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Banded Vegetation Patterning in Arid and Semi-Arid Environment

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Banded Vegetation Patterning in Arid and Semi-Arid Environment GCTE -, 2t8i- ss formations de type "brousse tirrée" des régions arides et semi-arides. Sponsored by: ORSTOM I'lnstitut Fronyis & Recherche Scientifique pour le Développement en (oopérotion CNRS-Programme Environnement Concepfin moquette, réahotion N. Zerbib - ORSTOM Bondy Distribution, structure, origine et devenir des brousses dites tigrées en Mauritanie sahélo-saharienne Rossetti Ch. 2- Existing theones A geomorphological based "Tiger Pattern" generated by a former dune pattern in Sokoto Nothern Nigeria Zonneveld 1. c methods of study 1- Pattern at a regiorial scale Vegetation pattern recognition using SPOT images at regional scale in Niger Mougenot B., d'Herbès ]. M., Hamani S. 2- Functioning at local scale Patterning and pioneer processes of the herbaceous front in a tiger bush Ehnnann M., Çalle S., Seghieri]. sses and models 1- Runoff and erosion processes Surface crusts of the tiger bush Valentin C, Bellier Ç., Malam 1.. Rajot1.L.. Pichet]. The importance of surface water redistribution for the water budget of banded vegetation structures (Spain) Bergkamp Ç., Cerda A., lmeson A., longejans]. The soi1 surface features of the vegetation striped patterns in Mapimi reserve. North Mexico and their influence on the hydrodynamic ]aneau 1.1.. Mauchamp A., Tarin Ç. Impact of water harvesting variations along a climatic transect in Niger upon produciivity and paüems of tiger bush Valentin C,d'Herbès].M. The distribution of soluble cations within a patterned ground gilgai complex. Western New South Wales, Australia MacDonald B.C.T, Melville M.D., White L. Erosion processes and polyphase mosaic components in a banded grassland. and Western New South Wales. Australia Dunkerley D., Brown K. Soil water balance Water balance in a banded vegetation pattern: the case of the tiger bush in Western Niger Galle S. Ehmann M., Peugeot C. - Soil and soi1 water balance in the watenhed of the riier Corouol - a case study in the Sahel of Burkina Faso Kappas M. Rainfall inputs and direct recharge to the deep unsaturated zone of southern Niger Bromleyj., Edmunds WM.. Fellman E., Brouwer]., Gaze S.R., Sudlow j., Taupin j.D. Soil and hydrologic characteristics of a banded vegetation site in Niger and their effect on tree establishment Zanguina 1.. Thurow IL., juo A.S.R., Manu A. Soil biotu Soil fauna and process regulation in patterned landscapes of serni-arid Australia Noble ]. C. Tenites-soil-vegetation interactions in a striped vegetation pattern (Burkina Faso) Ouedraogo P. iepage M. 4- Populations dynamics Cornparison of spatial patterns of woody species in a spotted savanna and a tiger bush of Northern Yatenga (Burkina Faso, West Africa) Couteron P Runoff contribution to a sahelian two-phase mosaic system: soi1 water regime and vegetation life cycles Seghieri 1.. Çalle S. 5- Syntheiic models of fundioriiiig Stripes, strands or stipples: modelling the influence of three banding patterns on resource capture and productivity in semi-and woodlands, Australia Ludwig 1.. Marsden S. 'Brousses tigrées": an example of pattern formation in systems with non local interactions. Lejeune O., Lefeue, R. 6 - Genesis of banding geneml niodeis Soil organic matter dynamic on Tiger Bush in Niger Çuillaume K.. Abbadie L. Using 137Cs to trace upslope migration of banded vegetation in South-west Niger. Chappe11 A., Valentin C,Warren A., Charlton M. d'Herbès ]. M. How do vegetated arcs move upward in Niger ? Mougenot, B., d'Herbès, ].M.. Ichaou, A. Banded vegetation patterning in a subantartic forest of Tierra del Fuego, as an outcome of the interaction between wind and tree growth. Puigdefabregas]., Çaliart E, Bianciotto O., Allogia M., Del Barrio Ç. sequences for Management 1- Productivity of patterned vegetation Does patchiness increase vegetation productivity, biodiversity and stability ? The case of the 'brousse tigrée" in the Sahel Hiemaux FI 2- Towards an iniproved land nianagenieni in the and and seniind zones The evolution of soil-vegetation patterns following land abandonment and fire in Spain Carnmeraat L. H.. lmeson A.C. Tiger bush that lost its stripes: the effect of grazing on the spatial pattern of herbage production in a banded semi-arid woodland in Eastern Australia Freundenberger D.,Palmer R. Vegetation arcs and litter dams: similarities and differences Eddy]., Humphreys Ç.S., Hart D.M., Mitchell PB., Fanning P C. Relationshps between rainfall. soil-water, and herbage production in three geomorphic zones in semi-arid wooded rangelands Çreene R.S.B., Noble 1.C. des brousses dites tigrées ette note n'a pas pour objectif de reproduire in extenso des observations fort longues effectuées en juin-juillet 94 en cours d'exploitation. mais de fournir une orientation générale sur ces observions qui avec d'autres observations portant sur une trentaine d'années doivent illustrer certains aspects quelque peu controversés sur l'évolution de la végétation en Afrique du NW suite aux grandes sécheresses. *:* *:* VUE GÉNÉRALI SUR LA QUESTION DU PCllNT DE VllE DE LA PHYTOECOLOGIE J'ai eu connaissance de l'existence de cette structure remarquable de la végétation par des collègues australiens en 1957 lors d'exploration dans la région d'Alice Springs en Territoire du Nord. L'équipe du CSIRO (Land Research Division) effectuait alors des relevés d'inventaires globaux par la méthode combinant une orientation morphologique combinée à des relevés de végétation, à partir de couvertures aériennes à l'échelle du 150 000ème. C'est sur la photographie aérienne qu'a été, sauf mieux informé, découverte la structure particulière en bandes de physionomies mixtes. essentiellement arbustives en Australie (Acacia aneura. sauf erreur), puis mixtes en Afrique de l'Est. et enfin, par la cartographie au 1 :200 000ème de I'IGN, en Afrique du NW. D'un double point de vue de la phytogéographie, et à une autre échelle de travail. de la phytoécologie, cette disposition de la végétation offre un exemple fort intéressant comme indicateur du milieu. Sur le plan climatique certains types de climat favorisent-ils cette disposition? Sur * Ingénieur agronome EPF PART I R BUSH AND RELATED STRUCTURES un plan écologique, quelles conditions de station permettent-elles cette constitution. Enfin se pose la question de savoir comment de telles dispositions peuvent-elles apparaître au moment de leur constitution, quelle est leur stabilité et quels facteurs peuvent modifier cette constitution. Accessoirement la phytoécologie s'intéressera à la composition botanique de ces végétations. mais ce n'est pas là. à mon avis, un problème crucial, car en l'occurrence c'est la structure qui est cause d'interrogations. non la floristique, trop fréquemment exhaustive d'études phytoécologiques. *:* *:* LA SITUATION EN MAURITANIE DU CENTRE NORD ET DU NE Notre préoccupation en 1959/61. il y a plus de trente ans, n'était nullement d'étudier en soi les BT. La prospection écologique engagée par la FA0 avait pour objet de rechercher en zone saharienne et sahélo saharienne les structures de végétation contrastées que l'on supposait alors favorables à la localisation pour la reproduction des essaims du criquet pèlerin (phase grégaire). Depuis la définition de ces zones par les travaux de POPOV s'est considérablement affinée. et le travail effectué sur les BT n'a. d'un point de vue acridien, qu'un intérêt tout à fait secondaire..Tel n'était point alors mon avis lors de la prospection effectuée avec P. AUDRY, pédologue de I'ORSTOM détaché au projet FA0 et avec qui un début d'investigation d'un échantillon de BT fut réalisé sur le plateau de Néma en Mauritanie de l'est. Avant d'examiner la structure caractéristique, car plus ou moins linéaire. en bandes, ou en "arcs" selon la terminologie anglo-saxonne, tâchons, tout au moins pour l'Afrique de NW de visualiser les zones où se produit ce phénomène. C'est vraisemblablement CLOS ARCEDUC, ingénieur géographe de I'ICN qui l'a, le premier, signalé en zone sahélienne a tenté de lui donner une interprétation. Dans les actes de la Conférence de Toulouse de 1964 (op. cit 1968) il révèle ce que l'accès libre à la photothèque (et du temps disponible !) lui permettaient de déceler : des images caractéristiques en dessein de pelage de tigre (d'où la dénomination) au Mali (entre 7 et 5" W. 15 et 16"N), dans le sud du pays Dogon toujours au Mali (3"W et O" et en écharpe entre les latitudes 14 et 16"N). enfin dans une zone d'extension considérable au Niger entre I " et 4" E et au delà ; puis en écharpe entre 12 et 16" de lat. N). II en avait fait mention précédemment dans une brève note publiée dans un bulletin de I'IFAN en 1956 que m'avait signalée Th. MONOD. mais TlGER BUSH AND RELATED STRUC dont je n'ai jamais disposé. C'est vraisemblablement à cette occasion que cet observateur averti de la photographie aérienne a proposé le nom de brousse tigrée dénomination qui fut reprise par les cartographes de I'lGN interprétant les photographies en termes d'images, non en termes écologiques. Je montrerai pourquoi je fais cette réserve.. Nulle mention n'est faite de la présence de BT en Mauritanie. En fait on les trouve en discontinuité sur des plateaux dans la région de Boûmdeit entre II "55'et II "30'W et 17O35'N. ceci à quelques minutes sexagésimales près. parfaitement portées sur la carte au 1 :200 000ème) comme sur les feuilles de Oualata et Néma. Sur la première avec les extensions nord extrêmes dans cette région 17" IO'par lambeaux entre 7" IO'et 7" W et sur celle de Néma .Le plateau de Néma présente un cas intéressant car les BT figurant sur la carte IGN et très bien repérés (des prospections extebsives l'ont confirmé se présentent en blocs disjoints entre les lastitudes i 6O28' et 17" puis légèrement à l'est de la longitude 7" ouest et 7'20' aproximativement.
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