The   map   of   vegetation   types   comprises   120   different   types   (without   RIVER)   -   28   plant   associations   (with   MB)   and   92   mosaics of plant associations. The principles governing the organization of the legend are as follows: The   plant   associations   are   ranked   according   to   a   decreasing   flood   level   -increasing   dryness:   PAK,   BP,   B,   VB,   PAM,   OP,   O, VOR,   EOR,   R,   ESP,   VSP,AC,   VH,   P,   AG,   ZB,   MB,   PAN,   PAS,   PAR,   TA,   TC,   TD,   TS,   TT,   TB,   THY.   The   ranking   by   decreasing flood   levels   presents   one   exception,   with   the   complex   mosaic   found   in   the   river   major   bed,   MB   ,   which   we   arbitrarily   placed between   river   flooded   associations   and   those   flooded   by   run-off   and   late   river   flood   (PAN,   PAS,   PAR).   The   flood-dryness   gradient applies,   with   local   run-off   and   late   flood   associations   PAN   being   more   heavily   flooded   than   PAS   and   PAR. At   the   end   of   the   gradient, dry   combinations   are   listed   in   alphabetical   order,   except TB   and THY   which,   being   on   sandy   substrate,   are   considered   to   be   the   driest of all. The   gradient   of   colors   used   in   the   legend   tries   to   translate   the   flood-dryness   gradient   as   closely   as   possible.   The   most   flooded vegetation   types   are   given   colors   ranging   from   dark   purple   to   light   violet   (PAK,   BP,   B,   VB,   PAM),   then   a   range   of   blues   applies   to the   combinations   with   wild   rice   (OP,   O,   VOR,   EOR,   R),   a   range   of   greens   to   the   less   deeply   flooded   combinations   (ESP,   VSP, AC) and   a   range   of   yellow   greens   to   the   weakly   flooded   associations   (P, AG,   ZB).   The   color   allocated   to   MB   is   specific   (a   slightly   green gray).   The   woody   savannas   flooded   by   local   run-off   and   late   river   flood   (PAN,   PAS,   PAR)   are   coded   with   three   specific   grays,   from darkest   to   lightest.   The   upland   associations   are   given   warm   colors,   ranging   from   yellow   to   brown.   The   mosaics   being   combinations of   associations,   the   120   vegetation   types   are   figured   on   a   square   matrix   of   28   by   28   associations   ranked   according   to   flood-dryness   as described   above.   The   upper   left   box   of   the   matrix   (row   1,   column   1)   is   a   combination   of   the   first   element   of   the   gradient   -   PAK   -   by itself.   The   diagonal   of   the   matrix   thus   represents   the   plant   associations.   The   mosaics   are   all   located   in   the   lower   half   of   the   matrix and at the intersection of the two component associations, i.e. VOR/ZB is located at the intersection of column VOR and line ZB.
The   map   of   the   vegetation   types   shows   the   difference   between   the   low   lands   of   the   inland   Delta,      where   the   tones   range   from   the purple   and   violet   of   the   deeply   flooded   associations   to   the   range   of   blues   and   greens.   Northeast,   the   Farimaké   is   distinguished   by   the mixture   of   gray   tones   of   the   flooded   acacia   plains   streaked   by   the   warm   tones   -   orange-brown   –of   the   fossil   dune   alignments,   oriented WSW   -   ENE.   The   western   margin   is   distinguished   by   its   warm   tones   from   the   low   lands,   with   the   greens   of   the   shallowly   flooded high   plains   of   Diafarabe   on   the   left   bank   of   the   Diaka,   a   tributary   of   the   Niger   River,   and   the   blue   tones   of   the   Tenenkou   basin   on   the right   bank.   Here   the   separation   between   the   inland   Delta   to   the   east   and   the   fossil   Delta   to   the   west   gradually   takes   place.   South   of   the inland   Delta,   the   dry   margin   presents   a   complex   structure   dominated   by   the   main   dune   orientation   WSW-ENE      which   takes   the southern   Delta   in   a   sling   and   finds   its   strongest   expression,   to   the   east,   along   the   shore   left   of   the   Bani,   whose   course   is   locally   guided by the imposing mass of the erg of Femaye. The    eastern    edge    of    the    Delta    a    contrario    appears    very    clear    with    almost    no    transition.    It    corresponds    to    a    very    clear morphological   contact   between   the   alluvial   basin   and   sloping   sandy   erosion   surface   (10   ‰   at   the   bottom   slope   N-E   and   S-E   of   the Somadougou   hills).   The   north   of   the   Delta   corresponds   to   the   most   inundated   and   deepest   vegetation   types,   where   the   "bourgou" associations   dominate,   mingling   with   the   open   waters   of   the   Debo   Walado,   which,   leaning   on   a   W-E   oriented   structural   lock   -   the Homborian   according   to   J.   Gallais   (1966)-   closes   the   inland   Delta.   Further   north   begins   another   land,   related   and   yet   different   by   its landscapes and ecology, that of the lake region. If   the   inland   Delta   basin   appears   well   delimited   by   the   extension   of   the   flooded   associations,   it   is   far   from   homogeneous.   The complexity   of   the   map   of   the   vegetation   types   suggests   basins   with   more   purple-violet   or   blue   tones,   less   flooded   plains   with   green tones,   or,   as   in   the   Dialloubé   region   south   of   Débo   lake,   a   complex   arborescence   combining   the   pink-gray   tone   of   the   mosaics   of   the banks   that   marks   water   arms   and   the   warmer   tones   unflooded   lands.   The   main   branch   of   the   Niger,   continuing   the   slow   west-east migration   of   the   hydrographic   network,   is   now   completely   rejected   at   the   eastern   boundary   of   the   Delta.   Floodways   deriving   from   it are   subtly   intertwined   with   a   fossil   arborescence   of   channels   that   are   not   flowing   anymore,   but   whose   presence   is   marked   in   the landscapes    by    the    fossil    banks    with    specific    vegetation.   The    precise    layout    of    some    of    these    fossil    banks    towards    Dialloubé corresponds to the course of the hydrographic network that J. Gallais (1966) dates from the 3 rd  Humid.(9300 to 6900 BP)   The   VEG4   cover   contains   14,535   map   units,   distributed   into   121   vegetation   types   over   a   total   area   of   ​​2,229,950   hectares.   Of   the 121   vegetation   types,   one,   "RIVER",   represents   open   water   composed   of   5   units   (the   minor   beds   of   the   Niger,   Bani   and   Diaka   rivers, and   the   lakes   -   53,497   ha).   Another   combination,   "TB/TC",   was   created   artificially:   it   occupies   731   units   figuring   the   built   surfaces with   a   total   area   of   2   947   ha.   Finally,   there   are   13,799   vegetation   units,   which   are   distributed   between   119   vegetation   types, associations   or   mosaics.   The   vast   majority   of   mosaics   (78   out   of   92)   represent   a   gradient   between   plant   associations   with   similar   or close   flood   depth   and   are   thus   considered   "ecological".   In   a   smaller   number   of   cases   (14),   the   mosaics   span   over   contrasted   flood regimes, and are thus "cartographic" mosaics. The   average   area   of   ​​a   vegetation   unit   is   158   ha,   with   extremes   ranking   ​​from      0.3   to   12,270   hectares   (excluding   built   sites   and open   water   surfaces).   The   mean   is   strongly   influenced   by   a   few   very   large   areas   and   poorly   reflects   the   size   distribution   of   the   Delta vegetation   units:   half   of   the   units   extend   over   less   than   72.8   ha   and   only   10%   have   extended   over   more   than   369.3   ha.   Units   larger than 1,000 ha only account for 1.8% of the total area. Only 0.2% reach 2,500 ha and 0,1% exceed 5,000 ha. The   splitting   of   the   mosaics’   area   into   their   component   associations,   carried   out   by   granting   each   association   half   the   mosaic   area, makes it possible to assess the area occupied by each of the 28 plant associations (including the bank mosaic, MB*). Table  1 : Codes and names of the twenty seven vegetation associations of the Inland delta of the Niger River
Vetiver    savannas    extend    over    about    30%    of    the    area    of    the    Inland    Delta    (including    Farimaké),    followed    by    unflooded associations,   but   their   extension   depends   on   the   delineation   of   the   margins      of   the   Inland   Delta,   in   particular   the   western   margin. Then come   the   wild   rice   savannas      which   occupy   15%   of   the   area   of   the   Inland   Delta.   The   most   sought-after   rangeland   in   the   Inland   Delta, the “ burgu ”, extends over only a little more than 7%, or about 160 000 ha. If   the   same   area   assessments   are   made,   excluding   the   plant   associations   of   the   dry   lands   and   the   woody   plains   irregularly   flooded by   run-off   and   late   river   flood,   the   distribution   of   the   plant   combinations   is   slightly   different   but   does   not   call   into   question   the hierarchy   observed.    Ultimately,   the   floodplain   of   the   Delta,   the   kingdom   of   grass   and   water,   to   use   Jean   Gallais ' s   expression,   is not   the   undivided   kingdom   of   the   burgu ”.   The   Vetiver   savannas   of   lower   pastoral   value   come   first,   followed   by   the   wild   rice stands. The “burgu” only comes at the fourth rank, with less than 10% of the area of flooded grasslands.
Codes   Name of the vegetation association    Area (ha)   VOR    Mid flood, savanna,  Vetiveria nigritiana, Oryza longistaminata   197,790   OP    Deep flood wild rice,  Oryza longistaminata, Eleocharis dulcis   197,217   VSP    Shallow flood, savanna,  Vetiveria nigritiana, Hyparrhenia rufa   197,140   TA    Upland, savanna,  Andropogon gayanus, Piliotigma reticulata   153,528   VH    Very shallow flood, savanna,  Vetiveria nigritiana   148,264   O    Mid flood, wild rice plain,  Oryza longistaminata, Setaria  anceps   145,158   B    Deep flood, plain,  Echinochloa stagnina   109,636   ESP    Shallow flood, grassland,  Eragrostis barteri, Setaria anceps   99,085   VB    Very deep flood, savanna,  Vetiveria nigritiana, Vossia  cuspidata   93,109   TS    Upland, shrubby savanna,  Acacia seyal, Acacia sieberiana   77,744   P    Marginal flood,  grassland, Panicum anabaptisum   74,934   MB *   Stream bead mosaic of vegetation associations   72,662   ZB    Edges of highest floods,  Bergia suffruticosa   68,697   PAN    Mid lacustrine flood, woodland,  Acacia nilotica   61,448   PAS    Slight lacustrine flood, woodland,  Acacia seyal   58,888   EOR    Mid flood, grassland,   Eragrostis barteri   57,465   THY    Palm grove,  Hyphaene thebaica   53,908   BP    Very deep flood, plain,  Echinochloa stagnina, Vossia cuspidata   51,645   AC   Very shallow  flood, savanna,  Eragrostis barteri ,  Andropogon  canaliculatus   50,078   TD    Upland, thicket,  Diospyros mespiliformis, Acacia pennata   44,565   AG    Sandy soil, savanna,  Andropogon gayanus   40,700   TC    Upland, anthropic woody savanna,  Celtis integrifolia, Borassus  aethiopum   34,781   TB    Palm grove,  Borassus aethiopum   28,100   PAM    Deep flood, thicket,  Mitragyna inernis   23,920   TT    Upland, shrubby savanna,  Terminalia macroptera   17,033   PAR    Shallow  lacustrine flood, woodland,  Acacia raddiana    8,485   R    Irrigated  rice fields,  Oryza sativa   5,812   PAK    Very deep flood, woodland,  Acacia kirkii   5,289
Shape ArcGis Veg4 and data.rar