Influence Of Water And Salinity In Soil-Groundwater System On Vegetation Distribution In Southern Qaidam Basin

The relationship between vegetation and water and salinity of the soil-groundwater in southern Qaidam Basin has important academic significance and application value for vegetation restoration,reconstruction and water resources management.In this paper,we studied the characteristics distribution of vegetation species and the main water and salinity of soil-groundwater?soil salinity,soil water content,soluble salt ions,groundwater depth?on regional scales,typical micro-geomorphology scales and vegetation disappearance zones around salt lakes.The study has achieved the following main results:?1?Vegetation in the southern Qaidam Basin is distributed in a zonation.The vegetation community from the upstream gobi to the Qarhan Salt Lake is followed by the ephedra,the dwarf Phragmites,the carex,the Tamarix+the Phragmites+the Nitraria,dwarf Phragmites,apocynum+dwarf Phragmites and dwarf Phragmite.The plants are mainly stressed by soil moisture in the upstream gobi desert,and the plants are mainly stressed by salinity around the downstream salt lakes.The number of vegetation species in the downstream gradually decreased,and the vegetation disappeared and evolved into the bare of salt marsh finally.?2?On the typical micro-geomorphological scale,the vegetation community distributed in zonation.From the west to the east,the Phragmites community,Tamarix+Phragmites community,dwarf Phragmite+lycium community,Tamarix+Nitraria+Phragmites community are distributed,respectively.Comparing the water and salinity of the soil-grondwater on different vegetation samples,the results show that the Phragmite community is mainly related to the groundwater depth.The dwarf Phragmite+lyceum community is mainly related to the soil moisture and soil salinity.Tamarix+Phragmite+Nitraria community is mainly related to high sulfate.The results of RDA analysis indicated that the first layer of soil had the greatest influence on the distribution of vegetation species,and the order of environmental variables that best explained the distribution of species was Na⁺>Cl^->EC>moisture>Ca²⁺/Mg²⁺.?3?Vegetation disappeared from south to north around the salt lake,and there were obvious Apocynum disappearance zones and Phragmite disappearance zones.The result indicated that soil moisture,water and solinity of soil-grounswater in two vanishing zones don't affect the disappearance of Apocynum and the disappearance of dwarf Phragmite by he comprehensive and RDA analysis.This disappearance of vegetation may be related to the natural succession of vegetation during geological history.