The   structure   of   the   database   has   been   divided   into   three   sections,   described   in   the   data   analysis:   flora,   ecology   and   production. The database is built with the software -RDBMS File Maker – which has proven efficient and relatively easy to use. The    difficulty    encountered    in    structuring    the    database    stems    from    the    fact    that    vegetation    types    are    sometimes    plant combinations   whose   characteristics   result   from   the   statistical   analysis   of   the   vegetation   and   the   observation   of   the   environment, summarized   in   tables,   and   sometimes   mosaics   of   plant   combinations.   In   the   original   study   (DELMASIG   :   J.   Marie,   2000),   we provided   only   the   characteristics   of   the   plant   combinations.   We   therefore   had   to   define   what   a   mosaic   represents   and   what   corpus   of rules   should   be   applied   to   compose   the   floristic,   ecological   and   production   characteristics   of   these   mosaics.   With   the   exception   of MB,   treated   separately   because   of   its   complexity,   the   codes   used   for   the   mosaics   are   formed   by   the   juxtaposed   acronyms   of   two elementary   plant   combinations   (e.g.   VOR/VH).   When   the   two   plant   combinations   indicated   are   ecologically   close,   because   they belong   to   the   same   level   of   flooding   or   to   adjacent   ones,    the   code   is   that   of   a   binary   mosaic   constituted   by   the   two   indicated   plant combinations.   By   convention,   the   order   in   which   the   combinations   are   indicated   places   first   the   one   corresponding   to   the   deepest flood.   If   the   combinations   have   the   same   flood   level,   alphabetical   order   prevails.   For   PAN,   PAR,   PAS,   which   are   flooded   by   local run-off   and   sometimes   by   late   river   flooding,   the   convention   has   been   adapted   as   follows.   If   one   of   these   three   associations   enters into   the   composition   of   a   mosaic   with   a   combination   that   is   regularly   flooded,   the   latter   association   prevails.   Thus   P   (level   3   ]-0.10   - 0.30])   combined   with   PAN   (level   4   ]-0.30   -0.60   ])   is   written   P/PAN   and   not   PAN/P,   according   to   the   depth   of   flood.   On   the   other hand,   if   the   associations   flooded   by   run-off   and   late   river   flood   are   combined   to   a   dry   savanna   combination   (type   TA,   TB,   ...),   the mosaic   is   written   in   the   order   of   decreasing   flood   levels   (e.g.   PAN/TA).   For   wide-gradient   mosaics,   that   is   to   say,   when   the   two associations   indicated   belong   to   distant   flood   levels,   the   indication   is   only   a   shortcut   to   note   a   more   complex   mosaic   in   which   not only   the   indicated   combinations   but   also   others   with   intermediate   flood   regimes,   participate.   For   example,   B/VSP   is   a   shortcut   to indicate   a   mosaic   that   includes,   in   addition   to   B   and   VSP,   plant   combinations   such   as   EOR,   O,   VOR.   The   difficulties   were   solved   by determining   the   characteristics   of   the   mosaic   on   the   basis   of   those   of   the   component   combinations.   Calculation   rules   have   been defined   so   that   this   can   be   done   systematically   and   automatically   on   the   basis   of   the   codes   given   to   the   combinations   and   their mosaics. However, these rules may differ, depending on the nature of the information processed. The    principle    that    guided    the    structuring    of    the    thematic    information    is    to    separate    the    attributes    of    the    28    basic    plant associations   (with   MB)   from   the   attributes   assessed   for   the   mosaics   of   associations   that   are   derived   from   that   of   the   component   plant associations.   The   relationship   between   the   source   file   and   the   resulting   file   is   performed   via   a   text   file   called   sigle.txt   that   lists   the acronyms   of   the   120   vegetation   types   (including   TB/TC,   treated   as   a   vegetation   type)   by   alphabetical   order.   When   a   mosaic composition   is   launched,   the   program   reads   the   file   sigle.txt   containing   the   acronyms.   For   each   acronym,   it   draws   the   necessary resources   from   the   source   file   and   composes   the   mosaic   by   computing   each   field   according   to   the   pre-established   rules. An   acronym with   a   single   plant   association   is   treated   as   a   mosaic   of   identical   plant   associations.   Special   "scripts"   allow   us   to   compose   tiles   by unit, by entering the acronym "by hand", which is convenient for tests. However, these rules may differ, depending on the nature of the information processed : 1   -   For   the   floristic   composition   of   the   mosaics,   it   was   decided,   regardless   of   the   nature   of   the   mosaic   (binary   or   complex   type), that   the   flora   of   the   mosaic   would   be   a   simple   "addition"   of   the   floristic   compositions   of   the   component   combinations.   The contribution   of   species   to   the   vegetation   mass   is   calculated   as   the   average   contribution   within   each   combination   listed   in   the   mosaic. In   the   case   of   a   complex   mosaic,   the   presented   floristic   profile   is   thus   a   "shortcut",   taking   into   account   only   the   "starting"   and   the "ending"   plant   associations.   This   simplification   of   information   dispenses   with   what   would   have   been,   in   particular   for   some   mosaics, long   floristic   lists   with   low   contributions   of   each   species.   Similarly,   the   indicator   value   of   the   presence/absence   of   each   species   in   the floristic   profile   of   the   association   was   abandoned   in   the   case   of   mosaics,   as   being   meaningless   in   this   case.   On   the   other   hand,   the status of a species in the mosaic is the highest  status in each of the two associations  (dominant/accompanying/occasional).  2   -   For   production   variables,   which   are   all   quantitative,   we   also   decided   that   the   values   ​​adopted   for   the   mosaics   would   be   simple arithmetic   means   of   the   values   ​​of   the   variables   of   the   two   component   associations.   Systematic   tests   for   complex   mosaics   were   carried out   with   alternative   methods,   taking   into   account   the   intermediate   association   values.   The   differences   observed   were   marginal   and did not justify the adoption of such methods. 3   -   For   ecological   variables,   however,   we   decided   to   take   into   account   the   real   complexity   of   the   mosaics.   When   the   two characterizations   of   the   mosaic   belong   to   the   same   flood   level   or   two   consecutive   ones,   that   of   the   mosaic   is      obtained   by   a   simple "average"   -   in   fact   a   combination   of   indices   as   set   out   in   the   table   below   –of   the   characterizations   of   each   component   associations.   On the   other   hand,   when   the   two   associations   belong   to   different   and   non-consecutive   flood   levels,   the   "average"   takes   into   account   the intermediate   levels.   For   example,   if   the   two   associations   belong   to   flood   levels   are   distant   from   one   level,   the   "mean"   is   established for   the   characters   of   each   of   the   two   associations   indicated,   and   also   those   of   the   intermediate   level,   with   equal   weight   given   to   each component,   which   therefore   participates   as   one   third   to   the   mosaic.   In   the   previous   example,   the   B/VSP   mosaic   must   be   understood as actually the B/LEVEL 5/VSP mosaic in which LEVEL 5 is a mosaic summarizing EOR/O/VOR. The   complexity   of   the   mosaics   is   therefore   taken   into   account   in   the   indexed   ecological   profiles.   Probability   profiles   are obtained   by   following   empirical   rules   already   used   by   Pierre   Hiernaux   for   the   determination   of   indexed   floristic   profiles   (eg   BP) from   the   probabilistic   indexed   relationships   linking   a   plant   species   (e.g. Echinochloa   stagnina )   and   a   state   of   the   variable   (e.g.   flood depth class). The combinatory results from the use of the following matrix as indicated in Table 1 Are replaced by a numerical code: +++ code 4; ++ code 3; + code 2; • code 1; 0 code 0
Cod e   Statistical significance   +++   The species is significantly  linked   to the state of the variable at  p<0.001   ++   The species is significantly  linked   to the state of the variable at  p<0.0 1  but not at p <0.001   +   The species is significantly  linked   to the state of the variable at  p<0.05but not at p <0.01      The species is  not  significantly  linked   to the state of the variable at  p<0.05   0   Sampling is not sufficient to conclude
Figure n° 1 :  Operating diagram of thematic databases FLORA part Res ource file    acronym list resulting file ECOLOGY  and PRODUCT part Resource file                  acronym list                                   resulting file      Sigle.txt   AFLORE   MXFLORE   XFLORE                       1   2   3   4   5   AECOLO     APRODUCT     MECOLO     MPRODUCT            Sigle.txt   1   2   3
The   resulting   file   is   always   in   command:   the   system   was   imagined   and   implemented   by   Isabelle   Louise   Bisson.   It   was   designed so as to make it possible to update that part of the GIS in several different ways : 1    -    the    "source"    file    may    be    modified    by    adding    files    for    new    plant    associations,    as    long    as    the    acronyms    used    are alphanumerical codes of no more than 3 characters 2 -   without adding new files, it is possible to modify any value related to an existing association file 3 -  should VEG4 be changed when updated, new mosaics could be composed simply by modifying the sigle.text list of mosaics. Example of a file processed in MX FLORE :
BP Bourgoutière  basse à  Vossia  cuspidata. Ipomoea  aquatica HA 2 3,75% Ipom_  aqu Nelsonia  canescens HA 2 3,75% Nels_ can Nymphaea lotus HA 4 3,75% Nymp_ lot Polygonum  spp. HA 2 3,75% Poly_  spp Echinochloa  stagnina HD 4 40,00% Echi_  sta Vossia  cuspidata HD 4 40,00% Voss_  cus Centrostachys  aquatica HO 2 1,25% Cent_  aqu Meremia  tridentata HO 2 1,25% Mere_  tri Sesbania  rostrata HO 2 1,25% Sesb_  ros Vetiveria  nigritana HO 2 1,25% Veti_  nig Ziziphus  spina-christi LA 3 15,00% Zizi_  spi Mimosa  pigra LD 2 80,00% Mimo_ pig Acacia  kirkii LO 2 5,00% Acac_  kir
MECOLO file with the names of the items in the database (see page 37 "Ecological variables")
Main Cover   VEG4   Map of plant associations     derived cover   FLORE1   TABLE FLORE         Request about flora     derived cover   CRUE 3   TABLE ECOLOG Y         Request about  ecology   discreet model   of floodable  areas   derived cover   SOL1 & SOL2   derived  cover    VEG 7   Map of the distribution          of vegetal species   Map of Soils   space  operator   Matrix   VEG7   Mathematical  morphology   Curves of equal  flood depth  model     1 -   calculating floodable areas   for all flood heights .  2  -   identifying the main basins 3  –   discretizing of vegetation  map  in main landscapes.   4 –   identifyi  ng the areas of useful  flood for rice crop   5 -   calculating a digital elevation model of the inner Delta   .........      map of floodable  areas for  different   levels  : 6.60 m; 6.50 m;    6,30 m; 6 m; 5.10 m  .
0 1 2 3 4 0 0 0 1 2 3 1 0 1 2 2 3 2 1 2 2 3 3 3 2 2 3 3 4 4 3 3 3 4 4 codes for the probability thresholds (plant association 1) codes for the  probability  thresholds  (plant  association 2)
Figure 2 : GIS organization for the vegetation part