Study On The Biomass And Root Distribution Of Different Vegetation Communities And Their Soil Physicochemical Properties In The Riparian Zone Of The Lower Yellow River

As a buffer zone between aquatic and terrestrial,riparian zones have been playing an important role in global ecological restoration because of their functions of water quality regulation,species habitat,prevention of riverbank erosion,energy conversion,and high spatial and temporal heterogeneity.The unique ecological characteristics of riparian zones determine them to be highly diverse ecosystems with complex dynamic characteristics.With the development of socio-economics and the intensification of human activities,a large number of wetlands have been encroached upon,resulting in the degradation of riparian zone vegetation,the destruction of function and structure,the degradation of vegetation and soil,soil erosion,and surface pollution have become one of the main ecological and environmental problems of the watershed.Riparian zone vegetation and soil are important components of the ecosystem and play a vital role in maintaining the ecological health,ecosystem services,and sustainability of the riparian zone.In this study,we investigate the biomass-root-soil interrelationship of typical vegetation in the Yellow River mudflat wetlands,five representative vegetation communities were selected in the study area of the middle and lower reaches of the Yellow River with less anthropogenic disturbance（.reed,reed-bermudagrass,reed-Calanus-bermudagrass,Calanus-bermudagrass,Calanus-bermudagrass-Cyperus）,The biomass,root distribution,and soil physicochemical properties of five typical riparian zone vegetation communities were investigated,and the response of vegetation community biomass,root distribution,and ecological stoichiometry characteristics to soil physicochemical properties were studied.The results show that:（1）In the Yellow River tidal flat wetland,the soil of the reed community and the reedbermudagrass community are mainly silty grains.The soil of the Calanus-bermudagrass community,reed-Calanus-bermudagrass community,and the Calanus-bermudagrass-Cyperus community are mainly sand grains.In the 0-40 cm soil layer,the soil moisture content,soil organic matter,available nitrogen,and available phosphorus content of the reed community and the reed-bermudagrass community are significantly higher than Calanus-bermudagrass community,reed-Calanus-bermudagrass community,and the Calanus-bermudagrass-Cyperus community.（2）The riparian region of the Yellow River is dominated by perennial graminaceous plants,with simple community species composition and simple life forms,and the biomass of different vegetation types varies greatly.The total community biomass of the riparian region ranges from 236.3 g·m^-2 to 4347 g·m^-2,with an average of 1454.5 g·m^-2.The biomass of the vegetation community was.reed(3272.43 g·m^-2)>.reed-bermudagrass(2484.65 g·m^-2)> reed-Calanus-bermudagrass(924.29 g·m^-2)> Calanus-bermudagrass(338.45 g·m^-2)> Calanus-bermudagrass-Cyperus(252.69 g·m^-2).Soil moisture content,organic matter,total carbon,total nitrogen,and aboveground and underground biomass of vegetation in the Study Area of the Yellow River Riparian zone were significant（P < 0.01）positive correlation.Soil bulk density and PH were significantly correlated with aboveground and underground biomass of vegetation（P < 0.01）negative correlation.The root-shoot ratio was significantly correlated with soil organic matter,total carbon,and total nitrogen（P < 0.01）were positively correlated with soil moisture content（P < 0.05）positive correlation.Path analysis and decision coefficient analysis showed that the decision coefficient of soil physical and chemical factors on vegetation biomass in the Yellow River bank was: R2TN>R2SBD>R2SWC>R2SOC>R2TC>R2p H,and soil moisture content was the main decision variable,and soil total nitrogen and soil bulk density were the main limiting variables.（3）In the 0-40 cm soil layer,the average value of root biomass density and root length density are both expressed as the reed community and the reed-bermudagrass community are larger than the reed-Calanus-bermudagrass community and the Calanus-bermudagrass community,the Calanus-bermudagrass-Cyperus community.The root characteristics of Calanus-bermudagrass,reed-Calanus-bermudagrass,Calanus-bermudagrass-Cyperus are mostly concentrated in the 0^-20 cm soil layer,but the root biomass of the reed community and reed-bermudagrass community is mainly distributed in the 10-40 cm soil layer.The root biomass density and root length density of the Yellow River tidal wetland vegetation community are significantly positively correlated with soil clay content,silt content,soil moisture content,and available nitrogen（P < 0.05）,which are extremely significantly negatively correlated with soil sand content（P < 0.01）.（4）The mean values of aboveground biomass C,N,and P of dominant vegetation communities in the riparian zone of the Yellow River study area were 390.71 g kg^-1, 10.69 g kg^-1,and 1.09 g kg^-1,respectively,and the mean values of root C,N,and P contents were 263.81 g kg^-1,9.23 g kg^-1,and 0.74 g kg^-1.The C,N,and P contents showed similar patterns in the aboveground biomass and root.The C,N,and P contents in the above-ground biomass and root showed similar patterns,with C,N,and P contents mostly higher in above-ground biomass than in the root system（except for N contents in the root of reed vegetation）.The vegetation communities had significant effects on soil nutrients and C: N:P stoichiometry and the differences were significant.The C,N,and P contents of the soils of reed and reed--bermudagrass vegetation communities were significantly higher than those of the other three vegetation communities（P < 0.05）,and the C/N and C/P of the soils of the fescue-dogwood vegetation community were significantly greater than those of the other three vegetation communities（P < 0.05）,and the differences in N:P ratios among the different vegetation communities were not significant.The aboveground biomass and belowground root N/P of the five vegetation communities in this study were less than 14 and the soil N/P was lower,the N constraint on the soil was somewhat greater,and the wetland ecosystem in the study area may be mainly N-limited.（5）The results of correlation analysis and redundancy analysis（RDA）showed that soil C,N,and P contents and CNP ecological stoichiometry ratios in the riparian zone of the Yellow River were significantly correlated with aboveground biomass and root CNP ecological stoichiometry ratios.Aboveground biomass N content was significantly and positively correlated with soil C,N,and P content.Root C content,root P content,and aboveground biomass C content were significantly and positively correlated with soil N/P.Root C/N,C/P,and aboveground biomass C/N were significantly and positively correlated with soil C/N,and aboveground biomass C/P and root C content were correlated with soil C/P.In addition,root C/P was significantly negatively correlated with soil C,N,and P content,and aboveground biomass P content was significantly negatively correlated with soil C/P.