Temporal And Spatial Changes Of Vegetation NPP And Hydrological And Meteorological Elements In Henan Province And Their Response Relationship

Net primary productivity(NPP)of vegetation is an important index to determine the carbon source,carbon sink and regulation capacity of ecosystem.Any change of natural factors or human activities will cause fluctuations in NPP.Since the 21st century,the net primary productivity of Henan Province has been affected by climate change.Therefore,dynamic monitoring of the spatiotemporal changes of vegetation net primary productivity and hydrometeorological factors in Henan Province,and analysis of the response relationship between the changes of Hydrometeorological factors and net primary productivity,is an important aspect to grasp the regional ecological environment changes and evaluate the ecosystem health,support ability and stability,and provides an important theoretical basis and practical significance for promoting regional ecological construction Righteousness.Based on MODIS/NPP,MODIS/ET data with spatial resolution of 500m and meteorological station data set from 2001 to 2019,this paper uses Sen trend analysis method and Mann Kendall trend test method to analyze the spatiotemporal variation characteristics of vegetation NPP and hydrometeorological elements in Henan Province,and analyzes the future trend of vegetation NPP in Henan Province according to Hurst index.On this basis,according to the standardized precipitation evapotranspiration index(spei),the temporal and spatial variation characteristics of meteorological drought in Henan Province from 2001 to 2019 were analyzed;then simple correlation analysis,first-order partial correlation analysis,second-order partial correlation analysis and other methods were used to analyze the relative influence of temperature and precipitation on ET in Henan Province,and the response mechanism of spei index,hydrometeorological factors and other factors to vegetation NPP The difference analysis method is used to elaborate the response relationship among hydrometeorological elements,human activities and vegetation NPP,and discuss the contribution rate of Hydrometeorological elements and human activities to NPP change in Henan Province.The results are as follows:(1)From 2001 to 2019,the spatial distribution pattern of NPP of annual average vegetation in Henan Province is high in the South and low in the north,high in the West and low in the East.The annual average NPP value of vegetation is 409.69g C·m^-2·a^-1,and the growth rate is 2.97,showing a fluctuating upward trend.The NPP of vegetation in Henan Province showed an increasing trend in space(the area of increasing area>the area of decreasing area).The proportion of the rising area of NPP of vegetation was 85.72%,and the largest area was 49.45%,followed by the extremely significant rising area and the significant rising area,which were 14.02%and 13.17%respectively development.As a whole,the proportion of strong and weak anti persistent sequences is slightly lower than that of weak and strong persistent sequences,which indicates that vegetation NPP in Henan Province will continue to increase in the future.(2)From 2001 to 2019,the spatial distribution of annual average precipitation in Henan Province presents a pattern of more in the South and less in the north,and the annual average precipitation presents a slow downward trend of"m"type;from 2001to 2019,the spatial distribution of annual average temperature in Henan Province presents a pattern of increasing from west to East and decreasing from south to north.The results show that the annual average temperature shows an upward trend;the annual average et change rate of Henan province fluctuates significantly from 2001 to2019,showing a ladder upward trend as a whole;the annual average temperature shows a cyclical trend,with strong seasonal differences.The correlation analysis between ET and climate factors shows that the driving mechanism of ET in Henan Province from 2001 to 2019 is the single driving effect of temperature or precipitation meteorological factors,in addition to other factors.(3)From 2001 to 2019,the spei of different time scales in Henan Province shows a downward trend of fluctuation,which indicates that Henan Province presents a trend of aridity as a whole;based on the statistical analysis of the occurrence time of continuous drought months,there is a general continuous drought in Northern Henan in 2001,2008,2010 and 2019;the spatial analysis of drought frequency shows that there is a significant spatial difference in drought frequency In general,the frequency of drought in central and Northern Henan Province is relatively high.(4)The correlation coefficient between spei and NPP decreased from northeast to southwest,and NPP and spei were positively correlated in most areas of Henan Province.According to the correlation analysis of vegetation NPP and hydrometeorological factors,the areas with positive correlation and negative correlation between vegetation NPP and temperature were basically in the same level;the areas with positive correlation between vegetation NPP and precipitation and et accounted for 79.14%and 90.2%of the whole region respectively.The relative importance analysis of temperature,precipitation and ET on NPP showed that temperature,precipitation and et accounted for 3.43%,34.74%and 61.85%respectively.Among the contribution of Hydrometeorological factors and human activities to NPP change of vegetation in Henan Province,the contribution of Hydrometeorological factors and human activities to NPP change is about 56.66%,which indicates that human activities have played a positive role in recent years.