Study On The Vegetation Response To Dynamic Change Of Groundwater Level And Climate Change In Minqin Oasis

Vegetation is an important component of the ecosystem, and can directly the most reflect the natural environment elements. Especially in arid areas, vegetation has greater sensitivity to environmental changes, to some extent, the vegetation changes can reflect the regional environmental changes. Studying vegetation change response to both groundwater depth and climate change has significant guidance for rational water resources utilization and ecological restoration in arid areas.Research region in this paper is Minqin Oasis downstream the Shiyang River Basin in Gansu Province. This paper analyzed the dataset Spot-Vegetation NDVI and climate elements(temperature, precipitation ,relevant humidity) from 1998 to 2008,land use types of Shiyang River in 2000,and calculated the spatial distribution of groundwater depth in Minqin Oasis, utilizing ENVI, ArcGIS, MATLAB .In Minqin Oasis downstream the Shiyang River Basin so the response relation of between the annual NDVI (1998~2008)and climate elements was analyzed ,later the response relation between NDVI of different vegetation types and groundwater depth also can be analyzed. The following conclusions:(1)In 1953 ~2008, 56years, in research region Minqin Oasis the annual average temperature and annual accumulated precipitation anomaly increased, however the relevant humidity anomaly reduced. But in 1998-2008, 11 years, the annual accumulated precipitation and relevant humidity increased, with the decline of annual average temperature, although the "moistening" trend is slow. On summer and autumn a consistent temperature and precipitation trends were showed, whereas trend of spring and winter was opposite.(2) In 1998 ~ 2008 ,11 years, the vegetation indexes of Minqin Oasis were lower overall, but the overall trend showed growth, including improved vegetation area ratio was 64.6%, compared to 35.4% degradation. Significant seasonal variation was shown during the year, NDVI of July in summer is the highest. The seasonal average NDVI increased significantly in summer and autumn, while in spring decreased significantly , and in winter NDVI changed little.(3)From 1998 to 2008 in Minqin Oasis the annual average groundwater level had been trending down, groundwater depth dropped from the average annual 12.48m in 1998 down to 16.05m in 2008, with a decrease of 3.57m, so the average decline rate is 0.32 m / a. In Minqin oasis there are two shallow groundwater depth , one is surrounding Hongyashan Reservoir, another is around Shoucheng Town, Zhenbao community, there also exists a groundwater funnel around Zhongqu Town.(4)According to the correlation analysis between NDVI and climatic factors of Minqin Oasis , NDVI has more relevance to precipitation than to temperature, indicating that the vegetation is less sensitive to temperature than to precipitation. But the relevance of temperature and precipitation are not significant, indicating that climatic factors in Minqin Oasis had limited impact on the natural vegetation. By further grouped into two kinds of vegetation types forestland and grassland, numerical analysis showed that zone where groundwater below 5m is small, and groundwater depth more than 10m had no obvious response to different vegetation types NDVI in Minqin Oasis.