[en] Timber production is an important economic sector in most forested countries of Central Africa, where about 14 million hectares of lowland moist forests are now planned for management. This production is expected to be sustainable, but the actual impact of logging on biodiversity is still questioned.
To answer this question, we used a unique long-term controlled experiment implemented more than 20 years ago in an old-growth semi-deciduous moist forest of the Central African Republic (CAR). We tested whether (i) anthropogenic disturbances associated with silvicultural operations had an effect on the composition and diversity of tree communities, and (ii) there is a relationship between diversity and disturbance intensity in those forests.
For this, we botanically identified all treesP10 cm DBH in 28 1-ha plots where no treatment (controls), logging and logging + thinning operations were implemented 24 years ago and created a strong gradient of disturbance. We investigated the relationships between five diversity indices and a disturbance index calculated for each 1-ha plot, for all species and separately for three regeneration guilds.
We found a strong positive monotonic relationship between the intensity of disturbance and the percentage of pioneer species in the tree communities, which proved to be equally detrimental, in terms of relative abundance, to the non-pioneer light-demanding and the shade-bearing species.
Overall, disturbance appeared to have a weak monotonous negative effect on diversity, irrespective to the index considered. The diversity of shade-bearers slightly decreased along the disturbance gradient without significant decrease in species density; disturbance had no effect on non-pioneer light demanders, but a clear significant negative effect on the diversity of pioneers, with a significant decrease in species density. This negative effect was associated with the massive recruitment of the early-successional, fast-growing Musanga cecropioides R. Br. (Urticaceae), which rapidly preempted space and resources in the most disturbed plots. Despite this effect, disturbance did not significantly affect the local heterogeneity in species distribution.
These results suggest that the semi-deciduous moist forests of CAR are locally resilient to small-scale disturbances associated with silvicultural operations. This may be a consequence of the past anthropogenic and/or climatic disturbances, which have been stronger and more long-lasting than elsewhere within the tropical forest biome, and would have removed the most vulnerable species. Because logging intensity in these forests is usually low, we do not expect any direct major impact on tree species diversity, at least after the first felling cycle.
Gourlet-Fleury, Sylvie; UPR BSEF, CIRAD, Campus International de Baillarguet, F-34398 Montpellier, France
Beina, D.
Fayolle, Adeline ; Université de Liège - ULiège > Forêts, Nature et Paysage > Gestion des ressources forestières et des milieux naturels
Ouédraogo, D.-Y.
Mortier, F.
Bénédet, Fabrice
Closset-kopp, Déborah
Decocq, Guillaume
Language :
English
Title :
Silvicultural disturbance has little impact on tree species diversity in a Central African moist forest
Publication date :
2013
Journal title :
Forest Ecology and Management
ISSN :
0378-1127
eISSN :
1872-7042
Publisher :
Elsevier Science
Issue :
304
Pages :
322-332
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
ARF Project (Appui à la Recherche Forestière) AFD - Agence Française de Développement [FR] CIRAD - Centre de Coopération Internationale en Recherche Agronomique pour le Développement [FR] ICRA (Institut Centrafricain de Recherche Agronomique) MEFCP (Ministère centrafricain des Eaux, Forêts, Chasse et Pêche) SCAC/MAE (Service de Coopération et d'Actions culturelles, Ministère des Affaires Etrangères) SCAD (Société Centrafricaine de Déroulage)
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