China’s Assertive Behavior – Part Two: The Maritime Periphery

In CLM 32, we examined how both Chinese and outside observers look at China’s growing assertiveness on the international stage, that is, the purely perceptual dimensions of the issue. In CLM 34, we assessed whether, to what extent, and in what manner the Chinese government is becoming more assertive in defining and promoting the concept of “core interests.

Patterns of tree species composition across tropical African forests and within central African moist forests: the need for adapted management and conservation strategies

Background: Differences in the distribution of biota across Africa have been described for well over 100 years. There is however little information on the forest types at a regional scale. In this study we aimed to identify large-scale variation in tree species composition across tropical Africa, and within central Africa, to detail the structure and functioning of moist forests. Methods: Distribution data were gathered for 1175 tree species in 455 samples from the literature scattered across tropical Africa, from Senegal to Mozambique, and including all types of tropical forests. The value of elevation and 19 climatic variables (BIOCLIM) were assigned to each sample. Management forest inventory data were assembled for 49,711 0.5-ha plots across central Africa, covering an area of more than six million hectares. Using ordinations, we determined the variations in species composition across tropical African forests and for central African moist forests we used both genus composition and forest structure. We defined floristic clusters and identified the characteristic species/genera at both levels of resolution. Results: We found floristic evidence for three main biogeographic regions across the tropical African forests, and described six floristic clusters with particular environmental conditions within these regions: Coastal and Upland for East Africa, Dry and Wet-Moist for West Africa, and Moist and Wet for Central Africa. Within the central African moist forests, we identified 7 forest types based on genus composition and forest structure. Most of these forests were composed of a mosaic of the structural derivatives of the Celtis (Ulmaceae) forest. Secondary Musanga (Moraceae) forest was located along roads and around main cities; mixed Manilkara (Sapotaceae) forest covers a huge area in the Sangha River Interval; and monodominant Gilbertiodendron (Fabaceae) forest was sparsely distributed along rivers. Conclusions: The forest types identified across tropical African forests and within central African moist forests call for adapted management and conservation strategies. Specifically, the old-growth secondary Celtis forests that cover huge areas in central Africa should be managed for future timber productions, possibly complemented by artificial regeneration while the very specific and low productive Manilkara forests should be carefully managed with lower intensity practices. (Texte intégral

Human urine decreases function and expression of type 1 pili in uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is the primary cause of community-acquired urinary tract infections (UTIs). UPEC bind the bladder using type 1 pili, encoded by the fim operon in nearly all E. coli. Assembled type 1 pili terminate in the FimH adhesin, which specifically binds to mannosylated glycoproteins on the bladder epithelium. Expression of type 1 pili is regulated in part by phase-variable inversion of the genomic element containing the fimS promoter, resulting in phase ON (expressing) and OFF (nonexpressing) orientations. Type 1 pili are essential for virulence in murine models of UTI; however, studies of urine samples from human UTI patients demonstrate variable expression of type 1 pili. We provide insight into this paradox by showing that human urine specifically inhibits both expression and function of type 1 pili. Growth in urine induces the fimS phase OFF orientation, preventing fim expression. Urine also contains inhibitors of FimH function, and this inhibition leads to a further bias in fimS orientation toward the phase OFF state. The dual effect of urine on fimS regulation and FimH binding presents a potential barrier to type 1 pilus-mediated colonization and invasion of the bladder epithelium. However, FimH-mediated attachment to human bladder cells during growth in urine reverses these effects such that fim expression remains ON and/or turns ON. Interestingly, FimH inhibitors called mannosides also induce the fimS phase OFF orientation. Thus, the transduction of FimH protein attachment or inhibition into epigenetic regulation of type 1 pilus expression has important implications for the development of therapeutics targeting FimH function

Adaptation of arginine synthesis among uropathogenic branches of the Escherichia coli phylogeny reveals adjustment to the urinary tract habitat

Urinary tract infections (UTIs) are predominantly caused by uropathogeni

Dissecting the difference in tree species richness between Africa and South America

peer reviewedSignificanceOur full-scale comparison of Africa and South America's lowland tropical tree floras shows that both Africa and South America's moist and dry tree floras are organized similarly: plant families that are rich in tree species on one continent are also rich in tree species on the other continent, and these patterns hold across moist and dry environments. Moreover, we confirm that there is an important difference in tree species richness between the two continents, which is linked to a few families that are exceptionally diverse in South American moist forests, although dry formations also contribute to this difference. Plant families only present on one of the two continents do not contribute substantially to differences in tree species richness

Consistent patterns of common species across tropical tree communities

D.L.M.C. was supported by the London Natural Environmental Research Council Doctoral Training Partnership grant (grant no. NE/L002485/1). This paper developed from analysing data from the African Tropical Rainforest Observatory Network (AfriTRON), curated at ForestPlots.net. AfriTRON has been supported by numerous people and grants since its inception. We sincerely thank the people of the many villages and local communities who welcomed our field teams and without whose support this work would not have been possible. Grants that have funded the AfriTRON network, including data in this paper, are a European Research Council Advanced Grant (T-FORCES; 291585; Tropical Forests in the Changing Earth System), a NERC standard grant (NER/A/S/2000/01002), a Royal Society University Research Fellowship to S.L.L., a NERC New Investigators Grant to S.L.L., a Philip Leverhulme Award to S.L.L., a European Union FP7 grant (GEOCARBON; 283080), Leverhulme Program grant (Valuing the Arc); a NERC Consortium Grant (TROBIT; NE/D005590/), NERC Large Grant (CongoPeat; NE/R016860/1) the Gordon and Betty Moore Foundation the David and Lucile Packard Foundation, the Centre for International Forestry Research (CIFOR), and Gabon’s National Parks Agency (ANPN). This paper was supported by ForestPlots.net approved Research Project 81, ‘Comparative Ecology of African Tropical Forests’. The development of ForestPlots.net and data curation has been funded by several grants, including NE/B503384/1, NE/N012542/1, ERC Advanced Grant 291585—‘T-FORCES’, NE/F005806/1, NERC New Investigators Awards, the Gordon and Betty Moore Foundation, a Royal Society University Research Fellowship and a Leverhulme Trust Research Fellowship. Fieldwork in the Democratic Republic of the Congo (Yangambi and Yoko sites) was funded by the Belgian Science Policy Office BELSPO (SD/AR/01A/COBIMFO, BR/132/A1/AFRIFORD, BR/143/A3/HERBAXYLAREDD, FED-tWIN2019-prf-075/CongoFORCE, EF/211/TREE4FLUX); by the Flemish Interuniversity Council VLIR-UOS (CD2018TEA459A103, FORMONCO II); by L’Académie de recherche et d’enseignement supérieur ARES (AFORCO project) and by the European Union through the FORETS project (Formation, Recherche, Environnement dans la TShopo) supported by the XIth European Development Fund. EMV was supported by fellowship from the CNPq (Grant 308543/2021-1). RAPELD plots in Brazil were supported by the Program for Biodiversity Research (PPBio) and the National Institute for Amazonian Biodiversity (INCT-CENBAM). BGL post-doc grant no. 2019/03379-4, São Paulo Research Foundation (FAPESP). D.A.C. was supported by the CCI Collaborative fund. Plots in Mato Grosso, Brazil, were supported by the National Council for Scientific and Technological Development (CNPq), PELD-TRAN 441244/2016-5 and 441572/2020-0, and Mato Grosso State Research Support Foundation (FAPEMAT)—0346321/2021. We thank E. Chezeaux, R. Condit, W. J. Eggeling, R. M. Ewers, O. J. Hardy, P. Jeanmart, K. L. Khoon, J. L. Lloyd, A. Marjokorpi, W. Marthy, H. Ntahobavuka, D. Paget, J. T. A. Proctor, R. P. Salomão, P. Saner, S. Tan, C. O. Webb, H. Woell and N. Zweifel for contributing forest inventory data. We thank numerous field assistants for their invaluable contributions to the collection of forest inventory data, including A. Nkwasibwe, ITFC field assistant.Peer reviewe

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

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives