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In addition to greater precipitation on extreme days of precipitation, preceding and succeeding precipitation (PSP) is often an objective component of flooding in the mid–lower reaches of the Yangtze River Basin (MLRYRB). In this study, focused on the temporal distribution pattern of precipitation, the concept of an extreme precipitation event (EPE), defined as a consecutive precipitation event having at least one daily precipitation extreme, is proposed to consider PSP in an extreme event. We analyzed the spatiotemporal variation of four types of EPEs based on daily data obtained from 130 monitoring stations covering 1960–2019. Extreme precipitation increased significantly over the last 60 years (p < 0.01). The frequency and precipitation amount of single-day EPEs accounted for only 13% and 21%, respectively, while multi-day continuous EPE types that are associated with PSP accounted for 87% and 79%, respectively, confirming the connotations of EPEs. The front and late EPEs under the 100-year return level reached 250 mm and 230 mm, respectively. Furthermore, climate warming could lead to significant increases in the frequency of single-day and late EPEs, particularly in the southern region. The EPE concept may be helpful in exploring disaster-causing processes under extreme weather, and it provides a theoretical basis for deriving the precipitation hazard chain, which is more applicable to basins with long precipitation durations. [ABSTRACT FROM AUTHOR]

Clarifying the changing trend in vegetation and its affecting variables is extremely valuable for natural resource management. Vegetation changes in the Yinshanbeilu grassland region, which is situated in the centre of Inner Mongolia in northern China and is part of the arid steppe region, are extremely sensitive to climatic factors. In this study, we investigated the changes in vegetation in the Yinshanbeilu grassland zone from the year 2000 to 2020 using the Normalized Difference Vegetation Index (NDVI) data. The contribution of climatic conditions and human activities to the annual and growing season vegetation changes was quantified. The findings revealed that vegetation cover in the Yinshanbeilu grassland zone increased at a rate of 0.00267/a between 2000 and 2020. Throughout the year and during the growing season, precipitation had a greater influence on the growth of vegetation than other climatological factors. In most places, there was a significant positive correlation between the NDVI and precipitation, which negatively correlated with other climatic factors. The average rates at which precipitation, temperature, cumulative sunshine hours, and potential evapotranspiration contributed to changes in NDVI were 0.00173/a, −0.00027/a, 0.00006/a, and 0.00074/a, respectively, for the entire year, and 0.00180/a, −0.00001/a, 0.00021/a, and 0.00059/a for the growing season. The impact of climate change on vegetation activities was more pronounced, accounting for 84.76% of annual NDVI change and 97.36% of growing season NDVI change. Humans contributed 15.24% of total annual NDVI change and 2.64% of growing season NDVI change. This research's findings serve as scientific support for preserving the environment in the Yinshanbeilu grassland region, as well as an essential reference for government decision making. [ABSTRACT FROM AUTHOR]

Soil water movement is an important component in water cycle, which is also closely correlated with the transport of nutrients and contaminants in the catchment. Although there have been many studies in quantifying the water residence in soil, the understanding of the controlling factors is limited and could be controversial. Here, stable isotopes of water to explore the water age distribution in a mountainous catchment in the southwest China are used. The results are consistent with the regional climate pattern that the water vapor of the study catchment is brought by monsoons from Pacific Ocean in summer and prevailing westerly winds in winter. The estimated young water fraction is found to be strongly correlated with topographic gradient but presents no significant correlation with drainage area or vegetation coverage. Comparison between the difference in young water fraction of two adjacent sub‐catchments suggests that soil water in the steeper sub‐catchment tends to favor deep vertical infiltration, resulting in longer flow path, longer mean residence time, and smaller young water fraction. This difference between the soil water movement and the hydrological response revealed in this study has impacts on the biogeochemical cycles in the catchment. [ABSTRACT FROM AUTHOR]

By observing the processes of infiltration, flow generation, water flow characteristics and the spatial distribution of erosion in a designed rainfall test, and analyzing the infiltration, flow generation characteristics, water content change characteristics, soil moisture parameters change characteristics, and changes in the spatial patterns of erosion and sediment yield, this study draws the following conclusions: under different rainfall densities, the initial runoff generation time of sand-covered slope is 1~12 min longer than that of loess slope, the initial soil infiltration velocity of sediment-covered slope is about 1.23 times that of loess slope, and the time to reach stable infiltration of loess slope is shorter than that of sediment-covered slope. Under different rainfall densities, the rising time of the water content curve of sand-covered slope is earlier than that of loess slope. For the same duration of rainfall, the vertical infiltration performance of soil water of sand-covered slope is higher than that of loess slope, and when the rainfall density on the slope increases by 0.5 mm/min, the increase in runoff shear stress of the sediment-covered slope is about 1.5 times that of the loess slope, and the runoff power is about 1.13 times that of the loess slope. [ABSTRACT FROM AUTHOR]

There is debating over the question of whether the large-scale 'Grain for Green' program on the Loess Plateau of China threatens regional food security. Self-sufficiency index and cropland pressure index were used to assess food security on the Loess Plateau after the implementation of revegetation program. The results showed that the 'Grain for Green' program initially had a considerable impact on regional food security, where grain yield fell from 1999 to 2001, resulting in a lower grain self-sufficiency and increased farmland stress. Subsequently, grain yield in this region increased due to the elevated agricultural material input and increased construction of terraces and check dams. The grain self-sufficiency index would have increased to 96.55% if there were improvements to the agricultural conditions, such as fertilization and irrigation, which would have resulted in an increase in the crop yield per unit of 20%. However, the grain self-sufficiency increased to 105.25% via the construction of terraces and check dams. Thus, the government should further expand the 'Grain for Green' program in coordination with improvements to the agricultural production conditions and the construction of terraces and check dams on the Loess Plateau. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of vegetation restoration on soil organic carbon (SOC) and its fractions, by exploring the SOC, particulate organic C (POC), mineralizable organic C (MOC), and light fraction organic C (LFOC) of three sloping land-use types (sloping farmland, forestland and grassland) and at four locations along each hillslope (30, 60, 90 and 120 m from the hilltop). Soil 137Cs was measured to calculate the soil erosion rate. The SOC, POC, MOC, and LFOC were significantly higher (p < 0.05) in the forestland and grassland than the sloping farmland. The SOC, LFOC, MOC, and POC of the grassland and forestland were higher in the lower than in the upper parts of the hillslope. The 137Cs activity was associated with soil loss rate and related to the redistribution of soil carbon fractions along the hillslope. The distribution of the soil carbon fractions and soil erosion in the forestland and grassland showed opposing trends. The soil labile organic carbon distribution and erosion of sloping farmland displayed a consistent distribution trend. Land-use changes and erosion were the most important factors that governed soil labile organic carbon: accounting for 21.7% and 25.7% of the observed variances, respectively. [ABSTRACT FROM AUTHOR]

Abstract The sediment-reducing effect of check dams and the safety issues following dam breaks are long-standing concerns. This study analyzed the runoff change and sediment source during rainstorms in a small watershed using a multivariate mixed model and a comparative analysis of watersheds. The problem of sediment loss from dammed farmland following check dam break during rainstorms was evaluated. The results showed that the flood peak lag time (PLT) was significantly influenced by pre-soil moisture in cases of small amounts of rainfall but not during rainstorms. Ecological construction significantly reduced the linear correlation between rainfall and runoff modulus (RM). The reduction in sediment delivery modulus (SDM) due to the check dam was more significant than that in RM. The reduction in RM and SDM under rainstorm conditions were 16%–74% and 53%–93%, respectively. The contributions of inter-gully and gully lands to the sediment deposited in dammed farmland during a large rainstorm on July 26, 2017 were 38.07% and 61.93%, respectively. Soil erosion remained significant during large rainstorms. The increase in vegetation coverage on the hill slope increased the amount of sediment from gully lands. Check dam breaches have accounted for a loss of only 1.2% of the total area of the dammed farmland, and thus have not caused a large loss of sediment. However, breaches in them clearly increased the coefficient of variation of RM and SDM. Therefore, check dams have a critical effect on controlling sediment delivery at the watershed scale. Dam breaks do not result in a large percentage of sediment loss in the dammed farmland. Graphical abstract Unlabelled Image Highlights • We investigate sediment source during heavy rainstorms. • Assess the effects of soil and water conservation measures on runoff and sediment • Examined the changes to check dam breaches [ABSTRACT FROM AUTHOR]

Abstract Surface water quality has a vital role in determining the ecological environment, public health, and social and economic development. This study analyzed the spatial and seasonal differences in surface water quality in the Dan River basin based on three monitoring sections over the period of 2009–2015. The main influencing factors and their contributions to water quality in different seasons were determined using statistical analysis, Hurst exponent and redundancy analysis. Results indicated that vegetation coverage in the Dan River basin increased substantially from 2009 to 2015, particularly forested land. Higher concentrations of major water pollution indicators were recorded in the downstream monitoring sites. Nitrate nitrogen (NN) and total phosphorus (TP) made the largest contributions to the pollution of water quality and indicated spatial and seasonal changes. Lower NN concentrations were more frequent during the summer, whereas TP concentrations were higher during the spring. Thus, the factor making the largest contribution to water quality varied with the season. The contribution of the normalized difference vegetation index (NDVI) to water quality gradually decreased from spring to winter, whereas contributions of land use to water quality gradually increased from spring to winter. Analyses of landscape metrics suggested that patch connectivity was the primary factor influencing water quality in the different seasons. Water level was the main hydrological parameter impacting stream water quality. These results suggested that seasonal differences in the major factors influencing water quality should be taken into account for effective water management. Highlights • The time series of vegetation coverage was a consistent sequence in Dan River. • Factors making the largest contribution to water quality varied with the season. • Patch connectivity was the primary factor influencing water quality. • Water level was the main hydrological parameter impacting stream water quality. [ABSTRACT FROM AUTHOR]

Highlights • Analyze the changes of vegetation coverage using trend analysis and Hurst index. • Examine the vegetation restoration response to precipitation and topography. • Evaluate the impact of vegetation restoration on runoff and sediment in China. Abstract The vegetation status in China has undergone obvious changes since vegetation restoration projects were widely implemented in 1999. Based on a statistical analysis and the Hurst exponent index method, the spatial and temporal characteristics of vegetation change and its influence on runoff and sediment in China was analyzed using the Normalized Difference Vegetation Index (NDVI). The results showed that the change of vegetation coverage (E) in China from 2000 to 2015 was 5.64%. There was substantial variation in the spatial distribution of E values. There was a significant increase in the vegetation coverage in the areas covered by five vegetation restoration projects. It was found that 83.34% of the whole of China had experienced a continuous improvement in vegetation coverage. The largest increase in vegetation coverage occurred in the middle of the Loess Plateau and the middle of northeast China, while the largest decrease occurred in some areas of the Qinghai-Tibet Plateau and Xinjiang. Areas of vegetation degradation should be given special attention, with suitable control measures put in place. The slope angle with the largest increase in vegetation coverage was in the range of 15°–25°. Aspect had little effect on vegetation restoration. Vegetation restoration around the Hu Line, in which the precipitation was between 400 and 500 mm, was better and faster than in other regions. Vegetation coverage was linked to annual precipitation, and increased steadily with precipitation until a value of 500 mm was reached, after which it remained stable. Vegetation restoration did not reduce runoff, but it did reduce the sediment concentration. This study provided useful information for decision-makers involved in vegetation restoration projects and environmental management, especially in fragile ecological environments in arid and alpine areas. [ABSTRACT FROM AUTHOR]

Highlights • STN concentration of sloping cropland was lower than any other land use. • Principal factors influencing soil nitrogen are clay content and slope. • STN concentrations generally decreased as soil depth increased. • Ecological construction reduces the effects of topographic factors on STN. Abstract The construction of check dams and terraces, and the ‘Grain-for-Green’ project are major soil and water conservation measures on the Loess Plateau, China. The sediment load of the Yellow River has decreased by approximately 90% over the past 60 years and its average annual runoff has reduced from 55.9 billion m3 to 45.6 billion m3. However, whether watersheds act as sources or sinks of soil nitrogen following ecological construction measures is unknown. To understand the impacts of check dams combined with forests, grasslands, and terraces on soil nitrogen content, soil samples were collected at 20-cm intervals down to a depth of 60 cm across a small watershed of the Loess Plateau. The probability density function of the Weibull distribution was used to analyze the nitrogen sources in dammed farmland. The results indicated the mean soil total nitrogen (STN) concentrations at soil depths of 0–20, 20–40 and 40–60 cm in the watershed were 0.45, 0.32 and 0.29 g/kg, respectively. The STN concentrations among the three soil layers showed significant differences (p < 0.01). The mean STN concentration decreased as follows: dammed farmland > grassland > forestland > terrace > sloping cropland. Slope and soil texture had a significant impact on STN concentration across the watershed. The STN density of terrace, grassland, forestland, sloping cropland and dam farmland at a soil depth of 0–60 cm were 0.271, 0.289, 0.279, 0.264, and 0.288 kg/m2, respectively. The source percentages of STN deposited in dam farmland were 51% (grassland), 34% (forestland) and 15% (sloping cropland). Thus, check dam constructions have made the role of gully in the small watershed as a sink for soil nitrogen. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) plays a significant role in land surface hydrological processes (e.g., evapotranspiration, infiltration and runoff) and the spatial and temporal distribution of vegetation in arid and semi-arid regions. The aim of this study was to analyze the temporal stability of the SWC distribution pattern and to examine the primary factors that influence SWC temporal stability over a year and during the rainy season at different soil depths in terraces. The SWCs in eight soil depths at intervals of 0.2 m down to a depth of 1.6 m were measured at 21 locations in terraces containing jujube trees ( Ziziphus jujuba Mill. ) over two periods (over a year and during the rainy season). The results showed that the mean SWC over a year was larger than that for the rainy season in the corresponding layers. The mean SWC was highest in the lower slope. Soil depth significantly affected the SWC distribution over time and space. Water uptake mainly occurred between 1.0 and 1.2 m soil depth in both the rainy season and over the whole season. Moreover, the SWC demonstrated moderate spatial variability and was normally distributed at each depth. The temporal stabilities of SWC spatial patterns were strong for both the year period and the rainy season. The number of SWC representative locations varied depending on the soil depth. The SWCs measured at the best representative locations correctly represented the mean SWCs. Soil particles were the primary influencing factor affecting the mean relative difference, and root density was the primary influencing factor affecting the standard deviation of the relative differences. In conclusion, the SWC in the terraces showed stronger temporal stability during the rainy season compared to the year period. [ABSTRACT FROM AUTHOR]

Since the implementation of "Grain for Green" program in 1999, remarkable changes have taken place in the vegetation of the Loess Plateau, China, especially in the forests. The Ziwuling Forest Region is an important ecological forest area in the central zone of the Loess Plateau. The spatiotemporal variation of the vegetation cover and vegetation restoration potential in the Ziwuling Forest Region was studied using the NDVI data, based on geographical spatial analysis technology, Hurst exponent analysis and statistical analysis. From 2001 to 2019, vegetation cover in forest region increased significantly. The average growth rate of vegetation cover was 6.49%, and NDVI increased significantly in 84.66% of the area (p < 0.05), with an average annual growth rate of 0.0045 a−1. In 2019, it reached the maximum value of 0.833, and the Hurst index indicates that 35.02% of the area will show a benign development trend in the future. The vegetation coverage was linear negatively correlated with the aridity index, and the fitting degree in steep slope area (R2 > 0.5) was better than that in gentle slope area (R2 > 0.4). The average vegetation restoration potential in the study area was 0.837. Of the regional vegetation coverage, 72.47% is close to or has exceeded the vegetation restoration potential, and the vegetation restoration degree in the northern and eastern regions is relatively high. The existing vegetation coverage and vegetation restoration potential in Ziwuling Forest Region are high, so the existing vegetation restoration measures should be maintained to avoid damage to the vegetation in the area. This study has important guiding significance for the implementation of vegetation restoration and ecological protection policies on the Loess Plateau. • "Grain for Green" and natural forest protection policy promoted forest region vegetation restoration. • Vegetation cover and aridity index in the study area are liner negatively correlated. • Quantitatively analyze the vegetation restoration potential and vegetation restoration potential index. • The effect of climatic factors on vegetation restoration potential is more significant than topographical factor. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is an important endogenous signaling molecule with a variety of biological functions. Development of fluorescent probes for highly selective and sensitive detection of H2S is necessary. We show here that dual-reactable fluorescent H2S probes could react with higher selectivity than single-reactable probes. One of the dual-reactable probes gives more than 4000-fold turn-on response when reacting with H2S, the largest response among fluorescent H2S probes reported thus far. In addition, the probe could be used for high-throughput enzymatic assays and for the detection of Cys-induced H2S in cells and in zebrafish. These dual-reactable probes hold potential for highly selective and sensitive detection of H2S in biological systems. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is essential for improving soil quality, sustaining food production and quality, and maintaining water quality, as well as for mitigating climate change. Understanding the impact of soil and water conservation on SOC content is important for the protection of soil and water quality. In this study, the impacts of soil and water conservation on SOC content and density in a small catchment of the middle Han River were studied based on a grid soil survey. A total of 583 soil samples from 207 sites were collected, primarily from 30 m × 30 m grids. The results indicated that SOC content generally decreased with increasing soil depth, and significant differences existed among the three examined soil layers (0-20, 20-40, and 40-60 cm, p < 0.01). The mean SOC content of the different land use types occurred in the following order: forestland > terraces > grassland > sloping cropland. The spatial variability of SOC decreased as soil depth increased. The mean SOC densities of terraces, forestland, grassland, and sloping cropland at the 0-60 cm soil depth were 4.40, 4.31, 3.86, and 3.62 kg/m, respectively. The high-value zones of SOC density were always observed in the upper slope and basin outlet. SOC storage in the 0-60 cm soil depth was 565.10 tons in the Yujiehe catchment. Land use was the main influencing factor for SOC content in the catchment. Forestland, grassland, and terraces exhibit higher SOC than does sloping cropland. In conclusion, the use of terraces can greatly increase SOC density. Much sloping cropland can be changed to terraces, forestland, or grassland to increase SOC and protect soil and water quality in the water source area of the Han River. [ABSTRACT FROM AUTHOR]

Wind-water compound erosion is a complex process that affects 260,000 km in China. Understanding the effects of wind erosion deposition on water erosion is essential to soil and water conservation and ecological construction. In this study, runoff and sediment yield on sand-covered slopes (SS) and bare loess slope (LS) were studied under simulated rainfall experiments. The results showed that runoff in response to 1.0 and 1.5 mm/min rainfall intensities on SS began 31.1 min and 17.5 min later than on LS, respectively, and that runoff start-time increased as the sand-covering thickness increased. The impact of rainfall intensity on the runoff process of SS was greater than that of LS. Sand-covering had a greater effect on increasing sediment yield than runoff amount. Analysis of variance (ANOVA) indicated that the runoff amount and sediment yields of the three sand-covering thicknesses (0.5, 1.0 and 1.5 cm) of SS were all significantly larger than those of LS under 1.5 mm/min rainfall ( p < 0.01). However, the runoff and sediment did not increase strictly with increasing sand-covering thickness. The total sediment yields from SS under 1.0 and 1.5 mm/min rainfall intensities were 23 times and 13 times greater than those from LS, respectively. The relationships between cumulative runoff and sediment yield on LS and SS could be fitted well by linear functions ( R > 0.98, p < 0.01). The sediment yields showed strong positive correlations with runoff amount on SS ( p < 0.01). In conclusion, the sand-covered slopes greatly increased soil erosion when compared to the loess slope. [ABSTRACT FROM AUTHOR]