BOIS ET FORÊTS DES TROPIQUES, 2015, N° 323 (1) SECONDARY FORESTS IN EQUATORIAL AFRICA 21 André Aubréville1 Translation Secondary Forests by Ilona Bossanyi2 1 Inspector-General for Water in Equatorial Africa and Forests in Overseas France Côte d’Ivoire - Cameroon - F. E. A. 2 Bois et Forêts des Tropiques Translation French to English from the original article published the issue n° 2 of the Journal Bois et Forêts des Tropiques, second quarter 1947. Photo 1. Forêt secondaire de la Nkoulounga au Gabon en 1958. Photograph P. Sarlin, CTFT-CIRAD 1958. BOIS ET FORÊTS DES TROPIQUES, 2015, N° 323 (1) André Aubréville 22 SECONDARY FORESTS IN EQUATORIAL AFRICA réSumé AbStrAct resumEn LES BROUSSES SECONDAIRES Secondary Forests LOS MATORRALES SECUNDARIOS EN AFRIQUE ÉQUATORIALE IN Equatorial Africa EN ÁFRICA ECUATORIAL La « brousse secondaire » s’oppose à “Secondary” forests are very different El “matorral secundario” se opone al “bos- la « forêt primaire », forêt « noble » aux to “primary”, “noble” forests with their que primario”, el bosque “noble” con ár- grands arbres. C’est une forêt exubérante, tall trees. Their exuberant, inextricable boles de gran porte. Es un bosque exube- inextricable, avec plus de lianes et de petits vegetation, with more lianas and small rante e intrincado, con más lianas y monte bois que d’arbres, succédant à l’agricul- shrubs than trees, grows on formerly bajo que árboles y que sucede a la agricul- ture sur brûlis. Dans les régions habitées, forested lands cleared for agriculture. tura de roza y quema. En las regiones ha- elle entoure communément les villages et In inhabited regions, they generally sur- bitadas, estas áreas boscosas suelen estar borde les routes, la forêt primaire étant round villages and grow along roadsides, alrededor de los pueblos y a lo largo de los reléguée aux collines rocheuses et maré- pushing the primary forest back to rocky caminos, mientras que el bosque primario cages. En Afrique équatoriale, la « brousse hillsides and swamps. In Equatorial Af- se ve relegado a colinas rocosas y esteros. secondaire » représente actuellement 50 rica, “secondary” forests account today En África ecuatorial, el “matorral secunda- à 75 % des surfaces forestières. La forma- for 50 to 75% of all forested areas. These rio” ocupa actualmente del 50 al 75% de tion des brousses secondaires procède en forests form in three stages: (i) seedlings las áreas forestales. La formación de estos trois phases : (i) l’apparition de semis d’es- appear of fast-growing sun-loving species matorrales se realiza en tres fases: a) apa- pèces héliophiles (Musanga sp., Vernonia (Musanga sp., Vernonia sp., Anthocleista rición de pimpollos de especies heliófilas sp., Anthocleista sp.) à croissance rapide, sp.), which are not the same as primary (Musanga sp., Vernonia sp., Anthocleista qui diffèrent des espèces de « forêt pri- forest species and which disperse their sp.) de crecimiento rápido diferentes de maire » et dont les graines sont dispersées seeds over long distances; (ii) formation las especies del “bosque primario” y cu- sur de longues distances ; (ii) la formation of an understorey, made up of the same yas semillas se dispersan en amplias dis- d’un sous-bois, constitué cette fois des shrub species as in “primary” forests but tancias; 2) formación de un sotobosque, mêmes espèces arbustives qu’en « forêt mixed in this case with a second group of compuesto ahora por las mismas especies primaire », et où se mêle un second groupe banal sun-loving species characteristic of arbustivas que el “bosque primario” y en d’espèces héliophiles banales, caractéris- “secondary” forests, which quickly grow el que se mezcla un segundo grupo de es- tiques de la « brousse secondaire » et rat- as high as the first group and sometimes pecies heliófilas comunes, típicas del “ma- trapant le précédent, voire le surcimant ; higher; (iii) gradual reconstitution of “pri- torral secundario”, que acaban alcanzando (iii) la lente reconstitution de la « forêt mary” forest with abundant Sapotaceae, e incluso superando en altura al grupo an- primaire », riche en sapotacées, guttifères Guttiferae and hard-wooded legu-minous terior; 3) lenta reconstitución del “bosque et légumineuses au bois dur, capables de species that are capable of regenerating primario”, con abundancia de sapotáceas, se régénérer dans les sous-bois, et parmi in the undergrowth and through which gutíferas y fabáceas de madera dura, ca- lesquelles de très grands arbres finissent some very tall trees eventually grow paces de regenerarse en el sotobosque y par percer la voûte des cimes. L’Okoumé through the canopy. Okoumé (Aucoumea que producirán árboles de gran porte que (Aucoumea klaineana), essence précieuse klaineana), a valuable species typical of acabarán perforando el dosel. El okumé typique des « brousses secondaires », est “secondary” forests, is common in the so- (Aucoumea klaineana), valiosa especie tí- ainsi fréquent dans les prétendues « forêts called “primary” forests of Gabon, which pica de los “matorrales secundarios”, está primaires » du Gabon, forêts qui ont été en in fact are on formerly cleared forest land. muy presente en los supuestos “bosques réalité autrefois défrichées. On ne saurait Today, the high potential of these “sec- primarios” de Gabón; unos bosques que, admettre aujourd’hui que le fort potentiel ondary” forests must not be allowed to en realidad, fueron en su día desbrozados. des « brousses secondaires » soit inva- “go up in smoke”. Quite the reverse: we No podemos permitir actualmente que el riablement réduit en cendres. Il faut au must learn to guide their development to importante potencial de los “matorrales contraire apprendre à guider et hâter leur hasten the establishment of commercially secundarios” acabe siempre reducido en évolution en faveur d’espaces à haute va- valuable species. cenizas. Se debe, por el contrario, guiar y leur économique. Abstract adapted by the editorial team. acelerar su evolución creando bosques de Résumé adapté par la rédaction de la revue. gran valor económico. Keywords: Aucoumea klaineana, Musan- Resumen adaptado por la redacción de la revista. Mots-clés : Aucoumea klaineana, Mu- ga sp., forest dynamics, heliophilous spe- sanga sp., dynamique forestière, espèce cies, functional groups, primary forest, Palabras clave: Aucoumea klaineana, héliophile, groupes fonctionnels, forêt secondary forest, Gabon. Musanga sp., dinámica forestal, especie primaire, forêt secondaire, Gabon. heliófila, bosque primario, bosque se- cundario, grupos funcionales, Gabón. BOIS ET FORÊTS DES TROPIQUES, 2015, N° 323 (1) SECONDARY FORESTS IN EQUATORIAL AFRICA 23 All those living in equatorial forest regions in the colonies for export. Yet if we look beyond the conventional merchant’s have become familiar with the term “secondary forests”, view of high quality wood produced by classic timber trees, which are visibly distinct from “primary forests”, those noble we will see that some secondary forest species, which may forests that stir the imagination with their mysterious be mediocre as trees but are fast-growing, could become shadows, their cathedral-like architecture, the impressive outstanding sources of cellulose that can be easily felled and size of their giant trees and their vast extent across the equa- used for new colonial industries, fibres, paper pulp, and torial regions where Pygmies formerly roamed and are now other purposes. Secondary forests could therefore be of the domain of loggers in search of african mahogany and considerable interest for the future. other fine timber for cabinet-making. Instead of giant trees, What assessment can be made of their current and these luxuriant secondary forests abound with lianas, potential value? foliage, woody vines and herbaceous stems, and trees are no For those who are unfamiliar with the equatorial regions, more than 20 to 25 m in height: these are the forests that it is hard to imagine the aspect of these forests, their struc- uniformly line the roads and tracks that criss-cross our forest ture, their composition and how they evolve. This article has colonies and mask the true rainforest, and more or less therefore been written for those who have never visited a densely surround the villages depending on how long they tropical country, and who therefore cannot have an accurate have been established: in regions that have long been inhab- picture of these banal forest formations. France also has ited by a relatively dense and stable population, they have secondary forests, formed by the untidy regrowth that entirely replaced the old-growth forests, fragments of which quickly appears after felling, but because it is temporary sometimes remain on rocky outcrops or in swampy valleys. and not extensive, nobody has thought to refer to it as Vast tracts of old-growth forest nevertheless remain in unin- “secondary forest”. In equatorial countries, they are indeed habited regions, but for how long? This is hard to say, given forests, of low height but so dense that, when the regrowth is the absence of maps, but the frenzied clearing by native recent, the only means of access is by wielding a machete to populations of ancient and magnificent stands along newly slash a narrow passage through the impenetrable tangle of opened roads, sometimes on slopes so steep one can barely stems, lianas, spiny palms and giant monocotyledons. walk upright, suggests that their years are numbered, except As we know, this secondary growth appears wherever a where the forestry services are taking measures to conserve clearing has been made in the uninterrupted blanket of them. When attempts are made to estimate the proportion of forest, which, we remind our readers, every native farmer secondary forests in a colony, the usual figure ranges from must do to expose his subsistence crops to the sunlight. 50 to 75%. A recent estimation made in Cameroon by Farmers cut down the trees and burn them during the dry M. Grandclément, the head of the forestry service for that season. This is a very rudimentary method of cultivation country, gives the following in the table I.