Although soil erosion and land use change have long been focuses in carbon research, the combined influence of soil erosion and vegetation rehabilitation on aggregate stability and the associated ...soil organic carbon (SOC) and total nitrogen (TN) remains unclear. The current study evaluated the effects of soil erosion on aggregate stability and the associated SOC and TN dynamics in relation to vegetation rehabilitation after the implementation of the “Grain-for-Green” project in the hilly Loess region. A check dam sediment sequence was dated using 137Cs activity and erosive rainfall events. The SOC and TN in the bulk soil and aggregate fractions were measured in soils from rehabilitated grasslands and sloping croplands and in sediments retained by the check dam. The results showed that vegetation rehabilitation led to 78%, 27% and 9% average increases in the macroaggregate amount, mean weight diameter (MWD) and mean geometric diameter (MGD), respectively. In addition, rehabilitation resulted in the highest SOC and TN concentrations and contents in macroaggregates among all the aggregate size fractions. Soil erosion facilitated the modification of the aggregate size distributions along with soil mineralization and induced the incorporation of deeper SOC-poor soils during transport. These processes resulted in the aggregate-associated SOC and TN concentrations and contents in the sediments being significantly lower than those in the eroding sloping cropland soils. The highest reductions were found in microaggregates, which exhibited decreases of 48% and 44% for SOC and TN, respectively. Moreover, reaggregation and gully soils incorporated during soil erosion led to higher values of macroaggregate amount and aggregate stability at depositional sites than those at eroding sloping cropland sites in this study. Our study contributes to the understanding of the effects of soil erosion and vegetation rehabilitation on SOC and TN dynamics, which is crucial for understanding the restoration efficiency in soil erosion control and ecosystem security evaluation.
Display omitted
•Vegetation rehabilitation significantly improved soil stability.•Rehabilitation contributed to the accumulation of SOC in each aggregate fraction.•Vegetation rehabilitation led to the highest increase in the macroaggregate amount.•Soil erosion caused SOC and TN losses in the study catchment.•Soil erosion and deposition induced SOC and TN sequestration in deep sediments.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The soil moisture (SM) dynamics change is mainly ascribed to the revegetation. The spatio-temporal dynamics of SM displays that the wet region with annual precipitation of >450 mm to be dry and dry ...region with annual precipitation of ≤450 mm to be wet. It is potentially beneficial to restore vegetation with the aim to further enhance the ecosystem services in arid and semi-arid areas, until the vegetation fraction reaches 1.4%–3.7% and 3.8%–7.2%, respectively. However, vegetation should be maintained rather than further expanded in semi-humid area.
Display omitted
•The wet area gets drier but dry area gets wetter from 1982 to 2015.•"Grain for Green" project drives the soil moisture change in the Loess Plateau.•An optimal green cover is 1.4%–3.7% in arid area and 3.8%–7.2% in semiarid area.•It is still potentially beneficial to restore vegetation for 8.5% of drylands.
The continuous afforestation has led to significant changes in soil moisture (SM) dynamics on the Loess Plateau, China (LPC). However, evaluating the spatio-temporal distributions and driving factors of the SM changes following afforestation is challenging because of the difficulty of accessing areas and the lack of long-term series records. Here, we evaluated the accuracy of Global Land Evaporation Amsterdam Model (GLEAM) SM product by comparing with in-situ SM data in LPC, and quantified the spatio-temporal variations of SM in different periods from 1982 to 2015 under the ‘Grain for Green’ program (GGP). The results showed that the Normalized Difference Vegetation Index (NDVI) was well matched with the SM variations in more than 46% area of LPC from 1982 to 2015, which mainly located at the vegetated areas. The variations of SM responding to revegetation displayed obvious southeast-negative and northwest-positive patterns, which was the wet region (annual precipitation >450 mm) to be dry and dry region (annual precipitation ≤450 mm) to be wet. Path coefficient value revealed that the positive effect of vegetation activity for grassland on SM was ascribed to its promotion on the occurrence of rainfall (mean path coefficient = 0.278). Precipitation played vital impact on the SM in bareland and sparsely vegetated area, and evapotranspiration played a dominant role in the SM dynamic of the forestland, especially at the early stage of GGP (From 2000 to 2010), while precipitation and NDVI had stronger effects than evapotranspiration on the SM dynamics of grassland. Our study suggests that in arid and semi-arid areas, vegetation achieves the optimal water retention capacity when the vegetation fractions are 1.4%–3.7% and 3.8%–7.2%, respectively. Hence, vegetation should not be further expanded in semi-humid areas, but should be further restored in arid and semi-arid areas with sparse or excessively sparse vegetation cover (especially in desert).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The soil erosion performances of frozen, nonfrozen and thawed soil were evaluated.•Four models were implemented to simulate the key parameters for thawed soil erosion.•The performance of SR and ...machine learning models were compared.•Influencing factors of straw returning on thawed soil were analyzed.
Snow and ice‐melted water flow over thawed soil cause severe soil erosion. The application of straw mulch has long been considered as an effective measure to reduce soil erosion, but the effects of straw mulch and straw incorporation on thawed soil erosion remain uncertain. This study conducted detailed laboratory experiments to investigate the effects of straw mulch and straw incorporation on soil erosion and sediment transport of thawed soil. The median particle size (D50) of transported sediment, flow velocity and sediment concentration for thawed soil were compared with that of unfrozen and frozen soil. Models based on Random Forest (RF), Support Vector Machine (SVM), Back Propagation Neural Network (BP) and stepwise regression (SR) were implemented to simulate the key parameters of thawed soil erosion, and the accuracy of the developed models was evaluated. The results showed that the sediment yield increased significantly in thawed soil compared with that in unfrozen soil. The maximum flow velocity over thawed soil decreased by 20.7 % compared with that over frozen soil. The D50 of transported sediment decreased by 29.4 % after the soil suffered the effects of freeze–thaw, and the finer sizes were more likely to be entrained. The straw mulch effectively reduced the D50 of transported sediment, flow velocity and sediment concentration. In addition, the RF model showed a better result to predict the sediment concentration, flow velocity and D50 of transported sediment (NSE > 0.849, RRMSE < 0.493) than the BP, SVM and SR models. Comparing the performance of the RF model with the models reported in previous studies, the RF model showed the best performance. In general, the results of this study provide important information for soil erosion in thawed soil.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•A novel superplasticizer, polymer nano-particle (PNP) was put forward and synthesized.•PNP can adsorb on cement surface and improve the fluidity of fresh cement pastes.•PNPs’ ...retardation effect on cement hydration is less significant than traditional PCEs.•PNPs reduce the connectivity of micro-pores in hardened cement pastes.
Polymer nano-particles (PNPs) with particle size range of 29.4–52.7nm were synthesized via emulsion polymerization. The mini-cone tests were conducted to evaluate the dispersion capability of PNPs in fresh cement pastes (fcps). Interactions of PNPs with cement were studied by measurements of total organic carbon, zeta potential, transmission electron microscopy, calorimetry and mercury intrusion porosimetry. Results show that the prepared PNPs can be adsorbed on to cement surface and improve fluidity of fcps effectively. The addition of PNPs leads to lesser retardation effect on cement hydration than popularly used polycarboxylate superplasticizers and reduces pore connectivity of micro-pores in hardened cement pastes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Hyperspectral reflectance derived vegetation indices (VIs) are used for non-destructive leaf area index (LAI) monitoring for precise and efficient N nutrition management. This study tested the ...hypothesis that there is potential for using various hyperspectral VIs for estimating LAI at different growth stages of rice under varying N rates. Hyperspectral reflectance and crop canopy LAI measurements were carried out over 2 years (2015 and 2016) in Meichuan, Hubei, China. Different N fertilization, 0, 45, 82, 127, 165, 210, 247, and 292 kg ha
, were applied to generate various scales of VIs and LAI values. Regression models were used to perform quantitative analyses between spectral VIs and LAI measured under different phenological stages. In addition, the coefficient of determination and RMSE were employed to evaluate these models. Among the nine VIs, the ratio vegetation index, normalized difference vegetation index (NDVI), modified soil-adjusted vegetation index (MSAVI), modified triangular vegetation index (MTVI2) and exhibited strong and significant relationships with the LAI estimation at different phenological stages. The enhanced vegetation index performed moderately. However, the green normalized vegetation index and blue normalized vegetation index confirmed that there is potential for crop LAI estimation at early phenological stages; the soil-adjusted vegetation index and optimized soil-adjusted vegetation index were more related to the soil optical properties, which were predicted to be the least accurate for LAI estimation. The noise equivalent accounted for the sensitivity of the VIs and MSAVI, MTVI2, and NDVI for the LAI estimation at phenological stages. The results note that LAI at different crop phenological stages has a significant influence on the potential of hyperspectral derived VIs under different N management practices.
This study aimed to investigate the value of sirtuin 1 (SIRT1) in differentiating sepsis patients from healthy controls (HCs), and its correlation with inflammation, disease severity, as well as ...prognosis in sepsis patients. Serum samples were collected from 180 sepsis patients and 180 age- and gender-matched HCs. The SIRT1 level in the serum samples was detected by enzyme-linked immunoassay. The clinical data of the sepsis patients were documented, and their disease severity scores and 28-day mortality rate were assessed. SIRT1 was decreased in sepsis patients compared with HCs, and the receiver operating characteristic curve (ROC) showed that SIRT1 distinguished sepsis patients from HCs (area under the curve (AUC): 0.901; 95% confidence interval (CI): 0.868-0.934). In sepsis patients, SIRT1 negatively correlated with serum creatinine (Scr), white blood cells (WBC), C-reactive protein (CRP), acute physiology, and chronic health evaluation II (APACHE II) score, and sequential organ failure assessment (SOFA) score, while it positively correlated with albumin. No correlation of SIRT1 with primary infection site or primary organism was observed. Furthermore, SIRT1 was reduced in 28-day non-survivors compared with 28-day survivors, and subsequent ROC showed that SIRT1 predicted 28-day mortality of sepsis patients (AUC: 0.725; 95% CI: 0.651-0.800), and its prognostic value was not inferior to Scr, albumin, WBC, and CRP, but was less than SOFA score and APACHE II score. In conclusion, measurement of serum SIRT1 might assist with the optimization of disease assessment, management strategies, and survival surveillance in sepsis patients.
As an important soil and water conversation endeavor, the ‘Grain for Green’ project launched by the Chinese Central Government almost doubled the vegetation cover on the Loess Plateau between 1999 ...and 2013. The corresponding vegetation restoration considerably diminished slope erosion throughout the Loess Plateau, although erosion in gullies remains poorly understood. In this paper, a composite fingerprinting approach was employed to assess the relative importance of the erosion of gully and slope soils within a typical dam‐controlled catchment of the Loess Plateau. A total of 23 couplets were identified based on the deposited layer thicknesses and extreme rainfall event records along the sediment profile. The results suggest that gullies contributed 71% to the overall sediment proportion, and those sediments had an increased tendency to accumulate during 2010–2016 under the ‘Grain for Green’ project. The sediment inputs from slope areas were predicted to be 29%. The eroded gullies materials mainly consisted of silt‐sized particles, which dominated the eroded sediment. Silt particles with sizes of 0.02–0.05 mm constituted the main particles in both deposit sediments and gully materials, whereas the slope areas mainly contained particle sizes of <0.01 mm. The check dam proved to be effective at trapping coarse silt with 27–42% of the total sediment content. This study presents reliable information on the importance of gullies as sediment source materials and verifies the applicability of tracing procedures for collecting information on sediment effluxes from both slopes and gullies.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Introduction
Obesity in patients undergoing hemodialysis is common. However, there is limited information on the relationship between obesity types defined by the combined body mass index (BMI) and ...waist circumference (WC) classification criteria and all-cause mortality in Chinese hemodialysis patients. Our objective was to determine the association between obesity types and all-cause mortality in hemodialysis patients.
Methods
We conducted a prospective cohort study including patients from 11 hemodialysis centers in Beijing. According to the World Health Organization’s standards, patients were classified into 2 categories with WC and 4 categories with BMI and then followed up for 1 year. Kaplan–Meier survival analysis was used to compare the difference in the cumulative survival rate in different BMI and WC groups. A multivariate Cox regression analysis was used to determine the association between different types of obesity and all-cause mortality.
Results
A total of 613 patients were enrolled, the mean age was 63.8 ± 7.1 years old, and 42.1% were women. Based on the baseline BMI, there were 303 (49.4%) patients with normal weight, 227 (37.0%) with overweight, 37(6.0%) with obesity, and 46 (7.5%) with underweight. Based on the baseline WC, 346 (56.4%) patients had abdominal obesity. During a median follow-up of 52 weeks, 69 deaths occurred. Kaplan–Meier plots demonstrated a significant association of BMI categories (log-rank χ2 = 18.574,
p
<0.001) and WC categories (log-rank χ2 = 5.698,
p
=0.017) with all-cause death. With normal BMI and non-abdominal obesity as a reference, multivariate Cox regression analysis results showed that obesity (HR 5.36, 95% CI, 2.09-13.76,
p
<0.001), underweight (HR, 5.29, 95% CI, 2.32-12.07,
p
<0.001), normal weight combined with abdominal obesity (HR 2.61, 95% CI, 1.20-5.66,
p
=0.016), and overweight combined with abdominal obesity (HR 1.79, 95% CI, 1.03-3.73,
p
=0.031, respectively) were significantly associated with higher risks of all-cause mortality.
Conclusion
Our study indicated that abdominal obesity is common and associated with all-cause mortality among Chinese hemodialysis patients.
Plant community characteristics and functional traits may respond to soil erosion due to their high plasticity in varied environments. However, the linkages between plant functional traits and soil ...properties under erosion stress remain poorly understood, despite the fundamental role they play in controlling soil erosion. Here, we selected 50 plots on degraded land caused by long‐term water erosion representing three degrees of erosion that differed in terms of soil profile and erosion landform. We measured aboveground plant characteristics, root functional traits, and soil properties to explore their responses to the degree of erosion and to identify the main factors mitigating soil erodibility (K
r). The results showed that vegetation cover and root length density (RLD) were the plant variables that were most sensitive to the erosion stress. Topographic parameters strongly affected plant community characteristics (vegetation cover and litter mass) by favouring thicker soil layers and lower bulk densities, and soil texture strongly affected root functional traits (root mass density RD and RLD) by favoring lighter soils. Importantly, plant community characteristics and root functional traits were the main drivers of K
r mitigation through their mediation effects on a range of soil properties (e.g., soil organic matter, aggregate stability, and shear strength) during the restoration, and vegetation can still be efficient in maintaining and restoring soil functions, even on severely degraded land. Overall, these findings could guide restoration practices to meet soil conservation and ecosystem function goals in degraded ecosystems.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Display omitted
•Accurate quantification of soil erosion sub-process by remote sensing and check dam.•Vegetation restoration significantly reduced soil erosion modulus.•Check dams effectively reduce ...sediment delivery on the watershed scale.•The variation of erosion and deposition changes the sediment delivery ratio.
China has implemented a series of ambitious soil and water conservation (SWC) projects on the Chinese Loess Plateau, which have significantly changed the erosion, transport, and deposition of sediment. As a result, the sediment flux of the Yellow River, once the largest carrier of fluvial sediment worldwide, has been reduced by approximately 85 % in the past 60 years. However, the effects of SWC measures on erosion, transport, and deposition of sediment are still difficult to quantify, which greatly limits the further planning and adjustment of SWC measures. Here, we determined soil erosion, sediment deposition, and sediment yield at different historical stages in a 187 km2 hilly and gully watershed on the Chinese Loess Plateau using the unmanned aerial vehicle (UAV) photogrammetry technology combined with check dam surveying and hydrologic monitoring. The results show that the construction of check dams and vegetation restoration significantly reduced the soil erosion rate, from 21,144 t km−2 yr−1 at Stage-1 (1960–1969) to 13,819 ± 3,622 t km−2 yr−1 at Stage-2 (1970–1999) and further to 4,723 ± 1,278 t km−2 yr−1 at Stage-3 (2000–2018). The sediment deposition rate was estimated to be 5,989 and 2,582 ± 351 t km−2 yr−1 at Stage-2 and Stage-3, respectively. The variation in the erosion and deposition of sediment led to a significant change in the sediment delivery ratio, from 1 at Stage-1 to 0.57 at Stage-2 and 0.45 at Stage-3. Our research results provide an important reference for further SWC planning.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
