Studv On The Relationship Between Soil Characteristics And Typical Plant Communities And Their Biomass And Carbon And Nitrogen Content In Riparian Zone Under Different Hvdrological Conditions

Riparian zone,as the ecotone of land-river ecosystem,is the key area for material exchange,energy transfer and information exchange.It is also one of the most complex and diverse ecosystems,and it has extremely important and irreplaceable ecological service function.With the increase of human activities and the change of climate,the excessive exploitation of land resources along the river and the expansion of agricultural land have seriously damaged the ecological environment of the riparian zone in the middle and lower reaches of the Yellow River.As an important part of riparian zone,the change of physical and chemical properties and growth characteristics of soil and plants play a decisive role in the ecological function of riparian zone.This study in order to the middle and lower reaches of the Yellow River is a typical natural recovery riparian zone as the research object,according to the dynamic change of river hydrology,natural precipitation area of the middle and lower reaches of the Yellow River near natural riparian zone caused by the flood situation,set a perennial not flooded riparian zone and seasonal flooding riparian zone,using the field investigation,experimental analysis and the method of redundancy analysis(RDA),The soil physical and chemical properties(soil water content,soil bulk density,soil particle size,soil C content,soil N content)and the characteristics of typical plants(aboveground biomass,underground biomass,plant C and N content)in two riparian zones with different hydrological conditions were compared and analyzed.The main research results are as follows:(1)in the middle and lower reaches of the Yellow River riparian zone area all the year round not flooded the zone of the typical plants(reed,brushed MAO,kochia scoparia,sedge)of soil moisture content,soil bulk density,soil C/N are less than seasonal flooding riparian zone,two kinds of riparian zone,soil particle size distribution in the powder and the proportion of very fine sand is bigger.In the riparian zone,the soil in the diskin community had the highest proportion of very fine sand,relatively loose soil texture and strong permeability,while the soil in the community of Phragmites australis,Fructus cuspidata and sedge had the highest proportion of coarse silt,and the soil texture was relatively heavy and poor permeability.(2)The Margalef richness index of the four typical plant communities in the perennial unflooded riparian zone of the middle and lower reaches of the Yellow River was lower than that in the seasonally flooded riparian zone.There were 18 species of 7 families in the unflooded riparian zone.The Margalef richness index,Shannon-Wiener diversity index and Pielou evenness index were the highest in the four typical plant communities,while the Margalef richness index and Shannon-Wiener diversity index of sege community were the lowest.Pielou evenness index of ground skin was the lowest.There were 22 species of 7 families in the seasonally flooded riparian reed community.The Margalef richness index and Shannon-Wiener diversity index were the highest in the four typical plant communities,while the Pielou evenness index of seeper was the highest.Among the four typical plants selected,the underground biomass of Phragmites australis was greater than the aboveground biomass,and the other plants showed the opposite trend.There was a significant difference in aboveground C/N and underground C/N of sedge only(P<0.05).(3)Soil water content in the unflooded riparian zone had significant positive correlation with soil bulk density,soil C content and soil N content(P<0.05),but had no significant correlation with the fractal dimension of soil particle size(P>0.05).Soil C content was significantly positively correlated with soil N content(P<0.01).There was a significant positive correlation between soil water content and soil bulk density and soil C content in riparian zone of seasonal flooding(P<0.01),and a significant positive correlation between soil bulk density and soil C content(P<0.05).However,there was a significant positive correlation between soil C content and soil N content(P<0.01).(4)There was a significant positive correlation between C content,N content and biomass of typical plants in perennial unflooded riparian zone and seasonally flooded riparian zone(P<0.05),and there was a significant positive correlation between N content and biomass of plants(P<0.05).Soil water content,soil bulk density,soil C and N contents were significantly correlated with biomass and C and N contents of typical plants,which were important factors affecting the growth and development of typical plants in riparian zone.(5)The contribution rate of soil water content to the change of plant diversity in the perennial unflooded riparian zone was 62.8%,indicating that it was the main factor driving the change of plant diversity in the perennial unflooded riparian zone.The contribution rate of soil water content to the changes of plant biomass and C and N contents was 23.1%,and it was the main factor affecting the changes of plant growth in the soil physical and chemical properties in the unflooded riparian zone.In the seasonally flooded riparian zone,the contribution rate of soil bulk density to the change of plant diversity was 59.3%,indicating that it was the main factor driving the change of plant diversity in the seasonally flooded riparian zone.The contribution rate of soil bulk density to the changes of plant biomass and C and N contents was 34.1%,which was the main factor driving the changes of plant biomass and C and N contents in the soil physical and chemical properties of riparian zone under seasonal flooding.