Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and wa...Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and water cycle mechanisms.In this study,we analyzed the stable isotopic composition,relationship and indicative significance of precipitation,soil water(0~100 cm depth)and xylem water of Qinghai spruce(Picea crassifolia)forest in the eastern Qilian Mountains,and explored the circulation process among different water bodies.The results show that the stable isotopes of precipitation vary greatly during the entire observation period.The values ofδ2H andδ^(18)O in the precipitation in the warm season are richer than those in the cold season,and the slope and intercept of local meteoric water line(LMWL,δ2H=6.79δ18O+7.13)are both smaller than global meteoric water line(GMWL,δ2H=8.17δ18O+10.56).The stable isotopes of soil water at different depths underwent different degrees of evaporative fractionation,and theδ18O andδ2H of shallow soil water varied greatly,while the deep soil water tended to be similar.The topsoil(0~10 cm)can respond quickly to precipitation,and the response of the deep soil has a time lag.In the whole growing season,0~30 cm and 60~100 cm soil water are the main water sources of Qinghai spruce.The water source of Qinghai spruce was from all soil layers in May and September,mainly from the shallow soil layer(0~30 cm)in August and October,and mainly from the deep soil layer(60~100 cm)in June and July.展开更多
HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant tr...HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant transpiration partitioning.For the above-ground part,a layer approach is used to partition available energy and calculate aerodynamic resistances,while a patch approach is used to derive sensible heat and latent heat fluxes from the two sources(soil and vegetation).For the below-ground part,soil water and heat dynamics are described by the mixed form of Richards equation,and the soil heat conductivity equation,respectively.These two parts are coupled through ground heat flux for energy transfer,root-zone water potential-dependent stomatal resistance,and surface soil water potential-dependent evaporation for water transfer.Evaporation is calculated from the water potential gradient at soil-atmosphere interface and aerodynamic resistance,and transpiration is determined using a Jarvis-type function linking soil water availability and atmospheric conditions.Some other processes,such as canopy interception and deep percolation,are also considered in the HDS-SPAC model.The hybrid dual-source approach allows HDS-SPAC to simulate heat and water transfer in an ecosystem with a large range of vegetation cover change temporally or spatially.The model was tested with observations at a wheat field in North China Plain over a time of three months covering both wet and dry conditions.The fractional crop covers change from 30% to over 90%.The results indicated that the HDS-SPAC model can estimate actual evaporation and transpiration partitioning and soil water content and temperature over the whole range of tested vegetation coverage.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41761047,41861040 and 41861034).
文摘Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and water cycle mechanisms.In this study,we analyzed the stable isotopic composition,relationship and indicative significance of precipitation,soil water(0~100 cm depth)and xylem water of Qinghai spruce(Picea crassifolia)forest in the eastern Qilian Mountains,and explored the circulation process among different water bodies.The results show that the stable isotopes of precipitation vary greatly during the entire observation period.The values ofδ2H andδ^(18)O in the precipitation in the warm season are richer than those in the cold season,and the slope and intercept of local meteoric water line(LMWL,δ2H=6.79δ18O+7.13)are both smaller than global meteoric water line(GMWL,δ2H=8.17δ18O+10.56).The stable isotopes of soil water at different depths underwent different degrees of evaporative fractionation,and theδ18O andδ2H of shallow soil water varied greatly,while the deep soil water tended to be similar.The topsoil(0~10 cm)can respond quickly to precipitation,and the response of the deep soil has a time lag.In the whole growing season,0~30 cm and 60~100 cm soil water are the main water sources of Qinghai spruce.The water source of Qinghai spruce was from all soil layers in May and September,mainly from the shallow soil layer(0~30 cm)in August and October,and mainly from the deep soil layer(60~100 cm)in June and July.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50879041 and 50939004)the National Hi-Tech Research and Development Program of China (Grant No.2011BAD25B05)
文摘HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant transpiration partitioning.For the above-ground part,a layer approach is used to partition available energy and calculate aerodynamic resistances,while a patch approach is used to derive sensible heat and latent heat fluxes from the two sources(soil and vegetation).For the below-ground part,soil water and heat dynamics are described by the mixed form of Richards equation,and the soil heat conductivity equation,respectively.These two parts are coupled through ground heat flux for energy transfer,root-zone water potential-dependent stomatal resistance,and surface soil water potential-dependent evaporation for water transfer.Evaporation is calculated from the water potential gradient at soil-atmosphere interface and aerodynamic resistance,and transpiration is determined using a Jarvis-type function linking soil water availability and atmospheric conditions.Some other processes,such as canopy interception and deep percolation,are also considered in the HDS-SPAC model.The hybrid dual-source approach allows HDS-SPAC to simulate heat and water transfer in an ecosystem with a large range of vegetation cover change temporally or spatially.The model was tested with observations at a wheat field in North China Plain over a time of three months covering both wet and dry conditions.The fractional crop covers change from 30% to over 90%.The results indicated that the HDS-SPAC model can estimate actual evaporation and transpiration partitioning and soil water content and temperature over the whole range of tested vegetation coverage.
