Study On Water Source Of Artificial Sand-fixing Plants On The Southern Margin Of Mu Us Sandy Land Based On Isotope Tracing Method

Moisture is a key factor affecting plant growth,life and distribution,especially in arid and semi-arid areas.The analysis of the water source of plants in arid and semi-arid areas helps to understand the adaptation of plants to arid environments in this area.The Mu Us Sandy Land is not only an important part of China's sandy land,but also a multi-level ecological transition zone such as climate,vegetation and landform.At present,the research on Mu Us Sandy Land mainly focuses on the prevention and restoration of desertified land,and there is not much research on the plant water use strategy and sand fixation vegetation combination.Therefore,in this paper,the main artificial sand-fixing vegetations on the southern margin of the Mu Us Sandy Land,Sabina vulgaris,Artemisia ordosica,Hedysarum leave,and Amorpha fruticosa,were used as the main research objects.The hydrogen stable isotopes were analyzed using direct linear correlation method and multi-source linear mixed model explore the water utilization strategies and response to precipitation of four artificial sand-fixing plants during different growth seasons.The main findings are as follows:(1)In different growth stages of the growing season,the soil moisture content of the four types of sand-fixing vegetation restoration areas differs significantly,and the peak growing season is significantly higher than the beginning and end of the growing season.At the beginning of the growing season and during the vigorous growing season,the soil water content showed a tendency to increase first and then decrease with the increase of the soil layer depth.The soil water content at the end of the growing season did not change significantly or decrease with the increase of the soil layer depth.The ?D values of soil water and plant samples indifferent types of sand-fixing vegetation restoration areas are obviously different.The ?D value of plant samples in the growing season was lower than that of the other two growth periods.big different.Analysis of plant water used sources and proportions shows that during the growing season,Artemisia ordosica's water used sources are mainly 0~40cm shallow surface soil water and 100 cm below soil water and groundwater.Hedysarum leave is similar to Artemisia ordosica but with a more average water source at the end of the growing season.Sabina vulgaris used 40~60cm soil water as the main water source in the early growing season,and the main water source depth in the peak growing season moves down to below 80 cm,and the water source is relatively average at the end of the growing season.Amorpha fruticosa mainly used the soil water below 80 cm soil layer at the beginning and the end of the growing season,except for the average water source during the growing season.The four sand-fixing plants use soil water below 80 cm to varying degrees,but Amorpha fruticosa and Sabina vulgaris mainly used deep soil water,and Hedysarum leave and Artemisia ordosica both used deep and shallow soil water.In order to avoid competition between water use of sand fixing plants,Amorpha fruticosa and Sabina vulgaris,Artemisia ordosica and Hedysarum leave should not be mixed and matched.(2)After the precipitation,the soil water and water used efficiency of the vegetation in the four artificial restoration areas all changed significantly.The water content of the soil surface layer increases,which is significantly higher than other soil depths,and the water gradually infiltrates with time.After a few days of precipitation,the deep soil water increased,which is significantly higher than the surface layer and other soil layers.The ?D value of the surface layer of soil water isotope before precipitation was higher,and gradually decreases with the increase of soil depth.The isotope ?D value of plant stem water and surface soil water changes with precipitation isotope ?D value after rain,and the isotopic composition after each precipitation was closer to the precipitationisotope value.The composition of deep soil water isotope ?D was affected by precipitation and plant water used.After precipitation,the water used strategies of sand-fixing plants changed to varying degrees.Before precipitation,Artemisia ordosica mainly used 0~60cm soil water,and the remaining three plants mainly used soil water and groundwater below 60 cm as the main water source.After precipitation,Artemisia ordosica increased the used of deep soil water below 40 cm,and converted to surface soil water before and after the restoration of precipitation to Sabina vulgaris,Hedysarum leave,and Amorpha fruticosa.The contribution rate of surface soil water after rain increased,and Amorpha fruticosa mainly Using 0~40cm soil water,Sabina vulgaris increased the contribution rate of soil water at a depth of 40~60cm,and Hedysarum leave simultaneously used surface soil water and groundwater.