| As a basic part of the national ecological security strategic pattern,the Qingjiang River Basin(QJRB)plays a significant role as a key ecological function and security barrier.However,affected by climate change and human activities,the regional ecological environment is facing threats and challenges.Vegetation net primary productivity(NPP)reflects the productivity of vegetation under natural conditions,is an important indicator to measure ecosystem health,which can be used to evaluate the quality of the regional ecosystem.Based on RS and GIS technology,this paper combined MODIS NDVI,spatial interpolation meteorological data,vegetation type,and other data to estimate the vegetation NPP of the QJRB from 2000 to 2018 by using a typical light energy utilization model,the Carnegie-Ames-Stanford Approach(CASA)model.Then,the spatiotemporal variation characteristics of vegetation NPP in the QJRB during the past 19 years were analyzed by means of the coefficient of variation,Sen trend,and Hurst index.Meanwhile,the effects of temperature,precipitation,elevation,slope,and land use on NPP were investigated by using partial correlation analysis and geo-detector.The main conclusions are as follows:(1)The multi-year mean value of NPP in the QJRB was 727.45 g C·m-2·a-1,showing a fluctuating increasing trend.July and January were the months with the highest and lowest NPP respectively,and April to September was the main months for NPP accumulation.(2)The spatial distribution pattern of vegetation NPP in the QJRB was"high in the east and low in the west".Wufeng,Hefeng,and Jianshi were the top three administrative regions in terms of the multi-year average NPP,and Lichuan contributes the most to the total NPP.Regarding monthly NPP,it increased from southeast to northwest from January to March,had no obvious spatial change from April to September,and gradually decreased from north to south from October to December.(3)The spatial variation of vegetation NPP in the QJRB was relatively low and in a stable state.The spatial variation trend was not significant,with a slight increase in the spatial"decreasing in the north and increasing in the south".The Hurst index was spatially"high in the east and low in the west",and the overall spatial change of NPP tends to be continuous,and the future trend will be mainly increased.(4)Climate in the QJRB tends to be warmer and wetter.The NPP of vegetation and temperature and precipitation were mainly positively correlated on the annual and monthly scales and had a closer relationship with temperature.Meanwhile,the correlation at the monthly scale was stronger than that at the annual scale.With the increase of elevation and slope,NPP shows"first increase and then decrease".(5)Forestland was the main land use type in the QJRB.The interchange between cultivated land and forestland was the main feature of land use change and the main land type conversion that causes the change of vegetation NPP.The continuous expansion of construction land is an important factor of NPP loss.(6)The sequence of factor detection q value was annual average temperature>annual precipitation>elevation>land use>slope.The annual average temperature was the dominant factor affecting the spatial differentiation of vegetation NPP.The interactions were enhanced by double factor,and the top three explanatory powers of the interaction are annual average temperature?land use,annual average temperature?slope and elevation?land use. |
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