Abstract
While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and-burn agriculture since 3000–2000 BP (Before Present) could be the main driver of the persistence of light-demanding tree species. In order to examine anthropogenic factors in the persistence of such populations, our study focused on Pericopsis elata, an endangered clustered timber species. We used a multidisciplinary approach comprised of botanical, anthracological and archaeobotanical investigations to compare P. elata patches with surrounding stands of mixed forest vegetation (“out-zones”). Charcoal samples were found in both zones, but were significantly more abundant in the soils of patches. Eleven groups of taxa were identified from the charcoals, most of them also present in the current vegetation. Potsherds were detected only inside P. elata patches and at different soil depths, suggesting a long human presence from at least 2150 to 195 BP, as revealed by our charcoal radiocarbon dating. We conclude that current P. elata patches most likely result from shifting cultivation that occurred ca. two centuries ago. The implications of our findings for the dynamics and management of light-demanding tree species are discussed.
Highlights
While tropical moist forests have long been viewed by the general public as pristine and stable ecosystems, the last three decades have seen a radical change in this preconception
Our findings suggest that anthropogenic activities occurred in southeastern Cameroon during both the Early and Late Iron Ages, the latter being very likely the origin of current P. elata patches
If we make the assumption that the studied forests have not undergone significant changes in tree species composition, the absence of P. elata in charcoal fragments appears contradictory to the high abundance of this species in extant vegetation
Summary
While tropical moist forests have long been viewed by the general public as pristine and stable ecosystems, the last three decades have seen a radical change in this preconception. While this hypothesis is probably true at large spatial scales over long time spans (10,000 years or more), humans may have strengthened the effects of climate variation on vegetation composition, mainly during the last 2000 years [3,4,5] This hypothesis is based on the current abundance of light-demanding tree species in most Central African moist forests; an unexpected outcome if we consider only the paleoclimate. Light-demanding species contribute to improving plant richness and represent the major part of timber production in Central Africa [10,11] Their regeneration rates are low [12], and some authors have argued that this may be due to the current absence of gap conditions needed for their development, since Bantu populations are settled on roadsides [13]. The implications for forest management and silvicultural treatments are discussed
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