Structural Characteristics and Forest Sites Indentification in Pahou Forest Reserve, South-Benin
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BOIS ET FORÊTS DES TROPIQUES, 2011, N° 308 (2) 47 STRUCTURES ET INDICATEURS ÉCOLOGIQUES Structural characteristics and forest sites indentification in Pahou forest reserve, South-Benin Augustin Kossi N. Aoudji1 Armand Sèdami Igor Yêvidé1 Jean Cossi Ganglo1 Gilbert Atindogbé1 Mireille S. Toyi1 Charles de Cannière2 Anathase Hessou Azontondé3 Victor Adjakidjè4 Bruno de Foucault5 Brice A. Sinsin1 1 Faculté des sciences agronomiques Université d’Abomey-Calavi Département d’aménagement et gestion de l’environnement 01 BP 526, Cotonou République du Bénin 2 Université libre de Bruxelles 50 avenue Franklin Roosevelt 1000 Bruxelles Belgique 3 Institut national des recherches agricoles du Bénin 01 BP 884, recette principale Cotonou République du Bénin 4 Faculté des sciences et techniques Université d’Abomey-Calavi 01 BP 526, Cotonou République du Bénin 5 Faculty of Pharmaceutic and Biological Sciences Départment of Botany BP 83 59006 Lille Cedex France Photograph 1. Chromolaena odorata and Triumfetta pentandra plant community. Photograph J. C. Ganglo. BOIS ET FORÊTS DES TROPIQUES, 2011, N° 308 (2) A. K. N. Aoudji, A. S. I. Yevide, 48 STRUCTURES & ECOLOGIC INDICATORS J. C. Ganglo, G. Atindogbé, M. S. Toyi, C. De Cannière, A. H. Azontondé, V. Adjakidjè, B. de Foucault, B. A. Sinsin RÉSUMÉ ABSTRACT RESUMEN CARACTÉRISTIQUES STRUCTURELLES STRUCTURAL CHARACTERISTICS AND CARARACTERÍSTICAS ESTRUCTURALES ET IDENTIFICATION DES STATIONS FOREST SITES INDENTIFICATION IN E IDENTIFICACIÓN DE ESTACIONES FORESTIÈRES DANS LA RÉSERVE PAHOU FOREST RESERVE, SOUTH-BENIN FORESTALES EN LA RESERVA FORESTAL FORESTIÈRE DE PAHOU, AU SUD DE PAHOU EN EL SUR DE BENÍN DU BÉNIN L’étude phytosociologique de la forêt The study was carried out in the Pahou El estudio fitosociológico del bosque classée de Pahou au Sud du Bénin a été forest reserve in southern Benin as a con- protegido de Pahou en el sur de Benín, réalisée dans une perspective de gestion tribution to sustainable management of se llevó a cabo enfocándolo al manejo durable. L’évaluation des communautés this forest. Plant communities’ assess- sostenible. La evaluación de las comuni- végétales a été menée suivant une ment was made using the synusial dades vegetales se realizó mediante un approche de phytosociologie synusiale approach to phytosociology. Soils were análisis de la fitosociología sinusial inte- intégrée. Les sols ont été caractérisés characterized according to their pedolog- grada. Se caraterizó los suelos en base al d’après leurs profils pédologiques et ical profiles and physico-chemical prop- perfíl edafológico y su naturaleza fisico- leurs propriétés physico-chimiques. Les erties. Silvicultural plantations parame- química. Los parámetros selvícolas se paramètres sylvicoles ont été collectés ters were studied using temporary sam- cosecharon en parcelas de muestreo au sein de placettes temporaires, cha- ple plots of 300 m² each in representa- temporales, de 300 m² cada una, esta- cune de 300 m² de surface, installées au tive sites of the forest. This study allowed blecidas en sitios representativos del sein de sites représentatifs de la forêt. to identify and to describe five phyto- bosque. Este estudio ha permitido iden- Cette étude a permis d’identifier et de coenoses (plant communities). Two hun- tificar y describir cinco fitocenosis (comu- décrire cinq phytocénoses (communau- dred and forty-seven (247) species were nidades vegetales). Se inventariaron tés végétales). Deux cent quarante-sept found in the undergrowth of Acacia auri- doscientas cuarenta y siete (247) espe- (247) espèces de plantes ont été inven- culiformis plantations in Pahou forest cies de plantas en el sotobosque de toriées dans le sous-bois des plantations belonging to two hundred and nine (209) plantaciones de Acacia auriculiformis del d’Acacia auriculiformis de la forêt de genera and seventy-one (71) families. bosque de Pahou, perteneciendo a dos- Pahou ; elles appartiennent à deux cent The mean annual increment in diameter cientos nueve (209) géneros y setenta y neuf (209) genres et soixante et onze and height of the plantations ranged una (71) familias. Los incrementos (71) familles. Les accroissements from 1.2 to 3.1 cm/year and 1.4 to medios anuales en diámetro y altura moyens annuels en diamètre et en hau- 4.2 m/year, respectively, indicating that variaron respectivamente entre 1.2 a teur variaient respectivement de 1,2 à acacias plantings of Pahou forest are 3.1 cm/año y 1.4 a 4.2 m/año. Estos 3,1 cm/an et 1,4 à 4,2 m/an. Ces résul- among the most productive in West resultados muestran que las plantacio- tats ont montré que les plantations Africa. The relationships between ecolog- nes de acacias de Pahou están entre las d’acacias de Pahou sont parmi les plus ical factors and productivity of the differ- más productivas del Africa occidental. productives d’Afrique de l’Ouest. Les ent plant communities enabled to iden- Las relaciones entre los factores ecológi- relations entre les facteurs écologiques tify and map four forest types among cos y la productividad de las diversas et la productivité des différentes commu- which the most productive was repre- comunidades vegetales permitieron nautés végétales, ont permis d’identifier sented by the Barteria nigritana – Rau- identificar y cartografiar cuatro estacio- et de cartographier quatre types de forêts volfia vomitoria plant community, while nes forestales, la más productiva dont la plus productive est représentée the least productive is the biotope sup- estando representada por la comunidad par la communauté végétale Barteria porting Axonopus compressus – Scleria vegetal de Barteria nigritana y Rauvolfia nigritana et Rauvolfia vomitoria et la depressa plant community. Recommen- vomitoria, y la menos productiva siendo moins productive par la communauté à dations are given on the use of these la comunidad de Axonopus compressus y Axonopus compressus et Scleria phytosociological indicators as tools for Scleria depressa. Se recomienda el uso depressa. Des recommandations ont été sustainable forestry management. de estos indicadores fitosociológicos faites pour utiliser ces indicateurs phyto- como instrumentos adecuados para el sociologiques en tant qu’outils de ges- Keywords: phytosociology, biodiversity, manejo sostenible del bosque. tion durable de la forêt. dendrometry, synusia, Benin. Palabras clave: fitosociología, biodiversi- Mots clés: phytosociologie, biodiversité, dad, dasonomía, sinusia, Benín. dendrométrie, synusie, Bénin. BOIS ET FORÊTS DES TROPIQUES, 2011, N° 308 (2) 49 STRUCTURES ET INDICATEURS ÉCOLOGIQUES Introduction respect to the planted acreage: about 10,000 hectares (ha). Despite its high importance, A. auriculiformis had deserved The basic objectives of the majority of forest plantation little interest in research in the country. Indeed in Benin programs in Benin are to address the shortage of natural for- sound research works that can profitably guide silvicultural est resources in the country, to produce high quality wood practices are still lacking. Especially, in Pahou forest reserve and firewood to supply the population’s needs and therefore where A. auriculiformis firewood plantations were estab- to reduce the pressure on natural forests. Any sustainable lished, the prevailing management plan was not based on management of forest resources must be based on the forest research results, hence, of limited use. It is therefore results of forestry research, especially forest site identifica- important to fill research gaps to help for sustainable man- tion and a sound knowledge of their potentialities and con- agement of the country’s forest resources. Since phytosociol- straints so that appropriate silvicultural techniques can be ogy has been introduced in Africa (Lebrun, 1947), it has applied. Among the most planted exotic trees in Benin, been used for various purposes including natural resources Acacia auriculiformis was introduced in the 1980s and since management. The study of natural undergrowth of forest then, has been planted in several parts of the country. Acacia plantations was done by many authors to appraise the rela- auriculiformis, a fast-growing medium sized tree species tionships between undergrowth plant communities, planta- (Hulikatti, Madiwalar, 2011), is a leguminous tree of the tion productivity and ecological factors (N’Zala et al., 1997; sub-family of Mimosoidae native to Australia (North- Loumeto, 1999; Ganglo et al., 1999; Noumon, Ganglo, Queensland), Papua New Guinea and the Moluccas Islands 2005; Ganglo, De Foucault, 2006; Aoudji, Ganglo, 2006). in Indonesia (Sahri et al., 1998). It can survive on many soil From these studies, clear relationships were established types such as ferralitic soils, ferruginous soils, heavy clayish between forest productivity, ecological factors and non-pio- soils, nutrient poor soils, fertile soils… Apart from the gov- neer undergrowth plant communities in particular. Therefore, ernmental plantations, A. auriculiformis is considerably phytosociology has been shown as a reliable tool for forest planted by smallholder farmers because of its capacity of management (Ganglo et al., 1999; Ganglo, 2005; Ganglo, soil conservation and useful products, especially poles. De Foucault, 2006). In the light of these findings, the Moreover, tables, chairs, and armchairs of Acacia timber hypothesis was formulated that plantation productivity wood are more and more found in several parts of Benin. varies with the biotopes of the undergrowth non-pioneer Because of its usefulness, A. auriculiformis has been