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| DOI：10.13522/j.cnki.ggps.2019268 |
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| Spatiotemporal Variation in NDVI and Its Response to Hydrothermal Change from 2000 to 2018 in Northern Shaanxi Province |
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CHENG Jie, YANG Liangyan*, LI Ya’nan,CHENG Jie, YANG Liangyan*, LI Ya’nan,CHENG Jie, YANG Liangyan*, LI Ya’nan
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1.Xi’an University of Technology, Xi’an 710048, China; 2. Shaanxi Provincial Land Engineering Construction Group Co., Ltd,Xi’an 710075, China; 3. Shaanxi land Engineering Technology Research Institute Co., Ltd., Xi’an 710021, China;4. Key Laboratory of Degraded and Unused Land Consolidation Engineering, the Ministry of Natural Resources, Xi’an 710021, China
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| Abstract: |
| 【Background】Northern Shaanxi province is located at the center of the gully region in the Loess Plateau, characterized by dry climate with seasonally variable rainfall. It is in the transition zone from forest to grassland. Unsustainable economic structure and over-exploitation in early stage of development in this region had resulted in soil and water loss, which has made its ecosystem extremely fragile. As a key component in hydrological cycle, vegetation plays an important role in moving water from soil to atmosphere and balancing thermal energy of the planet. Spatial variation in vegetation is a result of the interplay of soil moisture, shallow groundwater and air temperature, and it is especially sensitive to climate change in arid and semi-arid region.【Objective】 The objective of this paper is to analyze the spatiotemporal variation in NDVI in northern Shaanxi province in attempts to provide baseline data for restoring functions of its ecosystems and sustaining economic development.【Method】The data were derived from the MODIS remote sensing from 2000 to 2018. Finite difference method and linear regression slope method were used to analyze the NDVI of each pixel in the remote sensing imageries.【Result】Vegetation change in 2000—2009 differed from that in 2009—2018, with the average vegetation changing rate in the former being 0.013/10a compared to the 0.0076/10a in the latter. In terms of spatial distribution, the degraded soils from 2000 to 2009 were mainly in the western mountainous area and at the edge of the Maowusu sandy land, while the degraded soils from 2009 to 2018 were mainly in the periphery of Yanan and at the edge of other cities and towns. The annual NDVI change was consistent with rainfall and temperature, but their correlations were different. NDVI was positively related to annual rainfall at significant level with R=0.63 (P<0.01), while there was only a weak correlation between NDVI and temperature with R=0.23.【Conclusion】Linear regression slope method is more suitable for studying temporal change in vegetation dynamics. Vegetation growth in northern Shaanxi province is affected by rainfall more than by temperature. There was a lag between the time when a change in temperature and precipitation happened and the associated shift in vegetation. |
| Key words: NDVI; MODIS; temporal-spatial variation; northern Shaanxi; hydrothermal condition |
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