[en] Landscape Ecological Survey of the Bipindi-Akom II ... - ITTO

Next to to the detailed description of the sample points, the vegetation structure and land use along
the transects was indicated on drawings. These drawings give insight in the mosaic of the
vegetation in the different mapping units. In the second phase of the Lul project, will study these
mosaics are studied in more detail. Also some 20 incomplete or so-called 'quick releves' were
described. These incomplete descriptions do not support the classification of the vegetation, but
help to investigate the relations between vegetation and abiotic factors. Moreover, they are of
cartographic importance.
All vegetation data have been been stored in in TURBOVEG, a software package package for input, processing and
presentation ofphytosociological data (Hennekens, 1995). The output of this package is, in contrast
to TROFOLIN (Touber et al., 1993), compatible with vegetation classification programmes like
TWINSPAN (Hill, 1979a), SHAKE SHAKE (Tongeren, unpubl.), unpubl.), DECORANA (Hill, (Hill, 1979b) and
CANOCO (ter Braak, 1988).
3.4 CLASSIFICATION
Based on the variation observed within the TCP research area, preliminary classifications were
drafted for landforms, soils and vegetation. To describe the landscape as a complex of these
attributes, the relations between landforms, soils and vegetation types were studied by means of
cross-tables. cross-tables. The aim of of this exercise exercise was to trace trace the the parameters of the the abiotic environment environment which
may best best explain the the variation variation in vegetation types. Based on on these analysis, the landforms, soils
and vegetation classifications classifications were slightly modified to attain an optimal 'ecological' 'ecological' fit.
The classification classification of landforms is based on differences in relief characteristics, i.e. slope length,
slope steepness, relief intensity, and the number of interfluves. These characteristics are important
in the light of land utilization. utilization.
The classification of soils in the TCP research area is primarily based on soil drainage and soil
texture. Soil depth and stoniness are other differentiating criteria but could not be used at this scale.
Soil drainage and texture are found to have a correlation with vegetation in the TCP research area.
As soil texture and soil drainage are indicators for moisture availability, they are two of the
functional soil parameters for land evaluation as well.
The classification of the vegetation of the area was done by means of 'tabular comparison' of the
releve data using the computer programme TWINSP AN (Hill, 1979a). The programme performs
a multi-variate analysis of vegetation data and produces a hierarchical classification of both sample
points and species. Manual refinement of this this classification included the reallotment of a limited
number of borderline releves. Also some 11 releves were excluded from analysis because they
proved to represent either intermediate situations on the highest level of classification, or
represented ecologically ecologically aberrant aberrant situations situations that were not not considered relevant to the the reconnaissance
survey.
The cover values of of the three structural layers, i.e. i.e. tree, shrub and and herb layer, layer, have been combined combined
into one value for each species. species. Four coverage classes were used, 0-5%, > 5-25%, > 25-50% and
> > 50-100% cover, regardless of of the the abundance of the species. For classification of vegetation on
a reconnaissance scale, this is considered sufficiently detailed.
The classification by TWINSPAN is primarily based on the floristic composition of the sample
plots. Next, a a synecological interpretation of the vegetation types discerned has been carried out out
on the basis basis of the environmental data collected at the different plot sites.
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