New data on the recent history of the littoral forests of southern Cameroon: an insight into the role of historical human disturbances on the current forest composition

Abstract

Background and aims -Prior to European colonisation of Central Africa, human populations were dispersed through the forests, where they practiced slash-and-burn cultivation. From the 19 th century they were progressively concentrated in villages along roads, leaving large areas of forest derelict. In south-western Cameroon, and elsewhere in Central Africa, forest canopy is dominated by long-lived lightdemanding tree species, suggesting a possible role of human disturbance. The aim of this study was to bring new insights into the possible effect of historical human disturbances in terms of timing and spatial extent on the current forest composition. Location -Wet evergreen littoral forest in south-western Cameroon. Methods and key results -A combined vegetation sampling and archaeobotanical survey were conducted. Potsherds, oil-palm endocarps, and charcoal were found throughout the study area, suggesting generalised human occupation and anthropogenic fire. Human occupancy occurred in two periods: between 2200 and 1500 BP, and, more recently, beginning three centuries ago. High frequency of fire and the presence of Elaeis guineensis both dated recently (between 260 and 145 BP) suggest slash-and-burn shifting cultivation practices. These human-induced disturbances may coincide with the age of the current emergent lightdemanding species, the age of which can be estimated around 200 years, or with the phases of drying climate recorded in the Central African forest in the early 18 th century. Conclusions -These results support the idea that historical human disturbances are one of the major factors that shaped the current forest composition in Central Africa.

How Tightly Linked Are Pericopsis elata (Fabaceae) Patches to Anthropogenic Disturbances in Southeastern Cameroon?

“…Working in a forest concession is another innovative aspect of the methodology (but, see [53,66]). Large-scale forest management inventories have already been carried out by logging companies in Central African forests, providing a unique opportunity to identify in advance the best spots to investigate (e.g., high density of light-demanding tall trees).…”

Enrichment of Central African logged forests with high-value tree species: testing a new approach to regenerating degraded forests

“…If thinning fosters the growth of nonpioneer saplings, other techniques are necessary to regenerate pioneer timber species, which probably establish after larger perturbations such as cultivation and subsequent abandonment (Doucet 2003;Van Gemerden et al 2003;Biwolé et al 2015). In some areas, late secondary growth rather than pristine forests are indicated by abundant large pioneer tree species such as Pericopsis elata and Triplochiton scleroxylon, which were included in our study (Gillet & Doucet 2013;Biwolé et al 2015;Bourland et al 2015).…”

“…In some areas, late secondary growth rather than pristine forests are indicated by abundant large pioneer tree species such as Pericopsis elata and Triplochiton scleroxylon, which were included in our study (Gillet & Doucet 2013;Biwolé et al 2015;Bourland et al 2015). Management techniques such as enrichment planting have been recommended to promote these species Ouédraogo et al 2014).…”

Present-day central African forest is a legacy of the 19th century human history

“…Specifically, we postulated that the decrease in anthropogenic disturbances and the generalized land abandonment from ca. 165 ya were less favorable to the regeneration of light-demanding tree species (van Gemerden et al, 2003; Brnčić et al, 2007; Greve et al, 2011; Biwolé et al., 2015). Additionally, the present-day natural gap size has been shown to be insufficient for the regeneration of most of these species (van Gemerden et al, 2003).…”

“…Human activities in the Holocene, and particularly shifting cultivation, have been invoked to partially explain the low diversity of central African forests (Parmentier et al, 2007) and the abundance of light-demanding species in the canopy (White and Oates, 1999; van Gemerden et al, 2003; Engone Obiang et al, 2014; Vleminckx et al, 2014; Biwolé et al., 2015). The light-demanding species form, in some places, almost pure 0.5 to 1 ha stands that mirror the size of traditionally cultivated fields (van Gemerden et al, 2003).…”