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Blundo, C., Carilla, J., Grau, R., Malizia, M., Malizia, L., Osinaga-Acosta, O., et al.
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Dutech, C., Seiter, J., Petronelli, P., Joly, H. I., & Jarne, P. (2002). Evidence of low gene flow in a neotropical clustered tree species in two rainforest stands of French Guiana. Mol. Ecol., 11(4), 725–738.
Abstract: The spatial genetic structure of the neotropical, clustered tree species Vouacapoua americana (Aublet) was studied in two natural forest stands (Paracou and Nouragues) in French Guiana. Using eight microsatellite loci, V. americana is characterized by a marked genetic structure at small spatial distances (under 30-60 m), in agreement with the limited seed dispersal by rodent species. Gene flow through pollen is also shown to be mainly restricted to less than 100 m. This result suggests that most pollination events (mediated through small insects) are probably limited to within-patches of individuals, which might explain the high genetic differentiation among patches (F-ST = 0.11) separated by less than 2 km. We also assume that stronger genetic structure in Paracou is likely to be due to lower seed dispersal by rodents, large spatial distances separating patches, or a recent recolonization event.
Keywords: Caesalpiniaceae; gene flow; recolonization process; spatial genetic structure; tropical rainforest; Vouacapoua americana
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Konig, A. O., Ziegenhagen, B., van Dam, B. C., Csaikl, U. M., Coart, E., Degen, B., et al. (2002). Chloroplast DNA variation of oaks in western Central Europe and genetic consequences of human influences. For. Ecol. Manage., 156(1-3), 147–166.
Abstract: Oak chloroplast DNA (cpDNA) variation was studied in a grid-based inventory in western Central Europe, including Belgium, The Netherlands, Luxembourg, Germany, the Czech Republic, and the northern parts of Upper and Lower Austria. A total of 2155 trees representing 426 populations of Quercus robur L. and Q. petraea (Matt.) Liebl. were screened for polymorphism in up to four PCR-amplified cpDNA fragments. Eleven haplotypes belonging to four lineages were detected; these lineages were formerly restricted to glacial refugia in the Iberian Peninsula, the Apennine Peninsula and the Balkan Peninsula. The haplotypes originating from the Apennines are particularly well represented in the study region, but there is also a significant contribution from the other refugia, which explain the high overall level of cpDNA diversity. The strong human impact in western Central Europe during the past centuries, which has resulted in the clearance of most forests, was followed by reforestation, sometimes involving seed transfers. Despite this strong human impact, broad geographic patterns of lineages and haplotypes could still be detected. To evaluate further the consequences of the former human activities on the present day oak cpDNA genetic structure, four regions where increasingly strong human impact was anticipated (ranging from hilly regions in southern Germany to roadsides plantations in The Netherlands) were selected. There, a comparison of the levels of intrapopulation cpDNA diversity and spatial structuring was made. Over the whole area, within stand diversity was significantly higher in Q. robur than in Q. petraea (h(S) = 0.24 vs. 0.16). Since total diversity is identical for both species, this results in a significantly lower level of fixation for Q. robur than for Q. petraea (G(ST) = 0.68 vs. 0.79). The analyses also reveal a decrease of fixation with increasing human impact on oak populations. The Dutch roadside plantations (Q. robur) exhibit a very low level of fixation (G(ST) = 0.28) as compared to Q. petraea in southern Germany (G(ST) = 0.91). The significance of the spatial genetic structure was tested using geostatistical methods. For the complete data set, a strong spatial genetic structure is confirmed, with higher than average genetic similarities between populations distant from up to 270 km, whereas there is no spatial structure in the roadside plantations in The Netherlands or in the northern German lowlands. These results should help to differentiate introduced from autochthonous populations, and provide a framework for the identification of the geographic origin of seed lots. (C) 2002 Elsevier Science B.V. All rights reserved.
Keywords: Q. robur; Q. petraea; PCR-RFLPs; haplotypes; spatial genetic patterns; genetic differentiation; deforestation; seed transfer
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Sist, P., & Nguyen-The, N. (2002). Logging damage and the subsequent dynamics of a dipterocarp forest in East Kalimantan (1990-1996). For. Ecol. Manage., 165(1-3), 85–103.
Abstract: The effects of logging damage on forest dynamics processes were assessed in a lowland dipterocarp forest of East Kalimantan, Indonesia. From 1990 to 1991, twelve 4 ha plots (200 m x 200 m) each divided into four I ha subplots were set up and all trees with dbh greater than or equal to 10 cm measured and identified at least at the generic level. Logging was carried out from November 1991 to March 1992 in nine plots while three plots served as control. The 48 subplots were grouped according to the proportion Of remaining basal area after harvesting, as follows: group I with more than 80% of the original basal area remaining, group 2 with 70-79%, group 3 with less than 70%, and group 4 as control plots. Remeasurements were carried out just after logging in 1992 and then every 2 years until 1996. Felling intensity varied from I to 17 stems ha(-1) (50-250 m(3) ha(-1)). In primary forest, mean annual mortality remained constant to 1.5% per year throughout the study period while mean annual mortality rate was significantly higher in logged-over forest (2.6% per year). This higher rate resulted from a higher mortality of injured trees (4.9% per year). Four years after logging, mortality rates in logged-over and primary forest were similar. Recruitment remained constant at 8 trees ha(-1) per year in primary forest and varied from 14 to 32 trees ha(-1) per year in logged-over stand in proportion with the amount of damage. In stands with the lowest remaining basal area, the establishment and growth of dipterocarps was strongly limited by the strong regeneration of pioneer species. This study suggests that total basal area removed by logging in primary forest (harvested trees and trees killed during felling and skidding) should not exceed 15% of the original one; reduced-impact logging (RIL) techniques applied with a maximum harvesting intensity of 8 trees ha(-1), can keep logging damage under this threshold. (C) 2002 Elsevier Science B.V. All rights reserved.
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Sharma, K., Degen, B., Von Wuehlisch, G., & Singh, N. B. (2002). Allozyme variation in eight natural populations of Pinus roxburghii Sarg. in India. Silvae Genet., 51(5-6), 246–253.
Abstract: Seeds collected from eight populations of Chir pine (Pinus roxburghii SARG.) from the natural distribution range of the species in Himachal Himalayas in India were analysed isozymatically at 11 enzyme systems. For the enzyme systems studied, 25 gene loci were identified out of which 18 were polymorphic. The observed mean values for genetic variation were slightly lower than mean values reported for Pinus species (number of alleles: 1.65 compared to 2.36; effective number of alleles: 1.13 compared to 1.26; observed heterozygosity: 0.153 compared to 0.179). A small differentiation among populations and large variation within populations were reflected by small value of GST (0.04): Considering the different genetic parameters three populations seem favourable for gene conservation measures.
Keywords: Allozymes; Differentiation; Genetic distance; Multilocus diversity; Pinus roxburghii; Variation; Enzymes; Forestry; Genes; Allozyme variations; Genetic engineering; Enzymes; Genes; Genetic Engineering; Pinus Roxburghii; Embryophyta; Pinus roxburghii
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Picard, N., Gourlet-Fleury, S., & Sist, P. (2003). Using process-dependent groups of species to model the dynamics of a tropical rainforest. Modelling Forest Systems, , 237–248.
Abstract: The high tree species diversity in tropical forests is difficult to take into account in models. The usual solution consists of defining groups of species and then adjusting a set of parameters for each group. In this study, we address this issue by allowing a species to move from one species group to another, depending on the biological process that is concerned. We developed this approach with a matrix model of forest dynamics, for a tropical rainforest in French Guiana, at Paracou, focusing on the methodological aspects. The forest dynamics is split into three components: recruitment, growth and mortality. We then built five recruitment groups, five growth groups and five mortality groups. One species is characterized by a combination of the three groups, thus yielding in total 5 X 5 X 5 = 125 possibilities, out of which 43 are actually observed. The resulting matrix model provides a better view of the floristic composition of the forest, and does not have more parameters than it would have with five global species groups. However, its predictions are no more precise than those of the matrix model based on five global groups.
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Dutech, C., Maggia, L., Tardy, C., Joly, H. I., & Jarne, P. (2003). Tracking a genetic signal of extinction-recolonization events in a neotropical tree species: Vouacapoua americana aublet in french guiana. Evolution, 57(12), 2753–2764.
Abstract: Drier periods from the late Pleistocene and early Holocene have been hypothesized to have caused the disappearance of various rainforest species over large geographical areas in South America and restricted the extant populations to mesic sites. Subsequent improvement in climatic conditions has been associated with recolonization. Changes in population size associated with these extinction-recolonization events should have affected genetic diversity within species. However, these historical hypotheses and their genetic consequences have rarely been tested in South America. Here, we examine the diversity of the chloroplast and nuclear genomes in a Neotropical rainforest tree species, Vouacapoua americana (Leguminosae, Caesalpinioideae) in French Guiana. The chloroplast diversity was analyzed using a polymerase chain reaction-restriction fragment length polymorphism method (six pairs of primers) in 29 populations distributed over most of French Guiana, and a subset of 17 populations was also analyzed at nine polymorphic microsatellite loci. To determine whether this species has experienced extinction-recolonization, we sampled populations in areas supposedly not or only slightly affected by climatic changes, where the populations would not have experienced frequent extinction, and in areas that appear to have been recently recolonized. In the putatively recolonized areas, we found patches of several thousands of hectares homogeneous for chloroplast variation that can be interpreted as the effect of recolonization processes from several geographical origins. In addition, we observed that, for both chloroplast and nuclear genomes, the populations in newly recolonized areas exhibited a significantly smaller allelic richness than others. Controlling for geographic distance, we also detected a significant correlation between chloroplast and nuclear population differentiation. This result indicates a cytonuclear disequilibrium that can be interpreted as a historical signal of a genetic divergence between fragmented populations. In conclusion, the spatial genetic structure of contemporary V. americana populations shows evidence that this species has experienced large extinction-recolonization events, which were possibly caused by past climatic change.
Keywords: allelic richness; caesalpinioideae; chloroplast DNA; climatic changes; cytonuclear disequilibrium; legummosae; microsatellite loci; tropical rainforest
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Koponen, P., Nygren, P., Domenach, A. M., Le Roux, C., Saur, E., & Roggy, J. C. (2003). Nodulation and dinitrogen fixation of legume trees in a tropical freshwater swamp forest in French Guiana. J. Trop. Ecol., 19, 655–666.
Abstract: Nodulated legume trees comprised 43% of the stand basal area in the low, most frequently flooded microsites, and 23% in higher, drier microsites in a tropical freshwater swamp forest in French Guiana. Dinitrogen fixation in Pterocarpus officinalis, Hydrochorea corymbosa and Inga pilosula was confirmed by acetylene reduction assay (ARA), presence of leghaemoglobin in nodules and the N-15 natural abundance method. The results for Zygia cataractae were inconclusive but suggested N-2 fixation in drier microsites. Nodulated Inga disticha had a N-15-to-N-14 ratio similar to non-N-2-fixing trees, but ARA indicated nitrogenase activity and leghaemoglobin was present in nodules. All bacterial strains were identified as Bradyrhizobium spp. according to the partial 16S rDNA sequences, and they were infective in vitro in the model species Macroptilium atropurpuretan. About 35-50% of N in the leaves of P. officinalis, H. corymbosa and I. pilosula was fixed from the atmosphere. Dinitrogen fixation was estimated to contribute at least 8-13% and 1728% to whole-canopy N in high and low microsites, respectively. Symbiotic N, fixation appears to provide both a competitive advantage to legume trees under N-limited, flooded conditions and an important N input to neotropical freshwater swamp forests.
Keywords: acetylene reduction assay; Bradyrhizobium; flooding; microtopography; N-15 natural abundance method; 16S rDNA sequencing
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Clair, B., Jaouen, G., Beauchene, J., & Fournier, M. (2003). Mapping radial, tangential and longitudinal shrinkages and relation to tension wood in discs of the tropical tree Symphonia globulifera. Holzforschung, 57(6), 665–671.
Abstract: A method for measuring shrinkage resulting from drying in the three anisotropic directions is developed and tested. Measurements are performed on sawn discs, a technique which simplifies preparation and enables large numbers of measurements. Shrinkage values can be represented as a map of the disc surface. The results indicate that comparisons between shrinkage distribution and tension wood distribution on the discs show a clear relationship and can be measured with relatively high accuracy in reference to the shrinkage map. In the long term, this method could be useful in the timber industry as a means for choosing the direction in which logs are cut depending on their type of wood composition.
Keywords: drying shrinkage; tension wood; Symphonia globulifera L. f.
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Clair, B., Fournier, M., Prevost, M. F., Beauchene, J., & Bardet, S. (2003). Biomechanics of buttressed trees: Bending strains and stresses. Am. J. Bot., 90(9), 1349–1356.
Abstract: The different hypotheses about buttress function and formation mainly involve mechanical theory. Forces were applied to two trees of Sloanea spp.. a tropical genus that develops typical thin buttresses. and the three-dimensional strains were measured at different parts of the trunk base. Risks of failure were greater on the buttress sides, where shear and tangential stresses are greater, not on the ridges. in spite of high longitudinal (parallel to the grain) stresses. A simple beam model, computed from the second moment of area of digitized cross sections, is consistent with longitudinal strain variations but cannot predict accurately variations with height. Patterns of longitudinal strain variation along ridges are very different in the two individuals, owing to a pronounced lateral curvature in one specimen. The constant stress hypothesis is discussed based on these results. Without chronological data during the development of the tree. it cannot be proved that buttress formation is activated by stress or strain.
Keywords: biomechanics; buttress; Eleaocarpaceae; French Guiana; Sloanea spp.; tropical trees; wood
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