基于MODIS NDVI的攀枝花市植被覆盖变化及其驱动力#br#

攀枝花市位于金沙江与雅砻江的交汇处是长江上游生态脆弱区，也是天然林保护工程和退耕还林工程等的重点实施区。基于2001~2010年MODIS NDVI数据，以及同时期的气象数据和其他辅助数据，利用最大值合成法（MVC）、趋势分析法以及线性相关分析等方法研究了攀枝花市植被覆盖时空变化及其与气候因素和人类活动的关系。研究结果表明：攀枝花市植被覆盖整体较高，属于高植被覆盖区域，年际尺度上，植被覆盖呈上升的趋势，增长速率为0.02/10 a；从年内来看，9月NDVI达到最大值，NDVI最小值出现在3月；植被覆盖在水平空间上呈“南低北高”的分布特征，并在垂直空间上呈现出显著的差异性，研究区植被覆盖分别在海拔2 000~3 000 m、坡度30°~40°达到最大值；受水热条件的影响，阴坡（0°~45°, 315°~360°）植被覆盖高于阳坡（135°~225°），而平地（-1°）植被覆盖度最低；就整个研究区而言，植被退化的面积与增加的面积分别占0.7%和44.4%，增加的面积远大于退化的面积；年际尺度上植被受气温的影响高于受降水的影响；大规模生态工程建设是研究区植被覆盖增加的主要驱动因素。 关键词： 植被覆盖变化；归一化植被指数；气候变化；人类活动；攀枝花市

Analyzing Dynamic Vegetation Change and Its Driving #br# Factors in Panzhihua City Using MODIS NDVI Data

Panzhihua City is located in the confluence area of the Jinsha River and the Yalong River, which is an ecologically vulnerable region in the upper reache of the Yangtze River and a key area for implementing the “natural forest protection project” and the “returning cultivated land to forestry project” in China. Based on the MODIS NDVI data from 2001 to 2010, meteorological data and other ancillary data in the same period, in this paper we analyzed the spatial and temporal variation of vegetation NDVI and its relationship with climatic factors and human activities by using the methods of maximum value composites, trend analysis and linear regression analysis. The results showed that the vegetation cover in the Panzhihua City was high and belonged to the high vegetation cover area. On the inter annual scale, the vegetation cover showed an upward trend, with a growth rate of 0.02/10 a. During a year, NDVI was peaked in September and had the lowest value in March. The vegetation cover showed a horizontal spatial distribution pattern of “High in the north and Low in the south” and also showed significant differences in the vertical direction. The vegetation cover in the study area reached the maximum at the altitude range of 2 000 m-3 000 m and the slope range of 30 °-40 °, respectively. Constrained by hydrothermal conditions, the vegetation cover on shady slopes (0°-45°, 315°-360°) was higher than sunny slopes (135°-225°) , and the NDVI had the lowest value in the flat areas. For the entire study area, the areas with degraded vegetation and the vegetation greening areas accounted for 0.7% and 44.4% of the total area, respectively. The greening areas were much larger than that of the degraded area. Over the 10 years, the vegetation was more affected by temperature than precipitation. Besides, the large scale ecological engineering construction is the main driving factor for the increase of vegetation cover in the study area. Key words：vegetation cover change; MODIS NDVI; climate change; human activity; Panzhihua City