Vegetation’s Reaction to Rainfall Variability in the Sudano-Sahelian Ecological Zone of Nigeria.
Abstract:
Rainfall variability plays a crucial role in influencing shifts and dynamics in vegetation. The impacts of these changes are not only symmetric but also have significant multiplying effects on both ecosystems and human livelihoods. This study investigates the response of vegetation to rainfall variability in the Sudano Sahelian Ecological Zone of Nigeria (SSEZ). Rainfall data from the Climate Research Unit (CRU) and the United States Geological Survey (USGS) satellite imageries for the study areas were collected over a 37-year period (1981-2018).
To analyze rainfall patterns, the Interseasonal Rainfall Monitoring Index (IRMI) was utilized to calculate the “actual” or “real” onset and cessation dates of the rainy season. The onset of rains was defined as the pentad within which the index was greater than or equal to 1 (≥1) for the first time. Additionally, the Monsoon Quality Index (MQI) was employed to assess moisture quality in the study area, and the Perpendicular Vegetation Index (PVI) was used for satellite image analysis in the infrared (IR) and near-infrared (NIR) bands.
The findings revealed considerable rainfall variability across the ecological zone. For instance, Nguru had the lowest average rainfall (536mm), while Yelwa had the highest (1090.65mm). The Average Length of Raining Season (LRS) ranged between 120-140 days. The Monsoon Quality Index (MQI) was used to classify the rainfall quality, with values ranging from good (<0.005) to extremely poor (>0.02).
Satellite image analysis demonstrated changes in vegetation dynamics over the study period. The Normalized Difference Vegetation Index (NDVI) was used to determine vegetation vigour in the region, and areas were ranked as having poor, moderate, or healthy vegetation. For instance, Maiduguri and Nguru exhibited poor vegetation with an NDVI value of around -0.2, corresponding to an average annual rainfall of less than 600mm. Kano and Gusau showed moderate vegetation with an NDVI value of 0.0564 and an average annual rainfall of around 800mm. On the other hand, Yelwa and Bauchi exhibited healthy vegetation with an NDVI value of around 0.826 and an average annual rainfall of more than 1000mm.
In conclusion, the research demonstrates that vegetation growth is significantly influenced by rainfall. Vegetation responses can be positive or negative depending on the quality and quantity of rainfall received in a particular region.
Vegetation’s Reaction to Rainfall Variability in the Sudano-Sahelian Ecological Zone of Nigeria.