During the process of landslide, its dynamic mechanism is important to understand and predict these kinds of natural hazard. In this paper, a new method, based on concepts of complex networks, has been proposed to inv...During the process of landslide, its dynamic mechanism is important to understand and predict these kinds of natural hazard. In this paper, a new method, based on concepts of complex networks, has been proposed to investigate the evolution of contact networks in mesoscale during the sliding process of slope. A slope model was established using the discrete element method (DEM), and influences of inter-particle frictional coefficients with four different values on?dynamic landslides were studied. Both macroscopic analysis on slope?landslide?and mesoanalysis on structure evolution of contact networks, including the?average degree, clustering coefficient?and N-cycle, were done during the process?of landslide. The analysis results demonstrate that: 1) with increasing inter-particle?frictional coefficients, the displacement of slope decreases and the stable angle of slope post-failure increases, which is smaller than the peak internal frictional angle;2) the average degree decreases with the increase of inter-particle frictional coefficient. When the displacement at the toe of the slope is smaller,?the average degree there changes more greatly with increasing inter-particle?frictional coefficient;3) during the initial stage of landslide, the clustering coefficient?reduces sharply, which may leads to easily slide of slope. As the landslide?going?on, however, the clustering coefficient?increases denoting increasing stability?with?increasing inter-particle frictional coefficients. When the inter-particle?frictional coefficient is smaller than 0.3, its variation can affect the clustering coefficient?and stable inclination of slope post-failure greatly;and 4) the number of?3-cycle increases, but 4-cycle and 5-cycle decrease with increasing inter-particle frictional coefficients.展开更多
Agriculture has increased the release of reactive nitrogen to the environment due to crops’low nitrogen-use efficiency(NUE)after the application of nitrogen-fertilisers.Practices like the use of stabilized-fertiliser...Agriculture has increased the release of reactive nitrogen to the environment due to crops’low nitrogen-use efficiency(NUE)after the application of nitrogen-fertilisers.Practices like the use of stabilized-fertilisers with nitrification inhibitors such as DMPP(3,4-dimethylpyrazole phosphate)have been adopted to reduce nitrogen losses.Otherwise,cover crops can be used in crop-rotation-strategies to reduce soil nitrogen pollution and benefit the following culture.Sorghum(Sorghum bicolor)could be a good candidate as it is drought tolerant and its culture can reduce nitrogen losses derived from nitrification because it exudates biological nitrification inhibitors(BNIs).This work aimed to evaluate the effect of fallow-wheat and sorghum cover crop-wheat rotations on N_(2)O emissions and the grain yield of winter wheat crop.In addition,the suitability of DMPP addition was also analyzed.The use of sorghum as a cover crop might not be a suitable option to mitigate nitrogen losses in the subsequent crop.Although sorghum–wheat rotation was able to reduce 22%the abundance of amoA,it presented an increment of 77%in cumulative N_(2)O emissions compared to fallow–wheat rotation,which was probably related to a greater abundance of heterotrophic-denitrification genes.On the other hand,the application of DMPP avoided the growth of ammonia-oxidizing bacteria and maintained the N_(2)O emissions at the levels of unfertilized-soils in both rotations.As a conclusion,the use of DMPP would be recommendable regardless of the rotation since it maintains NH_(4)^(+)in the soil for longer and mitigates the impact of the crop residues on nitrogen soil dynamics.展开更多
文摘During the process of landslide, its dynamic mechanism is important to understand and predict these kinds of natural hazard. In this paper, a new method, based on concepts of complex networks, has been proposed to investigate the evolution of contact networks in mesoscale during the sliding process of slope. A slope model was established using the discrete element method (DEM), and influences of inter-particle frictional coefficients with four different values on?dynamic landslides were studied. Both macroscopic analysis on slope?landslide?and mesoanalysis on structure evolution of contact networks, including the?average degree, clustering coefficient?and N-cycle, were done during the process?of landslide. The analysis results demonstrate that: 1) with increasing inter-particle?frictional coefficients, the displacement of slope decreases and the stable angle of slope post-failure increases, which is smaller than the peak internal frictional angle;2) the average degree decreases with the increase of inter-particle frictional coefficient. When the displacement at the toe of the slope is smaller,?the average degree there changes more greatly with increasing inter-particle?frictional coefficient;3) during the initial stage of landslide, the clustering coefficient?reduces sharply, which may leads to easily slide of slope. As the landslide?going?on, however, the clustering coefficient?increases denoting increasing stability?with?increasing inter-particle frictional coefficients. When the inter-particle?frictional coefficient is smaller than 0.3, its variation can affect the clustering coefficient?and stable inclination of slope post-failure greatly;and 4) the number of?3-cycle increases, but 4-cycle and 5-cycle decrease with increasing inter-particle frictional coefficients.
基金supported by the Spanish Government(RTI2018-094623-B-C21 and C22 MCIU/AEI/FEDER,UE)the Basque Government(IT-932-16).Dr.Adrian Bozal-Leorri held a grant from the Basque Government(PRE-2020-2-0142)Dr.Mario Corrochano-Monsalve held a grant from the Ministry of Economy and Business of the Spanish Government(BES-2016-076725).
文摘Agriculture has increased the release of reactive nitrogen to the environment due to crops’low nitrogen-use efficiency(NUE)after the application of nitrogen-fertilisers.Practices like the use of stabilized-fertilisers with nitrification inhibitors such as DMPP(3,4-dimethylpyrazole phosphate)have been adopted to reduce nitrogen losses.Otherwise,cover crops can be used in crop-rotation-strategies to reduce soil nitrogen pollution and benefit the following culture.Sorghum(Sorghum bicolor)could be a good candidate as it is drought tolerant and its culture can reduce nitrogen losses derived from nitrification because it exudates biological nitrification inhibitors(BNIs).This work aimed to evaluate the effect of fallow-wheat and sorghum cover crop-wheat rotations on N_(2)O emissions and the grain yield of winter wheat crop.In addition,the suitability of DMPP addition was also analyzed.The use of sorghum as a cover crop might not be a suitable option to mitigate nitrogen losses in the subsequent crop.Although sorghum–wheat rotation was able to reduce 22%the abundance of amoA,it presented an increment of 77%in cumulative N_(2)O emissions compared to fallow–wheat rotation,which was probably related to a greater abundance of heterotrophic-denitrification genes.On the other hand,the application of DMPP avoided the growth of ammonia-oxidizing bacteria and maintained the N_(2)O emissions at the levels of unfertilized-soils in both rotations.As a conclusion,the use of DMPP would be recommendable regardless of the rotation since it maintains NH_(4)^(+)in the soil for longer and mitigates the impact of the crop residues on nitrogen soil dynamics.
