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.

A Bayesian network-GIS probabilistic model for addressing human disturbance risk to ecological conservation redline areas.

Population growth and associated ecological space occupation are posing great risks to regional ecological security and social stability. In China, "Ecological Conservation Redline" (ECR) that prohibited urbanization and industrial construction has been proposed as a national policy to resolve spatial mismatches and management contradictions. However, unfriendly human disturbance activities (e.g., cultivation, mining, and infrastructure construction) still exist within the ECR, posing a great threat to ecological stability and safety. In this article, a Bayesian network (BN)-GIS probabilistic model is proposed to spatially and quantitatively address the human disturbance risk to the ECR at the regional scale. The Bayesian models integrate multiple human activities, ecological receptors of the ECR, and their exposure relationships for calculating the human disturbance risk. The case learning method geographic information systems (GIS) is then introduced to train BN models based on the spatial attribute of variables to evaluate the spatial distribution and correlation of risks. This approach was applied to the human disturbance risk assessment for the ECR that was delineated in 2018 in Jiangsu Province, China. The results indicated that most of the ECRs were at a low or medium human disturbance risk level, while some drinking water sources and forest parks in Lianyungang City possessed the highest risk. The sensitivity analysis result showed the ECR vulnerability, especially for cropland, that contributed most to the human disturbance risk. This spatially probabilistic method can not only enhance model's prediction precision, but also help decision-makers to determine how to establish priorities for policy design and conservation interventions. Overall, it presents a foundation for later ECR adjustments as well as for human disturbance risk supervision and management at the regional scale.

Ecological engineering induced carbon sinks shifting from decreasing to increasing during 1981-2019 in China.

Substantial evidence shows that most of China's terrestrial ecosystems are important carbon sinks. However, the nonlinear trend of the carbon sinks and their nonlinear response to driving factors are unclear. Taking the net ecosystem productivity (NEP) as a proxy for the ecosystem carbon sink, the nonlinear relationships between the monotonically increasing trends and decreasing to increasing shifts in the carbon sink to climate change and ecological engineering were investigated based on ensemble empirical mode decomposition (EEMD) and machine learning algorithm (boosted regression tree model, BRT). The results suggest that 16.75 % of the carbon sinks in China experienced a monotonic increase. Additionally, 20.55 % of the carbon sinks shifted from decreasing to increasing trends, primarily after 1995, and these carbon sinks were located in the key ecological engineering areas, such as the middle reaches of the Yellow River shelterbelt program area, the Liaohe shelterbelt program area, the Grain to Green program area, and the Three-North Forest shelterbelt program area. Moreover, carbon sinks exhibited strong spatial autocorrelation with low-low clustering in the north and high-high clustering in the south. The increase in CO2 (slope of CO2 < 1.8 g/m2/s/y) and solar radiation (slope of radiation >1 w/m2/y) promoted the monotonic increase in the carbon sinks in the center of China. The increase in the areas of forest and grassland shifted the carbon sink trend from decreasing to increasing in the key ecological engineering program areas, and economic development reversed the carbon sink reduction in the Pearl River shelterbelt program area. These findings highlight the positive effect of ecological engineering on carbon sinks and provide adaptation strategies and guidance for China to achieve the "carbon neutrality" target.

Inter-annual variations of vegetation dynamics to climate change in Ordos, Inner Mongolia, China.

To reveal the characteristics of climate change and the controlling factors for vegetation dynamics in the Ordos, Inner Mongolia, China, 34 years (1982-2015) of regional climate variables and vegetation dynamics were investigated. The results show that: Annual mean air temperature (TMP) significantly increased with a linear slope of 0.473°C/10yr. Annual precipitation (PRE) had a non-significant positive trend nearly 5 times lower than the trend of potential evapotranspiration (PET). The average Normalized Difference Vegetation Index (NDVI) computed for the region was found to show a significant positive trend (6.131×10-4/yr). However, all climate variables displayed non-significant correlations with NDVI at annual scale. The reduction of desert and the increase of grassland over the past decades were accountable for the increased NDVI. Principal components analysis revealed that the regional climate change can be characterized as changes in temperature, humidity and the availability of radiant energy. Based on principal components regression coefficients, NDVI was mostly sensitive to humidity component, followed by growing season warmth (WMI). Spatially, 93.1% of the pixels displayed positive trend and 61.8% of the pixels displayed significant change over the past decades. Both principal regression analysis and partial correlation analysis revealed that NDVI in eastern part of Ordos was sensitive to TMP, whereas, NDVI in southern and western areas of Ordos displayed the high sensitivity to combined effects of PRE and cloud coverage (CLD). Partial correlation analyses also revealed that TMX was a surrogate for aridity, TMN was a representative of humidity, and temperature variations below the threshold of 5°C (CDI) were less important than WMI. We conclude that regional climate change can be characterized by warming and increased aridity. The significant positive trend of regional NDVI and the non-significant correlations between NDVI and climate variables at annual scale suggests the hidden role of the human activities.

Persistence of increasing vegetation gross primary production under the interactions of climate change and land use changes in Northwest China.

Substantial evidence suggests a widespread increase in global vegetation gross primary production (GPP) since the 1980s. If the increasing trend of GPP remains unchanged in the future, it is considered to be the persistence of increasing GPP. However, it is still unknown whether the vegetation increasing GPP is persistent under the interactive effects of climate change and land use changes in Northwest China. Using the Mann-Kendall and boosted regression tree models, we constructed the relationship between the increasing GPP and environmental variables, and further explored its persistence under the interactions between climate change and land use changes under SSP245 and SSP585 scenarios. The results indicated that: (1) Land use change (8.01%) was the most important variable for the increasing GPP. The surface net solar radiation (6.79%), and maximum temperature of the warmest month (6.78%) were also very important. Moreover, mean temperature of the warmest quarter had strong interactions with mean precipitation of the warmest quarter (9.82%) and land use change (8.24%). (2) Under the SSP245 scenario, the persistence of increasing GPP accounted for 65.06% of the area in 2100, mainly located in Qinghai, Ningxia, and Shaanxi, while it only accounted for 19.50% under the SSP585 scenario. (3) The SSP245 scenario moderate warming leads to a slight ecosystem benefit, with more areas developing an increase in GPP due to climate and land use change factors. On the other hand, under SSP585 scenario, there are widespread losses of increasing GPP, driven largely by climate change, while ecological engineering is conducive to the persistence of increasing GPP in southern Qinghai. The results highlight the importance of the interactive effects of climate change and land use changes for predicting the persistence of vegetation change.

Correction to: Organic Matter Pollution During the Spring Thaw in Hulun Lake Basin: Contribution of Multiform Human Activities.

In the original publication of the article, there was an error in the name of institution. The incorrect name of institution "Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, 8, Jiangwangmiao Road, XuanWu District, 210042 Nanjing, People's Republic of China" should be revised to "Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environmental, 8, Jiangwangmiao Road, XuanWu District, 210042 Nanjing, People's Republic of China". The institution was still the same, but the name of the institution was changed.

Organic Matter Pollution During the Spring Thaw in Hulun Lake Basin: Contribution of Multiform Human Activities.

It has recently been reported that plateau lakes have been seriously polluted by organic matter, however, the sources of this organic matter and their relative contributions remain unknown. In this study, to determine the sources and composition of the organic matter in the Hulun Lake basin during the spring-thaw period, a total of twenty-three sampling sites were investigated. Results showed high levels of organic matter pollution in the surface water of Hulun Lake, with an average COD values of 119.35 mg L-1. Organic matter came from natural sources as well as a variety of anthropogenic activities. The direct sources included urbanization, industrial and residential wastewater discharge, and emission from burning fossile fuels. A large indirect source was organic matter from tumbleweed decomposition, which had increased due to desertification caused by overgrazing. The principal component analysis showed that organic matter from Hulun lake shared composition and sources with the upstream sections of the natural tributaries and the downstream section of the artificial tributary. The artificial inflow river contributed more organic matter than the other tributaries. Notably, a large portion of organic matter in Hulun Lake came from decomposing tumbleweed concentrated in the downstream section of one of the natural rivers. New indirect consequences of human activities must be factored into the rule and regulations that protect plateau lake ecosystems alongside the direct effects of established human activities.

The establishment of Chinese ecological conservation redline and insights into improving international protected areas.

China proposed the Ecological Conservation Redline (ECR) strategy in 2011 and listed it as an important part of the ecological promotion process in 2013. In 2017, China implemented the designation of ECR at a national scale. The aim was to demarcate areas with unique ecological functions. Therefore, the ECR became a key part of national ecological security. Three major types of area are covered by the ECR so that important ecosystem functions can be protected. These are ecologically fragile zones, biodiversity, and natural landscapes. The ECR is characterized as being fundamental, systematic, and mandatory. This study summarizes the developmental background, theoretical framework, and structural composition of ECR, and highlights recent advances. A comparison of the ECR to international protected areas showed that they were generally similar, but there were differences in the methods used to protect targets, their system design, and their management, which provided insights and recommendations that could improve the construction and management of protected areas in the future. These included: (1) increasing the integrity of ecological protection by replacing dispersed protection with a more comprehensive and systematic approach, (2) increasing the spatial accuracy of protection to enhance the effectiveness of protection, and (3) implementing an overall-process management to guarantee the sustainability of protection. Finally, suggestions are made for further protected area improvements and ecological protection, including further theoretical exploration, strengthening management, and facilitating international cooperation.

China's ecological conservation redline: A solution for future nature conservation.

Globally, continuing environmental degradation is leading many countries to strengthen their systems of protected areas. However, this may not be sufficient to halt degradation and conserve biodiversity and ecosystem services. To supplement its growing system of protected areas, the Chinese government is adopting a strategy of Ecological Conservation Redlines (ECRs). The ECRs define limits to human encroachment into ecologically sensitive and vulnerable areas and enforce strict conservation in order to guarantee national ecological security. ECRs are integrated in their design, are based on sound science, and provide a systemic management mechanism. ECR supports the formation of a comprehensive ecological conservation system that will lead to effective conservation for the most ecologically valuable and fragile ecosystems. The ECR approach seeks to improve China's ecological security and guide nature conservation in the future. It could also provide a valuable example of an effective approach for improving nature conservation worldwide.

Dynamics of Soil Respiration in Alpine Wetland Meadows Exposed to Different Levels of Degradation in the Qinghai-Tibet Plateau, China.

The effects of degradation of alpine wetland meadow on soil respiration (Rs) and the sensitivity of Rs to temperature (Q10) were measured in the Napa Lake region of Shangri-La on the southeastern edge of the Qinghai-Tibet Plateau. Rs was measured for 24 h during each of three different stages of the growing season on four different degraded levels. The results showed: (1) peak Rs occurred at around 5:00 p.m., regardless of the degree of degradation and growing season stage, with the maximum Rs reaching 10.05 µmol·m-2·s-1 in non-degraded meadows rather than other meadows; (2) the daily mean Rs value was 7.14-7.86 µmol·m-2·s-1 during the mid growing season in non-degraded meadows, and declined by 48.4-62.6% when degradation increased to the severely degraded level; (3) Q10 ranged from 7.1-11.3 in non-degraded meadows during the mid growing season, 5.5-8.0 and 6.2-8.2 during the early and late growing seasons, respectively, and show a decline of about 50% from the non-degraded meadows to severely degraded meadows; (4) Rs was correlated significantly with soil temperature at a depth of 0-5 cm (p < 0.05) on the diurnal scale, but not at the seasonal scale; (5) significant correlations were found between Rs and soil organic carbon (SOC), between biomass and SOC, and between Q10 and Rs (p < 0.05), which indicates that biomass and SOC potentially impact Q10. The results suggest that vegetation degradation impact both Rs and Q10 significantly. Also, we speculated that Q10 of alpine wetland meadow is probable greater at the boundary region than inner region of the Qinghai-Tibet Plateau, and shoule be a more sensitive indicator in the studying of climate change in this zone.

Environmental, Ecological, and Economic Benefits of Biofuel Production Using a Constructed Wetland: A Case Study in China.

Here we show a constructed wetland (CW), a viable alternative wastewater treatment system, be used to produce biofuels from biomass by using nitrogen contained in domestic wastewater. We summarize the potential biomass yield evaluated as cellulosic ethanol bioenergy production, and combine the life cycle analysis with a mass balance approach to estimate the energetic, environmental, and economic performance of a CW biofuel system. The results showed that the annual aboveground biomass yield of a CW in Zhoushan, Zhejiang Province, China, averaged 37,813 kg ha-1 year-1 as the by-product of treating waste N, which is about one order of magnitude larger than traditional biofuel production systems. The biomass yield in the Zhoushan CW system had life cycle environment benefits of 8.8 Mg (1 Mg = 106 g) CO2 equivalent ha-1 year-1 of greenhouse gas emission reduction. The CW in Zhoushan had a net energy gain of 249.9 GJ (1 GJ = 108 J) ha-1 year-1 while the wastewater treatment plant (WTP) consumes 7442.5 GJ ha-1 year-1. Moreover, the CW reduced greenhouse gas emissions to 2714 times less than that of the WTP. The CW also provided various ecosystem services, such as regional climate regulation and habitat conservation. We suggest that the potential use of a CW as biofuel production and carbon sequestration via nitrogen-negative input can be explored more widely in the future.

Ecosystem services changes between 2000 and 2015 in the Loess Plateau, China: A response to ecological restoration.

The Loess Plateau of China is one of the most severe soil and water loss areas in the world. Since 1999, the Grain to Green Program (GTGP) has been implemented in the region. This study aimed to analyze spatial and temporal variations of ecosystem services from 2000 to 2015 to assess the effects of the GTGP, including carbon sequestration, water regulation, soil conservation and sand fixation. During the study period, the area of forest land and grassland significantly expanded, while the area of farmland decreased sharply. Ecosystem services showed an overall improvement with localized deterioration. Carbon sequestration, water regulation and soil conservation increased substantially. Sand fixation showed a decreasing trend mainly because of decreased wind speeds. There were synergies between carbon sequestration and water regulation, and tradeoffs between soil conservation and sand fixation. It was concluded that ecological projects have contributed significantly to the rehabilitation of the fragile ecosystems of this region. To make these projects more successful and sustainable, long-term management procedures are necessary to maintain and consolidate the improvements.

Temporal variation and spatial scale dependency of the trade-offs and synergies among multiple ecosystem services in the Taihu Lake Basin of China.

Grasping the temporal-spatial characteristics of interactions and spatial scales of multiple ecosystem services is the foundation for sustainable ecosystem management. Eight ecosystem services, including crop production, freshwater supply, aquatic production, net primary production, soil conservation, water retention, flood regulation, and forest recreation were measured at the 1-km2 pixel scale in the Taihu Lake Basin (TLB) of China from 1990 to 2010. Furthermore, we quantified the trade-offs and synergies of services at different periods of urbanization and across the 1-km2 pixel scale and the county scale. We aim to find which ecosystem services interactions temporally vary and depend on spatial scale. Our results found that: 1). Tremendous amount of cultivated lands were converted to construction land, and rapidly shrank from 1990 to 2010. 2). Determined by land use, different ecosystem services had spatial heterogeneity of their strength. Ecosystem services hot spots experienced an increasing trend while cold spots showed a trend of decreasing first and then increasing from 1990 to 2010. 3). Trade-offs between provisioning services and regulating services at the 1-km2 pixel scale changed over time. There was a new synergy between freshwater supply and aquatic production at the 1-km2 pixel scale in 2010 with the human demand. 4). From 1990 to 2010, the changes of provisioning services led to trade-offs among provisioning services, regulating services and cultural services at two scales. Taking temporal variation and scale dependence into account, this research is helpful to the delineation of "Ecological Conservation Redline" and implement the project of "Grain for Green". We also provide suggestions for maintaining ecosystem services with economic growth in China's Yangtze River Economic Belt for land use policies and decision making.

Effect of irradiation time on riboflavin-ultraviolet-A collagen crosslinking in rabbit sclera.

PURPOSE: To determine the effect of the duration of irradiation on the biomechanical parameters of combined riboflavin-ultraviolet-A (UVA) collagen crosslinking (CXL) in rabbit sclera. SETTING: Department of Ophthalmology, Provincial Hospital affiliated with Shandong University, Shandong, China. DESIGN: Experimental study. METHODS: Thirty-six New Zealand rabbits were divided into 6 groups based on the duration of irradiation (10, 20, 30, 40, 50, or 60 minutes). After the application of riboflavin 0.1% drops (without dextran) as a photosensitizer, the animals were irradiated with 3 mW/cm(2) UVA at 365 nm. Only the left eye of each rabbit was treated. All the animals were humanely killed 24 hours postoperatively. One eye in each treated group was used for light microscopy. The other treated eye and all control eyes were prepared for biomechanical testing. The biomechanical parameters were ultimate stress, Young modulus, and the physiological modulus. RESULTS: The eyes irradiated for 10 or 20 minutes did not differ significantly from the control eyes. Stress-strain measurement of scleral strips irradiated for 40 minutes or longer showed a significant increase in the ultimate stress, Young modulus, and the physiological modulus. There was a significant increase in the physiological modulus of scleral strips irradiated for 30 minutes or longer. Eyes that were irradiated for 50 minutes and 60 minutes had retinal damage. CONCLUSIONS: Riboflavin-UVA CXL can lead to a noticeable increase in the biomechanical stiffness of the sclera. The physiological modulus is the most sensitive tool to measure stiffness. In this study, the optimum duration of irradiation was 40 minutes.