Response Of Hippophaer Hamnoides Sap Flow And Fineroot Growth To Environmental Factors In Arsenic Sandstone Area

The arsenic sandstone area has vertical and horizontal gullies,exposed bedrock and scarce vegetation.It is the key area of ecological environment construction in the Loess Plateau.The large-scale planting of Hippophae hamnoides in this area is of great significance to improve the local fragile ecological environment.The experiment was conducted in Nuanshui Township,Jungar banner of Inner Mongolia,and it was from May to September in 2021.The thermal diffusion probe technology(TDP)was used to continuously monitor the flow rate of Hippophae rhamnoides liquid,the dynamic growth of Hippophae rhamnoides root system in 0～50cm soil layer was dynamically monitored by micro root canal,and the environmental factors were synchronously monitored by small meteorological station.The variation relationship between Hippophae rhamnoides liquid flow rate,root system and environmental factors was analyzed,In order to reveal the habitat adaptability of Hippophae rhamnoides in arsenic sandstone area,and provide a theoretical basis for vegetation construction and wind prevention and sand fixation in arsenic sandstone and other arid and water deficient areas.The main conclusions are as follows:(1)The diurnal variation of Hippophae hamnoides liquid velocity rate in arsenic sandstone area shows a typical"bimodal"curve.At about 11:00,the Hippophae hamnoides liquid velocity rate reached the first peak(40 g/h),and at about 14:30,the Hippophae hamnoides liquid velocity rate reached the second peak(38 g/h).During this period,the stomata of Hippophae hamnoides leaves are closed due to the influence of solar radiation,resulting in the phenomenon of"lunch break".There is no obvious change at night.In typical weather,it is sunny>cloudy>rainy,From May to September,the sap flow rate of Hippophae hamnoides showed a trend of low in the early stage(from May to June),high in the middle stage(from July to August),and gradually decreasing in the later stage(September).(2)In 0～50 cm soil layers,with the increase of soil depthes,Hippophae hamnoides fine root factors(root length density,fine root surface area density,growth rate,death rate and the ratio of life and death)first increased and then decreased.In 0～50 cm soil layer,the order of fine root factors from large to small is:10～20 cm>0～10 cm>20～30 cm>30～40 cm>40～50 cm.In the growing season,the surface area density and death rate of(3)Hippophae hamnoides fine roots gradually increased,the fine root length density and growth rate increased first and then decreased,and the ratio of life and death decreased gradually.(4)The soil water content in 0～50 cm soil layers increases first and then decreases with the increase of soil depthes.The water content of each soil layers from high to low is:10～20 cm>0～10 cm>20～30 cm>30～40 cm>40～50 cm.In the growing season,the soil water content showed a change trend of low in the early stage(from May to June),high in the middle stage(from July to August)and decreasing in the later stage(September).The solar radiation reached the peak at about 13:00(679 w/m~2),the atmospheric temperature reached the peak at about 14:00(38.55℃),the air relative humidity reached the maximum at about 24:00(72.32%),the water vapor pressure deficit reached the peak at about 13:00(3.5 kpa),and the 10 cm ground temperature reached the peak at about 14:00(33.5℃).(4)The change of Hippophae rhamnoides sap flow rate is affected by the joint action of fine roots and environmental factors,and the total explanation degree is about 89.3%.Among them,the effect of soil water content on Hippophae rhamnoides sap flow rate is highly significant positive correlation(P<0.01),the explanation degree is about 66.3%,and the explanation degree of other environmental factors is only 0.4%.In addition to soil water content,the influence of fine root correlation on it was greater than that of environmental factors(P<0.05),and the explanation degree was 19.1%.Among them,the growth rate of Hippophae rhamnoides fine root had the greatest influence,and the explanation degree was 16.1%.It shows that soil moisture and fine root growth rate of Hippophae rhamnoides in arsenic sandstone area are the main factors affecting the flow rate of Hippophae rhamnoides liquid.