Abstract
The Normalized Difference Vegetation Index (NDVI) can usually be used as a good proxy for evaluating potential variability in regional ecosystems and under climate change. We used 16-day MODIS-NDVI composite satellite data with 250-m resolution for the period 2000 to 2013 to assess the temporal and spatial variation of the NDVI among different alpine grassland classes and groups in northern Tibet. The annual average NDVI of the whole alpine grassland area in northern Tibet generally increased slightly from 2000 to 2003, and the annual average NDVI values ranged from 0.112 to 0.492 across all alpine grassland groups and years. The NDVI clearly decreased from the southeastern to the northwestern areas, with 22.50% of total grasslands significantly having increased or decreased, while 77.50% presented little change during 2000-2013. Both temperature and precipitation were key factors that controlled the NDVI variations of the entire alpine grassland. However, for different alpine grassland classes and groups, the NDVI displayed different correlation patterns with temperature and precipitation. Our results demonstrate that the NDVI variations of alpine grassland generally increased slightly but differed among different classes and groups. Although temperature and precipitation were the driving forces influencing the NDVI of the entire alpine grassland, it was more difficult to define the driving forces for the individual classes and groups, and more detailed analyses covering prolonged observation periods are still needed.
Highlights
Green vegetation cover is a significant component of terrestrial ecosystems and plays an important role in sustaining the planet’s habitability for humans (Aguilar et al 2012)
Temperature has been found to be the primary climatic factor associated with greening in the northern high latitudes (Zeng et al 2013), whereas precipitation has been shown to be a strong correlate of vegetation growth in fragmented or arid regions (Wang et al 2010)
Normalized Difference Vegetation Index (NDVI) variation in northern Tibet The NDVI of alpine grasslands generally appeared to have an increasing trend in northern Tibet during the period 2000–2013 (Figure 4A). This seems to confirm the findings of studies on NDVI time series over the whole Tibetan Plateau during the last two decades, which demonstrated a positive trend during the growing season (Mao et al 2007; Xu et al 2008; Zhao et al 2009)
Summary
Green vegetation cover is a significant component of terrestrial ecosystems and plays an important role in sustaining the planet’s habitability for humans (Aguilar et al 2012). The NDVI can be exploited because of the striking differences in spectral reflectance between the red and near-infrared wavelengths (Bremer et al 2011). It is a distinct biophysical phenomenon but is influenced by environmental factors such as climatic variables (Revadekar et al 2012). The monthly timing of NDVI variables is found to be closely associated with seasonal patterns in maximum and minimum temperature, as well as precipitation (Los et al 2001; Sen Roy and Yuan 2007).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
