2.1. 4. Data processing
All data recorded have been were entered into the computer and
analysed in Excel and in ArcGIS 9.2.
2.1.4.1. Floristic richness
To record plant species richness, a systematic list of plant
species encountered was established. The number of families, genera and species
identified was listed. For each species, the morphological type was also noted.
Examples of morphological data collected included tree, shrub, woody liana,
herbaceous liana, herb and fern
2.1.4.2. Quantitative study of the flora
Quantitative assessement of different observed features was
based on tree identified in different habitat types using DBH data, average
height (Hm), basal area (BA), the relative dominance (RDO) and the relative
density (RD).
Then determination of the diversity and equitability (H 'and
Hmax) of different habitat types was made by calculating the Shannon index for
each segment along the permanent transect. Hence, parameters measured for
plants with DBH = 10 cm and diversity are:
4 (d= diameter of the individual); (BA in m2/ha)
Page 16
Number of indiv. of a species or a familly
Total mumber of indiv. BA of a species
100
Do R =
. ×
Total BA of all the identified species Shannon's indice of
diversity, H
H = - Ó Pi (ln Pi)
Pi = proportion of the'species i over the total number of the
species S.
Shannon's equitability (EH) can be calculated by dividing H by
Hmax (here Hmax = lnS). Equitability assumes a value between 0 and 1 with 1
being complete evenness.
EH = H / Hmax
= H /lnS
The basal area provides information on the area occupied by
sections of truncks at 1.30 m above the ground.
The abundance of taxa is calculated to provide information on
the number of individuals of a species or family as well as information on how
to determine the relative density of taxa. The basal area was also used to
calculate the dominance. This reflects the size of individual plants and allows
highlighting taxa that occupy the most space in the vegetation.
Diversity of taxa is assessed taking into account the number
of individuals within a species or family or in a community. It is also called
specific heterogeneity and it is a unique characteristic at the level of
biological organization of a community.
Thus, a vegetal community is diversified when it comprises a
large number of plant species or families.
2.1.4.3. Vegetation stratification
Vegetation strata were determined according to the following
considerations: Superior tree layer (A): > 30 m - 40 m;
Average tree layer (B): 25 to 30 m;
Inferior tree layer (C): 15 to 20 m;
Shrub: 4 to 10 m.
Biodiversity survey of Mwaro corridor, Altitudinal
distribution of the vegetation and assessment of Gorilla food
availability
2.1.4.4. Geographic data
The geographical coordinates collected by GPS were downloaded
on a computer. We used Arc Map and Arc Catalog ArcGIS 9.2 software packages to
make shapefiles delimitation of vegetation types, animals and signs of human
activity on the transect. This, in combination with satellite image of Mikeno
sector and other shapefiles available at IGCP Goma office, allowed us to
produce various maps included in this report.
| 
