Effects Of Plant Species On Soil Denitrification In The Lakeshore Zone Of Yezhi Lake

The lakeshore zone is a transitional zone between aquatic ecosystem and terrestrial ecosystem,which can reduce the impact of non-point source pollution.Plants are key parameters to prevent and control nitrogen migration into the lakeshore zone.Denitrification is a key process in the nitrogen cycle for the effective removal of nitrogen in the lakeshore zone,which can be affected by plant species and soil microorganisms.In this study,the rhizospheric and non-rhizospheric soils of nine plant species in the lakeshore zone of Yezhi Lake were investigated.The denitrification rates of the soils were measured by acetylene inhibition method,and the abundance of denitrifying functional genes were measured by fluorescence quantitative PCR.The effects of different plant species planting on the denitrification function rate and functional genes were explored.Through the analyses of soil properties differences of rhizospheric and non-rhizospheric soils of different plants,the mechanism of plant groups affecting denitrification was also clarified.This study would provide a reference for vegetation restoration and optimal design of vegetation planting in the lakeside zone.The main results are as follows:（1）Different plant species changed the abundance of denitrifying functional genes in the soil of the lakeshore zone of Yezhi Lake.The abundance of denitrifying functional genes in rhizosphere soil was 1.14-12.11 times higher than those in non-rhizosphere soil.The abundances of nar G、nap A、nir S、nir K and nos Z genes in rhizosphere soil of Salix babylonica,Osmanthus fragrans and Jasminum nudiflorum were significantly higher than those of corresponding plant species.This indicated that denitrifying microorganisms growed more vigorously in the plants rhizosphere microenvironment.（2）The soil net denitrification rates varied among different plant species.The net denitrification rates of the rhizospheric soils of Salix babylonica,Osmanthus fragrans and Jasminum nudiflorum were significantly higher among the nine plant species,which were1.99,1.84 and 1.94 mg N kg^-1h^-1.The net denitrification rates of plant rhizospheric soils(0.44～1.99 mg N kg^-1h^-1)were 3.11-8.71 times that of non-rhizospheric soils(0.14～0.48 mg N kg^-1h^-1).It indicated that plants enhanced the denitrification intensity of the soil in lakeshore zone significantly,and denitrification intensity was affected by plant species.These three plants can be considered in the planting design of lakeshore zone.（3）Planting different plant species affected soil physical and chemical properties such as NN,AN,TC,TN and DOC in the lakeshore zone.The abundances of denitrification functional genes were mainly affected by soil TC、SWC、SOC、p H and AN in the lakeshore zone.Path analysis showed that p H,SOC,TN,nir S and nor B were the determinants of net denitrification rate in rhizosphere soil,while DOC,nor B and nap A were the determinants of net denitrification rate in non-rhizosphere soil.