Spatio-temporal Changes of Annual NPP in the Heihe River Basin and Its Response to Climate Factors

In recent decades,ecological environment has changed greatly,and net primary productivity of vegetation (NPP) of vegetation has become an important indicator to characterize the carbon sink status.In this study,the Heihe River Basin in the arid region of inland China was used as the research area,temporal and spatial variation characteristics of annual NPP was analyzed using monthly grid NPP,precipitation and average temperature data from 1985 to 2015,by applying Mann-Kendall trend test method and Pettitt change-point test method.The response of the annual NPP gravity shift to the climate factors gravity shift in different grids was investigated based on the fishing nets and the center of gravity shift model,the contribution rates of climate change and non-climatic factors to changes in NPP was quantified,and the influence of landform and climate factors on annual NPP changes was finally discussed.The results show that:(1) the annual NPP from 1985 to 2015 in 44.98% of the Heihe River Basin has a significant increase,while 35.27% of the basin has a significant decrease;(2) 80.12% of the total area has significant change-points from 1989 to 2010;(3) the shifting direction of the annual NPP gravity center from 1985 to 2015 is consistent with that of the annual precipitation and the annual average temperature in 21.69% and 26.78% of the grid numbers,respectively;(4) the average contribution rates of climatic factors and non-climatic factors to the annual NPP change are 16.13% and 83.87%,respectively.The research results are conducive to understanding the temporal and spatial characteristics of vegetation carbon sinks,thereby further providing a certain scientific basis for the formulation of environmental protection policies and plans in the Heihe River Basin.