Vegetation dynamical status in the Lake Qiandao drainage basin using time-series MO-DIS data (2001 2013)
The status of vegetation coverage in the drainage basin is an important indicator to eco-environmental conservation of the drinking water source reservoirs. Current water quality target management should not only focus on monitoring water quality parame-ters in the lake, but also maintain the ecological balance of the whole drainage basin. With this background, long-term MODIS time series were used to analyze the vegetation dynamical status during 2001 2013 for the Lake Qiandao drainage basin. The ND-VI was used as a proxy of vegetation cover, and the least squares regression trend analysis with the Mann-Kendall test were used to analyze the characteristics of distribution, time variations and spatial trends of the vegetations. The study showed that it’s an effec-tive way to reflect the spatial-temporal patterns of vegetation coverage for the Lake Qiandao drainage basin. The basic conclusions from the study are as follows:1) From the spatial distribution of the annual mean NDVI in the study area, the vegetation coverage performs well as a whole. However, the NDVI values at the locations disturbed by intensive human activities, such as urban con-struction land, agricultural land and garden plots sited near the river and lake, are obviously lower than those at natural woodland.2) Based upon the time series of annual mean NDVI in the vegetation area in the basin, the NDVI values fluctuate between 0. 69 and 0. 73 from 2001 to 2013, and have increased since 2008, indicating seasonal changes of phenological characteristics of ever-green from that of deciduous vegetation. This can be used to analyze the risk of nitrogen and phosphorus loss of different vegetation types. 3) From the spatial trends of NDVI, the area where the NDVI values increased is much larger than the area that the NDVI values decreased. The improved vegetation area occupies 55. 90% of the basin, while the degenerative vegetation-covered area ac-counts for 29. 60%. The other 14. 51% of the total area remained unchanged during the period of 2001 2013. We also found that the changes in vegetation coverage are more positively correlated with temperature in most part of the basin, while precipitation is not obviously sensitive to vegetation change in the water-rich eastern region, which suggested that temperature is the controlling cli-matic factor. Meanwhile, local vegetation changes are significantly affected by human activities. These results have provided scien-tific foundations for protecting the water resource and ecological environment of the drainage basin.
Lake Qiandao drainage basinvegetation dynamical statusspatial-temporal patternstrend analysis
国家科技期刊平台
NSTL
万方数据
