 8.00 × 10−4 year−1, respectively. However, they showed slight and significant (p < 0.05) increases after the GGP, with slopes of 4.75 × 10−3 and 2.32 × 10−3 year−1, respectively. (ii) Climate change (i.e., warming and drying) resulted in adverse effects on vegetation in the LP during the period before the GGP. However, the observed changes (i.e., wetting and reduced drought) exerted positive effects on the vegetation during the period after the GGP. (iii) Inter-annual variations of spatially averaged NDVI over the LP were primarily determined by RSM rather than any other climate related variables. In the southeastern LP, the inter-annual variation of GSM-NDVI was mainly determined by precipitation and SEDI, while the inter-annual variation of AM-NDVI was mainly caused by SEDI and RSM. Inter-annual variations of both GSM-NDVI and AM-NDVI were mainly determined by SEDI and RSM in the northwestern LP, and by temperature in the southwestern LP. Graphical abstract Unlabelled Image Highlights • The Grain for Green Program (GGP) greatly changed vegetation in the Loess Plateau. • Climate changes exerted adverse effects on vegetation in the LP before the GGP. • Wetting and reduced drought positively affected vegetation in the LP after the GGP. • The inter-annual variation of NDVI was primarily determined by soil moisture. [ABSTRACT FROM AUTHOR]

In order to improve the high-frequency performance of magnetostrictive composites, the work fabricated a polymer-bonded Tb-Dy-Ho-Fe fiber composite. Its magnetic properties were investigated and compared with that of polymer-bonded Tb-Dy-Fe fiber composite. An experimental system was setup to measure the major and minor hysteresis loops of the given magnetostrictive composites at different frequencies. The results showed that Tb-Dy-Ho-Fe fiber composites demonstrates superior magnetic properties, such as lower saturation magnetic field (220 kA/m), smaller coercivity force (5 kA/m) and less dynamic magnetic loss (115 W/m3 at 20 kHz, only 60% of Tb-Dy-Fe fiber composites), compared with Tb-Dy-Fe fiber composites. The proposed composite is suitable for the application of sensing and ultrasonic. [ABSTRACT FROM AUTHOR]

Grassland ecosystems act as a crucial role in the global carbon cycle and provide vital ecosystem services for many species. However, these low-productivity and water-limited ecosystems are sensitive and vulnerable to climate perturbations and human intervention, the latter of which is often not considered due to lack of spatial information regarding the grassland management. Here by the application of a model tree ensemble ( MTE- GRASS) trained on local eddy covariance data and using as predictors gridded climate and management intensity field (grazing and cutting), we first provide an estimate of global grassland gross primary production ( GPP). GPP from our study compares well (modeling efficiency NSE = 0.85 spatial; NSE between 0.69 and 0.94 interannual) with that from flux measurement. Global grassland GPP was on average 11 ± 0.31 Pg C yr−1 and exhibited significantly increasing trend at both annual and seasonal scales, with an annual increase of 0.023 Pg C (0.2%) from 1982 to 2011. Meanwhile, we found that at both annual and seasonal scale, the trend (except for northern summer) and interannual variability of the GPP are primarily driven by arid/semiarid ecosystems, the latter of which is due to the larger variation in precipitation. Grasslands in arid/semiarid regions have a stronger (33 g C m−2 yr−1/100 mm) and faster (0- to 1-month time lag) response to precipitation than those in other regions. Although globally spatial gradients (71%) and interannual changes (51%) in GPP were mainly driven by precipitation, where most regions with arid/semiarid climate zone, temperature and radiation together shared half of GPP variability, which is mainly distributed in the high-latitude or cold regions. Our findings and the results of other studies suggest the overwhelming importance of arid/semiarid regions as a control on grassland ecosystems carbon cycle. Similarly, under the projected future climate change, grassland ecosystems in these regions will be potentially greatly influenced. [ABSTRACT FROM AUTHOR]

Satellite observations of atmospheric carbon dioxide (CO) provide a useful way to improve the understanding of global carbon cycling. In this paper, we present a comparison between simulated CO concentrations from an inversion model of the CarbonTracker Data Assimilation System (CTDAS) and satellite-based CO measurements of column-averaged dry air mole fraction (denoted XCO) derived from version 3.3 Atmospheric CO Observations from Space retrievals of the Greenhouse Gases Observing SATellite (ACOS-GOSAT) L2 data products. We examine the differences of CTDAS and GOSAT to provide important guidance for the further investigation of CTDAS in order to quantify the corresponding flux estimates with satellite-based CO observations. We find that the mean point-by-point difference (CTDAS-GOSAT) between CTDAS and GOSAT XCO is −0.11 ± 1.81 ppm, with a high agreement (correlation r = 0.77, P < 0.05) over the studied period. The latitudinal zonal variations of CTDAS and GOSAT are in general agreement with clear seasonal fluctuations. The major exception occurs in the zonal band of 0°-15°N where the difference is approximately 4 ppm, indicating that large uncertainty may exist in the assimilated CO for the low-latitude region of the Northern Hemisphere (NH). Additionally, we find that the hemispherical/continental differences between CTDAS and GOSAT are typically less than 1 ppm, but obvious discrepancies occur in different hemispheres/continents, with high consistency (point-by-point correlation r = 0.79, P < 0.05) in the NH and a weak correlation (point-by-point correlation r = 0.65, P < 0.05) in the Southern Hemisphere. Overall, the difference of CTDAS and GOSAT is small, and the comparison of CTDAS and GOSAT will further instruct the inverse modeling of CO fluxes using GOSAT. [ABSTRACT FROM AUTHOR]

Highlights: [•] The EGS was extracted from the AVHRR LAI dataset. [•] The EGS spatiotemporal variations across the Qinghai–Tibetan Plateau were investigated. [•] The EGS significantly correlated with the vegetation types, altitude and climate. [•] The trends of EGS annual changes varied with time. [Copyright &y& Elsevier]

As the most frequent and longest-lasting climate-related disasters, droughts are complex processes caused by hydrological imbalance, and have significant effects on ecosystem function and socioeconomic development. However, most conventional satellite-based drought indices and combined drought indices are mechanically constrained by the fact that they were developed and evaluated for a specific climate or critical ecological region, especially in China. A comprehensive drought index should be developed for extensive application in different climate-hydrology regions. To address this problem, an optimised principal component analysis method (PCA-RF) was proposed to support drought assessment across the transitional area between the humid and arid regions in central China, including the Loess Plateau (LP) and Qinling Mountains (QL). This method eliminated the causal relationships of non-linear changes for multi-aspect parameters such as land surface temperature, precipitation and soil moisture, and was used in developing a new index named "Meteorological drought index by PCA-RF methods (PMDI)". The results showed that PMDI had higher correlations and lower root mean square error than other drought indices (established using the empirical-weights method) with the 1-month standardized precipitation evapotranspiration index (SPEI-1). That means PMDI performed well in meteorological drought monitoring. Additionally, the normalized difference vegetation index (NDVI) and solar-induced chlorophyll fluorescence (SIF) were utilised to evaluate PMDI effectiveness in detecting vegetation response to drought, which represents agricultural drought. The results indicated that correlations between PMDI and vegetation indices (VIs) were stronger when severe or extreme droughts occurred, and that their relationships were affected by the high spatiotemporal heterogeneity in vegetation change over the LP and QL. Overall, PMDI was shown here to be a very suitable index for monitoring meteorological drought (short-term) and has effective action in capturing the response of vegetation signals to agriculture drought events (long-term). Given the excellent performance of PMDI in diverse climate-hydrology conditions of our study regions, we concluded that the PMDI has considerable potential as a drought monitoring methodology on a larger spatial scale. • A new drought index was developed (PMDI), which integrated multiple sources of information describing different aspects. • PMDI performed well in different climate-hydrology regions for short- and long-term drought monitoring. • PMDI has reasonably good potential applicability in drought monitoring on a larger spatial scale. [ABSTRACT FROM AUTHOR]

Changes in the land use/cover alter the Earth system processes and affect the provision of ecosystem services, posing a challenge to achieve sustainable development. In the past few decades, the Yellow River (YR) basin faced enormous social and environmental sustainability challenges associated with environmental degradation, soil erosion, vegetation restoration, and economic development, which makes it important to understand the long-term land use/cover dynamics of this region. Here, using three decades of Landsat imagery (17,080 images) and incorporating physiography data, we developed an effective annual land use/cover mapping framework and provided a set of 90 m resolution continuous annual land use/cover maps of the YR basin from 1986 to 2018 based on the Google Earth Engine and the Classification and Regression Trees algorithm. The independent random sampling validations based on the field surveys (640 points) and Google Earth (3456 points) indicated that the overall accuracy of these maps is 78.3% and 80.0%, respectively. The analysis of the land system of the YR basin showed that this region presents complex temporal and spatial changes, and the main change patterns include no change or little change, cropland loss and urban expansion, grassland restoration, increase in orchard and terrace, and increase in forest during the entire study period. The major land use/cover change has occurred in the transitions from forests, grasslands, and croplands to the class of orchard and terrace (19.8% of all change area), which not only increase the greenness but also raised the income, suggesting that YR progress towards sustainable development goals for livelihood security, economic growth, and ecological protection. Based on these data and analysis, we can further understand the role of the land system in the mutual feedback between society and the environment, and provide support for ecological conservation, high-quality development, and the formulation of sustainable management policies in this basin, highlighting the importance of continuous land use/cover information for understanding the interactions between the human and natural systems. [ABSTRACT FROM AUTHOR]

Agricultural water resource, mainly consumed through evapotranspiration, plays a critical role in agricultural production of arid and semiarid regions. Quantifying the changes of evapotranspiration in cropland (ETc), and its driving factors, may provide rich information for improving human land-use and water resource management. Here we first investigated the multi-year (2000–2015) changes in the ETc (mm yr−1) and associated driving factors of the Loess Plateau (LP), using a combination of the Vegetation Interfaces Processes model and a factorial analysis of variance. We found that the ETc of the LP showed a significant upward trend of 0.31 km3 yr−2 (3.33 mm yr−2) (p <.05) over the last 16 years, mainly driven by cropland changes (3.77% per year), which combined the contribution of cropland area changes and cropland leaf area index (LAIc) changes. We then examined the changes of the dominant driving factor: cropland, and results indicated that the cropland changes consisted of the decrease in cropland area (net decrease of 10.50 × 103 km2) and the increase in LAIc (increased by 10.72%), which suggest the actual contribution of the ETc uptrend was the increasing LAIc. Our further analysis on the causes of the increasing LAIc by correlating the LAIc with land-use management factors revealed that the cropland greening on the LP showed high positive correlations with the increasing inputs of total power of agriculture machinery and farm plastic film, followed by chemical fertilizer. The increase of LAIc was also promoted by the increased ratio of the garden fruits output to total crops output (increased by 67.12%) and multiple cropping (increased by 21.66%). These results suggest that the ETc uptrend can be related to the agricultural intensification. Our study highlights the need for a realistic representation of socio-economic development and human land-use practices in the sustainable optimal allocation of agricultural water resources on the LP. Unlabelled Image • ET in cropland (ETc) showed upward trend over the Loess Plateau from 2000 to 2015. • Land-use optimization drives cropland greening and promotes multi-year rise of ETc. • Socioeconomic development and land-use practice affect agricultural water allocation. [ABSTRACT FROM AUTHOR]

Vegetation phenology is highly sensitive to climate change, and the phenological responses of vegetation to climate factors vary over time and space. Research on the vegetation phenology in different climatic regimes will help clarify the key factors affecting vegetation changes. In this paper, based on a time-series reconstruction of Moderate-Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data using the Savitzky–Golay filtering method, the phenology parameters of vegetation were extracted, and the Spatio-temporal changes from 2001 to 2016 were analyzed. Moreover, the response characteristics of the vegetation phenology to climate changes, such as changes in temperature, precipitation, and sunshine hours, were discussed. The results showed that the responses of vegetation phenology to climatic factors varied within different climatic regimes and that the Spatio-temporal responses were primarily controlled by the local climatic and topographic conditions. The following were the three key findings. (1) The start of the growing season (SOS) has a regular variation with the latitude, and that in the north is later than that in the south. (2) In arid areas in the north, the SOS is mainly affected by the temperature, and the end of the growing season (EOS) is affected by precipitation, while in humid areas in the south, the SOS is mainly affected by precipitation, and the EOS is affected by the temperature. (3) Human activities play an important role in vegetation phenology changes. These findings would help predict and evaluate the stability of different ecosystems. [ABSTRACT FROM AUTHOR]