Spatial Differentiation Of Freshwater Vegetation In The Yellow River Delta And Its Influencing Factors

Wetland in the Yellow River delta is the most perfect and youngest wetland ecosystem in warm temperate zone in the world,this area,especially the new wetland in the Yellow River delta is becoming a focus of research because the ecosystem of the area is fragile,and its ecological environmental problems are becoming more and more serious.As the primary producer of wetland,vegetation plays an irreplaceable role in the wetland ecosystem,it has important significance to research on the ecological environment of wetland because vegetation,species diversity and biomass can reflect the wetland vegetation growth distribution.The wetland of the Yellow River delta is taken as the research area in this paper,and the vegetation community,species diversity and biomass(dry weight)of the new wetland are taken as the research object.Based on processing the field data and remote sensing data,get samples' vegetation data,soil test data and the spectral reflectance and vegetation index;using decision tree classification method to build model and get the spatial distribution map of the community;through calculating the Margalef index,Shannon-Wiener index and Pielou index of species diversity distribution to establish the regression model of remote sensing and biological factors the map of spatial distribution of biomass generation;analyze the effects of environmental factors on vegetation spatial difference and correlation by using ArcGIS and SPSS.Results of this paper are as follows:(1)Vegetation in study area has obvious zonal distribution characteristics,TriarrhenaImperata cylindrica-Typha community and Phragmites community distribute in both sides of the river,Tamarix community,Suaeda salsa community concentrate in the central area of land,and there's a large number of pioneer vegetation along the coast and estuary area.(2)The species in study area are relatively single,and Margalef index,Shannon-Wiener index and Pielou index are all low.Margalef index of south coast is greater than that in north coast on average,and the index decreases as the distance from river course increases,but the index will increase when the distance is above a specific value.Shannon-Wiener index of south coast is greater than that in north coast on average,and it decreases as the distance from river course increases,but there's a clear fluctuation when the index varies.Pielou index is mainly concentrated from 0.5 to 0.8,and there's a clear fluctuation when the index varies.(3)Dry weight of biomass mainly distribute on both sides of the river and near the coast,while distribution in inland area is less,and distribution in north land is more than south land.Biomass of Triarrhena-Imperata cylindrica-Typha community near river course appears linear extension,Phragmites community in the central area of north coast(biomass in 700-1000g/m2 range)appears dendrogram distribution,and biomass of pioneer vegetation near the coast has a clear increasion.Biomass is totally high and reach the top in estuary area.(4)The Yellow River delta wetland salinity show an overall decrease from both sides of the river to the lateral trend,the northern part of the coast salt content is low;the total nitrogen showing an overall decreasing trend of outward from both sides of the river,the higher the total nitrogen content of the northern coast,high value areas are more concentrated in the river on both sides of the low value area for the offshore beach area;TP show an overall decrease from the sea to Lu Dizeng,outward from the river trend.(5)There's a clear correlation between vegetation community area and soil salt content,and both clear between vegetation community area and pH.It appears negative correlation between the percentage of Phragmites community,Triarrhena-Imperata cylindrica-Typha community and soil salt content,pH,while Tamarix community,Suaeda salsa community appears the opposite phenomenon.Correlation between vegetation community area and nitrogen,phosphorus is not clear.As for species diversity,there's a clear consistency in correlation between Margalef index,Shannon-Wiener index,Pielou index and environmental factors.It appears negative correlation between soil salt content,pH,distance from river course and the three indexes,whlie it appears positive correlation between nitrogen,phosphorus and the indexes.Observe from the whole area,correlation between indexes and distance from river course is the clearest,while it is not clear as for nitrogen,phosphorus.Among environmental factors,it appears positive correlation between soil salt content,pH,distance from river course and biomass,while it is positive as for nitrogen,phosphorus.Analyze from the value of correlation coefficient,value of distance from river course is greater than others,and as for indexes of species diversity,the correlation between Shannonwiener index and biomass is the clearest,then Margalef index,and Pielou index is the most non-clear.