•We investigate impacts of climate variability and human activity on annual flow in the midstream of the Yellow River.•Annual streamflow shows significant decreases from 0.10mm/yr to 1.61mm/yr at ...most stations.•Decreasing precipitation and increasing temperature are detected for the whole study area.•Climate variability has a greater effect on the streamflow decrease in the Beiluo and Yan Rivers.•Human activities accounted for more of the streamflow reduction in the majority of tributaries.
The middle reaches of the Yellow River basin (MRYRB) contribute significantly to the total streamflow and sediment discharge of the Yellow River. Significant changes in streamflow have been detected; these changes result in part from large number of soil and water conservation measures implemented over the past six decades in this area. This study investigates streamflow variations and evaluates the impacts of climate variability and human activity on the mean annual flow in the MRYRB. The non-parametric Mann–Kendall test and Pettitt’s test are applied to characterize the trends and abrupt changes of hydro-climatic variables in the MRYRB. The analysis was performed on streamflow data taken over the period from the 1950s to 2010 at 18 hydrological stations and on precipitation, temperature and potential evapotranspiration (PET) data from 43 climate stations. We find that 16 of these stations recorded significant decreases in annual streamflow, with reduction rates ranging from 0.10mm/yr to 1.61mm/yr over the study period. Precipitation at all of the stations also had negative trends, with changes ranging from −4.7mm/yr to −0.19mm/yr. Temperature increased significantly at most stations, while PET showed a mixed of upward and downward trend. Abrupt changes in streamflow at mainstream stations occurred when large reservoirs were built, while breakpoints of streamflow at tributary stations were mainly driven by the implementation of soil and water conservation measures. We used both Budyko’s curve (a simple water balance model) and linear regression to evaluate the potential impacts of climate variability and human activities on mean annual streamflow. Climate variability has a greater effect on the streamflow reduction in the Beiluo River and Yan River, while human activities accounted for more of the streamflow changes in other tributaries, especially in the northern catchments. In general, human activities, including soil and water conservation projects, the operation of dams and reservoirs, and water consumption, are found to be the dominant factors responsible for the significant decline in the annual streamflow in the MRYRB over the last six decades.
•Vegetation restoration could significantly decrease surface runoff and soil erosion.•There were no significant difference in runoff and soil loss between different vegetation types.•The runoff and ...soil erosion had significant difference between different erosive rainstorm events.
It has been widely known that vegetation restoration plays a vital importance in controlling surface runoff and soil erosion. The most of soil erosion were caused by erosive rainstorm events. Yet, the response of surface runoff and soil erosion to erosive rainstorm events and vegetation types has not been fully understood. In this study, we monitored the vegetation, rainfall, runoff and soil erosion on ten runoff plots under field conditions from 2015 to 2019 and examined the impact of erosive rainstorm events on runoff and soil erosion among different vegetation types (Artemisia scoparia → Stipa bungeana → Lespedeza davurica (Asc → Sb → Ld), Stipa bungeana → Artemisia gmelinii (Sb → Agm), Bothriochloa ischaemum (Bi), Artemisia gmelinii + Stipa bungeana (Agm + Sb), Artemisia gmelinii + Stipa grandis (Agm + Sg), Sophora viciifolia (Sv), Artemisia gmelinii + Artemisia giraldii (Agm + Agi)) and bare land on abandoned land slopes. The results showed that vegetation restoration could decrease 68.0% to 97.4% of runoff and 98.0% to 99.9% of soil erosion compared to the bare land and there were no significant difference of surface runoff and soil loss among different vegetation types under the 11 erosive rainstorm events. The average soil loss of erosive rainstorm events among vegetation types could be 2.1 to 15.6 times as those of ordinary erosive rainfall events. The erosive rainstorm events caused a significant variance of surface runoff and soil erosion because of variant antecedent soil moisture and rainfall intensity. In practice, the natural vegetation restoration should be recommended in semi-arid environment and, the erosive rainstorm events should be paid enough attention in causing intense soil erosion in the rainy reasons.
•In Robinia plots, available N was higher but PAR was lower than Control plots.•Soil moisture differed in Robinia and Control plots.•Robinia and Control plots differed in species composition.•Robinia ...plots had higher β-diversity but lower species number than Control plots.•R. pseudoacacia influenced vegetation through PAR, soil moisture and available N.
Revegetation is one of the primary management approaches for solving the problems caused by severe soil erosion worldwide. Robinia pseudoacacia was considered a promising tree for afforestation in the highly eroded region of the Loess Plateau due to its fast growth and ability to fix atmospheric nitrogen. However, its beneficial role protecting soils from erosion has been now questioned and several negative effects on soil and vegetation have been described. In this study we aimed to analyze the effects of R. pseudoacacia plantation on plant community composition and dynamics through the effects that R. pseudoacacia has on light, soil fertility and soil water availability. We used a chronosequence from 10–40-year-old plantations and compared the environmental and vegetation characteristics of that areas with that of natural control areas with similar age. The results showed that R. pseudoacacia plantations reached maturity around 30years and then declined in density and canopy cover. We also found that soil nutrients and moisture at the superficial soil layer improved with age until maturity of plantations, but photosynthetically active radiation at the ground level and soil moisture at deeper soil layers decreased with maturity in relation to control conditions. Plots with R. pseudoacacia of all ages had higher cover values, lower number of species but higher β-diversity values than control conditions and they also differed in species composition. These differences in structure and species composition were related to the fertilizer effect of R. pseudoacacia that favored colonization by weeds and ruderal species, and to the light interception by the canopy of trees that exclude light-demanding species, most of them perennial herbaceous species which were the dominant species in control conditions.
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•Macrophages play a pivotal role in the pathogenesis of pancreatitis.•Macrophages mainly differentiate into M1 macrophages that secrete proinflammatory cytokines and mediators, ...causing inflammatory cascade reaction and aggravating acute pancreatitis.•Macrophages interact with pancreatic stellate cells in a cytokines-dependent manner to accelerate the formation of pancreatic fibrosis in chronic pancreatitis.•Immunotherapy targeting macrophages has good application prospects in the treatment of pancreatitis.
Macrophages play a crucial role in the pathogenesis of pancreatitis that is a common gastrointestinal disease. Particularly, macrophages differentiate into different phenotypes and exert diverse functions in acute pancreatitis (AP) and chronic pancreatitis (CP), respectively. In AP, macrophages in the pancreas and other related organs are mainly activated and differentiated into a pro-inflammatory M1 phenotype, and furthermore secrete inflammatory cytokines and mediators, causing local inflammation of the pancreas, and even intractable systemic inflammatory response or multiple organ failure. In CP, macrophages often exhibit a M2 polarisation and interact with pancreatic stellate cells (PSCs) in an autocrine and paracrine cytokine-dependent manner to promote the progression of pancreatic fibrosis. As the severity of pancreatic fibrosis aggravates, the proportion of M2/M1 macrophage cytokines in the pancreas increases. The discovery of macrophages in the pathogenesis of pancreatitis has promoted the research of targeted drugs, which provides great potential for the effective treatment of pancreatitis. This paper provides an overview of the roles of various macrophages in the pathogenesis of pancreatitis and the current research status of pancreatitis immunotherapy targeting macrophages. The findings addressed in this review are of considerable significance for understanding the pivotal role of macrophages in pancreatitis.
•Freeze-thaw induced landslides (FTILs) on grasslands were systematically examined.•Soil characteristics and topography were intrinsic factors controlling FTILs.•Increased rainfall and thickening ...active layer were direct drivers of FTILs.•Combining multiple monitoring methods is the trend for early warning of FTILs.
Landslides induced by freeze–thaw processes on grasslands are one of the major geohazards, and their scale and frequency are increasing as the global warms. Freeze-thaw induced landslides degrade surface vegetation and soil properties, reduce biodiversity, intensify landscape fragmentation, and lead to losses in economy, human and animal lives. Despite substantial progress in research on landslides, there has been little study focused on how ground freeze–thaw events affect landslides. By critically analyzing previous studies, this paper proposes a conceptual framework for the forms and types, development, dominant factors, monitoring techniques, and impact mechanisms of freeze–thaw induced landslides. Landslides are controlled by soil characteristics and topographic slope, which are major intrinsic determinants. Increased rainfall, rising temperatures, and thickening active layer due to climate change are all direct drivers of freeze–thaw induced landslides. Vegetation conditions, animal behavior interference, and wind erosion all affect the occurrence and development process of landslides by modifying vegetation cover, soil physical and chemical properties, and structure. Currently, landslide monitoring techniques have evolved rapidly with improved efficiency and accuracy, but with only few applications for freeze–thaw induced landslides. There are a variety of prediction models for landslides, but few consider freeze–thaw effects and lack field validation. The new perspective on the occurring types and dominant factors enhances theoretical understanding of the formation mechanisms, which helps further monitor and analysis of freeze–thaw induced landslides. Future studies should concentrate on the coupling mechanism of multiple factors and the development of an accurate prediction system, which will greatly benefit the understanding and early detection of freeze–thaw induced landslides.
Under the background of global climate change, variations in streamflow and sediment discharge in the Yellow River would continue with intensified human activities and changes in the ecological ...environment. To harness the Yellow River, analyzing the degrees of change and the reasons for the streamflow and sediment discharge, as well as predicting the future trends, are urgently needed.
In this paper, the non-parametric Mann–Kendall test, Sen's estimator of slope, Pettitt's test and wavelet transform were applied to detect the trends, the magnitude of the trends and the abrupt changes and periodic variation in streamflow and suspended sediment discharge at eight hydrological stations from 1950 to 2013 along the mainstream of the Yellow River.
Over the past 64years (1950–2013), the spatial distribution of the annual average streamflow was of the “M” type, and the annual average suspended sediment discharge had a parabolic curve shape along the mainstream of the Yellow River. The temporal variation showed a distinct decreasing trend in streamflow since the 1990s and in suspended sediment discharge since the 1980s. Many cycles of oscillations occurred in the streamflow and suspended sediment discharge variation, leading to an alternate change in the wet/dry periods and the high/low sediment discharge periods.
In various regions of the Yellow River Basin since the 1970s, climate changes contributed reductions of 17.0–45.0% and 12.2–50.3% for streamflow and suspended sediment discharge, respectively, whereas human activities contributed reductions of 55.0–83.0% and 49.7–87.8%. Therefore, human activities were the major causes of the significant decline in the streamflow and the suspended sediment discharge of the Yellow River over the past six decades. Reasonable and possible measures should be taken to achieve water resources optimization and configuration and to promote watershed management and sustainability in the regions of the Yellow River Basin.
•The streamflow was mainly from above LZ and sediment discharge was TDG–TG section.•The hydrological time series exhibited a significant decreasing trend.•The transition years of hydrological time series were detected in 1985 and 1979.•Many times cycle oscillations led to the alternate change in hydrological series.•Human activities reduction rates were more than 50% for hydrological series.
•Effect of vegetation type on soil LOC fractions is greater than that of topography.•Soil LOC fractions increased with litter stock, coverage and thickness.•Soil LOC fractions are directly influenced ...by soil basic properties.•Soil LOC fractions are indirectly affected by litter stock, coverage and thickness.•Multiple factors explained over 50% of the variation in SOC and soil LOC fractions.
Vegetation type and topographic characteristics are important factors that affect the amount and spatial distribution of the forest floor and the soil carbon cycling. However, the relationships among vegetation type, topographic characteristics, forest floor properties, soil properties and soil labile organic carbon (LOC) fractions remain to be elucidated. Here, we conducted a field observational study to explore the relationships between the soil LOC fractions (microbial biomass carbon (MBC), extractable organic carbon (EOC) and permanganate oxidizable carbon (Pox-C)) and forest floor characteristics under various vegetation types (forest, forest-steppe and steppe) and topographic features (slope position and aspect). Our results showed that the vegetation type and topography are both important factors that significantly influence the forest floor properties (i.e., stock, thickness and coverage). The soil total nitrogen and phosphorus were significantly increased, and the soil pH and bulk density were decreased, with an increase in litter stock, coverage and thickness. Simultaneously, the SOC and soil LOC fractions were increased significantly with the increase in litter stock, coverage and thickness. Over 50% of the variation in the SOC and soil LOC fractions was jointly explained by environmental factors, litter properties and soil properties. Our results demonstrated that the SOC and soil LOC fractions are directly influenced by soil physical and chemical properties (e.g., pH, bulk density and soil total nitrogen) and indirectly affected by external environmental factors. Changes in vegetation and topography lead to increases in the litter stock, coverage, thickness and water content in the backslope position and northern slope, which could create favorable soil nutrient and environmental conditions (e.g., higher soil moisture and lower bulk density) to further enhance SOC and soil LOC fraction sequestration. The forest floor potentially links environmental factors and soil properties and serves as an important factor for soil C cycling.
Loess gullied-hilly landscape (right) and the processes by which SSC in flood events remains relatively stable at watershed scale in the wet season (left and middle).
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•Contribution of ...extremely high SSL events is dominant and it becomes larger by P2.•SSC decline is more evident than Q in Helong section and opposite in Jing River.•SSC tends to be stable for large Q in gully area.•The lower boundary of log-transformed SSC–Q data points fits a straight line.
Understanding of the relationship between water discharge (Q) and suspended sediment concentration (SSC) across the Loess Plateau is a prerequisite for evaluating different soil and water conservation measures. Using daily Q and SSC datasets, this study jointly analyzes changes in Q and SSC on the central Loess Plateau, a major sediment-producing area of China, during the periods 1971-1987 (P1) and 2008-2016 (P2). The results show that during both P1 and P2, the contributions of maximum-3-day-per-year sediment load (SSL) to the total SSL are almost invariably over 50% (dominant), with the majority increasing further between P1 and P2. The contribution of extreme high SSL events plays an overwhelming role in watersheds of area < 10,000 km2, and appears almost independent of change in land cover condition. In the Helong section of the Yellow River, there is more evident reduction in SSC than Q between these two periods (streamflow becomes clearer), while the opposite occurred in the Jing River (streamflow lowers). In addition, the range of variation in SSC is large for small Q values, whereas the SSC for flood events tends to be relatively stable in gullied-hilly and flat-surfaced (Yuan) loess areas, which are major sediment producers. Based on scatter plots of SSC against Q after logarithmic transformation, we find that the lower boundary of the mapped data points for an individual station fits a straight line. This boundary relates to riverbed erosion. Given that soil erosion weakened on slopes over time and there is generally reduced streamflow in channels during P2, the boundary tends to move downward between P1 and P2 for most watersheds, reflecting the reduction in SSC for the same value of Q in P2 compared to P1.
•Grazing intensity significantly decreased SOM, TN, AN, TP, CEC, but increased BD and pH.•TN, TP, TK, SOM, Sand, PHO, SUC, and CAT could well replace the TDS in soil quality evaluation.•The ...SQI-NL-MDS4 was the optimal SQI method in evaluating soil quality among four grazing intensities.•Heavy grazing had a stronger negative effect on alpine meadow soil quality than moderate grazing and light grazing.
Grazing plays a critical role in the sustainable development of grassland. It has been convinced that grazing affects grassland productivity, however, researches on the relationship between grazing intensity and grassland soil quality remain inadequate in the alpine environment. This study compared ten soil quality indexes (SQIs) to quantitative assess the effect of different grazing intensities no grazing (NG); light grazing (LG); moderate grazing (MG); heavy grazing (HG) on the soil quality of alpine meadow in the 0–10 cm and 10–20 cm soil layers. Principal component analysis (PCA) and minimum data set (MDS) were applied to indicator selection and weight assignment. The fitting relationship and correlation between SQI-TDS and SQI-MDSs and the sensitivity index (SI) of ten SQIs were used to select the optimal SQI method. Our results showed that compared with NG and LG, HG and MG significantly decreased soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and cation exchange capacity (CEC) (p < 0.05), whereas increased bulk density (BD) and pH. Besides, TN, TP, TK, SOM, Sand content, soil phosphatase activity (PHO), soil sucrase activity (SUC), and soil catalase activity (CAT) could well replace the TDS method to evaluate soil quality. The SQI calculated by the MDS4 with the non-linear scoring method (SQI-NL-MDS4) had the best performance in soil quality evaluation among ten SQIs. Compared with NG and LG, HG had a stronger negative effect on alpine meadow soil quality, especially in the 0–10 cm soil layer, which potentially aggravated leading to aggravating grassland degradation. We propose that reasonable grazing intensity management should be advocated to maintain the sustainable development of alpine meadow productivity.
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