Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010: implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus（SDM） in the study area decreased from 7,767.4 t/（km^2·a） in 1951–1969 to 980.5 t/（km^2·a） in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/（km^2·a） is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/（km^2·a）.

Phase transition of DNA compaction in confined space: Effects of macromolecular crowding are dominant

With a view of detecting the effects of macromolecular crowding on the phase transition of DNA compaction confined in spherical space,Monte Carlo simulations of DNA compaction in free space,in confined spherical space without crowders and in confined spherical space with crowders were performed separately.The simulation results indicate that macromolecular crowding effects on DNA compaction are dominant over the roles of multivalent counterions.In addition,effects of temperature on the phase transition of DNA compaction have been identified in confined spherical space with different radii.In confined spherical space without crowders,the temperature corresponding to phase transition depends on the radius of the confined spherical space linearly.In contrast,with the addition of crowders to the confined spherical space,effects of temperature on the phase transition of DNA compaction become insignificant,whereas the phase transition at different temperatures strongly depends on the size of crowder,and the critical volume fraction of crowders pertains to the diameter of crowder linearly.

Decoupling effects of driving factors on sediment yield in the Chinese Loess Plateau

Investigations of runoff and sediment yield changes and their relationships with potential driving factors provide good insights for understanding the mechanisms of hydrological processes.This study attempted to present a comprehensive investigation on the spatiotemporal variations of sediment yield in the Loess Plateau using continuous observed data at 46 hydrological stations during 1961-2016,and its responses to changes of precipitation,land use/cover and vegetation cover were analyzed by using the Partial Least Squares-Structural Equation Model(PLS-SEM).The results indicated that sediment yield reduced pro-nouncedly during 1961-2016 in the Loess Plateau,and 77.9%of this variation was explained by the combined effects of precipitation,land-use change,vegetation dynamics and runoff reduction.Indirect effects of precipitation,land-use change,and vegetation cover on sediment yield were 0.242,-0.528 and-0.630(P<0.05),respectively,and direct effect of runoff on sediment yield was 0.833(P<0.05).According to the Pearson Correlation Coefficient,the strongest positive correlation existed between annual sediment yield and runoff(r=0.88,P<0.05),followed by vegetation cover(r=-0.47,P<0.05)and land-use change(i.e.forest land and grassland)suggesting their significant trapping effects on soil erosion.However,lower correlations were examined between sediment yield and precipitation indices(-0.14<r<0.34),and a relatively higher relationship was examined between sediment yield and heavy rainfall(P_(25))(r=034).Overall,changes in runoff and land-use/vegetation cover well explained varia-tions in sediment yield in the Loess Plateau.The findings are expected to provide scientific and technical support for future soil and water conservation planning in the Loess Plateau,and are valuable for sus-tainable water resources and sediment load management in the Yellow River Basin.