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Plant diversity in a Central African rain forest: Implications for biodiversity conservation in Cameroon Data analysis The analysis focussed on family and species level floristic richness and diversity of the various life forms and forest strata within 145 plots recorded in the area. Although 11 vegetation types were identified for the Campo-Ma’an area (Chapter 2), the analysis was done on 6 main vegetation types by grouping some of the forest types for a better illustration of the diversity patterns. All coastal forest types were grouped as coastal forest, all Caesalpinioideae forests as forest rich in Caesalpinioideae, the Calpocalyx and Sacoglottis forests as forest rich in Calpocalyx heitzii and Sacoglottis gabonensis, and the mixed forests as mixed evergreen and semi-deciduous forest. The 2 plots recorded in mangroves were excluded from the analysis because mangroves form a mono-dominant community with only 4 species. In this study tree layer comprised all vascular plant species with DBH ≥ 10 cm, shrub layer (1.5 cm ≤ DBH < 10 cm) and herbaceous layer (1 cm ≤ DBH < 1.5 cm). Diversity was measured by recording the number of species (species richness) and their relative abundance in the different plots and vegetation types. This study focused on the α diversity (species richness), which is defined as the number of species within a chosen area, given equal weight on each species, and the β diversity, which is the difference in species diversity between areas or communities (Kent & Coker, 1992; Bisby, 1995). β diversity was quantified with the Shannon diversity index (H’) using all individuals above 1 cm DBH and all species per plot. Phytosociological parameters (relative density and relative frequency) and Shannon diversity index were calculated following Whittaker (1975), Kent & Coker (1992) and Magurran (1988). The SPSS package version 10.0 for Windows was used for statistical analyses. The Pearson’s correlation test was used to correlate the species richness and diversity between the various growth forms and forest layers. We compared the diversity and species richness within forest layers and within growth forms using a General Linear Model (GLM) followed by a Tukey Multiple Comparison test (P < 0.05). 3.3. RESULTS General patterns of species richness and diversity within forest types A total of 76360 trees, shrubs, climbers and other vascular plants with DBH ≥ 1 cm was recorded in 145 plots of 0.1 ha each in the various vegetation types. They belonged to 1112 species, 420 genera and 97 families. In addition, 759 species of vascular plants (herbs, hemi-epiphytes, shrubs and seedlings of tree species) belonging to 101 families and 327 genera were recorded in the subplots of 5 m x 5 m each located within the 0.1 ha plots. Overall, 1471 species of vascular plants, including ferns and fern allies belonging to 542 genera and 126 families were recorded. More than 73% of all specimens collected were identified at species level, 23% at generic level, 3% at family level and 1% unidentified. As shown in Table 3.1, the number of stems/ha for all vascular plants ≥ 1 cm DBH varied from 5798 in swamps to 6912 in the submontane forest. The number of species/ha for all vascular plants ≥ 1 cm recorded varied from 293 in swamps to 468 in the lowland evergreen forest rich in Caesalpinioideae. The Shannon diversity (H’) varied from 4.73 in coastal forests to 5.16 in forests rich in Caesalpinioideae. More than 57% of the plots have above 100 species/0.1 ha and a Shannon diversity (H’) > 4 with the most 44
Diversity patterns in the flora of the Campo-Ma’an rain forest, Cameroon: do tree species tell it all? Table 3.1 Summary of the number of species, number of families, number of stems/ha and Shannon diversity (H’) recorded in each vegetation types for all vascular plants with DBH ≥ 1 cm. Vegetation types No of species No of families No of stems/ha Shannon diversity index (H’) Coastal forest (mangroves excluded) 381 69 6208 4.73 Swamps 293 58 5798 4.58 Forest rich in Caesalpinioideae 468 68 6033 5.16 Forest rich in Calpocalyx heitzii and Sacoglottis 416 65 5990 4.93 gabonensis Mixed evergreen and semi-deciduous forest 441 66 5867 4.77 Submontane 412 64 6912 5.14 diverse and species-rich plots located in the submontane forests, forests rich in Caesalpinioideae, and forests rich in Calpocalyx heitzii and Sacoglottis gabonensis. Species richness and diversity within forest strata The number of stems/ha and the number of vascular plant species recorded were generally higher in the shrub layer (all vascular plant with diameter between 1.5 cm ≤ DBH
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Chapter 6 GENERAL CONCLUSIONS AND I
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REFERENCES
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ANNEXES
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SUMMARY Summary The fragile ecosyst
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Summary suggest that the Campo-Ma
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RESUME Résumé La biodiversité de
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Résumé nombreux auteurs qui argum
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SAMENVATTING Gildas Peguy Tchouto M
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