Characteristics Of Soil Aggregate Stability And Nutrient Distribution Under Different Land Use Patterns In The Beng River Basin

With the rapid development of agricultural economy,the interference of human activities on land use is increasing,and the impact on soil quality is also more profound.In particular,some unreasonable land use aggravates soil erosion and imbalance of soil environment,which eventually leads to the decline of crop yield and the sharpening of contradiction between human and land.Soil aggregate stability and nutrient distribution are important evaluation indexes of soil quality.It is helpful to optimize the land use type and improve the soil environment by studying the stability and distribution characteristics of soil aggregates under different land use types,which is of great significance for regional food security and farmers’income increase.As an important part of the hilly area in the middle and south of Shandong Province,the Beng River Basin is characterized by large undulating terrain,loose and shallow soil layer with gravel,dense population and frequent rainstorms,which lead to serious soil erosion and soil degradation.In view of this,this study took the Beng River Basin as the research object,and used classical statistics and geostatistics methods to analyze the soil aggregate stability and nutrient distribution characteristics at different soil depths.The effects of different land use patterns on the stability and nutrient distribution of soil aggregates were discussed,and the coupling relationship between soil aggregate stability index and nutrient factors was revealed.Then,with the help of CCA analysis,Duncan multiple comparison and other methods,the effects of climate,soil parent material,soil type and precipitation on the stability of soil aggregates and nutrient distribution are further discussed.The results are as follows:（1）Soil aggregate stability and nutrient content decreased with the increase of soil depth in the study area,and each nutrient index had significant spatial heterogeneity.The specific performance is as follows:With the increase of soil depth,R_0.25,GMD and MWD of soil aggregates decreased,D increased,and nutrient indexes decreased.TN content was higher in the East and lower in the west,TP and TK content was higher in the East and lower in the west,and the distribution of an content was similar to that of total nitrogen,AP content only has a zonal high value area in the East and a dot high value area in the south.AK content is high in the north and low in the south.OM content is average in the whole.IFI value is high in the West and low in the East.（2）There are some differences in the stability of soil aggregates under different land use patterns.Under the soil depth of 0～10 cm and 10～20 cm,R_0.25,MWD and GMD were forest land,grassland,garden land and cultivated land from large to small,and D was cultivated land,garden land,grassland and forest land in turn;Under the soil depth of 20～30cm,R_0.25was forest land,cultivated land and garden land,MWD and GMD were forest land,garden land and cultivated land,and D was garden land,cultivated land and forest land;Under 30～40cm soil depth,R_0.25,D:cultivated land>garden land,MWD,GMD:garden land>cultivated land.It can be seen that the stability of soil aggregate in forest land is the highest,followed by grassland,and the stability of cultivated land is the worst.With the increase of soil depth,the difference of soil aggregate stability among different land use types gradually decreases.（3）The land use in the study area has a certain influence on the distribution of soil nutrients,and has different effects on different nutrient indicators.In 0～10cm soil layer,the content of TN in the soil was forest land,grassland,cultivated land and garden land,the content of TP was grassland,garden land,cultivated land and forest land,the content of TK was grassland,garden land,forest land and cultivated land,the content of an and OM had the same relationship with the content of TN,AP was farmland,garden land,forest land and grassland,AK was forest land,cultivated land,garden land and grassland;In 10～20cm soil layer,TP content was garden land,cultivated land,grassland and forest land,TK was grassland,forest land,garden land and cultivated land,and the relationship of TN,AN,AP,AK and OM content was the same as that in 0～10cm soil layer;In 20～30cm soil layer,TP and AP were garden land,cultivated land and forest land,TK were cultivated land,garden land and forest land,AN were forest land,garden land and cultivated land,AK,TN and OM were forest land,cultivated land and forest land;In 30～40 cm soil layer,except AK,the contents of other nutrient indexes were garden land>cultivated land.（4）There is a significant internal relationship between soil aggregate stability and nutrient distribution in the Beng River Basin.R_0.25,MWD,GMD and D were positively correlated with TN,an and OM,and negatively correlated with AP;D was positively correlated with AP,and negatively correlated with TN,AN and OM.The results showed that the higher the content of TN,AN and OM,the lower the content of AP and the higher the stability of aggregates.The stability of soil aggregates is the highest at the first nutrient level,and the stability of the second nutrient is the lowest,indicating that the increase of the nutrient level within a certain range is beneficial to the stability of the aggregate.（5）In addition to land use,climate,parent material,soil type and topography also have certain effects on soil aggregate stability and nutrient distribution in the study area.Soil type and topography are the main influencing factors.The aggregate stability of cinnamon soil and brown soil was higher than that of coarse bone soil,and the nutrient content of cinnamon soil was the highest,followed by brown soil,and coarse bone soil was the lowest.With the increase of elevation,the stability of soil aggregates first decreases,then increases,and then decreases,and then increases.With the increase of slope,the stability of soil aggregates first increases and then decreases.The stability of soil aggregates on sunny slope is greater than that on shady slope.The contents of TN,TK and OM in topsoil were positively affected by horizontal curvature,TP and AN were significantly affected by slope variability and vertical curvature,respectively,while AP was affected by terrain humidity index,relative elevation and river kinetic energy index.Both AN and TP of deep soil are significantly affected by surface roughness,topographic relief,slope and slope variability.