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Precipitation trends, evapotranspiration and the ecological zones of Nigeria

Theoretical and Applied Climatology volume 39, pages 81–89 (1988)Cite this article

Summary

An attempt is made to use the ratio⋋ of precipitation to potential evapotranspiration to qualify earlier climatic classifications of Nigeria for proper ecological zonation.

Results show that in the pure forest belt located south of latitude 7° N the⋋ value is greater than 0.75, while in the middle belt (7–10° N) belonging to the wooded savanna and in areas further north gradually approaching steppe-type vegetation of pure Sahel, the values of⋋ below 0.40.

Modulations of⋋ values (hence the eco-zones) appear to be responses to variable precipitation, especially in drought years. It is suggested that this notwithstanding, irreversible trends in land-surface degradation are mainly due to uncontrolled human interference in relation to large-scale agriculture in areas where⋋ is less than 0.40 in the Sudan-Shael belt of Nigeria. This needs to be re-appraised, if this desertification trend is to be checked

Zusammenfassung

In vorliegender Arbeit wird der Versuch unternommen, mittels des Quotienten⋋ von Niederschlag und potentieller Evapotranspiration frühere klimatische Klassifikationen der ökologischen Zonen von Nigeria genauer zu bestimmen.

Die Ergebnisse zeigen, daß im reinen Waldgürtel südlich des 7. Breitengrades⋋-Werte über 0.75 auftreten, während im mittleren (7–10° N), zur Waldsavanne gehörigen Gürtel, und in weiter nördlich gelegenen Gebieten, die zunehmend die steppenartige Vegetation der reinen Sahelzone aufweisen,⋋-Werte unter 0.40 auftreten.

Die Schwankungen der⋋-Werte (forthin Ökozonen) scheinen die Reaktion auf unterschiedlichen Niederschlag besonders in Dürrejahren zu sein. Ungeachtet dessen ist die Annahme naheliegend, daß die irreversiblen Trends der Verschlechterung der Landoberflächen vor allem unkontrollierten menschlichen Eingriffen in Zusammenhang mit großflächigem Landbau in Gebieten des Sudan-Sahel-Gürtel Nigerias zuzuschreiben sind, wo⋋ weniger als 0.40 beträgt. Diesem Aspekt muß eine neuerliche Untersuchung gewidmet werden, um diesen Trend zur Desertifikation zu überprüfen.

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Authors and Affiliations

  1. Department of Geography School of Science and Science Education, Federal University of Technology, Minna, Nigeria

    D. O. Adefolalu

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  1. D. O. Adefolalu
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Adefolalu, D.O. Precipitation trends, evapotranspiration and the ecological zones of Nigeria. Theor Appl Climatol 39, 81–89 (1988). https://doi.org/10.1007/BF00866392

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Keywords

  • Precipitation
  • Nigeria
  • Potential Evapotranspiration
  • Ecological Zonation
  • Variable Precipitation