Distribution Characteristics And Influencing Factors Of Soil Physical And Chemical Properties In The Floodplain System Of Lower Jingjiang

This paper deals with the distribution characteristics of soil physical and chemical properties and their relationships with hydrogeomorphologic units and land use patterns in the river floodplain system,it provides reference for understanding soil-related ecological processes and river management in river system.Taking the lower Jingjiang River in the middle reaches of the Yangtze River as the research object,the distribution characteristics,differences and correlations of soil physical and chemical properties in 0 ー 20 cm soil layer of floodplain system in alluvial reach were analyzed,the effects of hydrogeomorphologic units and land use patterns on soil physical and chemical properties were discussed.(1)The influence of hydrogeomorphologic units on the distribution of soil bulk density was mainly concentrated in the soil layers of 0 ～ 5cm and 15 ～ 20 cm,and had little effect on the three kinds of porosity of soil layers;The results showed that the soil moisture content of 0 ～ 5cm,15 ～ 20 cm,silt content,sand content and available phosphorus content were significantly affected It had significant effects on soil organic carbon and total nitrogen in 0 ～ 15 cm soil layer,and on soil alkali-hydrolyzed nitrogen in 0 ～ 5cm soil layer The content of total phosphorus in 5 ～ 10 cm and 10 ～15cm soil layers was influenced by the content of total phosphorus.The effects of land use on the distribution of soil bulk density were mainly concentrated in the soil layers of 0 ～ 5 cm and 5 ～ 10 cm,and the effects on the total porosity and capillary porosity were mainly in the soil layers of 5 ～ 10 cm,10 ～ 15 cm and 15 ～ 20 cm The content of saturated water,field water holding capacity,silt,sand and available phosphorus in each soil layer were significantly affected,and the total carbon content was affected in 5 ～ 10 cm soil layer The soil organic carbon content was affected in 10 ～ 15 cm soil layer,total nitrogen and alkali-hydrolyzed nitrogen content in all layers,total phosphorus content in 5 ～ 10 cm soil layer and 10 ～15cm soil layer.When the two factors work together,the soil bulk density,total porosity,capillary porosity,soil saturated water content,field water holding capacity,silt content,sand content,alkali-hydrolyzed nitrogen content and available phosphorus content in each layer are affected It had an effect on total carbon,organic carbon and total nitrogen content in each layer from 0 to 15 cm,and on total phosphorus content in 5 to 10 cm and 10 to 15 cm soil layers.The above results show that when only one factor of hydrogeomorphologic unit or land use pattern is considered,it has certain influence on the distribution difference of soil physical and chemical properties in the study area,the distribution difference of soil physical and chemical properties is the most significant.(2)through the comparison of the soil physical and chemical properties of 0 ～20cm soil layer between three kinds of reed land,three kinds of poplar forest land and cultivated land,the soil bulk density showed as follows: cultivated land > Poplar forest land > Reed land;The total porosity and capillary porosity showed that reed land > poplar forest land > cultivated land,and the soil nutrients showed that reed land > flood bank > Poplar forest land > cultivated land.The above results showed that the Phragmites communis land soil physical and chemical properties are the best,therefore,Poplar forest land and arable land soil physical and chemical properties are poor.(3)the vertical distribution of soil samples under the seven combined models was as follows: soil water content(saturated water content,field capacity),porosity(total porosity,capillary porosity,non-capillary porosity),total carbon,organic carbon,total nitrogen,alkali-hydrolyzed nitrogen,total phosphorus,available phosphorus and total potassium decreased with the increase of soil depth;In general,the vertical distribution of soil bulk density and p H value increased with the increase of soil depth.The above results show that the soil physical and chemical properties in the study area have a certain regularity in vertical distribution,and the depth of soil layer has a certain influence on the distribution of soil physical and chemical properties.