The global abundance of tree palms

Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

The global abundance of tree palms

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location: Tropical and subtropical moist forests. Time period: Current. Major taxa studied: Palms (Arecaceae). Methods: We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results: On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions: Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

Appendix A. Sinharaja forest dynamic plot, topographic habitat variables, variation partitioning, eigenfunctions of dbMEM, percentage of variation of species composition explained by blocks of eigenfunctions, variation partitioning for species composition, and effects of sample size.

Sinharaja forest dynamic plot, topographic habitat variables, variation partitioning, eigenfunctions of dbMEM, percentage of variation of species composition explained by blocks of eigenfunctions, variation partitioning for species composition, and effects of sample size

Appendix B. Methodology of habitat variables, Hellinger transformation, reconstruction of habitat variables, distance-based Moran’s eigenvector maps (dbMEM), forward selection of habitat and dbMEM variables, and variation partitioning.

Methodology of habitat variables, Hellinger transformation, reconstruction of habitat variables, distance-based Moran’s eigenvector maps (dbMEM), forward selection of habitat and dbMEM variables, and variation partitioning

Effects of topography on structuring species assemblages in a subtropical forest

Aims Topography has long been recognized as an important factor in shaping species distributions. Many studies revealed that species may show species-habitat associations. However, few studies investigate how species assemblages are associated with local habitats, and it still remains unclear how the community-habitat associations vary with species abundance class and life stage. In this study, we analyzed the community-habitat associations in a subtropical montane forest. Methods The fully mapped 25-ha (500 x 500 m) forest plot is located in Badagongshan Nature Reserve in Hunan Province, Central China. It was divided into 625 (20 x 20 m) quadrats. Habitat types were classified by multivariate regression tree analyses that cluster areas with similar species composition according to the topographic characteristics. Indicator species analysis was used to identify the most important species for structuring species assemblages. We also compared the community-habitat associations for two levels of species abundances (i.e. abundant and rare) and three different life stages (i.e. saplings, juveniles and adults), while accounting for sample size effects. Important Findings The Badagongshan plot was divided into five distinct habitat types, which explained 34.7% of the variance in tree species composition. Even with sample size taken into account, community-habitat associations for rare species were much weaker than those for abundant species. Also when accounting for sample size, very small differences were found in the variance explained by topography for the three life stages. Indicator species of habitat types were mainly abundant species, and nearly all adult stage indicator species were also indicators in juvenile and sapling stages. Our study manifested that topographical habitat filtering was important in shaping overall local species compositions. However, habitat filtering was not important in shaping rare species' distributions in this forest. The community-habitat association patterns in this forest were mainly shaped by abundant species. In addition, during the transitions from saplings to juveniles, and from juveniles to adults, the relative importance of habitat filtering was very weak

Appendix A. Figures and tables showing detailed results of the analyses at the focal species level and the results for the second census.

Figures and tables showing detailed results of the analyses at the focal species level and the results for the second census

Effects on the growth rates of small (dbh 10–30 mm) focal trees in the presence and in the absence of annular heterospecific trees of species that are closely related to the focal tree.

<p>The annular trees consist of the species that lie within the interval 0–25 Ma since the time of their last common ancestor with the focal tree species. Data presented as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156913#pone.0156913.g002" target="_blank">Fig 2</a>.</p

Correction: Persistence of Neighborhood Demographic Influences over Long Phylogenetic Distances May Help Drive Post-Speciation Adaptation in Tropical Forests

<p>Correction: Persistence of Neighborhood Demographic Influences over Long Phylogenetic Distances May Help Drive Post-Speciation Adaptation in Tropical Forests</p

Analyses of variance that examine the relationships between the response variable of focal tree growth and the factors of annular tree basal area, focal tree size, plot topography, and focal tree autocorrelation.

<p>In this analysis, and in the analyses of Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156913#pone.0156913.t002" target="_blank">2</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156913#pone.0156913.t004" target="_blank">4</a>, the topographic factor is the topographic classification of the 20 x 20 m quadrat in which the focal tree is located, and the autocorrelation factor is the extent to which properties of focal trees are correlated when the focal trees share the same quadrat. Because of constraints in available computer programs that limit the number of interaction terms that can be estimated in an analysis, it was only possible to obtain interaction mean squares and F-values for 400 of the 1250 BCI quadrats and 400 of the 625 Sinharaja quadrats. Repeated random samplings of 400 quadrats from the data produced statistically indistinguishable results.</p