Water Use Efficiency In China Research Articles

Decadal variations in the driving factors of increasing water-use efficiency in China's terrestrial ecosystems from 2000 to 2022

Decadal variations in the driving factors of increasing water-use efficiency in China's terrestrial ecosystems from 2000 to 2022

Dissecting the characteristics and driver factors of potential vegetation water use efficiency in China

While large-scale vegetation greening in China has substantially influenced global vegetation dynamics, the specific impact of this restoration on water use efficiency (WUE) remained inadequately understood. This study employed both the Geodetector and structural equation modeling (SEM) methods, utilizing the Lund-Potsdam-Jena (LPJ) Global Dynamic Vegetation Model, to explore the contributions of various driving factors to China's potential vegetation WUE from 1982 to 2019. The results indicated: (1) there existed considerable further potential for vegetation recovery nationwide. Among them, the Loess Plateau, Inner Mongolia Plateau, and northern Xinjiang had relatively high potential for vegetation recovery. This potential was further amplified by the significant prospects for enhancing WUE in these areas; (2) The application of the Geodetector method revealed that the normalized difference vegetation index (NDVI) explained over 40 % of the variation in potential vegetation WUE in China, exerting a greater influence than climatic factors. In arid/semi-arid regions, precipitation (PRE), NDVI, and vapor pressure deficit (VPD) significantly influenced WUE. Temperature (TEM) was the dominant factor affecting WUE in humid and humid/semi-humid regions; (3) Utilizing the SEM analysis method, it was evident that NDVI exerted the most substantial direct positive influence on potential vegetation WUE in China, whereas VPD and PRE had notable negative impacts. In arid/semi-arid regions, PRE emerged as the primary determinant of WUE. Conversely, in regions where water resources were not limiting, TEM and VPD exerted a more pronounced influence on potential vegetation WUE. This indicated that while vegetation restoration generally enhanced potential vegetation WUE, other factors such as PRE, TEM, and VPD played critical roles in different climatic zones, shaping the regional variations in WUE.

Meta-Analysis of the Effects of Straw Incorporation on Maize Yield and Water Use Efficiency in China under Different Production Conditions

Maize plays a crucial role in China’s grain production, with a cultivation area reaching 44.22 million hectares and an annual yield of 289 million tons in 2023. However, the challenge remains on how to further increase maize yield and water use efficiency (WUE) without adding to the environmental burden. To systematically evaluate the impact of straw incorporation under varying production conditions on maize yield and WUE, this study collected experimental data from multiple locations across China. A meta-analysis was conducted to compare the effects of straw incorporation versus no incorporation, and the main influencing factors were identified using correlation analysis and a random forest model. The results indicate that straw incorporation significantly enhances both maize yield and WUE, with the most pronounced improvements observed under conditions of an average growing season temperature of 19–23 °C, soil pH of 6.5–7.5, low initial soil organic matter content, and deep plowing for straw incorporation. Additionally, moderate nitrogen application rates and straw incorporation amounts (9000–15,000 kg·ha−2) also significantly boost maize yield and WUE. Field management practices and meteorological conditions are identified as the primary factors affecting maize yield and WUE under straw incorporation conditions. Therefore, straw incorporation stands out as an effective agricultural practice for achieving high maize yields and efficient resource utilization. The findings of this study provide valuable insights for global food security and the sustainable development of agriculture.

Impact of extreme seasonal drought on ecosystem carbon‒water coupling across China

Water use efficiency (WUE) is a critical evaluation indicator of ecosystem responses to climate change and its extremes. However, the influence of the timing of extreme drought on the variation of ecosystem WUE under severe water stress has not been studied extensively. In particular, the modulation of drought impacts on WUE under regional hydro-climatic conditions and biome types is poorly understood. Considering observation-based ecosystem flux and drought index datasets, this study examined the impact of extreme seasonal drought on WUE in China and attempted to reveal the underlying drivers of seasonal variations in drought impacts. Results showed that the direction and magnitude of drought impacts on WUE depend on the occurrence time of extreme drought and the seasonal dynamics of regional ecological and climatic conditions. Across the vegetated regions in China, the most widespread reduction in WUE under extreme drought conditions was observed in summer, whereas approximately 60% of the study area showed positive changes in WUE under extreme drought conditions in spring. Furthermore, the co-regulation of drought characteristics and background environmental conditions in determining the impacts of extreme seasonal drought on ecosystem WUE is highlighted. Classification and regression tree analysis results illustrate that leaf area index (LAI) and drought timing dominated ecosystem WUE variation in response to extreme drought in China. Regions with lower LAI experienced more serious reductions in WUE under extreme drought. These findings indicate the importance of accounting for the interaction between drought seasonality and biome features in assessing drought impacts, thus contributing to improving the modelling of terrestrial ecosystem responses to climate extremes under global warming.

The Contributions of Climate and Human Activities to Water Use Efficiency in China’s Drylands

In the context of global warming, terrestrial ecosystems have undergone significant variations. China has implemented a variety of ecological engineering methods to enhance carbon stocks. However, understanding the spatial and temporal dynamics of carbon and water in drylands under climate change remains limited. Here, our research elucidates carbon and water dynamics in China’s drylands over the last two decades, with a focus on understanding spatial–temporal changes and the effects of ecological engineering on the carbon–water cycle. Furthermore, this study investigates the relationships among climate change, water use efficiency (WUE), and its components—Gross Primary Productivity (GPP) and Evapotranspiration (ET)—identifying key climatic drivers and assessing possible directions for enhancing WUE under changing climate conditions. Our research indicates that both GPP and ET have significantly increased over the past 20 years, with growth rates of 4.96 gC·m−2·yr−1 and 4.26 mm·yr−1, respectively. Meanwhile, WUE exhibited a slight declining trend, at a rate of −0.004 gC·mmH2O·yr−1. This confirms the positive impact of vegetation restoration efforts. We found that fluctuations in interannual WUE were influenced by human activities and climate change. Precipitation (Prec) was the key climatic factor driving the GPP increase. Both solar radiation (Solra) and Prec were crucial for the interannual variation of WUE. Interestingly, WUE was the main factor affecting GPP development. The decline in WUE in drylands is linked to interannual variability in WUE and increased Vapor Pressure Deficit (VPD) due to warming. Seasonal variations in how WUE responds to climatic factors were also observed. For instance, fall rainfall increased WUE, while spring rainfall decreased it. Fall WUE was highly sensitive to VPD. Spatially, we found higher WUE in China’s eastern and Xinjiang regions and lower in inland areas and the Tibetan Plateau. Geomorphologic factors and soil conditions were the main drivers of this spatial variability in WUE. Temperature (Tem), Solra, VPD, and relative humidity (Relah) also played significant roles. Our results show a generalized inverse persistence in WUE variability. This suggests a potential for increased WUE in the eastern regions and a risk of decreased WUE on the Tibetan Plateau. Addressing the threat of vegetation decline in arid regions, particularly within the Tibetan Plateau, is crucial. It is essential to adapt forestry practices to complement the carbon and water cycles in these landscapes.

Spatial difference analysis and dynamic evolution prediction of urban industrial integrated water use efficiency in China

Comprehensive quantitative assessment of China's urban industrial water use efficiency is effectively promote the green industrial development important steps in order to realize the overall development of high quality. Between 2009 and 2021, 290 in China based on ground level above the panel data of the city, this paper conducts research based on two principles of efficiency improvement and four models of efficiency analysis. The results show that: First, from the perspective of spatial differences, the integrated water use efficiency of urban industry in China presents a slow and uneven upward trend of “low in the east and high in the west, high in the middle and low in the north and south”. Second, from the perspective of driving factors, population density and government public investment on the whole inhibit the development of this efficiency, while GDP development and technological innovation promote it. Third, from the perspective of dynamic evolution prediction, the phenomenon of “beggar-thy-neighbor” and “neighborly kindness” coexist. Therefore, the government should implement industrial water-saving measures according to local conditions, the society should improve the supervision of the behavior of wasting industrial water, and the enterprises should speed up the integration process of industrial primary and repeat water efficiency, so as to promote the comprehensive green transformation of the economy and society.

Observed divergence in the trends of temperature controls on Chinese ecosystem water use efficiency

How have plants addressed the trade-off between carbon gain and water loss in this warming world? Ecosystem water-use efficiency (WUE), defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET), is a key indicator of the carbon–water relationship. WUE is expected to change due to climate change, yet the extent to which GPP or ET affects WUE changes remains unclear. Moreover, the potential time-varying variations in the WUE responses to recent warming have been overlooked. In this study, we assessed the relative contributions of GPP and ET to WUE using variance decomposition and investigated trends in temperature controls on WUE using moving windows and partial correlation analysis. Our results include: (1) the national multi-year average WUE in China increased significantly at a rate of 0.0174 gC·kg-1H2O·a-1, with 86.88% of the study area exhibiting increased trends. Forest ecosystems, except for ENF, had relatively higher WUE, and the highest value was observed in the deciduous broad-leaf forest (3.77 gC·kg-1H2O), while grassland ecosystems had the lowest WUE of only 1.05 gC·kg-1H2O. (2) GPP, rather than ET, primary drove WUE variations in most areas, except in Northeast China and Southwest China. GPP always contributed more to WUE than ET in each land cover type. In forests, ET contributed more to WUE than in other land cover types. (3) WUE exhibited significantly positive correlations with temperature and radiation, with a positive correlation with temperature in 63.73% (14.83% significant in level of p < 0.05 and the same as below) of the study area and positive correlation with radiation in 74.12% (20.71% significant) of the study area. The control of precipitation on the WUE was complex, with a positive correlation with precipitation in 54.29% of the study area (9.38% significant). (4) The correlation coefficients with temperature exhibited an increasing trend in 52.26% of the study areas and a decreasing trend in 47.74% of the study areas, with a notable divergence in the spatial distribution of the trend of the temperature controls on WUE. Warming is projected to enhance ecosystem functioning in northern regions but may have adverse effects in the south. These findings shed light on the dynamic response of ecosystem functioning to ongoing warming, and would improve our understanding of the terrestrial carbon–water cycle.

Spatial variations and mechanisms for the stability of water use efficiency in China.

A clearer understanding of the stability of water use efficiency (WUE) and its driving factors contributes to improving water use efficiency and strengthening water resource management. However, the stability of WUE is unclear. Based on the EEMD method, this study analyses the spatial variations and mechanisms for the stability of WUE in China, especially in the National Forest Protection Project (NFPP) areas. It is found that the stable WUE was dominated by non-significant trends and increasing trends in China, accounting for 33.59% and 34.19%, respectively. The non-significant trend of stable WUE was mainly located in the Three-North shelterbelt program area, and the increasing trend of stable WUE was in Huaihe and Taihu, Taihang Mountains, and Pearl River shelterbelt program areas. Precipitation and soil moisture promoted the stable WUE in these project areas. The unstable WUE was dominated by positive reversals or negative reversals of WUE trends. The positive reversals of unstable WUE were mainly located in the Yellow River shelterbelt program areas, which was promoted by temperature and radiation, while the negative reversals of unstable WUE were mainly distributed in the Yangtze River and Liaohe shelterbelt program areas, which were mainly induced by saturation water vapor pressure difference (VPD). Our results highlight that some ecological restoration programs need to be improved to cope with the negative climate impact on the stability of WUE.

Recent change in ecosystem water use efficiency in China mainly dominated by vegetation greening and increased CO2

Over the last two decades, the significant vegetation increase caused by the execution of several ecological restoration programs has modified the integrated carbon and water cycles. However, the underlying mechanisms of ecosystem water-use efficiency (EWUE) change remain unclear. The current study estimates the annual and seasonal variations in the spatiotemporal patterns of EWUE from 2000 to 2018 and quantifies its driving factors to distinguish the impacts of vegetation and environmental factors across China. The contribution of driving factors to EWUE dynamics is quantified using PML_V2 gross primary productivity (GPP) and evapotranspiration (ET) products by employing the partial derivative (PD) equation. The results reveal that the leaf area index (LAI) is the major contributor in altering the EWUE of China, followed by CO2. The mean seasonal contribution of LAI is dominated by summer (0.0044 gC mm−1H2O yr−1) and spring (0.0035 gC mm−1H2O yr−1), followed by winter (0.0029 gC mm−1H2O yr−1) and autumn (0.0013 gC mm−1H2O yr−1), while the annual contribution is calculated to be 0.0017 gC mm−1H2O yr−1. The rate of CO2 contribution to EWUE was highest in spring (0.0022 gC mm−1H2O yr−1), followed by winter (0.0012 gC mm−1H2O yr−1), autumn (0.001 gC mm−1H2O yr−1) and summer (0.0007 gC mm−1H2O yr−1), while the annual rate was calculated to be 0.001 gC mm−1H2O yr−1. The relative contribution of climatic factors is the most considerable in the summer season, with 8.6%. The negative contribution of CO2 to EWUE along south China coast may not be influenced by CO2, rather because of the seasonal variations in GPP and ET trends. Our findings suggest that vegetation greening taken place in the last couple of decades has significantly enhanced EWUE trends in China and could help to develop future ecological restoration programs considering EWUE variations for effective ecosystem management and efficient water use.

Water use efficiency of China's karst ecosystems: The effect of different ecohydrological and climatic factors

Water use efficiency (WUE) is an important indicator for understanding the coupled ecosystem carbon and water cycles. However, the effect and contributions of factors on WUE variations in China's karst ecosystems for different climatic conditions have not been extensively studied. Our studies on WUE variations of China's karst ecosystems from 2001 to 2021 based on evapotranspiration and net primary productivity (NPP) from Moderate-resolution imaging spectroradiometer revealed the contributions of soil moisture (SM), leaf area index (LAI), precipitation (P), temperature (T), vapor pressure deficit (VPD), and CO2 concentration (CO2). Results showed that the trend of WUE was similar to that of NPP in terms of the latitude, longitude, and elevation, and WUE started abruptly decreasing after an elevation >3000 m until it reached 0 at 4500 m. WUE was primarily “slightly increased” in the humid region (H) and “slightly decreased” in the semi-humid region (SH), arid and semi-arid regions (ASA), and Qinghai–Tibet plateau region (QTP). CO2 (0.34), LAI (0.60), P (0.58), and LAI (0.55) exhibited the strongest positive direct effects on WUE in H, SH, ASA, and QTP, while VPD exhibited the strongest negative direct effect. VPD (0.26), VPD (0.28), SM (0.47), and P (0.39) had the strongest positive indirect effect, while T (−0.24), T (−0.18), VPD (−0.35), and P (−0.03) had the strongest negative indirect effect on WUE. The positive contributions of WUE variations in H, SH, ASA, and QTP were dominated by T (47.96 %), CO2 (26.36 %), P (8.81 %), and CO2 (52.97 %), whereas the negative contributions were dominated by P (−7.95 %), LAI (−26.57 %), CO2 (−35.98 %), and VPD (−9.59 %), respectively. This study quantifies the spatial and temporal distribution patterns of WUE in China's karst ecosystems and the regional differences between the multiple ecohydrological factors, thereby facilitating in-depth understanding and effective regulation for the carbon and water cycles in karst ecosystems.

Exploring the spatial structure and impact factors of water use efficiency in China

Improving water use efficiency is an essential strategy in the response to the global water crisis. The assessment of water use efficiency serves as the foundation for improving water use efficiency and water governance. Based on the mixed methods including Super-SBM model, GML index, spatial analysis, and Tobit model, this study assesses the water use efficiency from the scales of regional and provinces in China from 2011 to 2020, explores the evolution characteristics and spatial pattern of water use efficiency, and identifies the impact factors of water use efficiency. The results indicate that regional water use efficiency in China varies significantly by space, the highest in the eastern region with an average value of 0.8052, and the lowest in the central region with an average value of 0.5709. From 2011 to 2020, the average water use efficiency in China is 0.7042, which is in a low efficiency state, and roughly two thirds of the country's provinces use water inefficiently or ineffectively. In addition, regional differences of water use efficiency in China have a tendency of divergence and polarization. The technological progress change is the major factor for promoting water use efficiency. Economic development, water endowment, water use structure, scientific and technological development, and urban development have significant effects on water use efficiency in different regions respectively, while industrial structure and water governance have insignificant effects. This study supports researchers and practitioners in comprehending the characteristics and spatial patterns of water use in China, and also enriches the research system of water governance and integrated water resources management.

Revisiting the role of transpiration in the variation of ecosystem water use efficiency in China

Efforts to develop effective climate strategies necessitate a better understanding of the relationship between terrestrial water and carbon cycles. Water use efficiency (WUE) has been often used to characterize this relationship, while the role of transpiration (T) in the variation of ecosystem WUE has been less investigated. Here, we partitioned WUEET (the ratio of gross primary productivity (GPP) to evapotranspiration (ET)) into a two-component process, i.e., the ratio of gross primary productivity to plant transpiration, GPP/T, that is WUET, and the ratio of plant transpiration to evapotranspiration, T/ET. Based on two GPP datasets (i.e., GPP based on the light use efficiency model or the vegetation index- NIRv) and the GLEAM ET dataset, this study investigated the role of T in the variation of WUE in the ecosystem level and how the role is affected by drought. We found that drought can lead to the change of ET partitioning, thus affecting the variability of WUE. The variability of WUEET was dominated by WUET. In general, the proportion of T increased gradually from humid to arid areas. To adapt to drought conditions, vegetation in arid areas tend to have a high stress resistance by increasing their WUE. We further found that WUET has stronger seasonal stability than WUEET. GPP dominated WUEET variability in humid/sub humid areas, while ET and GPP jointly dominated WUEET variability in semi-arid/arid areas. GPP dataset based on light use efficiency (LUE) could better reflect the impact of drought on vegetation. This study contributes to a better understanding of the change mechanism of ecosystem WUE and emphasizes the critical role of physiological process components in water-carbon cycling.

Heterogeneous impacts and spillover effects of green innovation network and environmental regulation on water use efficiency: A spatiotemporal perspective from 269 cities in China

Water is a strategic resource for economic and social development, and exploring the evolutionary mechanism of water use efficiency (WUE) is key to realizing regional sustainable development. This study takes 269 cities in China from 2008 to 2019 as the research unit and uses the spatial econometric model to reveal the spatial effect of the green innovation network (GIN) and environmental regulation on WUE. The results show that WUE in China shows a fluctuating upward trend and has strong spatiotemporal heterogeneity and spatial correlation characteristics. The high-value areas of WUE are mainly concentrated in the Shandong Peninsula urban agglomeration, and the low-value areas are mainly distributed in the middle reaches of the Yangtze River. The GIN and WUE have a significant U-shaped relationship, indicating that only by breaking through " Valley of Death" and "Darwinian Sea" can the GIN exert "network effects" and "technological effects" to improve WUE. Environmental regulation has a significant positive spillover effect on WUE, which verifies the rationality of the Porter hypothesis in WUE. In addition, the impact of the GIN on WUE has strong spatiotemporal heterogeneity, so when strengthening the GIN connection, the rebound effect must be prevented from negatively affecting WUE.

Contributory factors of the secular trends to changes in ecosystem water-use efficiency in China

Ecosystem water-use efficiency (WUE) is an effective indicator of ecosystem functioning, which is widely used to characterize the coupling relationship between terrestrial carbon and the water cycle. Although the linear trends in WUE have been well reported, the nonlinearity of the secular trends in WUE and their relative contribution to the overall changes were still poorly investigated. In this study, we used ensemble empirical mode decomposition (EEMD) to extract the secular trends of the WUE and their relative contribution (RC) to the WUE changes in China, which represents the stability of the ecosystem functioning. We found that although increasing trends dominated the secular trends of the WUE, nearly half of the study areas had experienced trend shifts. Except that deciduous forests and mixed forests were dominated by trend shifts, most of the land cover types were dominated by increasing trends. The RC exhibited a bimodal pattern along the elevation gradient, with peaks at 20 m and 5000 m. Similarly, the RC peaked at the east and south aspects, and was the lowest for the west and north aspects. In comparison, the RC exhibited a U-shaped pattern with the slope, and was the lowest at 80°. For the monotonically increasing trends and decreasing-to-increasing trends, the high RC mainly occurred on the North China Plain and Loess Plateau, indicating ecosystem improvement and strong stability. Meanwhile, it was low in northeastern China and southwestern China, indicating unsustainableecosystem improvement. The RC was always very low for increasing-to-decreasing trends and monotonically decreasing trends, indicating low ecosystem stability with a high possibility for improvement. Temperature and the atmospheric carbon dioxide (CO2) concentration were the two main climatic factors driving the WUE changes. The climatic mean state rather than the climatic variability affected the ecosystem stability. The results of this study highlight the relative contribution of the secular trends to WUE changes and provide a better understanding of the structure and the stability of ecosystem functioning.

Recent Seasonal Variations in Ecosystem Water Use Efficiency in China's Key Tropical‐Subtropical Transitional Zones in Response to Climate Change

AbstractUnderstanding the response of terrestrial ecosystem water use efficiency (WUE) to climate change is critical to accurately represent the carbon‐water cycle processes. However, how WUE dynamics are evolving under seasonal climate variations and biome‐specific characteristics remains still unclear. In this study, we integrated two state‐of‐the‐art retrieval algorithms to estimate gross primary productivity (GPP) and evapotranspiration (ET) from satellite MODIS records. Such metrics served as input to quantify ecosystem WUE, expressed as the ratio of GPP to ET, and explore its dynamics during the dry and wet season from 2001 to 2018 in China's key tropical to subtropical transitional zones, that is, Yunnan Province. Results show large spatial and seasonal variability in WUE over the observational period. During the dry season, the increasing trends in GPP and ET have led to contrasting WUE patterns in forest and non‐forest biomes, leading to positive and negative WUE trends, respectively. During the wet season, the declining trends in GPP occurring in combination with opposite trends in ET, have caused decreasing WUE consistently across all biomes except croplands, likely further modulated by human factors. The observed changes in WUE appear primarily driven by variations in air temperature (Ta) and vapor pressure deficit (VPD) during both dry and wet seasons. Overall, these results contribute to a better understanding of the carbon‐water interplay in tropical‐subtropical transitional zones and provide new insights to improve our capacity to predict the terrestrial ecosystem's response to climate change.

Agricultural water use efficiency and spatial spillover effect considering undesired output in China

Abstract Solving the problem of agricultural water use efficiency is an effective means to understand the agricultural ecological civilization and food security. In order to balance the relationship between agricultural water efficiency and regional economic size, this study examines the agricultural water use efficiency in China based on the Super-SBM model of unexpected output. At the same time, the Spatial Durbin Model (SDM) was introduced to analyze the spatial spillover effect and try to find ways to improve agricultural water use efficiency from the perspective of influencing factors. The present study used the panel data of 30 provinces in China from 1998 to 2018 to obtain empirical results. The results show that (1) China's agricultural water resources’ utilization efficiency in 21 years has not remained high: the results showed that it was 0.496 in 1998, 0.572 in 2008, and 0.657 in 2018, but it is slowly rising which explains that the low efficiency is mainly caused by the low pure technical efficiency. (2) The overall agricultural water use efficiency in China is in a situation of spatial agglomeration but there has been a trend of shifting positive correlations to negative correlations among neighboring provinces. It found that in 1998, the sum of the number of `High-high agglomeration type' and `low-low agglomeration type' provinces was 20, and the sum of `low-high agglomeration type' and `high-low agglomeration type' provinces was 10. In 2018, the total number of `high-high agglomeration type' and `low-low agglomeration type' provinces decreased to 12, while the total number of `low-high agglomeration type' and `high-low agglomeration type' provinces increased to 18, which specifically manifested as a negative spillover effect. (3) During the research period, the province's agricultural fixed asset investment, fiscal expenditure on agriculture, forestry, and water affairs, the number of years of education of rural residents and the increase in crop sown area have positive impacts on the efficiency of agricultural water use in the province. Meanwhile the transfer of labor and increase in the disposable income of rural residents reduced the efficiency of agricultural water use in the province. Fixed agricultural investment, labor transfers, and financial expenditures for agriculture, forestry, and water affairs in neighboring provinces have negative impacts on the province's agricultural water use efficiency. The impact is specifically manifested as a negative spatial spillover effect. As a result, China's agriculture will move towards healthy and green development. Therefore, the efficiency of agricultural water use needs to be comprehensively improved.

Vegetation restoration dominated the variation of water use efficiency in China

Implementation of numerous ecological restoration programs over the last two decades has significantly increased vegetation coverage in China. However, the response of the coupled carbon and water cycles to the large-scale vegetation restoration and the underlying mechanisms remain unclear. This study analyzed the spatiotemporal patterns of regional gross primary productivity (GPP), evapotranspiration (ET) and water use efficiency (WUE) in China using the two-leaf light use efficiency (TL-LUE) and the Priestley Taylor Jet Propulsion Laboratory (PT-JPL) models during the 2000–2017 period. The influencing mechanisms of anthropogenic re-vegetation and climatic factors on regional WUE were also analyzed. Results indicate that (1) both the GPP and WUE showed a significant increasing tendency with inter-annual change rates of 10.53 g C m−2 yr−1 and 0.01 g C kg−1 H2O yr−1, respectively; while the inter-annual change rate of annual ET was 1.43 kg H2O m−2 yr−1. (2) Spatially, the regional GPP dominated WUE variation of more than 79.51% of the total area. (3) Among the influencing factors, the greening of vegetation driven by human activities (LAIh) explained 35.27% of the WUE variation in China, much more than the climatic factors over during the study period. At the regional scale, human-driven vegetation greening also dominated the increasing WUE at regional scale. These findings provide important information to support large-scale ecological restoration policy/decision making to improve ecosystem services in China.

Assessing the Impact of the Strictest Water Resources Management Policy on Water Use Efficiency in China

The strictest water resources management policy plays a critical role in response to the challenge of water shortage, water security, and sustainable water development in China. Despite the varied analyses of the strictest water resources management policy, the relations between the strictest water resources management policy and water use efficiency remain under-researched. This study uses an interval event-analysis method to assess the strictest water resources management policy’s impact on water use efficiency in China based on data from 2007 to 2020. In addition, the study breaks down water use efficiency into eight indicators and divides the strictest water management policy into “pre-, middle, and post-” phases. The research results show the strictest water resources management policy has a significant positive effect on water use efficiency. Further research shows the total water consumption control system and water efficiency control system have the most significant effect. The strictest water resources management policy has a lasting impact on water use efficiency. This study contributes to the global knowledge body of water governance and provides a reference value for water policy decision-making and optimization in other countries.

Optimized farmland mulching improves alfalfa yield and water use efficiency based on meta-analysis and regression analysis

Alfalfa (Medicago sativa L.), a globally vital forage crop with abundant nutrition and high yield, is commonly planted in arid and semi-arid regions where water resources are scare, such as China. In order to adapt water limitation conditions, farmland mulching (FM) is gradually being applied in alfalfa production. However, the effects of FM on alfalfa in different climatic conditions and management practices should be investigated before concluding that it is universally effective. We performed a meta-analysis and regression analysis of 94 yield comparisons and 74 water use efficiency (WUE) comparisons from 19 peer-reviewed studies and founded that FM significantly increased alfalfa yield and WUE, on average by 38.5% and 43.7%, respectively, compared to non-mulching. However, the increase rate (IR) of yield and WUE varied with mulching type, region, management, and length of growth year. For yield, FM was more pronounced in Gansu, in regions with an average annual precipitation (AAP) of 400–600 mm, average annual temperature (AAT) < 0 °C, and altitude > 2000 mm, and with plastic film, all of the soil surface mulching, ridge–furrow planting, sowing rate (SR) < 20 kg ha–1 and nitrogen application rate (NAR) < 100 kg ha–1. Overall, AAP and altitude had significant positive effects on yield IR of mulching alfalfa, while AAT and SR had significant negative effects. The effects of these factors on yield IR varied across different quantiles. For WUE, FM was more beneficial in regions with AAP of 200–400 mm and AAT > 6 °C. Only SR had a significant negative effect on the WUE IR of mulching alfalfa as a whole, while the effects of AAP, AAT, and altitude were significant in some quantiles. Our findings confirm the benefits of FM to increase alfalfa yield and WUE in China, identify the conditions under which these results can be achieved, and also suggest that the benefits are site specific.

Exploring the Spatial Network Structure of Agricultural Water Use Efficiency in China: A Social Network Perspective

The exploration of the spatial network structure of agricultural water use efficiency (AWUE) and its influencing factors for promoting water saving and improving water use efficiency in regional agricultural production is of great importance. In this paper, the modified gravity model and social network analysis methods were used to study the spatial correlation characteristics and influencing factors of AWUE in China between the years 2008 and 2019. It was found that (1) the overall trend of AWUE in China has been fluctuating and declining, and there are obvious differences in AWUE in each region; (2) the spatial network structure of AWUE in China is complex and relatively stable, with close interprovincial connections and obvious spatial spillover effects; (3) Shanghai, Beijing, Jiangsu, and Zhejiang are at the center of the network; and (4) the differences between geographical adjacency, technological development level, farmers’ income, and natural resource endowment have significant effects on the development of the AWUE network. These results provide a theoretical basis for the government to improve AWUE and promote collaborative regional development.