Study On The Relationship Of Supergene Ecology And Groundwater In Minqin Basin Of Shiyang River Basin

Minqin Basin is located in the downstream area of Shiyang River Basin,located in the arid inland,and is a sensitive area of global environmental change.The climate in this region is dry,and the ecological environment is very fragile.The surrounding areas are gradually desertification,and some land in the basin is also facing salinization and desertification.In this paper,Minqin Basin in Shiyang River Basin is selected as the study area.Through laboratory tests,typical profile monitoring and field ecological quadrat investigation,the relationship between vegetation ecology and groundwater is studied by using the methods of metadata statistical analysis and numerical simulation.The distribution law of root water absorption rate of typical vegetation under different groundwater depths is simulated,which provides a theoretical basis for further study of groundwater ecological environment effect.The main conclusions are as follows :1.According to the field ecological quadrat survey,with the increase of groundwater depth,vegetation types gradually transit from herbaceous and aquatic plants to shrubs and trees.When the groundwater depth is 2 ～ 6 m,the species richness is the largest and the vegetation coverage is the highest.When the groundwater depth is 6 ～ 7 m,the species richness decreases,generally less than 4 species,the vegetation coverage is less than40 %,and the vegetation growth is not good.When the groundwater depth is greater than7 m,most vegetation withered and died,vegetation sporadic distribution,coverage is generally less than25 %,vegetation types are mainly dry Elaeagnus angustifolia,Haloxylon ammodendron,Nitraria tangutorum and other plants.2.In shallow groundwater area,vegetation grows healthy.With the increase of groundwater depth,vegetation grows worse or cannot survive at all.The suitable groundwater depth range of Elaeagnus angustifolia and Artemisia sphaerocephala is wide and grows well in 2 ～ 6 m.Nitraria tangutorum grows under different groundwater depths,but grows vigorously within 3 ～ 6 m.The suitable groundwater depth range of Tamarix chinensis is narrow,and the suitable groundwater depth is 3 ～ 5 m.For salty shrub salt claw and herbaceous plant reed,the suitable groundwater depth is shallow and grows well within0 ～ 4 m.3.By analyzing the distribution characteristics of soil water content and soil temperature in different groundwater depths and different vegetation structures,it is found that vegetation,soil temperature and groundwater level are the main factors affecting the change of soil water content in the shallow groundwater area.The more the surface vegetation structure is,the more frequent the soil moisture exchange is.The aeration zone is supported by atmospheric precipitation infiltration and capillary water,and the water content of the whole aeration zone is high.In the vertical distribution,the influence of soil temperature on water content in shallow soil is greater,and in deep soil,water content changes with the fluctuation of groundwater.In the deep groundwater area,the water content changes violently in the whole section,and the greater the groundwater depth,the more intense the change.The shallow soil water content is less affected by soil temperature and groundwater.When the burial depth is greater than 6 m,soil temperature and groundwater have little effect on the moisture content of shallow soil in the unsaturated zone.4.Hydrus-1D software was used to establish the vadose zone water transport model and root water absorption model.The model was used to analyze the distribution characteristics of root water absorption rate of typical vegetation from July to September.During the mature period of vegetation from July to August,due to the increase of temperature and evaporation,plant water demand increased,and root water absorption rate increased.In September the vegetation entered a recession,vegetation water absorption capacity gradually weakened.In addition,evaporation decreased relatively after September,rainfall increased,shallow soil water content increased,and root water absorption rate increased.With the increase of groundwater depth,the water absorption layer of vegetation root decreased gradually.The shallow root absorbed shallow water content,mainly concentrated in 10 ～ 40 cm.The deep root absorbed water to the place with high soil water content,and the root absorbed water in 70 ～ 150 cm and 300 ～ 400 cm.The water absorption of Tamarix chinensis roots was concentrated in the range of 180 ～ 220 cm;Salt claw root water absorption mainly concentrated in the 110 ～ 150 cm range;The water absorption of reed roots was concentrated in the range of 80 ～ 90 cm.5.According to the water absorption law of vegetation roots at different groundwater depths,the roots always grow towards the areas with sufficient water and the easiest water absorption.When the groundwater depth is less than 3.0 m,the soil moisture in the aeration zone can reach the required level for vegetation growth,and the water absorption rate of vegetation roots reaches the maximum within 10 ～ 40 cm.When the groundwater depth is greater than 3.0 m,the root system of vegetation is completely distributed in the aeration zone.Due to the decrease of soil moisture content in the upper layer,in order to maintain the growth of vegetation,some roots extend to the areas with high soil moisture content in the deep soil,and the water absorption rate of root system in the deep soil increases.