Analysis of Terrestrial Vegetation Trends and Correlation between Vegetation Indices and Climatic Factors

摘要

The outcome of decadal seasonal and annual trend analysis for NDVI and EVI under various land cover classes showed both negative and positive trends. Irrespective of land cover classes, NDVI and EVI during Kharif season showed a greening (positive) trend in vegetation growth whereas during Rabi season it is observed to have browning (negative) trend. The positive greening trend during the Kharif season might be due to the increased vegetation growth and productivity during the period. The declining vegetation (browning) trend in Rabi season might be due to changes in a crop choice or disruption of cropping lands. Decadal annual NDVI and EVI witnesses the positive greening trend except in some parts of Rajkot, Dwarka, Porbandar, Amreli and Jamnagar districts where browning in nature. During decadal Kharif season, weak to moderate positive correlation was noticed between LST and vegetation indices whereas during Rabi season it showed strong to weak negative correlation. It could be observed that about 70 percent of total pixels in all the land cover classes during Kharif season has moderate negative correlation between vegetation indices and net radiation. In Rabi season, the weak negative or positive correlation and moderately positive correlation classes occupies the major percentage of area. The correlation study between vegetation indices and TRMM rainfall showed a weak negative or positive correlation for both the seasons and annual duration which indicates that the rainfall is not a key factor for the vegetation growth in Saurashtra region. The historical trend derived from the time series analysis paved way in identifying the causes for degradation of vegetation coverage.