Analysis Of Soil Moisture Dynamics And Influencing Factors Of Different Landscape Types In The Middle Reaches Of Heihe River

The middle reaches of the Heihe River have scarce precipitation and shortage of water resources,but there are many types of landscapes in this region,and the ecological water requirements of each landscape type are different.Therefore,this paper takes the middle reaches of the Heihe River as the research area to explore the soil moisture status of different landscape types in this region,aiming to provide relevant basis for the rational allocation of water resources and the construction of windbreak and sand fixation projects in the middle reaches of the Heihe River.In this study,soil moisture was observed on 0-100 cm vertical sections of different landscapes in the study area from May to September 2021(rainy season),and relevant analysis was conducted.The main results are as follows:(1)The overall performance of the soil volumetric water content of each landscape type in the middle reaches of the Heihe River is as follows:riparian forest landscape>farmland landscape>farmland shelter forest landscape>desert-oasis transition With landscape>desert landscape.The variation coefficient of soil volumetric moisture content in each soil layer in desert-oasis transition zone and desert landscape are relatively large,and the changes in other landscapes are relatively small.SPSS was used to analyze the difference characteristics of soil volumetric moisture content of each landscape type.The results showed that:the soil layer between 0-40 cm soil layer of riparian forest landscape and 0-40 cm soil layer of farmland landscape,the soil layer between desert and oasis transition zone landscape and the soil layer of desert landscape,the differences of volumetric water content are not significant,and the differences of soil volumetric water content of each soil layer of other landscape types are significant.(2)The variation trend of soil volumetric moisture content on the vertical profile of the riparian forest landscape and the desert-oasis transition zone landscape from May to September is generally decreasing-increasing-decreasing,the changing trend of soil volumetric water content in farmland landscape and desert landscape is generally decreasing-increasing,the changing trend of soil volumetric water content in farmland shelter forest landscape is generally increasing-decreasing.(3)The soil volumetric water content in the surface layer(0-20 cm)and shallow soil(20-40 cm)of the farmland landscape,the desert-oasis transition zone landscape and the desert landscape changed relatively sharply during the simulation time period,while the The riparian forest landscape,the middle and deep layers(40-80 cm)of the farmland landscape and the shelter forest landscape have relatively gentle changes in soil volumetric water content.The main reason for the difference is that the vegetation coverage and soil physical properties of each landscape type are different.The variation trend of the results of the Hydrus-2D simulation on the vertical section is basically consistent with the measured results.The relative error range is generally between±10%,and the error of individual observation points exceeds±10%,but all are within±15%.The accuracy of the simulated values was tested,and the RMSE of the simulated and measured values of each landscape type is between 0.002-0.015 cm~3/cm~3,the MRE is between 4.22%and 5.29%,and the R~2is between0.57-0.93.The study concluded that,under the calibrated parameters,Hydrus-2D is suitable for this area.(4)Except for the desert landscape,which is negatively correlated with soil volumetric water content,the other landscape types were positively correlated with soil volumetric water content.The soil organic matter content of each landscape type and each soil layer is fitted with the soil volume water content,R~2is between 0.34-0.84,among which the farmland shelter forest has the best fitting degree,and the R~2is between 0.58-0.80,the desert landscape fitting effect Poor,R~2is between 0.34-0.69.Except for desert landscapes,other landscapes can adjust soil organic matter or soil moisture content through fertilization,irrigation and other measures to achieve the purpose of improving agricultural production and strengthening the construction of windbreak and sand fixation projects.(5)The soil temperature of each soil layer of different landscape types is negatively correlated with soil volume water content.The soil temperature and soil volume moisture content of each landscape type and each soil layer are fitted,and R~2is between 0.27-0.97.Among them,desert landscape and desert-oasis transition zone have the best fitting effect,and R~2is between 0.51-0.91,farmland The landscape fitting effect is poor,with R~2between0.36-0.68.Therefore,the soil temperature can be regulated by agricultural means such as irrigation,suppression and film mulching in a timely manner,thereby improving agricultural production and strengthening the construction of windbreak and sand fixation projects.(6)There are obvious differences in soil particle content of each particle size grade between different landscape types in the middle reaches of the Heihe River.The soil volumetric water content of each landscape type was positively correlated with the content of soil particles with a particle size of 0-2μm and 2-50μm,and negatively correlated with the content of soil particles with a particle size of≥50μm.The soil particle content and soil volume moisture content of each landscape type with different granularity levels were fitted,and R~2is between 0.41-0.88.Soil conditions can be improved by increasing organic fertilizers,using water-retaining agents,etc.,to enhance the water-holding capacity of the soil.