Temporal And Spatial Pattern Evolution And Influencing Factors Of Vegetation NPP In The Yellow River Basin

The Yellow River Basin（YRB）has complex geomorphic units,significant regional differences and fragile ecological environment.Studying the temporal and spatial pattern evolution and influencing factors of vegetation NPP can deepen the understanding of the ecological and environmental problems of the basin and provide a scientific basis for promoting the sustainable development of the basin.Based on the data of MOD17A3HGF NPP,meteorology,land use,topography,vegetation and social economy,this paper studies the change characteristics and influencing factors of vegetation NPP in the YRB from 2000 to2019 on a temporal and spatial scale by using the methods of deviation analysis,univariate linear regression,spatial autocorrelation,correlation analysis and geographic detector.On this basis,combined with the characteristics of the YRB,this paper deeply discusses the temporal and spatial pattern evolution and influencing factors of vegetation NPP in the typical area（Weihe River Basin）.The main conclusions are as follows:（1）The variation ranges of vegetation NPP in the YRB from 2000 to 2019 is204.3-337.5g C·m^-2·a^-1,and the multi-year average value is 273.3g C·m^-2·a^-1,which shows a fluctuating growth trend on the whole.The vegetation NPP in the upper,middle and lower reaches of the YRB showed a fluctuating and increasing trend,but the growth trend was different.The growth in the middle and lower reaches was faster and that in the upper reaches was slower;The vegetation NPP of nine provinces showed a fluctuating increasing trend,but the increasing degree was different;NPP of different vegetation types showed a fluctuating growth trend,but the mean change was significantly different.（2）From 2000 to 2019,the vegetation NPP in the YRB decreased spatially from south to north.The global autocorrelation results show that there is a strong positive correlation in the distribution of vegetation NPP in the YRB,and the agglomeration phenomenon is obvious.The local autocorrelation results show that vegetation NPP presents very similar agglomeration distribution characteristics,in which the“High-High”（H-H）type and“Low-Low”（L-L）type account for a significant proportion of the total area of the basin.In the vertical direction,the increasing area of vegetation NPP showed a“Rise decline stability”trend with the increase of altitude;In the horizontal direction,the increasing area of vegetation NPP shows a"Stable rising falling"trend from west to East and a“Rising falling rising”trend from south to north;In the verification of NPP data,the temporal and spatial changes of MOD17A3HGF NPP data and GLOPEM NPP data are consistent,both of which show an obvious increasing trend with the passage of time and decrease from south to north in space.（3）From 2000 to 2019,the temperature and precipitation in the YRB fluctuated and increased,while the relative humidity and sunshine hours fluctuated and decreased.The correlation between vegetation NPP and various meteorological elements showed positive and negative coexistence,and a few areas showed significant correlation.The vegetation NPP in these areas was greatly affected by the climate;There is no significant correlation between vegetation NPP and meteorological factors in most areas,and the vegetation NPP in these areas is less affected by climate.Vegetation NPP fluctuated with the increase of altitude;Vegetation NPP increased first and then decreased with the increase of slope;The mean NPP of vegetation on the southeast slope is the highest in all slope directions.（4）The results of geographical detector show that the q value of influencing factors in factor detection is as follows:Meteorological factor>Land use and Vegetation type>Topographic factor>Socio-economic factor;The combined effect of different factors in interactive detection has far more explanatory power on vegetation NPP than that of single factor,and the interaction between meteorological factors is the strongest;There are obvious differences in the impact of most influencing factors on vegetation NPP in ecological detection.（5）The analysis results of typical areas show that the variation ranges of vegetation NPP in Weihe River Basin from 2000 to 2019 is 276.4-519.4g C·m^-2·a^-1,and the multi-year average is412.0g C·m^-2·a^-1.The overall growth trend is fluctuating,and the spatial variation trend is decreasing from south to north.In factor detection,meteorological factors play a leading role in the spatial differentiation of vegetation NPP in Weihe River Basin,vegetation,land use type and topographic factors play a secondary role,and socio-economic factors have the least impact;The combination of strong interaction in interactive detection mainly occurs between meteorological factors and between meteorological factors and vegetation types,which is mainly enhanced by two factors;There are obvious differences in the impact of most influencing factors on vegetation NPP in ecological detection.