Study On Vegetation Water Use Efficiency In Guizhou Province Under The Synergistic Influence Of Climate Factors

Vegetation water use efficiency refers to the amount of assimilated substances produced by vegetation per unit of water.It is a comprehensive physiological and ecological index that reflects the relationship between vegetation water consumption and its own dry matter,and evaluates the appropriate degree of vegetation growth.It is one of the important indicators of ecosystem sensitivity to climate change,connecting the two key processes of terrestrial ecosystem carbon cycle and water cycle.Guizhou has abundant water resources.However,due to the unique karst landform type,the area has a typical engineering water shortage.The development and utilization rate of water resources is only 10.4%of the total water volume.The shortage of water resources seriously affects the ecological water use of vegetation.This article uses MODIS data(the full name is medium resolution imaging spectrometer)to obtain MOD16A2GF(ET)and MOD17A2HGF(GPP)to obtain vegetation WUE,and from the China Meteorological Data Network,Geospatial Data Cloud,Resource Environmental Science and Data Center,respectively,the meteorological data,elevation data and soil type maps of Guizhou Province were obtained.This paper uses trend analysis,correlation analysis,and stepwise regression analysis to analyze the spatiotemporal differences and trend of vegetation WUE on the annual average scale in Guizhou Province from 2000 to 2019.Research and systematically discuss the synergistic reaction between vegetation WUE and various climatic factors on different underlying surfaces to understand the distribution of vegetation WUE and the main climatic influencing factors in Guizhou Province.It is expected to provide useful scientific reference value for the rational development of ecological restoration projects and the implementation of the plan in Guizhou Province,so as to improve the rational use of water resources in typical karst areas in Guizhou.The main conclusions are:(1)In the past 20 years,the vegetation WUE in Guizhou Province during the Spring is 1.86g C·mm^-1·m^-2,1.97g C·mm^-1·m^-2 in summer,2.00g C·mm^-1·m^-2 in autumn and 1.07g C·mm^-1·m^-2 in winter,the annual averageis1.72g C·mm^-1·m^-2,theperformanceis autumn>summer>spring>annual average>winter.Among them,the vegetation WUE in autumn and winter is higher in the east than in the west,and the vegetation in the south is higher than the north.Vegetation WUE change rate is 0.0104g C·mm^-1·m^-2·a^-1 in spring,-0.0152g C·mm^-1·m^-2·a^-1 in summer,and 0.0025g C·mm-1·m^-2·a^-1 in autumn,0.0088g C·mm-1·m^-2·a^-1 in winter,0.0023g C·mm-1·m^-2·a^-1 every year,and the change rate is summer>spring>winter>Autumn>Annual average.Among them,the summer vegetation WUE shows a decreasing trend,there is an increasing trend in spring,autumn,winter and annual average scales.On the four seasons and annual average scale,Vegetation WUE is increasing in Qianxi,a small number of areas in Eastern Guizhou,Southern Guizhou and Northern Guizhou showed a decreasing trend.the annual average is 1.72g C·mm^-1·m^-2,the performance is autumn>summer>spring>annual average>winter.(2)The average WUE of different vegetation in spring,autumn,winter and year is mixed forest>coniferous forest>broad-leaved forest>shrub>grassland>paddy field>dry land,in summer,it is mixed forest>broad-leaved forest>shrub>coniferous forest>dry land>paddy field>grassland.The vegetation in summer and the mixed forest in autumn have a decreasing trend,and the vegetation in other seasons has an increasing trend.(3)Under different elevations,the WUE value of vegetation in spring,summer and annual average increases with the increase of elevation,and the WUE value of vegetation in autumn and winter decreases with the increase of elevation.The higher the altitude,the stronger the vegetation WUE is affected by climate factors,and the more obvious the synergy.The vegetation WUE of 500 to 1000m in winter and 1500 to 2000m of spring is only affected by temperature,and the influence of temperature on vegetation WUE at 1500 to 2000m elevation is higher than that of vegetation WUE at500 to 1000m elevation.Under 2000 to 2500m,the autumn vegetation WUE is affected by the synergistic effect of air temperature and air pressure,and the influence intensity is air temperature>air pressure;the winter vegetation WUE is affected by the synergistic effect of wind speed,rainfall and sunshine hours,and the influence intensity is wind speed>sunshine hours>rainfall.In the western Guizhou area above 2500m,the autumn vegetation WUE is affected by the synergy of wind speed,air temperature and air pressure,and the influence intensity is temperature>wind speed>air pressure;the winter vegetation WUE is affected by the synergy of sunshine hours,wind speed and rainfall,and the influence intensity is sunshine.Hours>wind speed>rainfall.The average annual vegetation WUE is under the synergistic effect of sunshine hours and air pressure,and the influence intensity is sunshine hours>air pressure.(4)There are obvious differences in vegetation WUE under different soil types.Under different soil types,only yellow soil in winter and yellow brown soil in autumn and winter are most affected by climate factors.The winter of yellow soil is only affected by temperature.The WUE of autumn vegetation under yellow brown earth is mainly affected by the synergistic effect of temperature and air pressure,and the influence intensity is air temperature>air pressure;the WUE of winter vegetation under yellow brown earth is mainly affected by the synergistic effect of air temperature,wind speed and rainfall,and the influence intensity is air temperature>wind speed>Rainfall.