Spatial-temporal Distribution And Driving Factors Of Vegetation NET Primary Productivity In North China Plain From 2000 To 2018

Net Primary Production(NPP)is an important index interpretation method for measuring the growth of vegetation and reflect the function of the ecosystem.Studying its temporal and spatial laws and its impact mechanisms can provide certain scientific basis for dealing with future climate change and formulating effective and reasonable ecological protection measures and policies.In this paper,the North China Plain is selected as the study area,combined with multi-source data,the CASA model and a variety of spatial analysis methods are used to discuss and analyze the spatio-temporal variation characteristics and main driving factors of NPP vegetation in the North China Plain under the long-term sequence from 2000 to 2018.The following conclusions are drawn:(1)From the time change process of vegetation NPP,from 2000 to 2018,the average NPP of perennial vegetation in north China plain was 526.68 g C·m-2·a-1.In the past 19 years,NPP of vegetation generally showed a weak rising trend,the minimum value appeared in 2002,the maximum value appeared in 2014,and the range reached 129.19 g C·m-2·a-1.From the perspective of time and month scale,the maximum NPP value of the North China Plain in July was 110.05 g C·m-2·a-1.Except for July,the NPP change rate of the North China Plain in other months was positive.From the perspective of time and season scale,NPP in all four seasons showed an overall trend of increasing fluctuation.Among them,NPP of vegetation in spring significantly increased with the rate of 2.6446 g C·m-2·a-1,followed by summer,and NPP of vegetation in autumn showed the smallest change trend.(2)From the perspective of the spatial distribution of vegetation NPP,the spatial distribution of NPP vegetation in the North China Plain is "high in the south and low in the north".The low-value areas are mainly distributed in the north of the North China Plain and coastal areas,especially in Beijing-Tianjin areas,while the high-value areas are distributed in Henan,Anhui and Jiangsu Provinces in the south.The NPP variation coefficient of vegetation is small,and the regional difference between the North China Plain is not significant,which is in a relatively stable state,showing a very stable regional area proportion of 32.1%,mainly distributed in the east of Shandong Province,the Jianghuai Plain of Jiangsu Province,the central Henan province and the central and northern areas of Hebei Province.In general,the percentage of NPP change in most areas of the North China Plain was more than 10%,indicating that the overall vegetation growth status of the region was continuously improving.(3)From the perspective of the relationship between climate change and vegetation NPP,the climate in the North China Plain has a “warm and dry” trend.The annual average temperature of 14 ? and annual average precipitation of 705.08 mm.From 2003 to 2014,the precipitation in the study area fluctuates and decreases with the rate of 18.33 mm·a-1,and the annual precipitation gradually decreases from southeast to northwest.The partial correlation coefficient between vegetation NPP and average air temperature was 0.1245,and that between vegetation NPP and precipitation was 0.3265.The areas positively correlated with air temperature and precipitation accounted for 67.86% and 93.93% of the total area,respectively.(4)From the perspective of the change driving force affecting NPP of vegetation,the distribution and change of NPP in most areas of the North China Plain are mainly affected by non-climatic factors,while the influence of climate change on NPP of vegetation is mainly caused by the joint driving effect of temperature and precipitation.Land use change is also an important factor affecting NPP,and the increase of land cover types such as farmland,woodland and grassland is an important reason for NPP growth.With the acceleration of urbanization,the continuous expansion of construction land is the main external driving force of NPP loss.Through the exploration and analysis of the dominant factors of NPP in North China Plain from different time scale,spatial scale and internal change,it can provide certain theoretical basis and decision-making basis for maintaining the good growth and development of vegetation,maintaining the balance of ecosystem functions and promoting the green development of human society in the future.