Éditeur(s) : HAL CCSD Springer Verlag
Résumé : The area of forest plantations is increasing worldwide helping to meet timber demand and protect natural forests. However, with global change, monospecific plantations are increasingly vulnerable to abiotic and biotic disturbances. As an adaption measure we need to move to plantations that are more diverse in genotypes, species, and structure, with a design underpinned by science. TreeDivNet, a global network of tree diversity experiments, responds to this need by assessing the advantages and disadvantages of mixed species plantations. The network currently consists of 18 experiments, distributed over 36 sites and five ecoregions. With plantations 1-15 years old, TreeDivNet can already provide relevant data for forest policy and management. In this paper, we highlight some early results on the carbon sequestration and pest resistance potential of more diverse plantations. Finally, suggestions are made for new, innovative experiments in understudied regions to complement the existing network.
ISSN: 0044-7447

hal-01204232
https://hal.archives-ouvertes.fr/hal-01204232
DOI : 10.1007/s13280-015-0685-1
PRODINRA : 324368
PUBMED : 26264716

Éditeur(s) : HAL CCSD Wiley
Résumé : White-sand forests represent natural laboratories of evolution over their long history throughout Amazonia and the Guiana Shield and pose significant physiological challenges to the plants and animals they host. The study of diversification in plant lineages comprising species endemic to white-sand forest can therefore give insights into processes of evolution and community assembly in tropical forests. In this article, we synthesize recent studies of white-sand forests to integrate patterns of plant species distribution with processes of lineage diversification and community assembly in the white-sand flora. We contrast lineages that have radiated uniquely in these habitats (e.g., Pagamea, Rubiaceae), with cosmopolitan lineages comprising specialists to white-sand forests and other habitats that may have arisen via ecological speciation across habitat gradients (e.g., Protium, Burseraceae). In both cases, similar suites of functional traits have evolved, including investment in dense, long-lived tissues that are well-defended structurally and chemically. White-sand endemics, therefore, play an important role in biodiversity conservation because they represent unique combinations of functional and phylogenetic diversity. Furthermore, white-sand endemics may respond differently than other tropical forest plant species to contemporary global changes because they comprise resilient functional types that may better withstand increased drought, temperature, and invasions of exotic pests in these regions.
ISSN: 0006-3606

hal-01531635
https://hal.archives-ouvertes.fr/hal-01531635
DOI : 10.1111/btp.12301
PRODINRA : 353397

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : International audience
Plant responses to natural enemies include formation of secondary metabolites acting as direct or indirect defenses. Volatile terpenes represent one of the most diverse groups of secondary metabolites. We aimed to explore evolutionary patterns of volatile terpene emission. We measured the composition of damage-induced volatile terpenes from 202 Amazonian tree species, spanning the angiosperm phylogeny. Volatile terpenes were extracted with solid-phase micro extraction and desorbed in a gas chromatography–mass spectrometry for compound identification. The chemical diversity of the terpene blend showed a strong phylogenetic signal as closely related species emitted a similar number of compounds. Closely related species also tended to have compositionally similar blends, although this relationship was weak. Meanwhile, the ability to emit a given compound showed no significant phylogenetic signal for 200 of 286 compounds, indicating a high rate of diversification in terpene synthesis and/or great variability in their expression. Three lineages (Magnoliales, Laurales, and Sapindales) showed exceptionally high rates of terpene diversification. Of the 70 compounds found in >10% of their species, 69 displayed significant correlated evolution with at least one other compound. These results provide insights into the complex evolutionary history of volatile terpenes in angiosperms, while highlighting the need for further research into this important class of compounds.
ISSN: 2045-7758

Droits : http://creativecommons.org/licenses/by/
hal-01296640
http://hal.upmc.fr/hal-01296640
http://hal.upmc.fr/hal-01296640/document
http://hal.upmc.fr/hal-01296640/file/ece31810.pdf
DOI : 10.1002/ece3.1810

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : We examined tree-soil habitat associations in lowland forest communities at Paracou, French Guiana. We analyzed a large dataset assembling six permanent plots totaling 37.5 ha, in which extensive LIDAR-derived topographical data and soil chemical and physical data have been integrated with precise botanical determinations. Map of relative elevation from the nearest stream summarized both soil fertility and hydromorphic characteristics, with seasonally inundated bottomlands having higher soil phosphate content and base saturation, and plateaus having higher soil carbon, nitrogen and aluminum contents. We employed a statistical test of correlations between tree species density and environmental maps, by generating Monte Carlo simulations of random raster images that preserve autocorrelation of the original maps. Nearly three fourths of the 94 taxa with at least one stem per ha showed a significant correlation between tree density and relative elevation, revealing contrasted species-habitat associations in term of abundance, with seasonally inundated bottomlands (24.5% of species) and well-drained plateaus (48.9% of species). We also observed species preferences for environments with or without steep slopes (13.8% and 10.6%, respectively). We observed that closely-related species were frequently associated with different soil habitats in this region (70% of the 14 genera with congeneric species that have a significant association test) suggesting species-habitat associations have arisen multiple times in this tree community. We also tested if species with similar habitat preferences shared functional strategies. We found that seasonally inundated forest specialists tended to have smaller stature (maximum diameter) than species found on plateaus. Our results underline the importance of tree-soil habitat associations in structuring diverse communities at fine spatial scales and suggest that additional studies are needed to disentangle community assembly mechanisms related to dispersal limitation, biotic interactions and environmental filtering from species-habitat associations. Moreover, they provide a framework to generalize across tropical forest sites.
ISSN: 1932-6203

hal-01260289
https://hal.archives-ouvertes.fr/hal-01260289
PRODINRA : 342930
DOI : 10.1371/journal.pone.0141488

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Arthropods represent most of global biodiversity, with the highest diversity found in tropical rain forests. Nevertheless, we have a very incomplete understanding of how tropical arthropod communities are assembled. 2. We conducted a comprehensive mass sampling of arthropod communities within three major habitat types of lowland Amazonian rain forest, including terra firme clay, white-sand and seasonally flooded forests in Peru and French Guiana. We examined how taxonomic and functional composition (at the family level) differed across these habitat types in the two regions. 3. The overall arthropod community composition exhibited strong turnover among habitats and between regions. In particular, seasonally flooded forest habitats of both regions comprised unique assemblages. Overall, 17.7% (26 of 147) of arthropod families showed significant preferences for a particular habitat type. 4. We present a first reproducible arthropod functional classification among the 147 taxa based on similarity among 21 functional traits describing feeding source, major mouthparts and microhabitats inhabited by each taxon. We identified seven distinct functional groups whose relative abundance contrasted strongly across the three habitats, with sap and leaf feeders showing higher abundances in terra firme clay forest. 5. Our novel arthropod functional classification provides an important complement to link these contrasting patterns of composition to differences in forest functioning across geographical and environmental gradients. This study underlines that both environment and biogeographical processes are responsible for driving arthropod taxonomic composition while environmental filtering is the main driver of the variance in functional composition.
ISSN: 0021-8790

hal-01531619
https://hal.archives-ouvertes.fr/hal-01531619
PRODINRA : 349695
PUBMED : 26346553
DOI : 10.1111/1365-2656.12445

Éditeur(s) : HAL CCSD Wiley
Résumé : In the Amazon basin and the Guiana Shield, white-sand (WS) forests are recognized as a low-resource habitat often composed by a distinct flora with many edaphic endemic plants. Small patches of nutrient-poor white-sand forests can pose a series of challenges to plants and animals. For plants, these challenges have been shown to function as strong filters that in turn drive taxonomic, functional and phylogenetic plant composition. However, very little is known about animal communities in WS forest and the effect that low-resource availability may have on higher trophic levels. Here, we investigate the diversity of both taxonomic and phylogenetic diversity of three Lepidoptera families' (Nymphalidae, Saturniidae, and Sphingidae) assemblages between low-resource (White-Sand Forest) and two adjacent high-resource habitats, terra firme clay and seasonally flooded forests. We found no clear effect of habitat type on taxonomic composition although butterfly and moth species abundance differed among the three contrasted habitats. The WS forest Lepidoptera community is significantly more phylogenetically overdispersed than expected by chance. We suggest that these low-resource habitats filter the number of plant lineages which, in turn, creates a bottom-up control structuring Lepidoptera phylogenetic structure. We recommend long-term sampling on Lepidoptera community both at larval and adult stages that may complement this study and test hypotheses linking herbivore phylogenetic structure to plant resource availability and trophic cascade theory.
ISSN: 0006-3606

hal-01532550
https://hal.archives-ouvertes.fr/hal-01532550
DOI : 10.1111/btp.12294
PRODINRA : 353400

Éditeur(s) : HAL CCSD
Résumé : International audience
The tropical rainforest of Amazonia is one of the most species-rich ecosystems on earth, with an estimated 16000 tree species. Due to this high diversity, botanical identification of trees in the Amazon is difficult, even to genus, often requiring the assistance of parataxonomists or taxonomic specialists. Advances in informatics tools offer a promising opportunity to develop user-friendly electronic keys to improve Amazonian tree identification.Here, we introduce an original multi-access electronic key for the identification of 389 tree genera occurring in French Guiana terra-firme forests, based on a set of 79 morphological characters related to vegetative, floral and fruit characters. Its purpose is to help Amazonian tree identification and to support the dissemination of botanical knowledge to non-specialists, including forest workers, students and researchers from other scientific disciplines.The electronic key is accessible with the free access software Xper², and the database is publicly available on figshare: https://figshare.com/s/75d890b7d707e0ffc9bf (doi: 10.6084/m9.figshare.2682550).
ISSN: 1314-2011

hal-01369143
https://hal-sde.archives-ouvertes.fr/hal-01369143
DOI : 10.3897/phytokeys.68.8707

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Functional traits provide insight into a variety of ecological questions, yet the optimal sampling method to estimate the community-level distribution of plant functional trait values remains a subject of debate, especially in species-rich forests. 2. We present a simulation analysis of the trait distribution of a set of nine completely sampled permanent plots in the lowland rain forests of French Guiana. 3. Increased sampling intensity consistently improved accuracy in estimating community-weighted means and variances of functional trait values, whereas there was substantial variation among functional traits and minor differences among sampling strategies. 4. Thus, investment in intensified sampling yields a greater improvement in the accuracy of estimation than does an equivalent investment in sampling design complication. 5. Notably, 'taxon-free' strategies frequently had greater accuracy than did abundance-based strategies, which had the additional cost of requiring botanical surveys. 6. We conclude that there is no substitute for extensive field sampling to accurately characterize the distribution of functional trait values in species-rich forests.
ISSN: 0269-8463

hal-01536541
https://hal.archives-ouvertes.fr/hal-01536541
PRODINRA : 343202
DOI : 10.1111/1365-2435.12433