关键词: 中巴经济走廊, NDVI, 趋势变化, 气候因素, 土地利用

Abstract: The China-Pakistan Economic Corridor is a flagship project of the Belt and Road Initiative, the change of the normalized differential vegetation index (NDVI) along the Corridor has a profound impact on the improvement of the local ecological environment. Based on the 1995-2015 AVHRR GIMMS NDVI data set, and in combination with data on the climate and land use types during the same period, the spatiotemporal shifts and trends of the vegetation NDVI of the Corridor, as well as the relationship between climate changes and land uses have been analyzed by using maximum value synthesis methods, the Sen+MK trend analysis and the partial correlation analysis. The results show that:(1) There is relatively poor vegetation coverage along the China-Pakistan Economic Corridor. Over the 20 years period, its overall vegetation NDVI had shown an upward trend, despite some fluctuations; however, the spatial difference is remarkable, showcasing a decreasing trend from the center to the north and south; (2) The vegetation NDVI along the Corridor has been generally improved and kept basically stable. The improved areas are mainly distributed in the northeastern part of Pakistan and the western part of Kashgar of Xinjiang, China, while the basically stable ones are located in the southwestern part of Pakistan and the eastern part of Xinjiang; (3) The average annual temperature and precipitation in the China-Pakistan Economic Corridor area demonstrated a fluctuating upward trend from 1995 to 2015, indicating a significant positive correlation with the changes in the vegetation NDVI. The temperature in the research area inhibits the growth of vegetation, whereas the precipitation promotes it. Among all the climate zones of the Corridor, the tropical monsoon climate delivers the highest vegetation NDVI, and with the fastest annual growth rate; precipitation and vegetation NDVI are positively correlated in all climate zones of the Corridor, but vegetation and temperature are negatively correlated in the tropical desert climate; (4) From 1995 to 2015, there was an increasing trend in the average NDVI of cultivated land, woodland and grassland in the Corridor. Specifically, the NDVI of cultivated land grew at the fastest speed (0.002 4 a-1), contributing the most to the total increase in NDVI across the entire region. The results of this study can provide a scientific basis and reference for vegetation enhancement and regional ecological environment protection in the China-Pakistan Economic Corridor.

Key words: China-Pakistan Economic Corridor, NDVI, trend change, climatic factor, land use