2000~2014年黑龙江流域（中国）植被覆盖时空变化及其对气候变化的响应

采用MODIS/NDVI数据,利用Theil-Sen Median 趋势分析、Mann-Kendall 以及Hurst指数方法分析2000~2014年黑龙江流域（中国）植被的时空变化特征、植被变化发展趋势及可持续性特征;应用相关分析法研究了气候变化对植被生长的影响。结果表明,2000~2014年黑龙江流域（中国）植被NDVI指数呈缓慢增加趋势,山区植被覆盖增加显著,东北部平原区植被覆盖持续退化,总体上植被覆盖持续改善能力较弱。植被NDVI对气候响应的季节差异显著,且不同类型植被对气候因子的响应不一致：春季植被NDVI主要受温度影响,夏季植被NDVI主要受降水量影响,秋季林地NDVI与温度正相关、草地NDVI与降雨量正相关。

Spatio-temporal Variations of Vegetation Cover and Its Responses to Climate Change in the Heilongjiang Basin of China from 2000 to 2014

Vegetation plays a critical role in global carbon, water and energy fluxes and the earth’s climate. Satellite remote sensing is the only practical approach to obtain observational evidence of trends and changes across large regions of vegetation cover. The Heilongjiang Basin within China is a critical hotspot for bio-diversity. In this paper, the spatial distribution and temporal variations of vegetation covered area in the Heilongjiang Basin within China was analyzed based on MODIS NDVI datasets with a spatial resolution of 250 m×250 m from 2000 to 2014. NDVI was used as a proxy for vegetation cover and the Theil-sen Median trend analysis with the Mann-Kendall test were both used to analyze NDVI trends. The combination of the result of Theil-Sen Median trend analysis and Mann-Kendall test,as well as the result of Hurst index were conducted to analyze the sustainability in NDVI trend．Patterns of change in NDVI and their linkage with climate change were also analyzed. The results indicate that: 1) The values of annual NDVI in the vegetation covered area fluctuated between 0.41and 0.46 in the Heilongjiang Basin within China from 2000 to 2014. The NDVI values had increased 0.06% annually over this fifteen-year period. 2) As to the spatial distribution of NDVI, high values of NDVI were located in Da Hinggan, Xiao Hinggan and the Changbai Mountains. Median values of NDVI were located in the northern Songnen Plain, the Sanjiang Plain and the north-central Hulun Buir Grassland. And low values of NDVI were in the western Hulun Buir. 3) From the spatial trends of NDVI, the ratio of increased NDVI values occupied 48.51% of the vegetation covered area, while decreased NDVI values occupied 37.15% and 14.39% remained unchanged. 4) Analysis of sustainability of NDVI trend indicated that 27.17% of the vegetation-covered area presented a sustainable-increased state, 26.62% of the vegetation-covered area presented a sustainable-decreased state, 7.2% of the vegetation-covered area showed a sustainable-unchanged state, and 39.01% of vegetation-covered area could not be identified in the future．5) The vegetation growth in the study area was regulated by climate change. Temperature was the most important driving factor in spring and autumn, whereas precipitation in summer. 6) Also human activity played dual influence on vegetation cover change. Farmland and grassland turned into forestry which led to vegetation cover growth somewhere, and forestry and grassland turned into farmland led to vegetation cover decreased elsewhere. This research is useful for identifying the driving forces behind vegetation cover changes and to support environmental policy development in the Heilongjiang Basin within China.