Spatiotemporal Distribution Of Vegetation Index/NDVI And Its Response To Climate Change In Guizhou Province

Global warming has posed a great threat to the terrestrial ecosystem on which human beings depend for survival.Vegetation is an important part of the terrestrial ecosystem and also a "indicator" of environmental change.Vegetation growth is affected by many factors,and the influence of climate can not be ignored.Among them,temperature and precipitation are the most obvious and also the important research factors in many studies.The spatial and temporal change of vegetation and its response to temperature and precipitation change are studied in depth,on the one hand,can evaluate the regional environmental state,reflect the characteristics of the regional climate changes on the other hand,the results of the study on the ecological environment sustainable development strategic policy and work is of great significance.Based on Normalized Difference Vegetation Index(NDVI)data and meteorological data,Normalized Difference Vegetation Index(NDVI)data were obtained.The maximum value synthesis method,Thil-Sen trend analysis,Mann-Kendall test,coefficient of variation,Hurst index and other methods were used to analyze the change characteristics and persistence of vegetation and climate in Guizhou Province from 2000 to 2019 from different spatial and temporal perspectives.Then,the partial correlation coefficient,F test and lag correlation coefficient were used to analyze the response of vegetation to climate change.Finally,the lag analysis of vegetation response to climate change was discussed from the perspectives of underlying surface(elevation,geomorphology,soil type and vegetation type)and human activities.The main conclusions of this paper are as follows:(1)The spatial distribution pattern of NDVI in growing season,spring,autumn and winter from 2000 to 2019 was low in the west and high in the east.During the 20 years,NDVI showed a significant increasing trend.In spring,NDVI showed a significant increasing trend in the western and northeastern regions,but not in the central and southeastern regions.In summer,the increase trend in the northwest is stronger than that in the southeast.In autumn,the strengthening trend was significant in most areas.In winter,the growth trend in the west is stronger than that in the east.In the growing season,the growth trend in the northwest is stronger than that in the southeast.In spring,summer and growing season,the east is more stable than the west.In autumn,the stability is high in the western and eastern regions,and low in the northern and central regions.They are lower in winter.The NDVI of four seasons and growing seasons was more negative than positive,and the area of increase and negative persistence were more than 55% of the total area.There were some spatial differences among different prediction types.(2)From 2000 to 2019,the average temperature of growing season and perennial temperature decreased from east to west in Guizhou Province,and there was one low temperature zone in the west.During the20 years,the overall temperature showed an upward trend,and the temperature increased significantly in summer and growing season,with differences in spatial distribution.There is a middle and high stability center in spring and autumn,a high stability center in summer,and a low stability area extending from northwest to middle in winter in the southeastern region of the study area.The stability of the southwest was higher than that of the northeast during the growing season.It is predicted that the temperature in spring will continue to increase positively.Summer,fall and winter and the growing season increased and continued in reverse.The spatial distribution of temperature Hurst index was high in the east and low in the west in spring.In summer and growing season,it was higher in the north than in the south.In autumn,it was slightly higher in the south than in the north,and the spatial characteristics were not significant in winter.(3)From 2000 to 2019,spring and winter precipitation in Guizhou Province decreased from east to west.The spatial distribution of precipitation in four seasons has obvious seasonal differences.In spring and summer,there is a big difference between east and west,and in autumn and winter,there is a big difference between north and south,but there is no obvious spatial difference in growing season.It is predicted that the precipitation in spring,autumn and growing season will increase and continue in the opposite direction,decrease and continue in the opposite direction in summer,and increase and continue in the positive direction in winter.The extremely significant/significant level test increased in autumn and the reverse persistence area was much higher than that in spring,summer and winter and the growing season.(4)The NDVI of vegetation in the growing season,spring,summer and winter in Guizhou Province from 2000 to 2019 was stronger than that of precipitation under the influence of temperature,and the precipitation in autumn was stronger than that of temperature,with significant interaction and strong spatial heterogeneity.In the past 20 years,NDVI in April has the strongest response to temperature and precipitation(that is,there is no lag).There was a lag between NDVI and temperature for 1-3months in May,and precipitation for 3-4 months.There was a lag between NDVI and temperature for 2-3 months in June,and precipitation was 0 months and 5 months.In July,August and September,the lag time area ratio of NDVI to temperature was relatively discrete,while the lag time of NDVI to precipitation was 0-2 months.The hysteresis of different months has strong difference in space.(5)Elevation,Geomorphic types,Soil types,Vegetation types and Human activities all affect the response time of vegetation to temperature and precipitation to some extent,but there are other important influencing factors besides these factors.