Variation of vegetation water use efficiency and its response to climate based MODIS products in Baoji area, China

Water use efficiency (WUE) is an important parameter of interaction between ecosystem and hydrological cycle. Based on the land evapotranspiration and total primary productivity of MODIS products, the water use efficiency of the ecosystem was calculated, and the changes of vegetation and meteorological elements of the regional grid point were analyzed by using the method of one-dimensional linear regression and person correlation coefficient. The results show that WUE and gross primary productivity (GPP) in most regions showed an increasing trend. The regional distribution of increase and decrease accounted for 92% and 8% of the whole basin, and evapotranspiration (ET) showed a slight upward trend. Vegetation types have different effects on WUE and GPP changes, WUE and GPP of forest and shrub were the largest. In addition, WUE and GPP vary with altitude, and WUE has a maximum in the range of 1600-2200m altitude. WUE, GPP and ET have different responses to meteorological elements. Especially, temperature, precipitation, relative humidity and sunshine hours have effects on WUE by influencing GPP and ET. Under the climate scenarios of RCP2.6, RCP4.5 and RCP8.5, WUE and GPP will increase in the future. These studies provide scientific basis for exploring and protecting the carbon water cycle process of ecosystems.