Floristic composition, growth temperament and conservation status of woody plant species in the Cameroonian tropical rainforests

Abstract

Introduction Cameroon’s tropical rainforests are nowadays strewn with rural forests maintained by local populations; however, these forests are not officially recognized in the non-permanent forest domain. Rural forests are non-delimited riparian areas within the dense moist forest, reserved for rural housing, agricultural activities and agroforestry practices, freely exploited by the local communities for their livelihood without them having any rights to artisanal and commercial logging. This study aimed at contributing to the flora knowledge and the conservation state of woody plant species in rainforests. The study was carried out in two rural forests located in the Eastern and Southern agroforestry zones of Cameroon. Methods The method adopted for floristic inventories combined a fixed area sampling unit and a variable area sampling unit. Woody individuals with diameter at breast height (dbh) < 3.2 cm were counted and shrubs of 3.2 ≤ dbh < 10 cm were measured to analyse the understorey, while trees with dbh ≥ 10 cm were measured and identified to characterize the canopy. Results In the Essiengbot-Mbankoho rural forest in Eastern Cameroon, 468 species belonging to 61 families were recorded in the understory while 227 species belonging to 53 families were identified at the canopy level. A total of 40 (7.68%) threatened species, 18 (3.45%) Near Threatened species and 408 (78.31%) Least Concern species were recorded. In the Nbgwassa-Opkweng rural forest in Southern Cameroon, 534 species belonging to 64 families were identified in the understory while 225 species belonging to 43 families were recorded in the canopy. A total of 54 (9.69%) threatened species, 25 (4.49%) Near Threatened species and 421 (75.58%) Least Concern species were identified in this forest. Shannon’s diversity indices were above five in the understories and canopies of both forests. Shade-bearer species were the most represented in the understories while the non-pioneer light-demanding and shade-bearer species were the most abundant in the canopies. Conclusions Despite the influence of slash-and-burn agriculture and subsistence farming practices, rural forests managed by local populations provide opportunities for preserving plant biodiversity. However, the presence of threatened species, pioneer species and non-pioneer light-demanding species in these forests is an indicator of moderate and man-induced disturbances that, in the absence of a forest management plan or sustainable management, may threaten this biodiversity. Legal management of rural forests could help in limiting the anthropogenic activities and pressures on community forests.

Changes in floristic composition, diversity and anthropogenic perturbations in an east African tropical forest

“…A systematic sampling procedure was used to collect data on vegetation and human activities following Kengne et al (2022); Shiferaw et al (2019); Yirga et al (2019). In June 2015, after a reconnaissance survey of the forest, six parallel transects separated from each other by 1 km intervals were systematically laid out across the forest running from the Northwest to the Southeast of ECFR (Figure 1).…”

“…A total of 272 nested quadrats were then placed systematically at every 100 m interval (starting from the forest edge) and alternating from left and right on the six transects following similar procedures by Fashing et al (2004); Kengne et al (2022); Yirga et al (2019). The nesting of the quadrats involved laying out main plots within which subplots were then embedded.…”

“…According to (Yirga et al, 2019), differences in floristic species composition between ECFR and the other tropical forests in the region could be attributed to the dissimilarities in human impacts, rainfall and other biotic and abiotic factors. Furthermore, according to Kengne et al (2022); Kessler et al (2005), the presence and dominance of the tree families of Euphorbiaceae, Monimiaceae, Stilibaceae, Rosaceae, Rubiaceae, Sapotaceae, Myrtaceae and Araliaceae in ECFR illustrates the secondary and non-climax character of the tree species in the forest.…”

“…The high densities of small sized individuals of the trees is an indication that the trees are responding to forest disturbances (Kengne et al, 2022). This is a characteristic of forest succession by the secondary forest tree species (Jayakumar & Nair, 2013;Kengne et al, 2022)…”

“…As reported byBanana and Tweheyo (2001);Bitariho and McNeilage (2008), the climate change impacts exacerbated by the overharvesting of the bamboo stems by the local people, has stimulated the invasion and taking over of the bamboo forest by the secondary forest tree species of M. capensis, N. macrocalyx, N. congesta, etc. This is the reason why those tree species belonging to families of Euphorbiaceae, Monimiaceae, Rubiaceae, etc (Kengne et al, 2022;Kessler et al, 2005). are the most dominant in ECFR.…”