| Low precipitation,high potential evapotranspiration,and low soil moisture content were the typical climate features of norestwestern China.Groundwater is the key water source for maintaining vegetation’s growth in this area.Desert plants are the main vegetation types in arid areas.With the impact of climate change and human activities,the drop of groundwater table caused by excessive exploitation of groundwater,causing a series of ecological and environmental problems such as vegetation degradation.Identifying the relationship between the depth to groundwater table and the root depth,transpiration characteristic of typical desert plant can provide scientific support for regional water resources management and ecological environment restoration.Following research is supported by National Key Research and Development Program of China(2017YFC0406101).We conducted a meta-analysis based on the literature dataset.The dataset includes thirteen kinds of plant and three types of vegetations(arbor,shrub,herbal).We identified the relationship between groundwater table depth and species diversity,species richness,and root depth with soil texture,and finally the suitable and extinction ecological groundwater depth for typical desert plants were obtained.Secondly,refer to the meteorological data of the Tarim River basin,the Heihe River basin,and the Shiyang River basin,the physiological parameters of seven typical desert plants,and soil hydraulic characteristics in the inland arid region of China.The transpirations of seven typical plants were simulated by the Tardieu-Davies model.Moreover,since the xeromorphic plants rely on depth to groundwater.The plant transpiration modelling was executed in the two soil moisture conditions in root zone maintained by groundwater.The soil moistures were roughly estimated by the Van Genuchten model at the two ecological depths.The modeling obtained hourly and daily transpiration in the ten years during 2009～2018.Compared to the collected data from the published literatures,our simulated transpirations of the seven typical plants during growing season(April～September)are proven to be reasonable.Finally,we used remote sensing technology to interpret the characteristic of vegetation distribution and fractional vegetation cover(FVC)of the Heihe River Basin during growth season.Based on the previous transpiration data of typical desert and the remote sencing data,transpiration at the basin scale was calculated.Finally,we used the"PML＿V2"data set to verify the rationality of the results.The main research conclusions of the three parts are as follows:(1)Ecological depth to groundwater table is quietly the same in different methods.In general,the suitable ecological depth to groundwater table is 2.9 m,and the intimidated ecological depth to groundwater table is 5.5 m,fluctuation range is 2.3～3.9 m,4.0～7.2 m.Suitable And intimidated ecological depth to groundwater table both have typical correlation with root depth.The rate of root growth and decline of groundwater table depth determines the status of plant growth;and soil texture control capillary rise and groundwater supply capacity,it is an important factor of ecological depth to groundwater table.(2)Under suitable and extinction ecological groundwater depth,the average transpiration water consumption during the growth season of the eight plants is 793 and611 mm,respectively.From suitable to limit ecological groundwater depth,plant transpiration water consumption is reduced by 27%on average.The response of Haloxylon ammodendron and Nitraria tangutorum with strong drought tolerance to water supply and climate change is greater than that of phragmites communis and tamarix with weak drought tolerance.(3)The desert plant in the Heihe River Basin is the most widely distributed,with an area of 14.3×10~4km~2,and Reaumuria soongorica is the most widely distributed desert plant,reaching 5.89×10~4km~2,accounting for 41.2%of the total desert area.The total water consumption of desert vegetation is 121.2×10~8～147.2×10~8m~3,and the transpiration water consumption per unit area of desert plants is 0.08～0.10m~3/m~2. |
