International Research Journal of Biological Sciences ___________________________________ ISSN 2278-3202Vol. 2(7), 25-29, July (2013) Int. Res. J. Biological Sci. International Science Congress Association 25 Dynamic of Sacoglottis gabonensis Aucoumea klaineana couple in the Congolese coast Forest (Brazzaville – Congo) Kimpouni V.1*, Loumeto J.2* and Mizingou J.3* École normale supérieure, Université Marien Ngouabi, B.P. 237, Brazzaville, CONGO Faculté des sciences, Université Marien Ngouabi, B.P. 2820, Brazzaville, CONGO Service National de Reboisement, B.P 839, Pointe-Noire, CONGOAvailable online at: www.isca.in Received 11th April 2013, revised 24th May 2013, accepted 30th June 2013Abstract The ecological markers of Sacoglottis gabonensis in the Congolese coast forest highlight that this species develops at the limit of its geographic area. This species is often associated to Aucoumea klaineana in forest typology or characterizing forest on the Atlantic littoral. It posts a degree of sociability contrary to the known data of the Gabonese forest. Moreover our study confirms the absence of the typical Biafra forests on the Congolese littoral, and the non concomitance of the distribution of Sacoglottis gabonensis and Aucoumea klaineana.Keywords: Costal forest, ecology index, geographic area, Sacoglottis gabonensis, Aucoumea klaineana. IntroductionAucoumea klaineana forests of the Atlantic littoral of the Nigero-Cameroono-Gabonese area are often characterized, in their typology, like facies with Aucoumea klaineana and Sacoglottis gabonensis (Baill.) Urban in co-dominance or monodominance1-4. Many data confirm the coupling from these two species like the symbol with the endemism low-Guinean with the Guineo-Congolese area, and especially characteristic of the “biafréennes” forests of the Atlantic element of the Nigero-Cameroono-Gabonese. In spite of Sacoglottis gabonensis presence on the Congolese littoral, the existence of the forests dominated by this species remains an enigma in this area. The typology studies on the forest facies with Aucoumea klaineana and Lophiraalata of the Congolese littoral, show that the ecological parameters raised on Sacoglottisgabonensis, are contrary to the known data of the Cameroono-Gabonese littoral1,6-9. Thus, the objective of this study is answer interrogations on existence of typical “biafréenne” forest on the Congolese littoral. This work is focused on the ecological and structural markers of Sacoglottis gabonensis in the Aucoumea klaineanaforest of the Congolese littoral. Physical data of the Congolese littoral: Climate: The various forest facies of the Congolese littoral develop under a climate qualified subequatorial or low Congolese6,7,10-16. Its main characteristics are: i. precipitations average ranging between 1200 and 1400 mm/year6,7,14-16, ii. one dry and fresh season of 4 - 5 months (May-September) and a rainy and hot season from October to May, with a very marked attenuation of precipitations during January and February1,15,16, iii. an annual average temperature of 25°C and an annual thermal amplitude of 4–6°C1,15,16. Soils: The general presentation of the soils of the area shows that they belong primarily to the subclass of the impoverished psammitic and ferrallitic soils17. Their description distinguishes three principal horizons: i. humus-bearing horizon (A1) of approximately 40 cm thickness. It consists of two pennies horizons: a surface horizon (0 – 10 cm), covered by a thick layer with litter (10 – 15 cm) often made up of the three horizons L, F and H. the subjacent horizon (10 – 40 cm) is distinguished from the precedent, primarily by its physical properties (compaction, structure) which are different; i. horizon of transition (A3 or B1), of colour brown dark having a thickness varying between 15 and 25 cm; iii. horizon of accumulation (B2), yellowish colour brown. It is characterized by a content of clay slightly more important than in the overlying horizons. Vegetation: The description and the characteristics of the natural vegetation and the flora of the Congolese littoral are reported by many authors6-10,12-14,18,19. Material and MethodsLocalization of the zones of the botanical statements: The various statements of inventory and floristic investigations are carried out in the sectors identified under the denominations of Kayes “A” and Kayes “B” (figure-1). These contiguous sectors cover each one an area going of the Atlantic border to the buttresses of Mayombe. The geographical contact of Kayes “A” is presented below: i. 11° 28’ 34’’.33 E – 03° 53’ 13’’.19 S, ii. 11° 39’2 2’’.19 E – 03° 53’ 13’’.21 S, iii. 11° 39’ 22’’.70 E – 03° 55’ 53’’.89 S, iv. International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(7), 25-29, July (2013) Int. Res. J. Biological Sci. International Science Congress Association 26 11° 40’ 04’’.66 E – 03° 55’ 53’’.37 S, v. located at the junction of the line of coordinate East of point 4 with sea border, vi. located at the junction of the line of coordinate East of point 1 with sea border. Figure-1a Localization of the zones of inventories and botanical prospection in the forests of the littoral and Mayombe (Western Congolese littoral sector) Figure-1b Localization of the zones of inventories and botanical prospection in the forests of the littoral and Mayombe (East Congolese littoral sector and buttresses of Mayombe) Methodology: The investigations on Sacoglottis gabonensisand Aucoumeaklaineana are based on two complementary approaches. They rest on: i. data collected on the station: inventories of vegetable biodiversity, ethnobotany investigations and botanical prospection; ii. bibliographical compilation: phytosociological and inventories flora data analysis are available. Inventories: The inventories are carried out according to the methodology of the transects, in forest facies of various ages and degree of disturbance. The trees selected have a diameter at breast height (dbh at 1.30 m from the ground) equal or higher than 10 cm. According to the dbh, the listed trees set out again in 9 classes of diameter, whose progression is of 10 in 10 cm. The 9th class gathers all the individuals having a dbh 90 cm. During the botanical prospection, all the Sacoglottisgabonensisindividuals are listed. The raised parameters are the biological type, of dbh, and the degree of sociability (isolated or gregarious individual). Data on the statements of floristic inventory: The floristic inventory of the monospecific forest with Aucoumeaklaineanaof the Congolese littoral is based on 22 statements. According to the surface of inventory and dbh, they divide into 3 category.13 raised of 1 ha for the trees of dbh 10 cm; 1 statement of 1.2 ha for the trees of dbh 10 cm; 8 statements of 0.04 ha for the trees of dbh 5 cm but lower than 10 cm. Results and DiscussionThe results presented in table-1 characterize the floristic statements of higher or equal to surface 1 ha; the statements of low area did not highlight the specimens of Sacoglottisgabonensis. This floristic inventory highlights 42 trees of Sacoglottisgabonensis for an area of approximately 13 ha, that is to say an average 3.2 trees.ha-1 (table-1). In this woody settlement, the densities of Sacoglottisgabonensis vary from 1 to 37 trees.ha-1; while basal area oscillate, of the young facies to oldest, between 0.75 and 1.8 m.ha-1. These specimens are distributed in 6 diameter classes, with a better representation of classes 1 (57.14%) and 2 (23.81%). They include almost 81% of individuals. The basal area by density report, which is an ecological index making it possible to characterize a population or a species, its lies between 0.45 and 5.7. The relative frequency of Sacoglottisgabonensis is on the other hand very weak. As a whole, the ecological markers of Sacoglottisgabonensisare parameters described as weak (table-1). The clearest traces are obtained in the young forest facies under installation where Aucoumeaklaineana typify a facies almost monospecific, as shows it statement 1 of the sector Kayes “B”. On the contrary, the oldest or disturbed forest stages, has a weaker presence of Sacoglottisgabonensis. International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(7), 25-29, July (2013) Int. Res. J. Biological Sci. International Science Congress Association 27 The botanical prospection made it possible to note a space and temporal distribution disparate specimens of Sacoglottisgabonensis. This species often meets in zone of savanna like precursor of colonization by Aucoumeaklaineana. The individuals observed are, as Table-1shows it, of low diameter with a clear predominance of classes 1 and 2, and low branchy. The maximum diameter recorded on three isolated specimens, in grassy savannas with Hyparrheniadiplandra and shrubby lies between 45 and 60 cm to 1.30 m of the ground. The phytopharmacological, traditional uses of its bark, and artisanal of the physical properties of its wood make Sacoglottisgabonensis well-known and is exploited by the populations10,20. The floristic composition of the various statements is very variable. It is function of the stage of development and the degree of disturbance of the forest4,7,8,9. In all the cases, the principal species is Aucoumeaklaineana. The ecological parameters of Sacoglottisgabonensis, compared to other species of the woody vegetation, show that this species does not accompany Aucoumeaklaineana in the forests by the Congolese littoral6,7,8,9. On the other hand, one notes on the Gabonese littoral perfect a co-dominance between Sacoglottisgabonensis and Aucoumea klaineana or with Lophira alata in the characterization of the forest facies, on the one hand, and, on the other hand, of the typical facies with Sacoglottisgabonensis1,3,4,10. That is not observed on the Congolese littoral. This species has behaviour different in these two parts of its area dispersion. The floristic statements being made between the Atlantic Ocean and the buttresses of Mayombe, the got results show that the Sacoglottisgabonensis area is restricted with the littoral fringe, whereas that of Aucoumeaklaineana reaches the buttresses of Mayombe. This reduced space-time distribution of Sacoglottis gabonensis is at the origin of the weak frequencies observed for the whole of the region6,7. Indeed, this species which is rather abundant in the young stages of installation of the forest with Aucoumeaklaineana, rarefies as progresses forest dynamics towards the old stages, as the curve of density offigure-2 shows it. The data analysis on the densities shows that Sacoglottis gabonensis badly supports the interspecific competition8,9,21. The dendrometric analysis reveals a bad recruitment of Sacoglottisgabonensis in the various classes of diameter. Indeed, except a statement which has 2 trees, it is recorded in the 4/5 only one class of diameter and a tree specimen (table-1). The inexistence of the individuals in certain classes of diameter reveals its bad regeneration on the Congolese littoral5,6,22. That is confirmed by the absence, in most statements, individuals whose diameter lies between 5 and 10 cm6,7. The data of basal area show that Sacoglottisgabonensis occupies a weak surface per unit of area. This one is in fluctuating from one statement to another (figure-2). The best occupancy rates of the soil are observed in the statements with strong density of Sacoglottis gabonensis or having trees of large diameter. This parameter coupled with biological specificities of the species, in particular its lack of interspecific competitiveness, is a factor limiting to its regeneration under dense cover. This observation is supported by the index of report ST/D (basal area /density). Indeed, the values are very weak and lower than 1, for the majority (Figure-2).Sacoglottisgabonensis is characterized on the Congolese littoral, whatever the stage of development forest facies, by weak parameters of density and diameter. Table-1 Ecological main features of Sacoglottis gabonensis in the forests of the Congolese littoral Sector Number of statements N° of order and area Structure and ecologic parameters of Sacoglottisgabonensis N° of statement Area (ha) Density (trees.ha-1) Classes of d.b.h. Density (%) Basal area (m.ha-1) Basal area /density Relative frequency Kayes B 3 1* 1 37 1, 2, 3, 4 7,06 1,80 0,73 3 2* 2 2 0,63 0,07 0,45 3* 1 8 0,29 0,50 0,77 6 3 1 2 0,45 0,05 0,48 2 5 1 9 0,53 0,75 5,70 Kayes A 5 4 - - weak weak weak weak 6 1,2 (*) Reference No. 8, 9, 4, 6. International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(7), 25-29, July (2013) Int. Res. J. Biological Sci. International Science Congress Association 28 Figure-2 Evolution of the structural and ecological parameters of Sacoglottis gabonensis (density and basal area) In spite of the mechanisms of dissemination which are respectively endozoochore for Sacoglottisgabonensis (mainly by the elephant: Loxodontaafricanacyclotis) and anemochore for Aucoumeaklaineana, these two taxa have biological and ecological behaviours very similar6,4,23,24. These qualified species pioneers and the heliophilous ones are at the base of the colonization of savannas by the forest. In this dynamics of occupation of the soil, the progression is assured almost exclusively by Aucoumeaklaineana which forms a monospecific pioneer face. Though these two species are badly adapted to the interspecific competition, taking into consideration Sacoglottisgabonensis, their ecological characteristic seems to be more vulnerable. The endozoochore dissemination seems to justify the precocity of this species in coastal savannas. Ecological characteristics of Sacoglottis gabonensis in the forest facies of the Congolese littoral, compared with those noted in the other zones of its dispersion area (ex: Gabonese littoral), show that this species seems badly adapted to the conditions of this station. This species which has a primarily low-Guinean distribution is restricted with the sector of the littoral of the Atlantic element of the Nigero-Cameroono-Gabonese area. In spite of a noticed presence, the conditions of an optimal development are not met on the Congolese littoral. The values of all its ecological parameters mentioned seem to prove that it would be found in extreme cases of its distribution area. This seems more obvious by integrating this data in the chorology system of the Guineo-Congolese area25,26,27. Sacoglottisgabonensis is a low-Guinean endemic species whose optimum of development is in the Cameroono-Gabonese forest sector of the Atlantic element of the Nigero-Camerouno-Gabonese area10. The comparison of the various ecological and structural parameters, characterizing Sacoglottisgabonensis on the Congolese littoral, shows that these forests form the skirt of biafréenne forest, which is the typical ecosystem of the Atlantic element of the Nigero-Cameroono-Gabonese area1,2,4. The development of Sacoglottisgabonensis would be correlated at the rhythm and the precipitation degree. Headings: Aucoumea klaineana forest of the Congolese coast ConclusionThe typology of the forest facies of the Congolese littoral shows that those are primarily in Aucoumeaklaineana in the first stages of development. These formations are definitely different from those of the Cameroono-Gabonese littoral, where the principal species, Aucoumeaklaineana and Sacoglottisgabonensis, are Co-dominant, or characterize facies individually. The supposed importance of Sacoglottisgabonensis in the formations with Aucoumeaklaineana of Congolese littoral is not found. To the phytogeographical plan, the various analyzed ecological parameters bring the proof on the southern limit of the geographical area of Sacoglottisgabonensis. Consequently, the forests with Aucoumeaklaineanawould be located at the edge of the Cameroono-Gabonese area of the Atlantic element. Notwithstanding the presence of Sacoglottisgabonensis within their floristic woody, the forests of the Congolese littoral are almost with the margin of the development area of this species. The data obtained on Sacoglottisgabonensis show that its duality with Aucoumeaklaineana is not proven in the floristic 0,010,11010012345relevés floristiqueslog densité - ST - ST/D Densité Surface terrière ST/D International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(7), 25-29, July (2013) Int. Res. J. Biological Sci. International Science Congress Association 29 contribution of the Congolese littoral, as it is the case in its field of optimal development. In our region, Sacoglottisgabonensisadopts an evolving degree of sociability in an opposite way to that observed in the Cameroono-Gabonese forest, of the Nigero-Cameroono-Gabonese area of the Atlantic element. So the analysis of the ecological and structure markers ofSacoglottisgabonensis confirms the inexistence of true forest facies characteristic of the biafréenne forest. References1.Aubréville A., Principe d’une systématique des formations végétales tropicales, Adansonia,5(2), 153-196 (1965) 2. Normand D., Forêts et bois tropicaux, Collection Que sais-je ? PUF, (1971)3. Saint-Aubin (de) G.P., La forêt du Gabon, CTFT, Publ. N° 21, 1-208 (1963)4. 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