Monitoring the trend of vegetation changes (NDVI) in Najaf Abad County using Time Series Images and Mann-Kendall test (2003-2019)

Vegetation plays an essential role in regional and global ecosystem stability. The change in terrestrial net carbon uptake is principally affected by varying vegetation productivity and the Earth’s climate is regulated by vegetation through evapotranspiration, surface albedo, and roughness. The purpose research is monitoring the trend of vegetation changes (NDVI) in Najaf abad County using Time Series Images and Mann-Kendall test (2003-2019). In this study, 16-day data of normalized vegetation difference index (NDVI) of MODIS Aqua in time interval 2003- 2019 temporal resolution of 500 meters have been used. Mann-Kendall test used for assessing trend of the index in Najafabad County. The results showed that in the first period (2003- 2013) the amount trend of vegetation is moderate and increasing. The peak of amount increase in vegetation 2005-2007. From 2013- 2016 year the increasing- decline trend shows itself in the same way, until from 2016- 2019 year, decline intense trend witness and once in amount of vegetation in this area, once land use changes and climate fluctuations and drought can be considered one of the main reasons the declining trend vegetation in Najafabad County. The greatest trend of declining vegetation in the southern and southeastern as occurred in urban areas, this trend can indicate high urban growth and land use change from vegetation to construction in this county. Aa well as, irrigated cultivation in the county has during the study period intense decline faced, this issue leads to change land use from irrigated cultivation to other uses in the area.