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ASSISTED NATURAL REGENERATION IN SLASH-AND-BURN AGRICULTURE: RESULTS IN THE DEMOCRATIC REPUBLIC OF THE CONGOHuman impacts on natural tropical forests in Central Africa are to a large extent linked to shifting cultivation and fuelwood extraction in peri-urban areas. This is especially true around the city of Kinshasa in the Democratic Republic of the Congo (DRC), which is why research was conducted in 2010 by the Makala Project in the city's fuelwood supply basin. The aims were to adapt and test Assisted Natural Regeneration (ANR), improve slash-andburn crop systems and contribute to the enrichment of forest fallows. Prior to slashing and burning, useful trees were selected for protection. Then, during cropping, the germination and multiplication of stump shoots and root suckers from existing local forest species were promoted by selective weeding, thinning, and pruning. Monitoring of the test areas found low survival rates for old trees conserved before the land was slashed and burned, due to the difficulty of controlling the fires. This means that the technique can only be used for the edges of plots, by gradually enriching hedgerows. In contrast, stumps shoots and root suckers from natural forest species protected by ANR during agricultural weeding grew rapidly inside the plots, thus rapidly establishing woody fallows without the need for costly inputs or heavy labour. In 2014, three and a half years after slashing and burning, biodiversity and biomass in these fallows is greater than in non-ANR fallows. Better charcoal and crop productivity and a slower rate of forest transition into savannah are expected. However, social acceptance, a critical factor in the large-scale dissemination of this innovation, must be investigated in the light of potential developments in traditional and modern land tenure rights.Keywords: assisted natural regeneration, agroforestry, improved fallows, charcoal, fuelwood, improved slash-and-burn farming systems, Democratic Republic of the Congo. Los impactos antrópicos en los bosques tropicales naturales de África Central están en gran medida vinculados a la agricultura itinerante y a la extracción de leña en áreas periurbanas. En particular, este es el caso en torno a Kinshasa, en la República Democrática del Congo (RDC). Por ello, en 2010, el proyecto Makala adaptó y experimentó la Regeneración Natural Asistida (RNA) en el área de suministro de leña de dicha ciudad. El objetivo era mejorar los sistemas de cultivo de tala y quema y contribuir al enriquecimiento de los barbechos forestales. Antes de la roza, se seleccionan algunos ár-boles útiles para protegerlos. Luego, durante el período de cultivos, se favorecen la germinación y multiplicación por brotes de cepa y de raíz de las especies locales preexistentes mediante escardas selectivas, raleos y podas. El seguimiento de estos experimentos mostró bajas tasas de supervivencia de los viejos árboles que se protegieron de la roza previa a los cultivos. Esto se debe a la dificultad de controlar los fuegos durante la quema y r...

En République démocratique du Congo, Kinshasa, la capitale accueillant les populations issues de l'exode rural et de l'insécurité accrue, concentre environ huit millions d'habitants. La ville est principalement entourée de savanes et d'îlots forestiers dégradés. La consommation en bois énergie est estimée dans une fourchette de trois à six millions de tonnes d'équivalent bois énergie par an (ce qui représenterait 0,6 à 1,2 million de tonnes de charbon de bois par an si tout le bois était carbonisé). Le projet Mampu a été conçu comme la phase pilote d'un projet de reboisement de cent mille hectares sur les sols sableux du plateau Batéké pour faire face à la pénurie de bois et de charbon. Malgré les conflits, environ huit mille hectares de plantations d'Acacia auriculiformis ont été principalement réalisées de 1987 à 1993. À partir de 1998, la plantation de Mampu a été divisée en lots de 25 ha attribués à 320 familles d'agriculteurs. La culture se fait suivant un modèle agroforestier de jachère améliorée, inspiré du modèle traditionnel de culture sur brûlis. La production totale de charbon de ce massif varie de 8 000 à 12 000 tonnes annuelles, à laquelle il faut ajouter 10 000 tonnes de manioc, 1 200 tonnes de maïs et 6 tonnes de miel. Pour le seul charbon, cela correspond à un revenu brut annuel de 2,6 millions de dollars US pour le pays. Au moins un quart revient aux propriétaires agrisylviculteurs. Le succès du projet incite à appliquer ce modèle sur les savanes des plateaux Batéké, en prenant en compte les droits fonciers traditionnels et en poursuivant la diversification et la transformation locale des produits. Cela contribuera à couvrir une part plus importante des besoins urbains en énergie renouvelable, tout en créant des emplois ruraux. Cependant, d'autres modèles de systèmes agroforestiers méritent d'être testés ou développés dans les autres conditions écologiques et socio-économiques du pays, comme la gestion du recrû naturel d'espèces locales à usages multiples appliquée dans le système traditionnel de jachère enrichie (nkunku) du Bas-Congo. (Résumé d'auteur)

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Introduction. C. Schweinfurthii (Burseraceae) grows as isolated trees in the wet savanna of Cameroon. In the West of the country, the interest of the tree specially lies in the production of fruits, but C. Schweinfurthii is also exploited for its wood. Preliminary work for a more advanced domestication has been undertaken by Irad (Cameroon) since 1987. Materials and methods. The domestication work began with the development of a seed germination technique which finally made it possible to obtain an average rate of seedling emergence of 95% at the end of a 3 month period. Plantations then stayed in a tree nursery for 6 months before being transplanted to an experimental plot. Growth, flowering and fruit formation were then followed. Results. In the C. Schweinfurthii stand, the average survival rate decreased year after year and was stabilized at 84% from 1992 to 1997. It was only 42% in 2000 as a result of the damage caused by a bush fire in March 1998. In 2000, the average total height of the 12-year old trees reached 6.8 m, and their trunks had a mean diameter of about 8.6 cm. The dominant height and diameter were 10.8 m and 14.3 cm, respectively. C. Schweinfurthii is a dioecious species. The formation of the first fruits happened with 8-year old trees. From 1996 to 2001, 19% of the studied trees within the plot entered blooming or fruiting. Floral analyses showed that, during the same period, the experimental C. Schweinfurthii stand presented a sex ratio of 38% of male individuals for 62% of female trees. Conclusions. The preliminary work on the C. Schweinfurthii's domestication showed that the tree could produce after 8 years and that its growth in stands was satisfactory. Complementary studies will have to be undertaken. For example, the highlighting of vegetative differences between male and female seedlings at the nursery stage could allow an early sexing. Besides, the use of vegetative multiplication techniques could make it possible to give interested farmers only female trees, which are the only ones capable of fruiting. Cameroon / Canarium Schweinfurthii / domestication / stand characteristics / population growth / flowering / fruiting / sex ratio / yields L'aiélé (Canarium Schweinfurthii Engl.) : premier essai de plantation dans l'ouest du Cameroun. Résumé-Introduction. L'aiélé (Burseraceae) pousse à l'état isolé en savane humide du Cameroun. Dans l'ouest du pays, l'intérêt de l'arbre réside surtout dans sa production de fruits, mais C. Schweinfurthii est aussi exploité pour son bois. En préalable à une domestication plus avancée, des travaux ont été entrepris par l'Irad (Cameroun) en 1987. Matériel et méthodes. Les travaux de domestication ont débuté par la mise au point d'une technique de germination des semences qui a finalement permis d'obtenir un taux moyen de levée de 95 % au bout de 3 mois. Les plants ont ensuite séjourné en pépinière pendant 6 mois avant d'être transplantés en parcelle expérimentale. La croissance, la floraison et la production des arbres ont alors été suivies. Résultats. Le ta...

Gum arabic production from Acacia senegal is lower in sub-humid areas than arid areas. Water stress is thought to be the reason for higher yields in arid areas. The application of ethephon is thought to mimic the effect of water stress in other plants. The objective of this study was to determine if the application of ethephon would increase the gum yields of Acacia senegal under sub-humid conditions in Cameroon. Trees receiving 40 or 120 mg ethephon were compared to controls in field experiments at a semi-arid and a sub-humid location in Northern Cameroon, over two seasons. Two provenances from drier areas (Sudan) were compared to the local one. In the first season, gum yield of the local provenance treated with ethephon was increased by 400-600 % compared to the untreated trees. Gum yield at the semi-arid location was 77, 313 and 214 g/tree with 0, 40 and 120 mg ethephon/tree, respectively, while at the sub-humid location, it was 30, 186 and 114 g/tree with 0, 40 and 120 mg ethephon/tree. However, in the second season, the effect of ethephon was not significant in the semi-arid area, whereas it was evident in the sub-humid area (up to 478 g/tree). Moreover, ethephon did not affect gum yield of provenances from drier areas (Sudan). This showed that the water-stress hypothesis has to be refined. The development of ethephon-based tapping systems is promising, but requires further studies with a wider range of environmental conditions and A. senegal provenances.

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The Chilgoza of Kinnaur. Influence of the Pinus gerardiana edible seed market chain organization on forest regeneration in the Indian Himalayas. Abstract-Context, objective and methods. In the north of India, in the Himalayas, the high-altitude slopes [(between 1800 and 3300) m] are covered by forests where Pinus gerardiana dominates. This pine is known for its edible seeds (Chilgoza). The recent evolution of nut harvest methods means that there is danger of the disappearance of natural seedlings and the ageing of the forests. Therefore, a survey was carried out from 1998 with a hundred farmers, which was supplemented with field visits and discussions with resource people involved in the commercial chain. Results. In the 1950s, traditional harvesting rules made it possible to respect trees and to allow a small portion of seeds to reach the ground. So, in spite of particularly difficult ecological conditions, the forest was able to regenerate. During the five last decades, the roads opening have allowed an irrigated cash-arboriculture development in the valleys. The village communities have become less dependent on the Chilgoza trade and sell the nut harvest contracts to private contractors who employ foreign workers, cut many branches and practically collect all the seeds. So, regeneration has become practically non-existent. The poorest inhabitants cannot have access to this resource anymore. In town, the retail sale of Chilgoza represents a market of (100 to 300) t•year-1 , at a price from (15 to 20) €•kg, i.e., a market chain from (1.5 to 6) M€•year-1. Discussion and conclusion. The authors put forward a proposal to substitute for the two private platforms (purchase and drying) of New Delhi an organization with a non-lucrative purpose, concerned with a more respectful socioeconomic development of the environment. This unit would centralize Chilgoza buying, drying and storage in the production place. Then, it would ensure sales to urban sellers, at the time of the peak of market demand. This would allow for a more significant part of the market chain added value to remain in the valley; this money at the same time would make it possible to fight against poverty and to regenerate natural resources. The authors are campaigning to see that research and development projects, financed with national or international funds, come to support these proposals. India / Pinus gerardiana / Himalayan region / highlands / seeds / nonwood forest products / natural regeneration / sustainable land management / marketing channels