Tree diversity and its relation to habitat was examined using the tree dataset of 57 linear transects totaling 70.2 ha in the Mengamé Gorilla Reserve (MGR), south Cameroon. In nine different habitats defined based on physiognomy and ecological criteria, all trees with average dbh ≥ 10 cm were enumerated. Caesalpiniaceae is the leading dominant family in MGR. Tree diversity totaled 304 species in 192 genera of 51 families. Included are 31 species cited in the IUCN red list of threatened species. Tree density varied from 80 to 366 stems⁄ha, basal area from 0.06 to 19.82 m²⁄ha, species richness from 11 to 269 species in each of the nine habitats. When compared with other tropical rainforests in Congo Basin, the results showed great similarities in tree density, family occurrence and Shannon diversity index values. Excluding the marshy grasslands where only 24 trees were recorded, 27 families and 30 species appeared common in the other eight habitats. We examined floristic similarities among the nine habitats using the NNESS similarity index, followed by a Chi-square test. The results revealed that habitat type affected tree composition, the main triggering factors being soil hygrometry, stage of stand development and disturbance. The study emphasizes the importance of the MGR as a refuge of threatened species and reinforces the idea of its inclusion in the African biodiversity hotspot.

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This study aims to holistically examine the process of integration of rubber production into swidden society, based on observations of Benuaq Dayak society in East Kalimantan. Before the introduction of rubber production, villagers’ livelihoods were based on swidden and rattan production, but household economies fared poorly owing to stagnating rattan prices. There was a high rate of rice self-sufficiency, while various work organization types and a collaborative work and profit-sharing system played an important role in their livelihoods as a social safety net. The collaborative work and profit-sharing system was supported by a philosophy of mutual aid. After rubber production began, about half the villagers gave up swidden and the others switched to practicing swidden and rubber fields together. Their living standard was improved by cash income from rubber, and their rate of rice self-sufficiency dropped. A cash-income differential emerged among villagers, which caused social disruption such as arson and theft. The work organization was simplified from a collaborative work and profit-sharing system to an individual work and private-profit system. These livelihood changes and increasing cash income caused a social safety net malfunction, and impaired the philosophy of mutual aid. It is inferred that the introduction of rubber production offers the possibility of both environmental and economic improvements, but to accomplish the well-balanced development of swidden society it is important to reconstruct and maintain the social ties that have been weakened by rising cash income and simplified types of work organization. It is also necessary to establish new institutional social networks for cooperation with the government to adapt to market economy conditions.

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The ground-dwelling ant fauna in tropical forests remains the “final frontier” in the study of Formicidae biodiversity. This is mainly due to a lack of convenient sampling methods for the inventory of ants in soil. In the present study, employing the hand-sorting of small soil cores, we carried out the first survey of ground-dwelling ants in Maliau Basin Conservation Area, in Sabah, Borneo, to compare disturbed and undisturbed forest ant communities and to evaluate the sampling method’s performance in assessing species richness and characterizing community structure of the ant fauna. For this purpose we set a 5 m long and 1 m wide transect, consisting of five 1-m² sections, in disturbed and undisturbed forest plots in the area, and compared the sampling results of hand-sorting between the two plots. A total of 50 ant species, in 28 genera and eight subfamilies, were collected in the two plots, of which 32 species in 20 genera were collected from the undisturbed plot and 24 species in 18 genera from the disturbed plot. According to estimates of expected species richness, the hand-sorting of soil cores allowed for the collection of 66.7 to 80.0% of the ant species expected in the undisturbed plot, and 83.3 to 88.9% in the disturbed plot. Besides lower species richness, the ant community in the disturbed plot had lower species evenness and a different species composition in comparison to undisturbed plot, which may be related with environmental changes in the plot, due to open canopy. These results indicate that hand-sorting of small soil cores is a method that could provide reliable information, not only to estimate species richness at a site, but also to evaluate differences in community structure between sites.

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The catenary sequence of vegetation in tropical peat swamp forest has been attributed to reduced nutrient availability along the gradient of peat depth. The objective of this study was to assess the phylogenetic structure of tropical peat swamp forest vegetation with the aim of clarifying the community assemblages. We laid out six plots along the gradient of peat depth in the upper catchment of the Sabangau river, Central Kalimantan, Indonesia and investigated forest phylogenetic structure. We found a tendency for phylogenetic diversity to decrease as peat depth increased. Higher phylogenetic diversity in the forest zone closest to the river could be attributed to competitive exclusion in a relatively benign peatland environment, whilst lower phylogenetic diversity further from the river could be attributed to the filtering effect of a more stressful environment. There was, however, unexpected low phylogenetic diversity in the tall interior community in the Sabangau forest, where environmental conditions were less extreme. This observed low phylogenetic diversity is possibly related to the history of peat development and degradation in this location as the ombrogenous peat is undergoing long-term oxidation due to reduced precipitation and lowering of the water table. We conclude that not only environmental filtering but also biotic filtering through such mechanisms as competitive exclusion contribute to the catenary sequence of tropical peat swamp forest vegetation

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