关键词: 植被覆盖, MODIS-NDVI, 动态变化, 中老缅交界区

Abstract: [Objective] The spatiotemporal differentiation and evolutionary trends of vegetation coverage in the border region of China, Laos and Myanmar (BRCLM) from 2000 to 2015 were discussed in order to provide support for scientific management and effective protection of vegetation in the region.[Method] Based on the time series of MODIS-NDVI in the BRCLM in recent 16 years, GIS,GPS,and Remote Sensing technologies in combination with statistics-related research method such as averaging, trend analysis,variation coefficient, Hurst index were used to investigate, the spatiotemporal pattern, evolution, variation and developmental trend in the future of vegetation coverage in the region.[Result] For NDVI annual mean,the maximum and minimum appeared in 2013 (0.779 4) and 2002 (0.725 9), respectively, it showed an increasing trend as a whole, with the growth rate increased by 1.05% every 10 years. Monthly average of NDVI showed a changing trend of "S" type with turning pointsin March and September. In addition, it ranged from 0.698 6 to 0.831 6 indicating a rising trend, with an average monthly growth rate of 0.50%. The vegetation coverage rate in the area was relatively high. Regions with 16-year average of NDVI larger than 0.6 accounted for 97.45% and most of which were concentrated in the mountainous areas where the tropical rain forest was distributed in succession. On the other hand,the areas with NDVI's average smaller than 0.6 accounted for only 2.55%, in which the main urban centers and peripheries in three countries, large areas of bare land in mountainous areas and along the Lancang-Mekong River Basin were the main areas. NDVI in the regions showed a decreasing trend with the increase of altitude. In addition, we found that the areas with high NDVI values (≥ 0.6) were mostly concentrated in the middle and low altitude areas below 1 500 m. From 2000 to 2015, the regions which NDVI time series showed improvement, degradation and stable accounted for 54.06%, 15.62%, and 30.32%, respectively, variation coefficient of NDVI time seriesranged from 0.024 4 to 0.468 8, and the spatial distribution was as follows:lower fluctuation region > low fluctuation region > medium fluctuation region > higher fluctuation region > high fluctuation region, the total proportion of low fluctuation region and lower fluctuation region was 78.49%. It was found thatregions with degradation of NDVI time series have obvious spatial consistency with those with large fluctuation, which mainly concentrated on construction land such as cities and towns, major traffic roads, and extensive bare land in mountainous areas. In terms of developmental trend in the future, the areas where vegetation coverage continue tobe the same trend as in the past 16 years accounted for 57.15%, and the areas with contrary trend accounted for 41.09%. Combined with the characteristics of spatial evolution, it was found that about 39.63%, 29.83% and 28.98% of the regions would develop in the direction of benign, unchanged and malignant in the future, respectively, while 1.56% of the regional development trend would be uncertain.[Conclusion] The vegetation coverage in BRCLM was generally good. In the past 16 years, the changing range of vegetation coverage in the area was relatively small.Andon this basis, it showed an increasing trend as a whole, the developmental prospects of vegetation were good. However, in the future, vegetation coverage in some areas with construction land and bare land would be degraded. Countries in the region should plan for economic development rationally, economical and intensive utilization of land resources, and carry out ecological restoration such as afforestation, converting the land for forestry and pasture according to local conditions to promote the healthy development of regional ecological environment.

Key words: vegetation coverage, MODIS-NDVI, dynamic change, border region of China, Laos, and Myanmar