Mixed-forest species establishment in a monodominant forest in Central Africa: Implications for tropical forest invasibility

Background: Traits of non-dominant mixed-forest tree species and their synergies for successful co-occurrence in monodominant Gilbertiodendron dewevrei forest have not yet been investigated. Here we compared the tree species diversity of the monodominant forest with its adjacent mixed forest and then determined which fitness proxies and life history traits of the mixed-forest tree species were most associated with successful co-existence in the monodominant forest. Methodology/Principal Findings: We sampled all trees (diameter in breast height [dbh]≥10 cm) within 6x1 ha topographically homogenous areas of intact central African forest in SE Cameroon, three independent patches of G. dewevrei-dominated forest and three adjacent areas (450-800 m apart). Monodominant G. dewevrei forest had lower sample-controlled species richness, species density and population density than its adjacent mixed forest in terms of stems with dbh≥10 cm. Analysis of a suite of population-level characteristics, such as relative abundance and geographical distribution, and traits such as wood density, height, diameter at breast height, fruit/seed dispersal mechanism and light requirement-revealed after controlling for phylogeny, species that co-occur with G. dewevrei tend to have higher abundance in adjacent mixed forest, higher wood density and a lower light requirement. Conclusions/Significance: Our results suggest that certain traits (wood density and light requirement) and population-level characteristics (relative abundance) may increase the invasibility of a tree species into a tropical closed-canopy system. Such knowledge may assist in the pre-emptive identification of invasive tree species. © 2014 Peh et al

Long-term thermal sensitivity of Earth’s tropical forests

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Synopsis of the genus Chamaeangis (Orchidaceae), including two new taxa

A synopsis of Chamaeangis (Orchidaceae) with a taxonomic key to the genus is provided. Twelve taxa are recognized. Detailed examination of the specimens revealed two novelties: Chamaeangis spiralis from Nigeria and Cameroon, and Chamaeangis lecomtei var. tenuicalcar, a new variety from Ivory Coast, Ghana, and Gabon. Chamaeangis pauciflora is shown to be synonymous with Chamaeangis letouzeyi, which is here redescribed in detail. Chamaeangis thomensis is neotypified, and Chamaeangis lecomtei var. lecomtei is lectotypified. Chamaeangis gracilis is treated as an excluded species. Several new country records of Chamaeangis are provided. © Copyright 2009 by the American Society of Plant Taxonomists.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Relationship between traits of mixed-forest tree species and their occurrence in monodominant <i>Gilbertiodendron</i> forests.

<p>The response variables are “absence” (code = 0) and presence (code = 1). N denotes the number of species; CI stands for confidence interval; <i>P</i><0.001 is denoted by ** and <i>P</i><0.05 by *. Complete information is not available for all species.</p

Final multiple logistic regression model explaining the establishment of mixed-forest tree species in the monodominant <i>Gilbertiodendron</i> forest.

<p>Model concordance = 78.7%; n = 140.</p

Sample-based rarefaction curves of the tree communities found in monodominant <i>Gilbertiodendron</i> forests (red dots and line) and mixed forests (blue dots and line) comparing number of species (A), species density (B) and population density (C).

<p>Error bars represent 95% confidence interval.</p

The association of wood density categories and successful mixed-forest species in the monodominant <i>Gilbertiodendron</i> forest.

<p>The white bars represent the species absent in the monodominant forest and the grey bars represent those present in the monodominant forest.</p

Ordination of wood density, light requirement and relative abundance in the non-metric multidimensional scaling space of tree species.

<p>NMD1 and NMDS 2 represent axis 1 and axis 2 of the non-metric multidimensional scaling. The red open circles represent all established tree species (i.e., dbh≥10 cm) found in the three mix-forest plots.</p