89
high in the Douala port (Wouri river). Baltzer et al. (1995) explained the local stability of salinity in the mangrove of Wouri river estuary by the existence of stabilizing
factors. Din (2001) associated the distribution of salinity in this estuary with three
areas of mangrove vegetation structures:
– Seawaters predominance with a salinity between 15‰ and 20‰ coincide with
areas of pioneer vegetation largely dominated by Rhizophora spp. and sometimes Nypa fruticans in degraded recolonization zones;
– Intermediate waters with a salinity between 5‰ and 10‰ characterize the
regressive series composed of small stunted Rhizophora generally associated
with Acrostichum aureum and Dalbergia ecastaphyllum or Hibiscus tiliaceus;
– Low salinity waters with concentrations between 0‰ and 5‰ sheltered in the
river front large Rhizophora spp. trees and in the transitional zone, a forest vegetation dominated by Guibourtia demeusei or Cynometra mannii or species of
Arecaceae family in degraded areas.
The salinity of soil water is much higher. Important values were found in the
Avicennia germinans stands. The distribution of forest plant species follows the
salinity gradient. True mangrove plants tolerate medium level of salinity while mangrove associate plants are commonly found in low salinity areas (Din et al. 2002).
Salinity also varies within the sediments (along a core), the surface portions being
less salty.
3.3 Mangrove Composition
Mangrove landscapes in Cameroon are slightly different in structure from other
mangrove ecosystems in the Gulf of Guinea, but the composition remain the same.
The flora and fauna are not very diversified in comparison with other types of forest
in the country.
3.3.1 Flora
The flora of the Cameroon mangroves and associates presents 63 species divided
into 54 genera and 29 families. The herbaceous stratum represents less than 1% of
all vegetation. There are seven indigenous species consisting of Acrostichum aureum
L., Avicennia germinans (L.) Stearn, Conocarpus erectus L., Laguncularia racemosa (L.) Gaertn. F, Rhizophora racemosa GFW Meyer, R. harrisonii Leechman,
and R. mangle L. Nypa fruticans Wurmb. is often considered as an introduced species from Indo-Malaysian mangroves (Din 2001).
These previous species, considered as true mangrove species live in association
with others considered like associates (Tomlinson 1986). Most frequent plant species include Alchornea cordifolia Müll. Arg., Annona glabra L., Anthocleista
3 Impact of Urbanization on the Evolution of Mangrove Ecosystems…
high in the Douala port (Wouri river). Baltzer et al. (1995) explained the local stability of salinity in the mangrove of Wouri river estuary by the existence of stabilizing
factors. Din (2001) associated the distribution of salinity in this estuary with three
areas of mangrove vegetation structures:
– Seawaters predominance with a salinity between 15‰ and 20‰ coincide with
areas of pioneer vegetation largely dominated by Rhizophora spp. and sometimes Nypa fruticans in degraded recolonization zones;
– Intermediate waters with a salinity between 5‰ and 10‰ characterize the
regressive series composed of small stunted Rhizophora generally associated
with Acrostichum aureum and Dalbergia ecastaphyllum or Hibiscus tiliaceus;
– Low salinity waters with concentrations between 0‰ and 5‰ sheltered in the
river front large Rhizophora spp. trees and in the transitional zone, a forest vegetation dominated by Guibourtia demeusei or Cynometra mannii or species of
Arecaceae family in degraded areas.
The salinity of soil water is much higher. Important values were found in the
Avicennia germinans stands. The distribution of forest plant species follows the
salinity gradient. True mangrove plants tolerate medium level of salinity while mangrove associate plants are commonly found in low salinity areas (Din et al. 2002).
Salinity also varies within the sediments (along a core), the surface portions being
less salty.
3.3 Mangrove Composition
Mangrove landscapes in Cameroon are slightly different in structure from other
mangrove ecosystems in the Gulf of Guinea, but the composition remain the same.
The flora and fauna are not very diversified in comparison with other types of forest
in the country.
3.3.1 Flora
The flora of the Cameroon mangroves and associates presents 63 species divided
into 54 genera and 29 families. The herbaceous stratum represents less than 1% of
all vegetation. There are seven indigenous species consisting of Acrostichum aureum
L., Avicennia germinans (L.) Stearn, Conocarpus erectus L., Laguncularia racemosa (L.) Gaertn. F, Rhizophora racemosa GFW Meyer, R. harrisonii Leechman,
and R. mangle L. Nypa fruticans Wurmb. is often considered as an introduced species from Indo-Malaysian mangroves (Din 2001).
These previous species, considered as true mangrove species live in association
with others considered like associates (Tomlinson 1986). Most frequent plant species include Alchornea cordifolia Müll. Arg., Annona glabra L., Anthocleista
3 Impact of Urbanization on the Evolution of Mangrove Ecosystems…