Impact of Abiotic Factors on Woody Communities Distribution in Peri-urban Wetlands of Yaoundé, Cameroon

Abstract

Variations in spatial distribution of tree species groups according to environmental factors were assessed in peri-urban wetlands on Yaounde. In particular, swamp forests are fragile formations with floristic and ecological specificities with the need for conservation. The flora data collection was carried done using the Braun-Blanquet method of 30 rectangular phytosociological surveys of 25 mx 20 m. Dendrometric measurements were taken on five woody groups which are Mitragyna stipulosa and Raphia mombuttorum group (GI); Raphia mombuttorum and Alchornea cordifolia group (GII); Raphia mombuttorum and Alstonia boonei (GIII); Mitragyna stipulated and Uapaca guineensis group (GIV) and Uapaca guineensis and Raphia mombuttorum group (GV). R software was used to discriminate clusters and perform principal component analysis. Shannon wiener diversity index were calculated for each cluster. In total, 45 plant species divided into 44 genera and 24 families were identified. The specific diversity is low in the five woody plant groups identified. The spatial distribution of these woody plant groups does not only depend on the heterogeneity of edaphic conditions but is also determined by microtopography and anthropization. Thus, the group of Raphia mombuttorum and Alstonia boonei and the group of Uapaca guineensis and R. mombuttorum with little human impact and occupying the clay-textured soils of steep-sided land with poor drainage present a stable structure. On the other hand, the grouping with Mitragyna stipulosa and R. mombuttorum ; the group with R. mombuttorum and Alchornea cordifolia and the group with M. stipulosa and U. guineensis which are highly anthropized and developed on clayey-sandy textured soils of flat, well-drained land are formations with an unbalanced structure. Despite human activities affecting the integrity of the groups, the swamp forests under study have great ecological value.