Research On Identification Method Of Rubber Plantations In Yunnan Province Based On Spatio-temporal Data Fusion Technique

Yunnan province is the origin of natural rubber planting in China,and it is a typical representative of the replacement of natural forest by rubber plantations in the northern tropical area of the tropics,Since the economic benefits of planting rubber plantations are good,rubber plantations areas have been in Yunnan Province since the1950 s.Rapidly expanding,the statistical results in 2015 showed that Yunnan has become the province of Chinese largest rubber planting area.With the economic benefits of planting rubber,it also causes damage to the local ecological environment.The evaluation of the relationship between the rubber plantations and the change of ecological environment is vitally important in the region.Aiming at the problem of similarity of vegetation's spectral feature and complexity of topography and climatic conditions,combined with the phenological characteristics of rubber plantations fallen leaf in winter in the region.This paper use multi-source remote sensing data,analyzing the applicability of spatio-temporal data fusion model in mountainous regions and analyzes the factors affecting fusion accuracy,and obtains a time-series normalized differential vegetation index with high spatial-temporal resolution in the region.This data was used to extract the phenological change characteristics of rubber plantations and realize the extraction method of rubber plantations based on high spatial-temporal resolution visible light remote sensing data.Using this method,the data of spatial distribution of rubber plantations in Yunnan Province in 2015 was finally obtained.Based on this data,it is to analyze the latitude and altitude expansion characteristics of the northern boundary of rubber plantations in the northern tropical region of Yunnan Province.The results show:(1)High spatiotemporal resolution data fusion accuracy in tropical mountain areas are affected by 1)The length of the time interval of the input data;2)the degree of sensor spectral matching of the two fusion data sources;3)topographic factors.The shorter the time interval between the input of the fusion model data,the higher the accuracy of the data.In the data used in this paper,the spectral matching accuracy between OLI and MODIS data is higher than that of OLI and VIIRS,Sentinel-2A and MODIS,Sentinel-2A and VIIRS.The accuracy of data fusion in the study area issignificantly influenced by the terrain elements.The highest fusion accuracy is801-1000 m above sea level,and the lowest is 1201-1400 m.The influence of altitude on the near-infrared band is more significant than that of the red band,and the fusion accuracy decreases with the increase of the slope,and has a great influence on all the bands,When the gradient increased to more than 40 degrees,the correlation between fusion results and observed values decreased from 0.85 to 0.75.The slope direction had little influence on the fusion accuracy of red light band,and had a significant impact on the near infrared band.The fusion precision of each slope to the Middle East and southeast is the lowest,and the other orientation has no significant influence on the fusion precision.(2)In the classification results,the high spatial-temporal resolution vegetation index acquired by the fusion data can effectively improve the rubber forest's identification accuracy,and the classification accuracy of the vegetation change characteristics in the extracted key phonological period is higher than that of the directly applied time series NDVI dataset.When classifying a time series data set,the characteristics of the time series are extracted,and the use of an RF classifier is a better choice.(3)The northernmost part of the large-scale rubber plantations in Yunnan province is close to 24°20?.The lowest altitude of the rubber plantations is located at100 m in Honghe Prefecture,The highest in Pu'er Prefecture of more than 1500 m.The area of rubber plantations has increased rapidly in recent 15 years,and its planting range is expanding northward.The planting area is also expanding from low elevation Valley to high altitude mountain area,rubber plantations continue to expand in areas that are not suitable for rubber planting.