Response Of Vegetation Spatial And Temporal Pattern Evolution To Hydrothermal Factors In "Golden Triangle" Region From 2000 To 2018 Based On MODIS Time Series Data

The "Golden Triangle" area is located at the border of Myanmar,Laos and Thailand.The long-term practice of slash-and-burn agricultural cultivation and the introduction of poppy replacement planting projects introduced in recent years are bound to cause a strong change in the vegetation information of the area.Green vegetation occupies an important role in the surface ecosystem.Research on regional vegetation information and its spatial and temporal changes can help to understand the changes in the ecological environment and the response of vegetation to climate change,so as to better protect the ecosystem.This study selects foreign "Golden Triangle" regions(Myanmar Kachin,Shan State,Chiang Mai Province,Chiang Rai Province,Thailand,Luang Prabang,Laos,Udom Sai,Bocho,Luang Namtha,Funchal(Province)As the research object,MOD13Q1-NDVI time series remote sensing data,DEM data,meteorological data and MCD12Q1 data from 2000 to 2018 are used.Based on ENVI,ArcGIS,IDL language and SPSS tools,the mean value method and trend analysis method are used.,Band analysis,spatial autocorrelation,partial correlation analysis and other methods.The spatial and temporal pattern of vegetation in the study area over the past 19 years was analyzed from the spatial and temporal changes of vegetation,and then the vegetation response to water and heat factors(temperature,precipitation)was explored.The following conclusions are drawn:(1)Vegetation spatiotemporal pattern evolution trend in the "Golden Triangle" area over the past 19 years.The study area has dense jungle and good vegetation coverage.With regard to the spatial distribution of vegetation,the difference between north and south of vegetation coverage is significant.Vegetation coverage tends to be fragmented,and the distribution pattern of NDVI changes from agglomerated distribution to discrete sporadic distribution.The Kayin State of Myanmar has the highest average NDVI,while Shan State,Chiang Mai Province and Chiang Rai Province are relatively low.Vegetation coverage in this area has exhibited significant spatial agglomeration characteristics in the past 19 years.The global Moran I of the vegetation has reached a significant level of 0.01,but the global Moran I has shown a declining trend.The decline rate in the past 19 years is 0.0011,indicating that the spatial concentration of vegetation has weakened and the vegetation The spatial heterogeneity of the region increased,and the connections between the regions gradually weakened.The overall NDVI of the whole region showed an improvement trend,and the improved area was larger than the degraded area.Over the past 19 years,the study area has scattered vegetation types such as broad-leaved forests,shrubs,and savannas.In the study area,there were more areas where the vegetation types showed improvement and non-significant changes,and there were few areas with extremely significant improvement and significant degradation.(2)Over the past 19 years,the partial correlation between NDVI and water and heat factors in the "Golden Triangle" region has been strong.The partial correlation coefficient between vegetation and precipitation over the years is significantly greater than the partial correlation coefficient between NDVI and temperature over the years.The leading factor of change is more conducive to the growth of vegetation.On the seasonal scale,the correlation between spring and summer climatic factors and NDVI in this area is relatively low,and the vegetation is less affected by air temperature and precipitation.The correlation of winter temperature is significantly better than that of precipitation.