Research On The Spatio-temporal Pattern Changes And Driving Factors Of Vegetation NPP In Shandong Province Based On CASA Model

Vegetation Net Primary Productivity(NPP)is an important indicator to measure ecosystem functions,studying the temporal and spatial patterns of NPP and its driving factors are of great significance for estimating the terrestrial carbon cycle and its driving mechanism.This study uses Shandong Province as the research area,using remote sensing data,meteorological data and CASA model to estimate the vegetation NPP value of Shandong Province from 2000 to 2019,and uses a combination of correlation analysis,regression analysis and spatial analysis.To study the characteristics of the spatio-temporal changes of vegetation NPP in Shandong Province from 2000 to 2019,and analyze the response of vegetation NPP in Shandong Province to climate factors from the three perspectives of temperature,precipitation,and temperature-precipitation.Finally,the relative effects of temperature-precipitation and land cover changes on vegetation NPP were examined.Research indicates:(1)The range of vegetation NPP change in Shandong Province from 2000 to 2019increased from 301.51 g C m^-2 a^-1 in 2000 to 435.28 g C m^-2 a^-1 in 2019,with an average of 380.76 g C m^-2 a^-1,the vegetation NPP showed a fluctuating upward trend in 20 years,and the inter-annual increase rate was 4.16 g C m^-2 a^-1.On the time-seasonal scale,the highest average annual vegetation NPP in summer is 192.13 g C m^-2 a^-1,and the lowest in winter is 25.07 g C m^-2 a^-1.The average annual NPP of different vegetation types is significantly different,and the highest average annual NPP of farmland is 323.11 g C m^-2 a^-1.(2)The spatial distribution of vegetation NPP in Shandong Province from 2000 to2019 showed a trend of high in the west and low in the east,decreasing from inland to the coast.The area with vegetation NPP greater than 300 g C m^-2 a^-1 accounted for 34.3%of the total area.On the spatial seasonal scale,except for autumn,the spatial distribution characteristics of vegetation NPP in other seasons all present a distribution pattern of high in the west and low in the east.The average value of the coefficient of variation of vegetation NPP is 0.21,and the degree of variation is relatively stable.The overall trend of change is mainly increasing,and the area showing an increasing trend account for85.1%.In the future,vegetation NPP will continue to increase in most areas of Shandong Province.(3)From 2000 to 2019,the vegetation NPP of Shandong Province was positively correlated with precipitation and temperature.The areas with significant positive correlation were mainly concentrated in southern Shandong,and the impact of precipitation on NPP was more significant.Areas with significant multiple correlations between vegetation NPP and climatic elements are concentrated in the central Shandong region,and the area affected by temperature and precipitation accounts for 38.1%of the province's area.Land cover change is an important factor that affects the change of vegetation NPP.The contribution of climate change to the total NPP changes of different land cover types in Shandong Province is much higher than that of land cover changes,and the contribution rate to farmland is more than 60%.