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• Multiple scales analysis method is effective for exploring vegetation coverage. • Precipitation is the main impact factor of vegetation growth. • The vegetation coverages around the CHSs were affected by their constructions. • It can be helpful for the sustainable ecosystem management in the DRR system. Along with the development of large-scale hydropower projects, many changes are arising both on the river channel and the ecosystems, which leads to the formation of a dam-reservoir-river system. The system is of significance to China due to the large-scale utilization of hydropower. However, such projects may cause significant impacts on local vegetation dynamics, which is of importance to local decision makers and water resources managers. In this research, the spatio-temporal variations of normalized difference vegetation index (NDVI) and climatic factors (CFs) under multiple time scales (i.e., annual, seasonal, and wet/dry periods) and the spatio-temporal pattern of the correlation of NDVI-CFs under the scales of annual and wet season were analyzed in the system by using the statistical methods. The response of NDVI to CFs in the basin was explored at the monthly scale. The main results indicated that from 1999 to 2013, the annual average NDVI had a significant overall upward trend. The distributions of the NDVI and its trend had the spatial and seasonal differences, with majority areas showing medium-high and high vegetation cover and a slight improvement in the grade of vegetation cover change of more than 40% of the total area. In the basin, temperature (T) and evapotranspiration (ET0) showed an upward trend, and precipitation (P) and the humidity index (HI) were the opposite. The corrections of NDVI-T and NDVI-ET0 were positive, and that of NDVI-P and NDVI-HI were negative. Also, the vegetation growth was mainly affected by the amount of P, and its time-lag period to the P was two months. In the scale of the eight cascade hydropower stations, the vegetation coverage and the correlation of NDVI-CFs around the Jinanqiao and Longkaikou hydropower stations were the best, and those near the Ludila and Guanyinyan were the worst, indicating that the vegetation coverage was affected by the cascade hydropower stations development. Therefore, the results may be beneficial for sustainable watershed ecosystem management in the system, as well as ecological development planning around the cascade hydropower stations. [ABSTRACT FROM AUTHOR]

Excessive anthropogenic nitrogen discharges have led to increasing nitrogen in aquatic systems, resulting in eutrophication problems. To address this problem, urban wetlands are used to remove nitrogen from wastewater treatment plant tailwater because of their efficient nitrogen removal capabilities. At the same time, high‑nitrogen tailwater can exert numerous impacts on the sediment denitrifier communities and denitrification of urban wetlands, and it is necessary to clarify this impact. In this research, we investigated denitrifier (nirK -, nirS - and nosZ -denitrifier) abundances and potential denitrification rate of 30 sediment samples from two urban wetland rivers in Haizhu National Wetland Park (China). One river called experimental river (ER) receives tailwater from a wastewater treatment plant, and the other called control river (CR) is unaffected by the tailwater. Moreover, we also determined the environmental variables to distinguish their relative effects on the variance of denitrifier abundances and denitrification rate in the two rivers. The results showed that the water quality was significantly different between ER and CR, while sediment property was not significant (p < 0.05). And it is unable to distinguish which has the greater denitrification rate between ER and CR. The redundancy analysis and path analysis indicated that riverine nutrient concentrations (e.g., ambient carbon and nitrogen) and physicochemical parameters (e.g., ambient temperature, dissolved oxygen and pH) were important determinants for denitrifier abundances and denitrification in ER and in CR, respectively. Furthermore, denitrifier abundances had an insignificant impact on denitrification in ER, but a considerable impact on denitrification in CR. The findings of this research can help to further understand how the tailwater affects sediment denitrifier communities and denitrification in urban wetland rivers, and to make better use of urban wetlands as a natural purification method. [Display omitted] • Tailwater significantly affected water quality but not sediment properties. • Nutrient concentrations were determinants for N removal in the river with tailwater. • Physicochemical parameters controlled the N removal in the river without tailwater. [ABSTRACT FROM AUTHOR]

In the upper reach of the Yangtze River Basin in China, changes of the runoff and sediment yield in the middle reach of the Jinsha River Basin have been given close attentions because of their declination trends over recent years. Then, the impact factors for the variations of runoff and sediment yield were urgent need to be investigated through a distributed hydrological modelling under multi spatiotemporal scales. The results showed that climate change had a significant impact on runoff and sediment yield of the basin before the operation of cascade reservoirs. The contribution rate of the reservoirs operation to the reduction of the annual runoff and sediment yield in the watershed was 48.90% and 28.75% respectively. The Ludila reservoir played an important role in reducing annual runoff and sediment yield of the basin. The location of reservoirs with the sequence of Ludila, Longkaikou, Jin'anqiao, and Ahai from upstream to downstream had the greatest effect on the annual sediment yield of the basin. The function of multiple reservoirs on the monthly runoff and sediment yield of the basin was not the superposition of a single one. Under the simultaneous change of temperature and precipitation, the precipitation had a greater impact on runoff and sediment yield of the basin than temperature. Spatially, the annual runoff and sediment yield in the middle and upper reaches of the basin were sensitive to changes of temperature and precipitation. This research provides scientific support for management of water and sediment resources in watersheds with cascade reservoirs. • The response of runoff and sediment yield (RSY) was assessed under multi scales. • The impact of reservoir scale on RSY was not superimposed. • The impact of temperature and precipitation on annual RSY was spatially different. [ABSTRACT FROM AUTHOR]

In recent decades, land use/land cover change caused by rapid economic development has led to a sharp decline in the values of ecosystem service. Based on the land use/land cover change images of the PRD in 1990, 2000, 2010 and 2020, the land use change was analyzed and the corresponding Ecosystem Service Values (ESVs) were evaluated. In addition, a future land use simulation model was developed to simulate multiple scenarios in 2030. The results show that the area of construction land increased nearly 166.05% from 1990 to 2020, and the total ESVs decreased by 11.20 billion yuan. The contribution order of the four types ecosystem service to ESVs is regulating services > supporting services > provisioning services > cultural services. Compared with 2020, the values of ecosystem service of all the five scenarios shows a downward trend, and the order is the Ecological protection scenario (EPS) > the Natural development Scenario (NDS) > the Carbon neutral scenario (CNS) > the Production priority scenario (PPS) > the Economic development scenario (EDS). The CNS may be the most suitable scenario for the PRD region among the five scenarios. • Changes of Ecosystem service values in the PRD from 1990 to 2020 were analyzed. • Future LULC change and ESVs under five scenarios were simulated based on the FLUS model. • The carbon neutral scenario may be the best model for the development of the PRD. [ABSTRACT FROM AUTHOR]

With the studies of ecological stoichiometry changing from global to regional and smaller scales, it is of great significance to know how, for a single species in a typical ecosystem, the carbon (C), nitrogen (N) and phosphorus (P) stoichiometry varies with the seasons and responds to environmental stresses. In this study, taking T. chinensis ( Tamarix chinensis Lour.) in the Laizhou Bay coastal wetland as a test object, seasonal variations in leaf C, N and P stoichiometry and their correlations with soil salt were analyzed. The results showed that leaf C, N and P contents and the ratios of C:N, C:P and N:P of T. chinensis exhibited large variations. The leaf C, N and P contents were 388.56–472.07, 18.39–32.86 and 1.02–3.16 g kg −1 , respectively. Also, the ratios of C:N, C:P and N:P were 11.83–24.78, 125.98–425.98 and 8.62–23.66, respectively. The seasonal variation of the leaf C content presented an increasing trend while the leaf N and P contents indicated a trend of first increasing and later decreasing. However, a trend contrary to the leaf N and P was observed for the ratios of leaf C:N, C:P and N:P. There was a significant negative correlation between leaf P content and soil salt. Conversely, a positive correlation was found between the ratios of leaf C:P, N:P and soil salt. Generally, T. chinensis in the Laizhou Bay wetland took a defensive life-history strategy during the growth process. The growth of T. chinensis was limited by N at the beginning of the growing season, and by P in the middle and final stages of the growing season. [ABSTRACT FROM AUTHOR]

River restoration is the re-establishment of a river to a state that is more reflective of its predisturbance form. To restore a river polluted by human interference, we conducted an ecological restoration study from 2009 to 2011 on parts of the Yitong River, which is a typical non-point source polluted river in Northern China. The engineering included three parts: riparian vegetation buffering strip (part 1); multi-functional ecological fishponds (part 2), and river channel enhancement zone (part 3). By monitoring and evaluating the pollution indices of the study area's inlet and outlet, we found that the ecological engineering could significantly enhance the reduction rate of NH 3 -N, COD, and BOD 5 , which had increased from −14.29%, 1.81%, and −0.5% before restoration to 66.29%, 10.81%, and 7.25% in 2011 (post-restoration), respectively. The diversity of planktonic algae became rich, and in particular the species number representing clean water increased from 1 before restoration (2009) to 8 after the restoration (2011). Our results indicate that ecological engineering can significantly reduce non-point source pollution and improve the water quality, biodiversity, and economic benefits, and it is therefore an effective scientific approach for restoring the integrity of the river ecosystem and achieving continuous social and economic development. [ABSTRACT FROM AUTHOR]

Peat wetlands have widely been considered the carbon storage warehouse of the world and contribute to mitigating the global greenhouse effect. Nevertheless, this stored carbon and other greenhouse gasses are slowly being released into the atmosphere as the world's average temperature rises, leading to an even faster rise in temperature. CO 2 management in the Zoige Wetland of the Tibetan Plateau, the largest alpine peat wetland in the world, was estimated as a focal ecosystem service. Knowing landscape changes as the combined expression of social, economic, and natural factors, we firstly analyzed the effects of landscape change on CO 2 emissions during 1980–2005 with a comprehensive consideration of the area and the corresponding emission rate of both water-covered areas and non-water-covered areas. A comparison with baseline emission data showed enhanced eco-environment protection of the Zoige Wetland helped reduce emissions of CO 2 during 1990–2000 and 2005. Then we developed a principal component analysis method to analyze how CO 2 emissions were influenced by human–social factors and natural factors, showing human–social factors cause most of the natural CO 2 emissions in the Zoige Wetland. Finally we accounted the ecosystem service valuation of CO 2 management by using a mandatory CO 2 trade price in China. It indicated that CO 2 reductions in 2005 were valued at 588.90 × 10 4 CNY (95.8 × 10 4 USD), and it needed about 20 years for the Zoige Wetland ecosystem to recover after disturbance. [ABSTRACT FROM AUTHOR]

As an intersection that links terrestrial and aquatic ecosystems, river ecosystems are hotspots for nitrogen (N) removal. Nitrification and denitrification processes have been recognized as the primary mechanisms behind permanent N removal in rivers, which can be influenced by a variety of environmental factors. However, in rivers characterized by low carbon to nitrogen (C/N) ratio, the interaction among environmental factors and their effects on the sediment N-removal rates remain to be elucidated. In this study, we conducted six surveys in the Chuanfang River (an urban low C/N ratio river flowing into the Dianchi Lake) to investigate the effects of four categories of environmental variables on sediment N-removal rates (water physicochemical properties, water nutrients, sediment characteristics, and submerged vegetation) and their respective contribution to sediment N-removal rates. The results showed that sediment N-removal rates increased along the river reach, accompanied by a gradual improvement in water quality, sediment fertility, and submerged vegetation. Furthermore, comprehensive results of multiple analysis indicated positive effects of water physicochemical properties (e.g. dissolved oxygen, pH, temperature, etc.), sediment characteristics (e.g. sediment C, N, etc.), and submerged vegetation (e.g. tissue C, N, etc.) on the N-removal rates but emphasized the restriction of water nutrients (e.g. water N, etc.). In addition, the significant negative correlation between nitrification and denitrification in path model signified the decoupled nitrification–denitrification in the Chuanfang River. This study suggested that river ecosystems that received low C/N water had a great N-removal capacity, which could be further enhanced by the improvement of water quality, sediment fertility, and submerged vegetation. Unlabelled Image • Chuanfang River dominated by low C/N water exhibited great N-removal capacity. • Sediment N-removal rates increased along the river reach. • Improving water quality, sediment fertility, and vegetation can enhance N removal. • Excessive nutrient loading in water can restrict sediment N-removal rates. • Decoupled nitrification–denitrification was observed in the presence of low C/N. [ABSTRACT FROM AUTHOR]