Study On The Natural Vegetation And Its Relationships With Groundwater And Soil Salinity In Kaidu-Kongque River Basin

Taking natural vegetation distribution regions as studied objects in Kaidu River(Yanqi Basin)-Kongquehe Basin,taking the current survey data which are natural vegetation,soil salinity,ground water level,groundwater mineralization in 2007 and 2008,and taking the growing season of ALOS remote sensing data in 2007 as message sources,taking quantitative vegetation ecology,vegetation restoration ecology and landscape ecosystem as theory basis,using statistics analyse,geostatistics analyse and remote sensing- geographical information technology,to study the relationship betwee n the different water,soil conditions and natural vegetation.The main results showed:In the bank area of Kaidu River,when the groundwater mineralization is about 0.62g/l and th e groundwater level is 0.5～2.4m,arbor,shrub and grass vegetations are grew well.When the soil salinity at 0.46g/kg～1.59g/kg,the arbor and the grass vegetation degree of coverage reduced along with the soil salinity increased.The west and north areas in desert of Yanqi Basin,the soil salinity is less than 3g/kg.In thi s context,the natural vegetation degree of coverage reduced along with the soil salinity increased. When soil salinity is 6g/kg～10g/kg in south area,the natural vegetation degree of coverage reduc ed and vegetation types decreased significantly along with the soil salinity increased.Using the geostatistics and analyzing the water and salt in Yanqi Basin shows that:in the ba nk area of Kaidu river,the desert area of Yanqi Basin and the side area of Bosten Lake,the grou ndwater level,the groundwater mineralization have a medium-intensity variability and the groundwa ter mineralization has a weak spatial correlation.The soil salinity in the above three areas appears normal distribution,the coefficient of determination is above 0.7,the variation in line with the in dex curve,respectively,Gaussian and spherical model,fitting results are very remarkable.In the area of Bosten Lake,the soil salinity increased along with the distance from the lake,t he shrubs and grass vegetation degree of coverage decreased like tamarix.When the groundwater mineralization is less than 0.6g/l,the shrub and grass vegetations are in good condition;when gro undwater mineralization is 3～5g/l,the tamarix and salt desert vegetations are grow well;when gro undwater mineralization is 5～10g/l,while the growth of vegetation mainly is salinity,community c over is 20%or so.When groundwater mineralization reached above 10g/l,the vegetation is sparse. coverage reduced.The vegetation coverage,abundance and the groundwater level,groundwater mi neralization and soil salinity have a better associated changes.Analysis on the relations between vegetation index(NDVI) and water,soil in Kaidu river area shows that:NDVI of grass,agricultural land and the salt desert vegetation descend along with th e groundwater level increased.The groundwater level of 1～2m,groundwater mineralization＜1.1g/l is the appropriate scope of grass and agricultural land;The groundwater level at 3～4m,groundwater mineralization＜3g /l is suitable for the growth of the scope of forest vegetation.When soil salin ity＜3g/kg,all vegetations are grow well(except the salt desert vegetations);When soil salinity＞3 g/kg,the surface have only a small number of the salt desert vegetation coverage,less or almost n o vegetation is covered.Analysis on the relations between the water,soil conditions of different sections,different dist ance from the Kongque river and the diversity of natural vegetation shows that:groundwater level＜3.6m and soil PH value of＜8.56 are suitable for the local natural vegetation.They are the two critical indicators of growth.Along the vertical and horizontal from Kongque river,when soil sali nity＞20g/kg,which is severe soil salinization,the diversity of vegetation is overall lower.Using the geostatistics and analyzing the water and salt in Kongque river basin shows that:in Kongque river basin,the salinity groundwater basin obeys the lognormal distribution,groundwater level and soil salinity obey normal distribution,soil salinity variations are in line with the expone ntial model curve.Its coefficient of determination(R~2) above 0.88 is with well fitting effect.The groundwater level and soil salinity have a weak spatial correlation,the spatial correlation of ground water mineralization is moderate.