| As an important transition zone between river ecosystem and terrestrial ecosystem,riparian zone is recognized as one of the best models for river ecosystem protection.In recent years,due to human disturbance,the ecological system of riparian zone was destroyed,thus the cyclic process of nitrogen and phosphorus in riparian zone is seriously affected.The mode of existence of nitrogen and phosphorus in riparian zone is the basis to control the migration and transformation of nitrogen and phosphorus,which affects the stability and balance of the ecosystem of riparian zone.It is of great significance to clarify the spatiotemporal distribution characteristics of nitrogen and phosphorus in riparian zones to reveal the environmental effects in riparian zones.In this study,three typical riparian zones of Linfen section of Fenhe River were taken as the research object,and the nitrogen and phosphorus elements in soil and plants in riparian zones were studied.The temporal and spatial distribution of nitrogen and phosphorus in riparian zone with different characteristics was analyzed,and the response relationship between the distribution of nitrogen and phosphorus in riparian zone and environmental factors was clarified.The effects of soil texture,vegetation type and river water quality on the distribution of nitrogen and phosphorus in riparian zones were studied by establishing a model,and the reasonable suggestions for riparian zone construction were put forward according to the results.The main research contents and results were as follows:(1)TN and TP reserves of soils in three typical riparian zones of Linfen section of Fenhe River were showed as the artificially restored riparian zone>the strong artificial disturbance riparian zone>the natural riparian zone.The contents Soil N and P in the riparian zone showed strong spatial and temporal heterogeneity with seasonal variation,and decreased first and then increased with the dry season-normal season-wet season.Soil N and P contents in the adjacent part of the riparian zone were higher than those in the far part of the riparian zone in each water period.In the direction of soil depth,the contents of nitrogen and phosphorus decreased with the increase of soil depth,and the spatial difference in the surface soil was small,while the spatial difference in the deep soil was large.For natural riparian zone and strong artificial disturbance riparian zone,the main factors affecting soil TN in riparian zone are soil bulk density,soil porosity,river evaporation and river TN content,while the main factors affecting soil TP in riparian zone are soil bulk density,porosity,pH value and N/P.However,the contents of TN and TP were only related to soil bulk density and soil moisture content in artificial restoration riparian zone.(2)A total of 38 species,35 genera and 15 families were found in three typical riparian zones of Linfen section of Fenhe River,all of which were herbaceous plants.The number of plant species was shown as the natural riparian zone<the artificial restoration riparian zone<the strong artificial disturbance riparian zone.In natural riparian zone,artificially restored riparian zone and strongly disturbed riparian zone,the plant biomass and the contents of TN and TP of vegetation decreased firstly and then increased during the dry season-normal season-wet season.There was a significant negative correlation between TN of plants and soil pH(P<0.05)in three typical riparian zones,the plant TP in natural riparian zone and strong artificial disturbance riparian zone was significantly negatively correlated with soil pH(P<0.01).Soil pH value,N and P accounted for the changes of N and P stoichiometry in riparian zone.Soil pH value and soil TN and C/N values in natural riparian zone and artificial restoration zone had obvious interaction with plant N and P contents,and strong artificial disturbance of soil TN and TP had obvious effect on plant N and P contents.(3)Due to the disturbance of human factors,in three typical riparian zones of Linfen section of Fenhe River,TN and TP of the artificially repaired riparian zone and the strongly artificially disturbed riparian zone showed dual effects of preventing river pollution and non-point source pollution,while the ability of natural riparian zone to trap river pollution was stronger than that of non-point source pollution.The infiltration rates of TN and TP in natural riparian zone were 68.974%and 57.221%,respectively.The infiltration and interception rates of TN and TP were 39.097%and 14.105%,respectively,and 54.769%and 57.811%,respectively.The infiltration rate of TN in the riparian zone with strong artificial disturbance is 47.397%,and the infiltration rate and interception rate of TP are 15.795%and 8.936%respectively.The infiltration and interception ratios of soil in three typical riparian zones were all higher than those of plants,while the infiltration and interception ratios of plants were higher.The content of TN in riparian zone responds to soil moisture content,river discharge and river TN.The TP in riparian zone responds to soil moisture content and soil C/P in riparian zone.(4)According to the migration regularities of TN and TP of natural riparian zone,with the river infiltration,TN and TP migrate from near shore to far bank and gradually penetrated from the surface to the deep soil,indicating that the ability of the riparian zones to intercept river pollution was stronger than that of non-point source pollution in the study area.The river water quality has a significant influence on the concentration of TN and TP in the riparian zone.The average contents of TN and TP in the riparian zone corresponding to the poor V class water quality are higher than those in the V and VI class water quality.The migration rate of TN in loam soil is smaller than that in sand soil.The migration rate of TP in sandy soil is lower than that in silty soil.Silt soil is easy to store nitrogen and phosphorus. |
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