Study On Sources Of Soil Water Absorbed And Numerical Simulation Of Water Flux By Oil Peony In Typical Location Of The Loess Tableland

With the development of economy,people are more aware of the importance of the ecological environment to mankind than the past.There are arid climate and serious soil erosion in the Loess Plateau.In recent years,in order to maintain water and soil to build lucid waters and lush mountains,many ecological restoration projects for soil and water conservation have been implemented.In the Loess Plateau,water is a key factor limiting the effectiveness of ecological engineering and the foundation for the construction and stability of ecosystem structures.As a high-grade oil crop,if oil peony can be planted reasonably,it can not only control soil erosion and restore ecosystems in the Loess Plateau,but also use peony seeds to produce edible oil to ensure the safety of edible oil in China.Therefore,studying the water source and water use strategy of oil peony can help to promote the industry of oil peony and improve the survival rate of peony to provide scientific and theoretical basis.In this paper,two kinds of oil peony in different growth years were used as research materials,the stable hydrogen and oxygen isotopes were used to explore the water source during its growth period,and the Hydrus-1d software was used to construct a mathematical model of water flux of oil peony to explore its water consumption rules.The main research results are:(1)Using stable hydrogen and oxygen isotopes,the distribution of stable hydrogen and oxygen isotopes in rainwater,soil water,groundwater and tissues in oil peony at representative points in the Loess Plateau during different seasons was measured.The water source of oil peony was judged by graphic method and multi-source linear(Iso Source)model.Oil peony grew during different seasons and different years could use different water sources.Mature individuals for oil peony had an optimal water use strategy than young ones because they had formed developed root systems.Specifically,in spring,the peony of the two ages mainly used the water in surface soil from 0 to 20 cm.The difference between the two ages for peony is only that mature peonies used more water than young ones in topsoil.In summer,the peony of the two ages showed identical in the water use efficiency from 0 to 10 cm soil layer,but below 10 cm soil layers,the water use efficiency of the mature peonies obviously decreased in turn and the seedlings tended to use water below the 40 cm soil layer rather than that from 10-40 cm soil layer.In autumn,at the end of the growing period of oil peony,peonies of both ages absorbed water within 1 meter of soil layers.Mature individuals for oil peony mainly absorbed water from 40 to 60 cm soil layers,but their utilization rate of water below 40 cm soil layers and groundwater were far higher than that of young ones.(2)By the analysis of the relationships between soil water contents and the contribution rates of water absorbed by peonies from different sources,it was concluded that the soil layer with the high contribution rates of water to oil peonies has low soil water content.Oil peony tends to absorb water in soil with low water contents during a growing period.The present study verifies the tolerance of oil peony to drought but intolerant to waterlogging.This provides a scientific basis for the drought resistant planting of oil peony in the Loess Plateau.(3)According to the local meteorological data,and the physiological and ecological indicators(plant height,leaf area index,etc.)of oil peony and the soil physical indicators(particle size,bulk density,etc.).The soil physical parameters,root water absorption parameters and potential evapotranspiration were determined.Hydrus-1d software was used to establish one-dimensional mathematical model for calculating the water flux of oil peony,and the soil physical parameters were corrected by inversion based on the measured soil water content data.This provides scientific methods for the simulation of regional soil water transport and plant water flux.(4)Based on the established model,the water consumption of oil peony with the two ages was simulated.Compared with the water consumption under bare land conditions,the evapotranspiration under different site conditions was significantly different.Planting oil peony could better suppress the surface evaporation.During the growth period,the transpiration of mature individuals for oil peony was greater than that of young ones(210mm> 142mm).By comparing the lower boundary fluxes of oil peony sample plot and bare land,the differences between them were very small.By comparing the upper boundary fluxes,it was concluded that the water content in this area could satisfy the growth and development of oil peony with two ages.Although the mature individuals of oil peony needed more water than young ones in growth and development,adult oil peony sample plot could better retain water.