Document Type : Research Paper
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Abstract
Precipitation is one of the factors affecting vegetation. Nowadays, satellite images are broadly used for monitoring the effects of precipitation variations on the vegetation changes. The aim of this study was to investigate the relationship between vegetation dynamic and precipitation variations using NOAA AVHRR images during the period of 1982-2006. Precipitation maps were created using the inverse distance weighting interpolation (IDW) method and time intervals of precipitation data. The study area was a forestland beside Caspian Sea, four rangeland vegetation types with grasses and shrubs, farmland areas and urban areas, located in Ardabil and Guilan provinces. To monitor the relationship between the precipitation and vegetation changes, the linear regression (NDVI, Y & Rainfall, X) method was employed. Based on the results, depending on the precipitation time, plant species, and growth form, the effect of precipitation on vegetation was different so that no significant relationship was observed between vegetation and precipitation in forestlands, farmlands, and urban areas. The highest correlation coefficient between spring precipitation and vegetation was related to the rangelands. In grassland areas, the correlation coefficient was higher than that of shrublands, whereas the reaction of grasslands to precipitation in various parts was different.
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