References of "Bauman, David"
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See detailInterspecific trait integration increases with environmental harshness: a case study along a metal toxicity gradient
Delhaye, Guillaume; Bauman, David; Seleck, Maxime ULiege et al

in Functional Ecology (2020)

1. Functional traits are commonly used to calculate a wide array of functional diversity indices to infer different mechanisms of community assembly and spe-cies coexistence. Recently, the degree of ... [more ▼]

1. Functional traits are commonly used to calculate a wide array of functional diversity indices to infer different mechanisms of community assembly and spe-cies coexistence. Recently, the degree of interspecific covariation between multi-ple functional traits has been suggested as a mechanism influencing both species distributions and abundances in communities. However, empirical assessments of this theory along environmental gradients are still scarce due to the lack of an appropriate method and of sufficiently strong environmental gradients.2. Here we compare interspecific trait integration (ITI) across plant communities along a marked gradient of copper toxicity in the soil, using new multivariate and bivariate indices. This was achieved using the range of the eigenvalues of a princi-pal component analysis on the traits of the species in a local community (multivari-ate ITI index) and the correlations between traits in local communities (bivariate ITI index).3. We show that the plant metal tolerance strategy (i.e. leaf metal content) is rela-tively independent from leaf economics, while negatively correlated to plant size. In addition, our results indicate a weak support for the expected general patterns of trait syndromes, such as the ‘leaf economics spectrum’ or the ‘leaf–height–seed’, at the whole-community scale. This arises from an increase in multivariate trait in-tegration along the soil copper gradient. The strongest trait integration is caused by an increase in the degree of association between certain traits on metal-rich soils. The multivariate trait integration explains species richness better than other commonly used functional diversity indices.4. Our study highlights the power of ITI, as well as its complementarity to other functional diversity indices, to investigate the variation in functional strategies and their drivers along environmental gradients. The increase in trait integration with soil metal toxicity in plant communities supports that highly constraining en-vironments select increasingly coordinated sets of functional traits, in turn pos-sibly driving the decrease in species richness. Further studies should assess the generality and underlying physiological mechanisms of such ecological patterns. [less ▲]

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See detailPast human disturbances and soil fertility both influence the distribution of light-demanding tree species in a Central African tropical forest
Vleminckx, Jason; Bauman, David; Demanet, Marine et al

in Journal of Vegetation Science (2020), 31

Questions: In vast areas of Central African forests, the upper canopy is presently dominated by light-demanding tree species. Here, we confront three hypotheses to explain this dominance: (a) these ... [more ▼]

Questions: In vast areas of Central African forests, the upper canopy is presently dominated by light-demanding tree species. Here, we confront three hypotheses to explain this dominance: (a) these species have expanded their distribution because of widespread past slash-and-burn activities, as suggested by important charcoal amounts recorded in the soils of the region; (b) their abundance is rather explained by soil properties, as this guild establishes preferentially on favourable physico-chemical conditions for rapid growth; (c) soil properties have been substantially influenced by past human disturbances and those two effects cannot be disentangled. Location: Pallisco-CIFM logging concession, southeastern Cameroon (300,000 ha). Methods: We quantified soil charcoal abundance and measured ten soil variables at the basis of 60 target trees that belonged to a list of three long-living pioneer lightdemanding (LLP) and four shade-bearer (SB) species. We identified all stems with a diameter at breast height (DBH) ≥ 20 cm within a distance of 15 m around each target tree. Species were characterised by their wood-specific gravity (WSG), which reflected their light requirement. Multiple regression models were used to quantify and test the relative effects of charcoal abundance and soil variables on the mean WSG of the 60 tree communities, as well as the abundance of three guilds: LLP, SB, and non-pioneer light demanders (NPLD). Results: The mean WSG was the only response variable significantly explained by soil variables and charcoal abundance combined. It was significantly negatively associated with soil calcium and Mg content and with charcoal abundance, with soil and charcoal influencing the mean WSG independently. Conclusion: Our study provides evidence that past human disturbances and soil fertility have independently promoted the establishment of light-demanding species in western Central African forests, thereby shedding light on tree community assembly rules in these ecosystems which remain considerably understudied compared to the tropical forests of other continents. [less ▲]

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See detailA sharp floristic discontinuity revealed by the biogeographic regionalization of African savannas
Fayolle, Adeline ULiege; Swaine, Michael D.; Aleman, Julie et al

in Journal of Biogeography (2019)

Aim: In tropical Africa, savannas cover huge areas, have high plant species richness and are considered as a major natural resource for most countries. There is, however, little information available on ... [more ▼]

Aim: In tropical Africa, savannas cover huge areas, have high plant species richness and are considered as a major natural resource for most countries. There is, however, little information available on their floristics and biogeography at the continental scale, despite the importance of such information for our understanding of the drivers of species diversity at various scales and for effective conservation and management. Here, we collated and analysed floristic data from across the continent in order to propose a biogeographical regionalization for African savannas. Location: We collated floristic information (specifically woody species lists) for 298 samples of savanna vegetation across Africa, extending from 18° N to 33° S and from 17° W to 48° E. Taxa: We focused on native woody species. Methods: We used ordination and clustering to identify the floristic discontinuities and gradual transitions across African savannas. Floristic relationships, specificity and turnover, within and between floristic clusters, were analysed using a (dis‐)similarity‐ based approach. Results: We identified eight floristic clusters across African savannas which in turn were grouped into two larger macro‐units. Ordinations at species and genus levels showed a clear differentiation in woody species composition between the North/ West macro‐unit and the South/East macro‐unit. This floristic discontinuity matches to the High (i.e. N&W) and Low (S&E) division of Africa previously proposed by White (1983) and which tracks climatic and topographical variation. In the N&W savannas, the floristic gradient determined by rainfall was partitioned into the Sudanian (drier) and Guinean (wetter) clusters. Within the highly heterogeneous S&E savannas and woodlands, six clusters were identified: Ugandan, Ethiopian, Mozambican, Zambezian, Namibian and South African. Main conclusions: The proposed pan‐African classification of savannas and woodlands might assist the development of coordinated management and conservation policies. [less ▲]

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See detailThe influence of spatially structured soil properties on tree community assemblages at a landscape scale in the tropical forests of southern Cameroon
Vleminckx, Jason; Doucet, Jean-Louis ULiege; Morin, Julie ULiege et al

in Journal of Ecology (2016)

Species distribution within plant communities results from both the influence of deterministic processes, related to environmental conditions, and neutral processes related to dispersal limitation and ... [more ▼]

Species distribution within plant communities results from both the influence of deterministic processes, related to environmental conditions, and neutral processes related to dispersal limitation and stochastic events, the relative importance of each factor depending on the observation scale. Assessing the relative contribution of environment necessitates controlling for spatial dependences among data points. Recent methods, combining multiple regression and Moran's eigenvectors maps (MEM), have been proved successful in disentangling the influence of pure spatial processes related to dispersal limitation, pure environmental variables (not spatially structured) and spatially structured environmental properties. However, the latter influence is usually not testable when using advanced spatial models like MEM. To overcome this issue, we propose an original approach, based on torus-translations and Moran spectral randomizations, to test the fraction of species abundance variation that is jointly explained by space and seven soil variables, using three environmental and tree species abundance data sets (consisting of 120, 52 and 34 plots of 0·2 ha each, located along 101-, 66- and 35-km-long transect-like inventories, respectively) collected in tropical moist forests in southern Cameroon. The overall abundance of species represented by ≥30 individuals, and 27% of these species taken individually, were significantly explained by fine-scale (<5 km) and/or broad-scale (5–100 km) spatially structured variations in soil nutrient concentrations (essentially the concentration of available Mn, Mg and Ca) along the 120-plots area. The number of significant tests considerably decreased when investigating the two smaller data sets, which mostly resulted from low statistical power rather than weaker floristic and/or edaphic variation captured among plots. Synthesis. Our results provide evidence that tree species turnovers are partly controlled by spatially structured concentrations in soil nutrients at scales ranging from few hundreds of metres to c. 100 km, a poorly documented subject in Central African forests. We also highlight the usefulness of our testing procedure to correctly interpret the space-soil fraction of variation partitioning analyses (which always accounted here for the most important part of the soil contribution), as this fraction was sometimes relatively high (R2 values up to c. 0·3) but nearly or not significant. [less ▲]

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