Spatial And Temporal Variations Of Vegetation Coverage In The Dongting Lake Basin Over The Last 13 Years (2001-2013)

Based on the multi-temporal MODIS NDVI and meteorological data for the period 2001-2013 and aided with dimidiate pixel principle, linear regression analysis, correlation analysis and significance testing, etc., the spatial-temporal variations of vegetation coverage in the Dongting Lake Basin and the determinants driving the observed variations are explored in this paper. The results showed as follows:(1) During the last 13 years, the vegetation coverage decreased slightly with an average annual speed of 0.03%. Significant to highly significant changes in vegetation coverage were observed for approximately 5.3% and 4.29% of the study area, respectively. Take Hunan Province for example, the area of significant increase of vegetation coverage was much smaller than that of significant reduction. The change of average annual maximum FVC showed that: on the whole, the vegetation coverage was high while the change was not significant. Secondly, the western cities (or autonomous prefecture) vegetation coverage was slightly higher than the east. Thirdly, the change tendency of FVC was divided by 112 ° E; cities (or autonomous prefecture) located in the west of the line showed increase whereas others cities presented reduction.(2) Generally, the ground surface of the whole basin was well-covered with vegetation, i.e. vegetation coverage in 88.63% of the total area was categorized as high and moderately high cover. And the vegetation coverage presented declining trend from west to east.(3) Geographically, these changes mainly occurred in the vicinity of water bodies (rivers and lakes) and densely populated areas. In contrast, the rest parts of the basin, which were mainly covered by perennial vegetation, did not show any recognizable change. Taken together, it is suggested that both climate variations and human activities are the major driving factors behind the spatial-temporal patterns/variations in vegetation coverage in the study area. It is also noteworthy that former factor tends to exert a profound impact on the vegetation coverage over large spatial and temporal scales, whereas the latter could change the vegetation coverage in disseminated areas (e.g., cities, river) within a relative short time period.