Diop, A. T.

Diouf, A.

Wane, A.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Diachronic Analysis of Vegetation in the Sylvopastoral Zone (Senegal): What Lesson to Learn from? A. T. Diop PPZS, Senegal A. Diouf PPZS, Senegal A. Wane PPZS, Senegal Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/1-4/26 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]175　 瞯Grasslands/Rangelands Resources and Ecology ——— Ecology of Grasslands/RangelandsDiachronic analysis of vegetation in the Sylvopastoral zone (Senegal) :what lesson to learn from ?A .T . D IOP １ ,A . D IOUF , A . WA NE１ PPZS/ ISRA / L NERV P .O . Box ２０５７‐Dakar H ann ( Senegal) . E‐mail : amtadiop＠ sentoo .snKeys words : diachronic , sylvopastoral , drought , ecological monitoring , vegetation densityIntroduction The Sylvopastoral zone ( ZSP ) of Senegal has been occupied for several centuries by pastoralists . During thisperiod , frequent bush fires traversed the zone . During the １９５０摧s the installation of boreholes allowed a permanent settlement ofan increasing livestock population . Since １９７０ , the modifications due to these factors were reinforced with rainfall deficits inparticular . To better understand this phenomenon , monitoring was initiated , but discontinued . However , the changes relatedto these factors continued . The objective of this study was to identify the recent dynamics of the vegetation .Methods of study An inventory of the woody species ( sp) was made in the north at F砪t砪Ol砪 ( FO ) and in the centre at Dahra(Dh) . FO was studied between １９７１ to １９７６ ( Poupon , １９８０ ) and Dh between １９９０ to １９９８ . The same experimental designswere used again in ２００３ . The study of herbaceous species was done through the exploitation of the data from the EcologicalMonitoring Centre ( CSE) at three sites according to a north‐south axis [Souillène (So),Kalossi (Ka)and Ndioumanane (Nd)]from １９８８ to ２００３ .Results and discussion Data on woody species at FO ( between １９７２ and ２００３ ) and at Dh ( １９９６ and ２００１ ) do not indicatevariation in the number of species ( sp .) but woody density was reduced by ４４％ and ５８％ respectively . The number ofindividuals species has increased in the case of Boscia senegalensis and Calotrop is p rocera at FO ; but decreased for Balanitesaegy p tiaca , Commiphora a f ricana , Guiera senegalensis and A cacia senegal at FO and Calotrop is p rocera and A . senegal inDh . The study of the structure of the settlements shows that some sp have a high number of young individuals at FO and Dh ,Boscia senegalensis and only at FO , C .p rocera , B . aegy p tiaca and G . senegalensis .These results show that the environmental conditions in the ZSP are favourable to B . senegalensis and less favourable in somesites to B aegyp tiaca . C . p rocera is maintained with rather old plants in Dh and continues its regeneration in the North . Sp .like G . bicolor and A . senegal are suffering everywhere . Others sp found only in FO like C . af ricana and only in Dh likeA cacia seyal and A cacia nilotica show the same difficulties of grow th . In comparison with studies conducted by Poupon(１９８２ ) , the progression of woody sp drought resistance continues , especially in north .The data for herbaceous sp from １９８８ to ２００３ indicated that both the north and the center ( with low rainfall) have values thatare higher than those from the south . This was not expected . Some sp can also be regarded as characteristic of these sites sincethey were regularly collected : A ristida mutabilis and Chloris p rieurii in So ; Cenchrus bi f lorus and A lysicarpus ovali f olius inKa ; Schoene f eldia gracilis , Zornia glochidiata in Nd . The relationship between the number of sp/ year and the amount ofrainfall is not significant as well is the diachronic analysis of herbaceous data . Six year‐groups could be highlighted but thediscrimination factors were not identified ; the presence of annual sp . depended on several variable factors in the Sahel such asthe characteristics of the sp and the environment (Diouf and Lambin , ２００１) .Conclusions The study of the vegetation in ZSP from １９８８ to ２００３ showed that biodiversity was maintained . A very clearreduction in of the density of some woody sp . , however , was noted , but was compensated by an increase in sp adapted todrought . The number of herbaceous sp did not seem to vary according to rainfall or years and it is very often higher in north orthe centre than in the more rainy southern zone .ReferencesDiouf A . , Lamblin E .F . , ( ２００１ ) . Monitoring land cover changes in semi arid regions : remote sensing data and fieldobservations in the Ferlo , Senegal ; Journal o f A rid Env ironnments ２８ , １２９‐１４８ .Poupon H . ( １９８０ ) . Structure et dynamique de la strate ligneuse d摧une steppe sah lienne au Nord du S砪n砪gal . Paris :ORSTOM , ３５１ p .

Diachronic Analysis of Vegetation in the Sylvopastoral Zone (Senegal): What Lesson to Learn from?

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Diachronic Analysis of Vegetation in the Sylvopastoral Zone (Senegal): What Lesson to Learn from?

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