Diversité floristique sous canopée en plantation forestière de Mangombe-Edea (Cameroun)

Floristic diversity under canopy in forest plantation of Mangombe-Edea (Cameroon). Trees plantation of Mangombe is situated in rain forest of low altitude. Six plots among which one of Mansonia altissima (A.Chev.) A.Chev., 2 of Lovoa trichilioides Harms, 3 of Terminalia ivorensis A.Chev. and one perturbed natural forest are concerned by this study. The work consisted to the evaluation of the floristic diversity under canopy in order to appreciate the influence of forest plantation on natural regeneration. A total of 26 families, 42 genders and 46 species were censured. Meliaceae and Apocynaceae are present in all the plots. In plot one of T. ivorensis, M. altissima and natural forest, the low value of equitability of Pielou traduces the dominance of flora by few species and the transitory situation of the ecosystem. On contrary the rest of plots present a good repartition of individuals among the species. One can notice a weak organization of the ecologic system in M. altissima plot, this corresponds to favourable conditions of environment for installation of many species represented by a few number of individuals. Shannon indices, relatively low in plot one of T. ivorensis characterize an ecosystem where one species is dominant. Globally, the regeneration under canopy is reconstituted progressively and remains less diversified than the nearest natural forest. Creation of genetic pool through selective entertainment under canopy will permit polycyclic management of plots for sustainable production of wood

Facteurs climatiques et productivité des variétés de canne à sucre (Saccharum officinarum L.) dans les plantations industrielles de la vallée du Niari (Congo-Brazzaville)

L’objectif de cette étude est de démontrer les incidences des principaux facteurs climatiques sur la productivité des variétés de canne à sucre dans les plantations industrielles de la vallée du Niari. Les données proviennent des différentes campagnes agricoles de 2000-2001 à 2006-2007 de la Société agricole et de raffinage industriel de sucre au Congo (Saris-Congo). Elles concernent les précipitations, les températures, le rayonnement global solaire, les rendements de production et les hauteurs des différentes variétés de canne à sucre. L’évapotranspiration réelle (ETR) est calculée selon le modèle du bilan hydrique de Thornthwaite. Les résultats montrent que les coefficients de détermination entre les principaux facteurs climatiques et la croissance des variétés de canne à sucre sont de l’ordre de 0,974 à 0,980. L’évolution des rendements en fonction des indices de satisfaction des besoins hydriques (ETR/ETM) est de l’ordre de 0,664 à 0,845. Ceci met en exergue les incidences des facteurs climatiques sur la productivité des variétés de canne à sucre de la vallée du Niari. Ces facteurs climatiques, permettent d’expliquer par les différentes approches méthodologiques, l’évolution des rendements en canne et d’estimer la production dans les périmètres sucriers.Mots clés: Variétés de canne à sucre, rendements de production, plantations industrielles, facteurs climatiques, vallée du Niari (Congo)

Timber Production In The Dense Humid Forest Of Cameroon

About 60% of all timber exploited in Cameroon is made of a few species, namely, Triplochiton scleroxylon (Ayous), Entandrophragma cylindricum (Sapelli), Lophira alata (Azobe), Baillonella toxisperma (Moabi), Afzelia bipindensis (Red Doussie) and Afzelia pachyloba (White Doussie).Triplochiton scleroxylon is the most highly exploited timber species in Cameroon reaching a volume of 608,599m3 from the East province in 2004, followed by Entandrophragma cylindricum (403,942m3 in 2001) still from the East Province. For the period 1998 to 2004, the volume of timber of these species exploited fluctuated from year to year, with no steady increase or decrease. This was probably as a result of the uncertainty of their availability even though logging companies open up unexploited areas in search of more timber. The highest volume of timber for most of these species came from the East province, followed by the South and then Centre, except Afzelia pachyloba with highest volumes for this period (24,396m3 in 1999) coming from the Centre province. It is possible that these species have been logged out in areas closer to the ports of export and, so logging companies go further (East and South provinces) to find timber of these species

Ecological research in the perspective of using forest in adaptation to climate change in Cameroon (Central Africa)

Understanding the vulnerability of forest and forest related sectors to climate change, mainstreaming the use of forest into adaptation strategies are some of the challenges faced by forestry research, developers and stakeholders. Despite the multiple efforts to mitigate climate change, it is well established that climate change will occurred and will increase the vulnerability of developing countries, particularly the poorest population. This group of population is well reprented in developing countries and depends mainly on rain related activities for their basic subsistence. As they rely on forest resources for their subsistence, looking in these natural resources ways to help them cope with these changes is the challenge of the forest and climate change managers. For the research communities of the developing countries, it not always evident on how to shift from the existing ecological research framework to the new one in which they assess vulnerability of forest but also their use in the adaptation to climate change. The current presentation in the context of Cameroon highlighted (1) the impact of climate change in forestry related sectors, (2) The current ecological research infrastructure, (3) what is needed to properly integrate forest resources uses in adaptation plan and thus enable the proper use of forest resources to adapt to climate change

DATES DE PLANTATION ET DE R\uc9COLTE DES VARI\uc9T\uc9S DE MANIOC DANS LA VALL\uc9E DU NIARI (CONGO)

In the valley of Niari, Republic of Congo, two cassava varieties were studied in relation to the agricultural calendar. one of these varieties is local (Boulabipaki) and the other comes from IITA (I92-0325). The objective of the study is to evaluate the effect of planting and harvesting dates on the production yields. The experimental device is a bi-factorial of 4 blocks, set up at Loudima during 2OO7-2OO8 and 2OO8-2OO9 agricultural campaigns respectively for the dates of planting and harvesting. Four (4) planting dates separated by an interval of seven (7) days were selected for yield assessment at 14 months. Harvesting dates at 6, 8, 10 and 12 months of planting were taken into account. Results show that the first two decades of November give production yields of about 37 t ha-1 (I92-0325) and 45 t ha-1 (Boulabipaki). Production yields at 6 and 8 months are about 16 and 21 t ha-1 respectively for IITA (I92-0325) against 5.2 and 12 t ha-1 for Boulabipaki. At 10 and 12 months of planting, two varieties of cassava have production yields of about 30 t ha-1. Thus, for the period tested (November, Decem- ber), the first two decades of November are favorable for planting while staggered crops become effective at 14 months.Dans la vall\ue9e de Niari en r\ue9publique du Congo, 2 vari\ue9t\ue9s de manioc ( Manihot esculenta Crantz ) ont \ue9t\ue9 \ue9tudi\ue9es en rapport avec le calendrier agricole. L\u2019une de ces vari\ue9t\ue9s est locale (Boulabipaki) et l\u2019autre provient de l\u2019IITA (I92-0325). L\u2019objectif de l\u2019\ue9tude est d\u2019\ue9valuer l\u2019effet des dates de plantation et de r\ue9colte sur les rendements de production. Le dispositif exp\ue9rimental est un bi factorielde 4 blocs, mis en place \ue0 Loudima lors des campagnes agricoles 2007-2008 et 2008-2009 respectivement pour les dates de la plantation et celles de la r\ue9colte. Quatre(4) dates deplantation s\ue9par\ue9es de sept (7) jours d\u2019intervalle ont \ue9t\ue9 choisies pour une \ue9valuation des rendements \ue0 14 mois. Les dates de r\ue9colte\ue0 6, 8, 10 et 12 mois de plantation ont \ue9t\ue9 prises en compte.Les r\ue9sultats montrent que les deux premi\ue8res d\ue9cades de novembre donnent des rendements de production de l\u2019ordre de 37 t ha-1 (I92- 0325) et de 45 t ha-1 (Boulabipaki). Les rendements de production \ue0 6 et 8 mois sont respectivement de l\u2019ordre de 16 et 21 t ha-1 pour IITA (I92-0325) contre 5,2 et 12 t ha-1 pour Boulabipaki.A 10 et 12 mois de la plantation, les deux vari\ue9t\ue9s de manioc pr\ue9sentent des rendements de production de l\u2019ordre de 30 t ha-1. Ainsi, pour la p\ue9riode test\ue9e (novembre, d\ue9cembre), les deux premi\ue8res d\ue9cades de novembre sont favorables \ue0 la plantation alors que les r\ue9coltes \ue9chelonn\ue9es deviennent effective \ue0 14 moi