Trend Dynamics of Rainfall on Vegetation Pattern in parts of Niger State Nigeria.

Abstract

An increasing population and demand for land are threatening the existence of vegetal cover not only in the study area but the world over. This threat to vegetal cover calls for a sufficient understanding and measurement of the dynamics of vegetal cover. This study aimed at analyzing the trend in rainfall and vegetation dynamics over Mokwa Local Government Area of Niger State, Nigeria. The study used gridded satellite daily rainfall data for the period of 31 years (1987-2017). Data of remote sensing images for the periods of 1987, 2002 and 2017 were extracted and used for Land Use Land Cover (LULC) change and Normalized Difference Vegetation Index (NDVI) analysis. Standardised Precipitation Index (SPI) and simple linear regression were used in rainfall and trends analysis. Findings show that the year 1994 had the highest positive value of SPI (1.62) and lowest value was witnessed in 2000 (-2.75).The result showed that four years were observed to be above normal wetness with five years below normal dryness. The NDVI value was observed to be between 0.81 and -1 in 1987 but decreased to NDVI values between 0.405 and -0.12 in 2017.LULC change shows a decrease of 15.5% in vegetation cover from 1987 to 2017.Similarly,an increase of 15.42% in non-vegetation areas and a 0.13% increase were observed in the water body during the study period. The linear regression of R2=0.743 indicated a significant positive relationship between rainfall and vegetation cover. It was concluded that the trend in rainfall is not spatially distributed along with longitudinal or latitudinal directions.