Monitoring of Vegetation Dynamics in the Mongolia Using MODIS NDVIs and their Relationship to Rainfall by Natural Zone

Abstract

Vegetation plays a very important role conserving the natural environment and improving the living environment for humans. Thus, investigating spatio-temporal changes in vegetation is a crucial indicator to understand natural environmental changes. We explored the spatio-temporal trends of changing vegetation cover in Mongolia from 2002 to 2010 by investigating changes in the normalized difference vegetation index (NDVI) with rainfall. The 16-day composite NDVI time series Terra MODIS (MOD13A2) and the gridded rainfall data of the Inter-governmental Panel on Climate Change (IPCC) were used to identify the relationship between vegetation dynamics and rainfall. Residual NDVI trends were computed. Following our general procedure, monthly NDVI and annual rainfall were correlated for each pixel. The resulting regression equation represented the statistical association between observed NDVI and rainfall, and the model predicted NDVI according to rainfall. Residuals of NDVI (differences between the observed and predicted NDVI) for each pixel were calculated, and the trends in these residuals was analyzed by linear regression. From the 12 months NDVI and rainfall values they determine a linear regression line for each pixel. The positive or negative slope of this line is considered to reflect an increase or decrease in green biomass. Our results show that vegetation cover changes in Mongolia were caused by both natural factors and human activities. The natural vegetation change, such as those in forests was influenced by climate change, whereas human activities were the main reason for the change in vegetation planted.

Assessing environmentally sensitive land to desertification using MEDALUS method in Mongolia

“…Mongolia ranges in longitude from 98 58 0 to 105 1 0 and in latitude from 49 6 0 to 46 41 0 (Figure 1), with area of approximately 1,565,000 km 2 . Mongolia contains a large area of grass and shrub steppe grazing lands, which allows a large number of animals to graze there (Lamchin et al 2015). Mongolia also has mountainous regions to the north and south, while the Gobi Desert comprises its southern region.…”

“…Precipitation is the most important factor affecting land degradation and desertification, as it controls the drainage and water capacity of the soil (EC-European Commission 1999). The average annual precipitation of Mongolia, by land cover type, is 300-400 mm in mountainous areas, 150-250 mm in steppe areas, 100-150 mm in the steppe desert, and 50-100 mm in the Gobi Desert area (Lamchin et al 2015). This indicates a high gradient depending on the longitude and land cover.…”

Assessing the spatio-temporal variability of NDVI and VCI as indices of crops productivity in Ethiopia: a remote sensing approach

“…Following a strong association of NDVI with rainfall as also confirmed by Richard and Poccard (2010); Lamchin (2004); Martiny et al (2006), the NDVI can serve as a reliable proxy evaluation of inter-annual variability of the climatic system, with rainfall considered as a crucial climatic factor in vegetative growth. NDVI is considered among the most reliable vegetation index of greenness, with a strong correlation of biomass, which is also an indicative of growth.…”

“…The choice of NDVI and VCI as indicators for monitoring drought has been evaluated worldwide. A strong association of NDVI with rainfall has been confirmed by (Al-Bakri and Suleiman 2004;Lamchin 2004;Martiny et al 2006;Richard and Poccard 2010).…”

Assessing the Impacts of Extreme Climate Events on Vegetation Activity in the North South Transect of Eastern China (NSTEC)

“…In detail, monthly and yearly NDVIs were synthesized from the original weekly data. A simple linear regression was then conducted to examine the linear trend of the NDVI (Y) [40,41]…”