Study On Water Absorption Law Of Poplar Based On Hydrogen And Oxygen Stable Isotope In Otinday Sandland

In order to improve the serious desertification situation in Otinday Sandland,poplar is widely cultivated for its characteristics of wind and sand fixation and drought resistance.Based on the stable isotope tracing technique,this paper compares the changes of precipitation,soil water,plant stem water and groundwater isotope characteristics in the region from 2015 to 2018.The direct contrast method,the water absorption depth model,the multivariate linear mixed model and the Bayesian model are used to analyze the combination of qualitative and quantitative sources of water absorption,and then compare the four methods to obtain a reliable source of water absorption,and then determine the unique water absorption of poplar.The law provides a theoretical basis for the rational use of water resources in desert areas and the optimal allocation of water resources in and and semi-arid regions.The main results are as follows:(1)The change of soil moisture content is affected by climate and plant growth.The shallow soil moisture content is susceptible to precipitation,evaporation,and plant roots.The deep soil moisture content is stable.The change of soil moisture content during the geraiination period and winter preparation period of poplar is small,and the soil moisture content varies greatly due to the unstable changes of environmental factors during the growing season,the soil moisture content of each layer increases after precipitation.(2)Analysis of different water isotope characteristics between the interannual and the annual analysis,the local atmospheric precipitation line can be obtained as ?=7.6937?8O+5.014,R2=0.9457,and the isotope is subjected to unbalanced secondary fractionation.The hydrogen and oxygen isotope of precipitation is affected by environmental factors such as temperature,rainfall and relative humidity.Temperature is dominant and temperature effect is significant.Precipitation replenishes soil water and groundwater.Precipitation makes the water hydrogen and oxygen isotopes of shallow soils depleted.Precipitation infiltration makes the groundwater hydrogen and oxygen isotopes smooth,resulting in the stability of groundwater hydrogen and oxygen isotopes.(3)Using direct contrast method,water absorption depth model,multivariate linear mixed model and Bayesian model to analyze the main water-absorbing sources and components of poplars before and after the growth period and precipitation,revealing the uniqueness of poplars in the face of drought.Water absorption mechanism.The water absorption source of poplar can be flexibly changed between different potential water sources.The plants experience long-term drought,and the poplars mainly use deep soil water and groundwater.In the rainy season,the poplars are preferentially used for precipitation.After the replenishment of the shallow soil water,the water absorption layer moves down.(4)Quantitative analysis of the influence factors of poplar water mechanism,it is concluded that groundwater depth,soil moisture content and pre-precipitation all affect the use of soil water by plants,and the groundwater depth is negatively correlated with the proportion of groundwater used by plants.And the utilization rate of groundwater in the dry season is higher than the precipitation season.