Institute Agronomique Neo Caledonien IAC

Paita, France

Institute Agronomique Neo Caledonien IAC

Paita, France
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Ibanez T.,Institute Agronomique neo Caledonien IAC | Hequet V.,IRD Montpellier | Chambrey C.,Institute Agronomique neo Caledonien IAC | Jaffre T.,IRD Montpellier | Birnbaum P.,Institute Agronomique neo Caledonien IAC
Landscape Ecology | Year: 2017

Context: The biodiversity hotspot for conservation of New Caledonia has facing high levels of forest fragmentation. Remnant forests are critical for biodiversity conservation and can help in understanding how does forest fragmentation affect tree communities. Objective: Determine the effect of habitat configuration and availability on tree communities. Methods: We mapped forest in a 60 km2 landscape and sampled 93 tree communities in 52 forest fragments following stratified random sampling. At each sampling point, we inventoried all trees with a diameter at breast height ≥10 cm within a radius of 10 m. We then analysed the response of the composition, the structure and the richness of tree communities to the fragment size and isolation, distance from the edge, as well as the topographical position. Results: Our results showed that the distance from the forest edge was the variable that explained the greatest observed variance in tree assemblages. We observed a decrease in the abundance and richness of animal-dispersed trees as well as a decrease in the abundance of large trees with increasing proximity to forest edges. Near forest edges we found a shift in species composition with a dominance of stress-tolerant pioneer species. Conclusions: Edge-effects are likely to be the main processes that affect remnant forest tree communities after about a century of forest fragmentation. It results in retrogressive successions at the edges leading to a dominance of stress-tolerant species. The vegetation surrounding fragments should be protected to promote the long process of forest extension and subsequently reduce edge-effects. © 2017 Springer Science+Business Media Dordrecht


Demenois J.,Institute Agronomique neo Caledonien IAC | Carriconde F.,Institute Agronomique neo Caledonien IAC | Rey F.,IRSTEA | Stokes A.,Montpellier University
Ecological Engineering | Year: 2017

Soil aggregate stability is viewed as a promising indicator of the restoration status in eroded ecosystems, where the change in plant community composition through successional dynamics is a key driver of ecosystem restoration. In many tropical regions, ecological restoration is an important issue, but the relationship between different types of plant communities and soil aggregate stability is poorly understood. We examined how tropical plant communities modified soil aggregate stability along a successional vegetation gradient on a Ferralsol in New Caledonia. We identified five plant communities, ranging from an early (sedge dominated ecosystems) to a late successional stage (well-established, dense, mixed rainforest). Aggregate stability, total soil organic carbon (SOC) and iron and aluminium sesquioxides were measured in soil originating from each community. Results showed that aggregate stability of the Ferralsol was very high, even on eroded sites, likely due to the high levels of iron and aluminium sesquioxides. The levels of iron sesquioxides were particularly high (>10%), due partly to the frequency of wildfires in the region. Total SOC increased from sedge-dominated communities (<1%) to mixed rainforest (>3.5%). Aggregate stability was modified by plant cover and community composition and increased from sparse, early successional vegetation to late successional dense, mixed rainforest. Our study showed that certain plant species have a positive impact on soil aggregate stability and should be considered for ecological restoration on Ferralsols. e.g., Costularia arundinacea, Garcinia amplexicaulis and Myodocarpus fraxinifolius. In conclusion, we suggest that vegetation dynamics should be taken into account when investigating changes in aggregate stability in a context of ecosystem restoration. © 2017 Elsevier B.V.


Fogliani B.,Institute Agronomique neo Caledonien IAC | Fogliani B.,University of New Caledonia | Gateble G.,Institute Agronomique neo Caledonien IAC | Villegente M.,University of New Caledonia | And 6 more authors.
Annals of botany | Year: 2017

Background and Aims: Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda , the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade.Methods: Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms.Key Results: Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth.Conclusions: Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.


Munzinger J.,Montpellier University | Gateble G.,Institute Agronomique neo Caledonien IAC
Phytotaxa | Year: 2017

A new species, Acropogon mesophilus Munzinger & Gâteblé (Malvaceae, Sterculioideae), is described from New Caledonia. This species is endemic to non-ultramafic areas, along the southwestern coast of Grande-Terre. The species has large leaves, widely ovate to ovate, and entire, and might be confused with only two other endemic species, namely A. bullatus (Pancher & Sebert) Morat and A. veillonii Morat. However, A. mesophilus differs from the other two species most evidently by its leaves 3-nerved, flat, and with truncate to rounded bases, versus leaves 5-nerved, bullate, and with cordate bases. A line drawing and color photos are provided for the new species, along with a discussion of its morphological affinities and a preliminary risk of extinction assessment of Endangered. © 2017 Magnolia Press.


Ibanez T.,Aix - Marseille University | Ibanez T.,Institute Agronomique Neo Caledonien IAC | Munzinger J.,IRD Montpellier | Gaucherel C.,French Institute of Pondicherry | And 2 more authors.
Australian Journal of Botany | Year: 2013

A direct consequence of deforestation and forest fragmentation in the tropics is the increased importance of boundaries between forest fragments and savannahs. These boundaries are critical zones for understanding the dynamics of savannahs and forests. In the present study, the spatio-temporal dynamics of a savannah-forest boundary in New Caledonia were inferred from the analyses of vegetation structure and composition along three transects. Remnant savannah trees (Melaleuca quinquenervia (Cav.) S.T.Blake) in the forest part of the transect indicated that the forest edge has shifted towards savannah. This margin-forest expansion hypothesis was reinforced by gradual changes from the forest edge to the forest core in species composition (e.g. increase in the frequency of forest-core species) and population structure (e.g. increase in forest tree-stem diameter). However, sharp changes at the forest edge (mainly the increased frequency of small forest trees) suggested that forest expansion has likely been stopped. This suggested that different phases may alternate in the dynamics of savannah-forest boundaries, including stable phases where the boundary does not move, and unstable phases where the boundary moves or expands towards savannah or forest. Variations in the fire regime as a result of the interactions among climate, fire use by humans and vegetation are likely to drive these dynamics. © CSIRO 2013.


Isnard S.,IRD Montpellier | L'huillier L.,Institute Agronomique Neo Caledonien IAC | Rigault F.,IRD Montpellier | Jaffre T.,IRD Montpellier
Plant and Soil | Year: 2016

Background: New Caledonia is renowned as one of the world’s most significant biodiversity hotpots. The nutrient-deficiency and cations imbalances of ultramafic soils, which cover a third of the island, harbor a disproportionally high proportion of the plant diversity and endemism of New Caledonia. Scope: This review explores how ultramafic soils have influenced the exceptional endemism and richness of New Caledonia trough the concomitant occurrences of habitat patchiness, climatic instability, environmental gradient, and edaphic heterogeneity of ultramafic soils. We focus on the unique ‘maquis’ vegetation where selective pressures by nutrient deficiency and trace element surplus are at their acme. We aim to synthesize our current understanding of diversification and speciation of lineages that have been phylogenetically studied to date. Conclusions: Fragmentation of the peridotite mantle in isolated massifs, and as such spatial heterogeneity of ultramafic soils types, appear to promote plant endemism and speciation. Repeated independent dispersal events of pre-adapted species and persistence of paleo-endemic lineages have contributed to the phylogenetic diversity and the endemism of the ultramafic flora. Finally, historical climatic instability has caused shifts of rain forest species in refugia thereby favoring the extension of maquis species. © 2016, Springer International Publishing Switzerland.


Majorel C.,Center IRD | Hannibal L.,Center IRD | Soupe M.-E.,Center IRD | Carriconde F.,Institute Agronomique Neo Caledonien IAC | And 5 more authors.
Molecular Ecology | Year: 2012

The fungus Pisolithus albus forms ectomycorrhizal (ECM) associations with plants growing on extreme ultramafic soils, which are naturally rich in heavy metals such as nickel. Both nickel-tolerant and nickel-sensitive isolates of P. albus are found in ultramafic soils in New Caledonia, a biodiversity hotspot in the Southwest Pacific. The aim of this work was to monitor the expression of genes involved in the specific molecular response to nickel in a nickel-tolerant P. albus isolate. We used pyrosequencing and quantitative polymerase chain reaction (qPCR) approaches to investigate and compare the transcriptomes of the nickel-tolerant isolate MD06-337 in the presence and absence of nickel. A total of 1 071 375 sequencing reads were assembled to infer expression patterns of 19 518 putative genes. Comparison of expression levels revealed that 30% of the identified genes were modulated by nickel treatment. The genes, for which expression was induced most markedly by nickel, encoded products that were putatively involved in a variety of biological functions, such as the modification of cellular components (53%), regulation of biological processes (27%) and molecular functions (20%). The 10 genes that pyrosequencing analysis indicated were induced the most by nickel were characterized further by qPCR analysis of both nickel-tolerant and nickel-sensitive P. albus isolates. Five of these genes were expressed exclusively in nickel-tolerant isolates as well as in ECM samples in situ, which identified them as potential biomarkers for nickel tolerance in this species. These results clearly suggest a positive transcriptomic response of the fungus to nickel-rich environments. The presence of both nickel-tolerant and nickel-sensitive fungal phenotypes in ultramafic soils might reflect environment-dependent phenotypic responses to variations in the effective concentrations of nickel in heterogeneous ultramafic habitats. © 2012 Blackwell Publishing Ltd.


Duron Q.,Aix - Marseille University | Garcia-Iriarte O.,Aix - Marseille University | Brescia F.,Institute Agronomique Neo Caledonien IAC | Vidal E.,Aix - Marseille University
Biological Invasions | Year: 2016

Native frugivores play an important role in native plant community dynamics by participating in seed dispersal. Today many island forests are invaded by introduced omnivores, such as rats, but their role in dispersing native plants is still little known. Here, we evaluated whether native seeds from New-Caledonian rainforests can germinate after passing through an invasive rat digestive tract and compared seed germinability and germination time between seeds ingested by invasive rats and native frugivores. We offered native fruits of Ficus racemigera and Freycinetia sulcata to the rats Rattus rattus and R. exulans, three flying foxes Pteropus spp. and the pigeon Ducula goliath. Our results showed that seeds can germinate after passing through an invasive rat digestive tract, and suggest that rats can disperse seeds of both plant species. However, invasive rats may be less efficient than native frugivores, as more seeds were destroyed when passing through rat digestive tracts than through native frugivores, and because germinability was lower and germination time was longer for seeds passing through invasive rats than through native frugivores. The reduced efficiency of rats may result from their generalized diet, the structure of their digestive tract, and/or their feeding behavior. In New-Caledonian rainforests, dispersal services on both plant species are likely well fulfilled by flying foxes and Ducula pigeons, but rats do not seem to be as efficient dispersers. Consequently, management measures to protect native frugivores should help to conserve seed dispersal services. © 2016 Springer International Publishing Switzerland


Wulff A.S.,University of New Caledonia | Wulff A.S.,Institute Agronomique neo Caledonien IAC | Hollingsworth P.M.,Royal Botanic Garden Edinburgh | Ahrends A.,Royal Botanic Garden Edinburgh | And 4 more authors.
PLoS ONE | Year: 2013

New Caledonia is a global biodiversity hotspot facing extreme environmental degradation. Given the urgent need for conservation prioritisation, we have made a first-pass quantitative assessment of the distribution of Narrow Endemic Species (NES) in the flora to identify species and sites that are potentially important for conservation action. We assessed the distributional status of all angiosperm and gymnosperm species using data from taxonomic descriptions and herbarium samples. We characterised species as being NES if they occurred in 3 or fewer locations. In total, 635 of the 2930 assessed species were classed as NES, of which only 150 have been subjected to the IUCN conservation assessment. As the distributional patterns of un-assessed species from one or two locations correspond well with assessed species which have been classified as Critically Endangered or Endangered respectively, we suggest that our distributional data can be used to prioritise species for IUCN assessment. We also used the distributional data to produce a map of "Hotspots of Plant Narrow Endemism" (HPNE). Combined, we used these data to evaluate the coincidence of NES with mining activities (a major source of threat on New Caledonia) and also areas of conservation protection. This is to identify species and locations in most urgent need of further conservation assessment and subsequent action. Finally, we grouped the NES based on the environments they occurred in and modelled the habitat distribution of these groups with a Maximum Entropy Species Distribution Model (MaxEnt). The NES were separable into three different groups based primarily on geological differences. The distribution of the habitat types for each group coincide partially with the HPNE described above and also indicates some areas which have high habitat suitability but few recorded NES. Some of these areas may represent under-sampled hotspots of narrow endemism and are priorities for further field work. © 2013 Wulff et al.


PubMed | University of Kentucky, CNRS Laboratory of Plant Reproduction and Development, University of New Caledonia and Institute Agronomique neo Caledonien IAC
Type: | Journal: Annals of botany | Year: 2017

Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda, the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade.Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms.Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth.Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.

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