Biology subjects

Herault, B.

Publications and source records attributed to Herault, B..

3 recordsLinked to original sources

bioRxiv2024

Land-use impacts on plant functional diversity throughout Europe

AimGlobal biodiversity loss resulting from anthropogenic land-use activities is a pressing concern, requiring precise assessments of impacts at large spatial extents. Existing models mainly focus on species richness and abundance, lacking insights into ecological mechanisms and species roles in ecosystem functioning. To bridge this gap, we conducted an extensive analysis of the impact of human land use on vascular plant functional diversity, across diverse land-use classes and bioregions in Europe, comparing it to traditional metrics. Location: Europe Time period: 1992-2019 Major taxa studied: Vascular plants MethodsIntegrating extensive databases of vegetation plots with spatial data on land use and land cover, we paired plots from areas actively used and modified by humans with plots from natural habitats under similar environmental conditions. Using species occurrences and traits, in each plot we computed three complementary functional diversity metrics (functional richness, evenness, and divergence), species richness and abundance. We assessed the impact of land use by comparing the metrics in the paired plots. ResultsOur findings revealed that, compared to natural habitats, anthropogenic land use exhibits lower functional richness and divergence but higher functional evenness across most land-use classes and bioregions. The response of functional richness was more marked than the other two metrics and especially pronounced in croplands and urban areas and in northern bioregions. Functional richness exhibited a pattern that did not fully overlap with the trend in species richness, providing useful complementary information. Main conclusionsWe provide a large-scale precise assessment of anthropogenic land-use impacts on functional diversity across Europe. Our findings indicate that: (i) human disturbance significantly alters plant functional diversity compared to natural habitats; (ii) this alteration goes in the direction of functional homogenization; (i) functional diversity metrics complement traditional metrics by offering deeper insights into the ecological mechanisms in response to anthropogenic land use.

ecology↗

bioRxiv2023

Tree demographic strategies largely overlap across succession in Neotropical wet and dry forest communities

Secondary tropical forests play an increasingly important role for carbon budgets and biodiversity conservation. Understanding successional trajectories is therefore imperative for guiding forest restoration and climate change mitigation efforts. Forest succession is driven by the demographic strategies - combinations of growth, mortality and recruitment rates - of the tree species in the community. However, our understanding of demographic diversity in tropical tree species stems almost exclusively from old-growth forests. Here, we assembled demographic information from repeated forest inventories along chronosequences in two wet (Costa Rica, Panama) and two dry (Mexico) Neotropical forests to assess whether the range of demographic strategies present in a community shifts across succession. We calculated demographic rates for >500 tree species while controlling for canopy status to compare demographic diversity in early successional (0-30 years), late successional (30-120 years) and old-growth forests. We quantified demographic diversity using two-dimensional hypervolumes of pairs of demographic rates and assessed whether shifts in demographic strategies were caused by intra-specific changes in demographic rates across succession or by species turnover. We expected that demographic strategies would shift from faster life-histories (fast growth, high mortality, high recruitment) in early successional forests to slower life histories (slow growth, low mortality, low recruitment) in old-growth forests and that shifts would be stronger in wet than in dry forests due to more pronounced differences in environmental conditions between early successional and old-growth forests. We also expected that demographic diversity would increase with succession. We found that demographic strategies largely overlapped across successional stages and that early successional stages already covered the full spectrum of demographic strategies found in old-growth forests. An exception was a group of species characterized by exceptionally high mortality rates that was confined to early successional stages in the two wet forests. Demographic diversity did not increase with succession. Our results suggest that current understanding of demographic strategies of tropical tree species, which has been generated mostly from long-term forest monitoring plots in old-growth forests, is largely representative of demographic diversity in general, and that demographic diversity recovers quickly during succession.

ecology↗

bioRxiv2022

High intraspecific growth variability despite strong evolutionary heritage in a neotropical forest

Individual tree growth is a key determinant of species performance and a driver of forest dynamics and composition. Previous studies on tree growth unravelled the variation in species growth as a function of demographic trade-offs that are partially predicted using functional traits. They have explored the environmental determinants of species growth potential and the variation of intraspecific growth over space and time due to environment and biotic factors. However, variation in individual growth within species remains underexplored for a whole community and the relative role of species evolutionary heritage and of local environments remains unquantified. Here, based on 36 years of diameter records for thousands of mapped individuals belonging to 138 species, we assessed individual tree growth potential in a local neotropical forest community in the Amazon basin. We further related variation in individual growth potential with taxonomic levels, local topography, and neighbourhood crowding, before exploring species growth potential link to functional traits and distribution along the phylogeny. We found that most of the variation in growth potential was individual, and that taxonomic structure explained a third of the observed variation. Species growth potential was phylogenetically conserved with positive conservatism up to the genus level in the vast majority of species. Functional traits of roots, wood and leaves together predicted species growth potential. Phylogeny suggested joint selection of species growth strategies and associated functional traits during convergent evolutions. Finally, neighbourhood crowding had a significant effect on individual growth potential, although much of this inter-individual variation remains largely unexplained and the underlying ecological and evolutionary factors are still little explored. The high intraspecific variation observed could allow individuals in these hyperdiverse ecosystems to respond to the variable light and competitive conditions offered by successional niches during forest gap dynamics.

ecology↗