| At present,some hilly area of the middle basin of the Yangtze River is suffering from serious soil and water loss,which brings great challenge to the protection of the Yangtze River.Plinthosol is widely distributed in the mountains,and hilly areas of southern China,especially in the middle reaches of the Yangtze River.The study on stability of the aggregates is essential not only to reveal the mechanism,process,and formation of soil erosion in the watershed,but to provide a scientific basis for regional ecological construction and soil and water conservation.This study selected Wuhan(W),Yueyang(Y),and Jiujiang(J)Plinthosol profiles as study objects,the mean weight diameter(MWD),geometric mean diameter(GMD),relative slaking index(RSI),relative mechanical breakdown index(RMI),fractal dimension(F)and the erodibility(K)were calculated to determine the stability of aggregates.Revealed the stability characteristics in different depth of profile and the erodibility of Plinthosol in middle reaches of Yangtze River basin.This study may provide reference for the Yangtze river middle reaches of the ecological environment construction.The major conclusions of this study are as follows:(1)In the middle reaches of the Yangtze River basin,the origin of Plinthosol is not consistent.Discriminant analysis results showed that origin of J profile was eolian sediment,but the parent material of W and Y profiles were alluvial or diluvial sediment.The difference of parent material is a vital factor that leading to the erodibility difference of Plinthosol in middle reaches of Yangtze River basin.(2)The initial water content has a great influence on the stability of Plinthosol,and there are some differences among different profiles.With the increase of initial water content,the stability of W profile continues increasing,and reach the maximum when the water content is about 20%.The stability of Plinthosol aggregates in profile Y and J also tends to be enhanced with the increase of water content.The stability of aggregates was the best when the initial water content was about 15%of Plinthosol in profile Y.When the water content was more than 15%,the stability decreased.The stability of Plinthosol in profile W and Y is the weakest when the initial water content was 0%,while in profile J was the 5%,which was different from that of both W and Y profiles.(3)The break down mechanism of Plinthosol aggregates was mainly caused by the explosion of compressed air in the pores during aggregates was wetted rapidly.Results showed that the slacking caused by rapid wetting leads to the Plinthosol aggregates disintegrate into small particles quickly.After removing the disintegration caused by slacking by adding ethanol,the stability of the three profiles was obviously improved.The RSI of W,Y and J profile was 0.48,0.36 and 0.48,respectively.RMI was 0.28,0.37 and 0.27,respectively.These results indicate that the slacking during rapid wetting was the main force for the disintegration of Plinthosol aggregates,while the external forces were less important than slacking.(4)The stability of white reticulate was different from red matrix in Plinthosol,and the largest stability difference among them was J profile and the smallest was W profile.This difference was mainly due to the migration of iron in Plinthosol during the formation process.The iron in the white reticulate migrated to the red matrix,which lead to the greater stability of the red matrix thane white reticulate.At the same time,the formation of reticulate changed the Plinthosol pore structure,that lead to the changes of water conductivity.The saturated water conductivity(Ks)varies greatly at different depths of each profile.The Ks values were small with the minimum Ks value of 0.01cm·d-1 at 60-70 cm depth of J profile.(5)In the vertical direction,the stability of W and Y profiles aggregates decreased with the increase of depth.It is mainly due to the higher OM content in the upper soil layers,which enhanced the aggregation of soil particles.The OM content of Plinthosol in profile J was lower,and the stability of aggregates does not change significantly with the increase of sampling depth.(6)The erodibility of Plinthosol in different profiles was different,but the erosion resistance of Plinthosol was greater than general soils.The results showed that the erodibility factor(K)of all profiles is low,and the K values of W,Y and J profiles was 0.008,0.007 and 0.004,respectively.The results indicates that Plinthosol erosion resistance was great,but the difference between white reticulate and red matrix of K value was obvious.This difference leads to white reticulate is vulnerable to water erosion,and original structure of Plinthosol is destroyed.Therefore,pay attention to prevent the loss of white reticulate is important for the region’s soil and water conservation work. |
