Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few 'hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.
ISSN: 2041-1723

hal-01204225
https://hal.archives-ouvertes.fr/hal-01204225
DOI : 10.1038/ncomms7857
PRODINRA : 305614
PUBMED : 25919449

Éditeur(s) : HAL CCSD Elsevier
Résumé : While around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production [1] . Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity [2,3] . Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al. [4] found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin [5] to assess the main drivers of time-to-recovery of post-logging tree carbon ( Table S1 ). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions.
ISSN: 0960-9822

hal-01536542
https://hal.archives-ouvertes.fr/hal-01536542
DOI : 10.1016/j.cub.2015.07.034
PRODINRA : 343217
PUBMED : 26394096

Éditeur(s) : HAL CCSD Wiley
Résumé : The allocation and cycling of carbon (C) within forests is an important component of the biospheric C cycle, but is particularly understudied within tropical forests. We synthesise reported and unpublished results from three lowland rainforest sites in Amazonia (in the regions of Manaus, Tapajos and Caxiuana), all major sites of the Large-Scale Biosphere-Atmosphere Programme (LBA). We attempt a comprehensive synthesis of the C stocks, nutrient status and, particularly, the allocation and internal C dynamics of all three sites. The calculated net primary productivities (NPP) are 10.1 +/- 1.4 Mg C ha(-1) yr(-1) (Manaus), 14.4 +/- 1.3 Mg C ha(-1) yr(-1) (Tapajos) and 10.0 +/- 1.2 Mg C ha(-1) yr(-1) (Caxiuana). All errors bars report standard errors. Soil and leaf nutrient analyses indicate that Tapajos has significantly more plant-available phosphorus and calcium. Autotrophic respiration at all three sites (14.9-21.4 Mg C ha yr(-1)) is more challenging to measure, with the largest component and greatest source of uncertainty being leaf dark respiration. Comparison of measured soil respiration with that predicted from C cycling measurements provides an independent constraint. It shows general good agreement at all three sites, with perhaps some evidence for measured soil respiration being less than expected. Twenty to thirty percent of fixed C is allocated belowground. Comparison of gross primary productivity (GPP), derived from ecosystem flux measurements with that derived from component studies (NPP plus autotrophic respiration) provides an additional crosscheck. The two approaches are in good agreement, giving increased confidence in both approaches to estimating GPP. The ecosystem carbon-use efficiency (CUEs), the ratio of NPP to GPP, is similar at Manaus (0.34 +/- 0.10) and Caxiuana (0.32 +/- 0.07), but may be higher at Tapajos (0.49 +/- 0.16), although the difference is not significant. Old growth or infertile tropical forests may have low CUE compared with recently disturbed and/or fertile forests.
ISSN: 1354-1013

hal-01032150
https://hal.archives-ouvertes.fr/hal-01032150
DOI : 10.1111/j.1365-2486.2008.01780.x

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Losses of corals worldwide emphasize the need to understand what drives reef decline. Stressors such as overfishing and nutrient pollution may reduce resilience of coral reefs by increasing coral–algal competition and reducing coral recruitment, growth and survivorship. Such effects may themselves develop via several mechanisms, including disruption of coral microbiomes. Here we report the results of a 3-year field experiment simulating overfishing and nutrient pollution. These stressors increase turf and macroalgal cover, destabilizing microbiomes, elevating putative pathogen loads, increasing disease more than twofold and increasing mortality up to eightfold. Above-average temperatures exacerbate these effects, further disrupting microbiomes of unhealthy corals and concentrating 80% of mortality in the warmest seasons. Surprisingly, nutrients also increase bacterial opportunism and mortality in corals bitten by parrotfish, turning normal trophic interactions deadly for corals. Thus, overfishing and nutrient pollution impact reefs down to microbial scales, killing corals by sensitizing them to predation, above-average temperatures and bacterial opportunism.
ISSN: 2041-1723

Droits : http://creativecommons.org/licenses/by/
hal-01340547
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547/file/ncomms11833.pdf
DOI : 10.1038/ncomms11833

Éditeur(s) : HAL CCSD Elsevier
Résumé : Guadua sarcocarpa and Guadua weberbaueri (Poaceae: Bambuseae) have a negative influence on tree regeneration and recruitment in bamboo-dominated forests of southwestern Amazonia. The lack of advanced regeneration and sparse canopy in this forest type present a considerable challenge for developing sustainable timber management plans. We conducted field studies in the Porto Dias Agroextractive Settlement Project in Acre, Brazil to assess influences of logging in bamboo-dominated forest sites. Taxonomic composition, stand structure, aboveground biomass, commercial timber volume, and commercial tree seedling and bamboo culm density were compared between five logged vs. unlogged sites in different landholdings, using modified 0.5 ha Gentry plots. No differences in taxonomic composition, aboveground biomass, adult and juvenile stem density, or woody seedling and bamboo culm density were detected between paired logged and unlogged sites. Commercial timber volume, however, was reduced by almost two-thirds in logged plots, suggesting that long-term timber management goals in this forest type are compromised since so few future crop trees remained onsite. Our findings indicate that in order to maximize local management objectives, community forest managers must approach logging in bamboo-dominated forests with caution. We suggest an integration of non-timber forest product extraction with low harvest intensity and low-impact logging, tending of natural regeneration, and diversification of commercial species.
ISSN: 0378-1127

hal-01204213
https://hal.archives-ouvertes.fr/hal-01204213
DOI : 10.1016/j.foreco.2013.12.022
PRODINRA : 263103

Éditeur(s) : HAL CCSD Wiley
Résumé : [b]1.[/b] Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates.[br/][br/][b]2.[/b] If community-level relationships between traits and growth have general predictive value, then similar relationships should also be observed in analyses that integrate across taxa, biogeographic regions and environments. Such global consistency would imply that traits could serve as valuable proxies for the complex suite of factors that determine growth rate, and, therefore, could underpin a new generation of robust dynamic vegetation models. Alternatively, growth rates may depend more strongly on the local environment or growth–trait relationships may vary along environmental gradients.[br/][br/][b]3.[/b] We tested these alternative hypotheses using data on 27 352 juvenile trees, representing 278 species from 27 sites on all forested continents, and extensive functional trait data, 38% of which were obtained at the same sites at which growth was assessed. Data on potential evapotranspiration (PET), which summarizes the joint ecological effects of temperature and precipitation, were obtained from a global data base.[br/][br/][b]4.[/b] We estimated size-standardized relative height growth rates (SGR) for all species, then related them to functional traits and PET using mixed-effect models for the fastest growing species and for all species together.[br/][br/][b]5.[/b] Both the mean and 95th percentile SGR were more strongly associated with functional traits than with PET. PET was unrelated to SGR at the global scale. SGR increased with increasing SLA and decreased with increasing wood density and seed mass, but these traits explained only 3.1% of the variation in SGR. SGR–trait relationships were consistently weak across families and biogeographic zones, and over a range of tree statures. Thus, the most widely studied functional traits in plant ecology were poor predictors of tree growth over large scales.[br/][br/][b]6.[/b] Synthesis. We conclude that these functional traits alone may be unsuitable for predicting growth of trees over broad scales. Determining the functional traits that predict vital rates under specific environmental conditions may generate more insight than a monolithic global relationship can offer.
ISSN: 0022-0477

hal-01204226
https://hal.archives-ouvertes.fr/hal-01204226
DOI : 10.1111/1365-2745.12401
PRODINRA : 307144

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages , we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.
ISSN: 0962-8452

hal-01323255
https://hal.archives-ouvertes.fr/hal-01323255
DOI : 10.1098/rspb.2015.0418

Éditeur(s) : Center for Latin American Studies Center for Latin American Studies ( Gainesville Fla )
Résumé : (Additional Physical Form) Also issued online.
(Dates or Sequential Designation) Vol. 1, no. 1 (Feb. 3, 1964)-
(Numbering Peculiarities) Suspended between v. 35, no. 1 (fall 1999) and v. 36, no. 1 (spring 2005).
Title from caption.
Latest issue consulted: Vol. 36, no. 2 (fall 2005).
Latin America
Latin America
Florida

05269284
sc 84001784
0502-6660

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Growth defense tradeoff theory predicts that plants in low-resource habitats invest more energy in defense mechanisms against natural enemies than growth, whereas plants in high-resource habitats can afford higher leaf loss rates. A less-studied defense against herbivores involves the synchrony of leaf production, which can be an effective defense strategy if leaf biomass production exceeds the capacity of consumption by insects. The aim of this study was to determine whether leaf synchrony varied across habitats with different available resources and whether insects were able to track young leaf production among tree habitat specialists in a tropical forest of French Guiana. We predicted that high-resource habitats would exhibit more synchrony in leaf production due to the low cost and investment to replace leaf tissue. We also expected closer patterns of leaf synchrony and herbivory within related species, assuming that they shared herbivores. We simultaneously monitored leaf production and herbivory rates of five pairs of tree species, each composed of a specialist of terra firme or white-sand forests within the same lineage. Our prediction was not supported by the strong interaction of habitat and lineage for leaf synchrony within individuals of the same species; although habitat specialists differed in leaf synchrony within four of five lineages, the direction of the effect was variable. All species showed short time lags for the correlation between leaf production and herbivory, suggesting that insects are tightly tracking leaf production, especially for the most synchronous species. Leaf synchrony may provide an important escape defense against herbivores, and its expression appears to be constrained by both evolutionary history and environmental factors.
ISSN: 1385-0237

hal-01204221
https://hal.archives-ouvertes.fr/hal-01204221
DOI : 10.1007/s11258-013-0290-y
PRODINRA : 288500

Éditeur(s) : Center for Latin American Studies, Center for Latin American Studies ( Gainesville, Fla ) Center for Latin American Studies, Center for Latin American Studies ( Gainesville, Fla )

337250
5269284
http://ufdc.ufl.edu/UF00066464/00025

Éditeur(s) : Center for Latin American Studies Center for Latin American Studies ( Gainesville Fla )
Résumé : (Additional Physical Form) Also issued online.
(Dates or Sequential Designation) Vol. 1, no. 1 (Feb. 3, 1964)-
(Numbering Peculiarities) Suspended between v. 35, no. 1 (fall 1999) and v. 36, no. 1 (spring 2005).
Title from caption.
Latest issue consulted: Vol. 36, no. 2 (fall 2005).
Latin America
Latin America
Florida

05269284
sc 84001784
0502-6660

Éditeur(s) : University Gallery, College of Fine Arts, University of Florida University Gallery, College of Fine Arts, University of Florida ( Gainesville )
Résumé : (Bibliography) Bibliography: p. 16-19.
(Statement of Responsibility) by John F. Scott.
"Exhibiting institutions The University Gallery ... The Brevard Art Center and Museum."
Presented by the University Gallery and Center for Latin American Studies.
Mexico
Mexico
Central America
Amérique centrale
Mexique
Mexique
Amérique centrale

187344282
0813008824
ocn187344282

Éditeur(s) : University of Florida University of Florida ( Gainesville, FL )

http://ufdc.ufl.edu/UF00091464/00001

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1).
ISSN: 1726-4170

hal-01557759
https://hal.univ-lorraine.fr/hal-01557759
https://hal.univ-lorraine.fr/hal-01557759/document
https://hal.univ-lorraine.fr/hal-01557759/file/bg-13-2537-2016.pdf
DOI : 10.5194/bg-13-2537-2016

Éditeur(s) : Center for Latin American Studies Center for Latin American Studies ( Gainesville Fla )
Résumé : (Additional Physical Form) Also issued online.
(Dates or Sequential Designation) Vol. 1, no. 1 (Feb. 3, 1964)-
(Numbering Peculiarities) Suspended between v. 35, no. 1 (fall 1999) and v. 36, no. 1 (spring 2005).
Title from caption.
Latest issue consulted: Vol. 36, no. 2 (fall 2005).
Latin America
Latin America
Florida

05269284
sc 84001784
0502-6660

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
ternational Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.
ISSN: 0020-6814

hal-01685628
https://hal.archives-ouvertes.fr/hal-01685628
DOI : 10.1080/00206814.2016.1276482

Éditeur(s) : Institute of Food and Agricultural Sciences, University of Florida, Institute of Food and Agricultural Sciences, University of Florida,
Résumé : "August 10, 1980."
Cover title.
"The attached research proposal constitutes the ...IFAS... faculty input into the Soil Management Collaborative Research Support Project. We have emphasized the Steeplands in the Dominican Republic because of our previous experiences with steeplands in El Salvador, Guatemala, and Costa Rica and with mineral-deficient soils in Florida, and the nearness of the Dominican Republic to Florida."--P.(i).
"Submitted to AID and JRC by Soil Sciences, Agronomy and Food and Resource Economics Departments, Institute of Food and Agricultural Sciences in cooperation with Center for Latin American Studies, Center for Tropical Agriculture, University of Florida."
Includes bibliographical references.
(Funding) Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
Caribbean
Dominican Republic.
Latin America.

ocm7006

Éditeur(s) : Center for Latin American Studies, Center for Latin American Studies Center for Latin American Studies, Center for Latin American Studies ( Gainesville, Fla )
Résumé : (Additional Physical Form) Also issued online.
(Dates or Sequential Designation) Vol. 1, no. 1 (Feb. 3, 1964)-
(Numbering Peculiarities) Suspended between v. 35, no. 1 (fall 1999) and v. 36, no. 1 (spring 2005).
Title from caption.
Latest issue consulted: Vol. 36, no. 2 (fall 2005).
Latin America
Latin America
Florida

05269284
sc 84001784
0502-6660

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 : International audience
AimThe global biodiversity crisis requires the identification of regions with high evolutionary potential, i.e. evolutionary hotspots (evospots). We created an analytical framework based on comparative phylogeography and coalescent methods to assess the dynamics of diversification and population persistence in the reef ecosystem of a little-studied region: the Southwestern Indian Ocean (SWIO).LocationCoral reefs of the SWIO, with comparative data from the Pacific Ocean.MethodsWe generated sequences of mitochondrial DNA (COI and 16S) for 10 widespread brittle-stars (345 specimens) from 21 localities (8 in the SWIO). We analysed them by combining comparative phylogeography approaches, coalescent-based methods, molecular clocks and the concept of evolutionarily significant units (ESUs) to draw conclusions about the drivers of biodiversity in the region.ResultsCryptic diversity was prevalent, increasing lineage diversity within the 10 nominal species by 70% within the SWIO and by 200% across the Indo-West Pacific. All seven new SWIO lineages meet the criteria for ESUs and at least six are biological species. We detected likely intraregional diversifications dating to the Plio-Pleistocene, supporting the SWIO as a generator of biodiversity. Geographical restriction of ESUs, long coalescent times (> 80 ka) and old in situ diversification (> 1 Ma) point to the persistence of populations over multiple glacio-eustatic cycles. We provide data suggesting demographic expansion during sea-level high stands. Regional connectivity was lower, and cryptic differentiation higher in lecithotrophs than in planktotrophs.Main conclusionsThe analytical framework based on a biodiversity survey makes it possible to identify evospots by assessing the potential of a region to maintain and generate biodiversity and by evaluating the evolutionary processes and potential drivers at play.
ISSN: 0305-0270

hal-01369697
http://hal.univ-reunion.fr/hal-01369697
DOI : 10.1111/jbi.12155