Rainfall Trend and Its Relationship with Normalized Difference Vegetation Index in a Restored Semi-Arid Wetland of South Africa

Florence M. Murungweni, Onisimo Mutanga and John O. Odiyo
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Florence M. Murungweni: Department of Ecology and Resource Management, School of Environmental Science, University of Venda, Thohoyandou 0950, South Africa
Onisimo Mutanga: Pietermaritzburg Campus, School of Agricultural, Earth and Environmental Sciences, Private Bag X01, University of KwaZulu-Natal, Scottsville 3209, South Africa
John O. Odiyo: Department of Hydrology and Water Resources, School of Environmental Science, University of Venda, Thohoyandou 0950, South Africa

Sustainability, 2020, vol. 12, issue 21, 1-22

Abstract: Clearance of terrestrial wetland vegetation and rainfall variations affect biodiversity. The rainfall trend–NDVI (Normalized Difference Vegetation Index) relationship was examined to assess the extent to which rainfall affects vegetation productivity within Nylsvley, Ramsar site in Limpopo Province, South Africa. Daily rainfall data measured from eight rainfall stations between 1950 and 2016 were used to generate seasonal and annual rainfall data. Mann-Kendall and quantile regression were applied to assess trends in rainfall data. NDVI was derived from satellite images from between 1984 and 2003 using Zonal statistics and correlated with rainfall of the same period to assess vegetation dynamics. Mann-Kendall and Sen’s slope estimator showed only one station had a significant increasing rainfall trend annually and seasonally at p < 0.05, whereas all the other stations showed insignificant trends in both rainfall seasons. Quantile regression showed 50% and 62.5% of the stations had increasing annual and seasonal rainfall, respectively. Of the stations, 37.5% were statistically significant at p < 0.05, indicating increasing and decreasing rainfall trends. These rainfall trends show that the rainfall of Nylsvley decreased between 1995 and 2003. The R 2 between rainfall and NDVI of Nylsvley is 55% indicating the influence of rainfall variability on vegetation productivity. The results underscore the impact of decadal rainfall patterns on wetland ecosystem change.

Keywords: Mann-Kendall; NDVI; quantile regression; rainfall; Ramsar; vegetation; wetland (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
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