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Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage— increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute treemass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth,inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence. Fil: Blundo, Cecilia Mabel. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Grau, Hector Ricardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Malizia, Agustina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Malizia, L. R.. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; Argentina

While the importance of local-scale habitat niches in shaping tree species turnover along environmental gradients in tropical forests is well appreciated, relatively little is known about the influence of phylogenetic signal in species' habitat niches in shaping local community structure. We used detailed maps of the soil resource and topographic variation within eight 24-50 ha tropical forest plots combined with species phylogenies created from the APG III phylogeny to examine how phylogenetic beta diversity (indicating the degree of phylogenetic similarity of two communities) was related to environmental gradients within tropical tree communities. Using distance-based redundancy analysis we found that phylogenetic beta diversity, expressed as either nearest neighbor distance or mean pairwise distance, was significantly related to both soil and topographic variation in all study sites. In general, more phylogenetic beta diversity within a forest plot was explained by environmental variables this was expressed as nearest neighbor distance versus mean pairwise distance (3.0-10.3 % and 0.4-8.8 % of variation explained among plots, respectively), and more variation was explained by soil resource variables than topographic variables using either phylogenetic beta diversity metric. We also found that patterns of phylogenetic beta diversity expressed as nearest neighbor distance were consistent with previously observed patterns of niche similarity among congeneric species pairs in these plots. These results indicate the importance of phylogenetic signal in local habitat niches in shaping the phylogenetic structure of tropical tree communities, especially at the level of close phylogenetic neighbors, where similarity in habitat niches is most strongly preserved.

Tetagastris panamensis is a tropical forest canopy tree that is broadly distributed across Central and South America. We isolated 15 microsatellite loci and characterized them in populations from Panama and Ecuador. The number of alleles per locus in 61 individuals ranged from 4 to 22, and expected heterozygosity ranged from 0.044 to 0.909. The high overall single-parent exclusion probability (P = 1.00) highlights the utility of these loci for parentage-based analyses of gene flow.

In temperate regions the chemistry of the lower troposphere is known to be significantly affected by biogenic volatile organic compounds (VOCs) emitted by plants. The chemistry of the lower troposphere over the tropics, however, is poorly understood, in part because of the considerable uncertainties in VOC emissions from tropical ecosystems. Present global VOC models predict that base emissions of isoprene from tropical rainforests are considerably higher than from savannas. These global models of VOC emissions which rely mainly on species inventories are useful, but significant improvement might be made with more ecologically based models of VOC emissions by plants. Ecosystems along a successional transect from woodland savanna to primary rainforest in central Africa were characterized for species composition and vegetation abundance using ground surveys and remotely sensed data. A total of 336 species (mostly trees) at 13 sites were recorded, and 208 of these were measured for VOC emissions at near-optimal light and temperature conditions using a leaf cuvette and hand-held photoionization detector (PID). A subset of 59 species was also sampled using conventional VOC emission techniques in order to validate the PID technique. Results of ecological and VOC emission surveys indicate both phylogenetic and successional patterns along the savanna-rainforest transect. Genera and families of trees which tend to emit isoprene include Lophira, Irvingia, Albizia, Artocarpus, Ficus, Pterocarpus, Caesalpiniaceae, Arecaceae, and Moraceae. Other taxa tend to contain stored VOCs (Annonaceae and Asteraceae). Successional patterns suggest that isoprene emissions are highest in the relatively early successional Isoberlinia forest communities and progressively decrease in the later successional secondary and primary rainforest communities. Stored VOCs appear to increase along the savanna-rainforest succession, but these data are more tentative. These findings are consistent with successional patterns of isoprene and terpene fluxes in North American forests and highlight the feasibility of constructing better predictive models of VOC emissions.

Tropical tree communities are shaped by local-scale habitat heterogeneity in the form of topographic and edaphic variation, but the life-history stage at which habitat associations develop remains poorly understood. This is due, in part, to the fact that previous studies have not accounted for the widely disparate sample sizes (number of stems) that result when trees are divided into size classes. We demonstrate that the observed habitat structuring of a community is directly related to the number of individuals in the community. We then compare the relative importance of habitat heterogeneity to tree community structure for saplings, juveniles and adult trees within seven large (24–50 ha) tropical forest dynamics plots while controlling for sample size. Changes in habitat structuring through tree life stages were small and inconsistent among life stages and study sites. Where found, these differences were an order of magnitude smaller than the findings of previous studies that did not control for sample size. Moreover, community structure and composition were very similar among tree sub-communities of different life stages. We conclude that the structure of these tropical tree communities is established by the time trees are large enough to be included in the census (1 cm diameter at breast height), which indicates that habitat filtering occurs during earlier life stages.

Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24–50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9–34% and 5–29%, respectively), and all environmental variables together explain 13–39% of compositional variation within a plot. A large fraction of variation (19–37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe.

DNA barcoding of rain forest trees could potentially help biologists identify species and discover new ones. However, DNA barcodes cannot always distinguish between closely related species, and the size and completeness of barcode databases are key parameters for their successful application. We test the ability of rbcL, matK and trnH-psbA plastid DNA markers to identify rain forest trees at two sites in Atlantic central Africa under the assumption that a database is exhaustive in terms of species content, but not necessarily in terms of haplotype diversity within species., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

L'arbre. Les arbres du genre Carapa (Meliaceae) sont presents dans toutes les forets d'Afrique tropicale au niveau de l'equateur, du rift d'Albertine jusqu'au Senegal et au Mali pour sa distribution la plus septentrionale. En Afrique comme en Amerique tropicale, le carapa est une source importante de Produits Forestiers ligneux (bois) et Non-Ligneux (PFNL). Le fruit et les graines. Le fruit typique de carapa est une capsule a quatre ou cinq valves qui renferment chacune deux a cinq graines, soit un total de huit a vingt graines par fruit. L'extraction de l'huile. Les villageois ramassent les graines tombees au sol avant qu'elles ne soient parasitees ou germees, ce qui est defavorable a la production d'une huile de qualite. L'extraction de l'huile se fait par ebouillantage des graines. L'huile extraite, polyvalente, est la substance issue de la plante qui est la plus utilisee devant les extraits de feuilles, d'ecorce et de racines. Le marche. En Afrique, le commerce de l'huile de carapa est essentiellement local et reste une activite tres marginale. Une demande accrue emane toutefois de l'utilisation de cette huile comme insecticide naturel dans la culture du coton biologique. Discussion. Compte tenu du potentiel economique de l'huile de carapa, sa commercialisation devrait respecter une retribution equitable des paysannes afin de mieux rentabiliser la production. Des mesures de protection des arbres de carapa et de leur habitat doivent egalement etre prises pour permettre une gestion de la production d'huile a long terme. La plantation semble etre une option durable en vue de la conservation des peuplements naturels de carapa. (Resume d'auteur)

Carapa akuri, a new species endemic to central Guyana, is described and illustrated. It is compared to the two other species (C. guianensis and C. surinamensis) occurring in the Guianas.

The theory of metabolic ecology predicts specific relationships among tree stem diameter, biomass, height, growth and mortality. As demographic rates are important to estimates of carbon fluxes in forests, this theory might offer important insights into the global carbon budget, and deserves careful assessment. We assembled data from 10 oldgrowth tropical forests encompassing censuses of 367 ha and > 1.7 million trees to test the theory’s predictions. We also developed a set of alternative predictions that retained some assumptions of metabolic ecology while also considering how availability of a key limiting resource, light, changes with tree size. Our results show that there are no universal scaling relationships of growth or mortality with size among trees in tropical forests. Observed patterns were consistent with our alternative model in the one site where we had the data necessary to evaluate it, and were inconsistent with the predictions of metabolic ecology in all forests.

Between 1990 and 2000 a number of vegetation surveys were undertaken on the Mount Cameroon area using mainly three methods: 0.25 ha sample plots, 20 m wide transects and rapid botanical surveys. A comparison of these methods in terms of data collected, operational characteristics and output relevance, revealed their strengths and weaknesses. The methods vary markedly in their ecological value (0.25 ha sample plots superior), taxonomic scope and rigour (rapid botanical survey superior) and logistic efficiency (transects superior). The combined outcome of all these surveys is discussed and recommendations made on the use of the rapid botanical survey in order to rapidly fill the remaining gaps on plant distribution.

Ecologists have historically used species-area relationships (SARs) as a tool to understand the spatial distribution of species. Recent work has extended SARs to focus on individual-level distributions to generate individual species area relationships (ISARs). The ISAR approach quantifies whether individuals of a species tend have more or less species richness surrounding them than expected by chance. By identifying richness ‘accumulators’ and ‘repellers’, respectively, the ISAR approach has been used to infer the relative importance of abiotic and biotic interactions and neutrality. A clear limitation of the SAR and ISAR approaches is that all species are treated as evolutionarily independent and that a large amount of work has now shown that local tree neighborhoods exhibit non-random phylogenetic structure given the species richness. Here, we use nine tropical and temperate forest dynamics plots to ask: (i) do ISARs change predictably across latitude?; (ii) is the phylogenetic diversity in the neighborhood of species accumulators and repellers higher or lower than that expected given the observed species richness?; and (iii) do species accumulators, repellers distributed non-randomly on the community phylogenetic tree? The results indicate no clear trend in ISARs from the temperate zone to the tropics and that the phylogenetic diversity surrounding the individuals of species is generally only non-random on very local scales. Interestingly the distribution of species accumulators and repellers was non-random on the community phylogenies suggesting the presence of phylogenetic signal in the ISAR across latitude.

During the past decade, two long-term studies of tropical forest trees and lianas were initiated in the Korup National Park, Cameroon and in the Reserve de Faune 'a Okapis, Democratic Republic of Congo. These two large forest dynamics programs are part of a global network of research sites coordinated by the Smithsonian Tropical Research Institute, and are leading to the discovery of many new plant species (e.g., Gereau & Kenfack 2000; Ewango & Breteler 2001; Sonk6 et al. 2002). During the study of the Korup plot vouchers at BR, MO, K, SCA and YA, some specimens belonging to the genus Manilkara Adans. could not be matched, and did not fit any of the species described from western and central Africa (Aubreville 1961, 1964; Gautier 1997). Critical examination of the Korup specimens revealed sufficient differences to justify the description of a new species. Further surveys in the Korup area to collect additional specimens of this taxon have so far been unsuccessful. This description is therefore based on a very small number of individuals, and we have little data on intra-specific variation. However, since we have both flowering and fruiting material showing a suite of distinctive characters, there is no reason to delay publication. The new species clearly belongs in the genus Manilkara because of the calyx, which has two whorls of 3 sepals each. Although Manilkara species are often difficult to separate, ours does not resemble any other described species very closely. M. pellegriniana Tisser. & Sillans is the only other species from the region with persistent stipules and glabrous, laciniate staminodes, and the new species can be distinguished from it by a number of well-defined characters. Manilkara lososiana Kenfack & Ewango sp. nov. Manilkarae pellegrinianae Tisser. & Sillans similis, sed stipulis triangularibus non filiformibus, petiolo breviore 5 15 non 20 40 mm longo, pedicello longiore, foliorum indumento brunneo (nec griseoargenteo) distinguitur. Typus: Cameroon, Southwest Province, Korup National Park, Kenfack 625 (holotypus YA; isotypi SCA, MO, K).

Uvariopsis submontana Kenfack, Gosline & Gereau (Annonaceae) is described from premontane habitats in western Cameroon. The new species is morphologically most similar to U. korupensis Gereau & Kenfack, recently described from lower elevations in western Cameroon. The monotypic genus Dennettia Baker f. is completely consistent with the morphological and palynological circumscription of Uvariopsis Engler, and is included in the latter genus under the new combination U. tripetala (Baker f.) G. E. Schatz. A key to the 16 species of this tropical African genus is presented. R1ASUM£. Uvariopsis submontana Kenfacke Gosline & Gereau (Annonaceae) est decrit d'habitats premontagnards de l'Ouest du Cameroun. Quant a sa morphologie, la nouvelle espece ressemble au plus pres 1'U. korupensis Gereau & Kenfack, recemment decrit d'altitudes plus basses de l'Ouest du Cameroun. Le genre monotypique Dennettia Baker f. est tout a fait consistent avec la circonscription morphologique et palynologique d'Uvariopsis Engler et est inclu dans celui-ci sous la nouvelle combinaison Uvariopsis tripetala (Baker f.) G. E. Schatz. Une cle des 16 especes de ce genre de l'Afrique tropicale est presentee.

Proceedings of the 18th AETFAT Congress held in Yaounde, Cameroon; International audience; Carapa species are trees and shrubs of tropical forests. In Africa, although Carapa species are widely distributed and diversified from Senegal to Rwanda, their commercial exploitation remains restricted despite their known domestic uses. In Senegal, Carapa is most abundant in Mid and lower Casamance and in the gallery forests of East Senegal. Carapa species are recognised for socio-cultural or medicinal importance throughout their area of distribution.Traditionally the oil is extracted by women in menopause and is used to treat dozens of illnesses and in cosmetics. Leaves, bark and roots are also used.; Les Carapa sont des arbres et arbustes des forêts tropicales. En Afrique, si les Carapa sont largement distribués et diversifiés du Sénégal au Rwanda, leur exploitation commerciale demeure cependant embryonnaire malgré des usages domestiques reconnus. Au Sénégal les Carapa sont plus abondants en moyenne et basse Casamance et dans les galeries forestières des savanes du Sénégal oriental. Les Carapa sont d'importance socio-culturelle ou médicinale reconnue sur toute leur aire de distribution. L'huile est traditionnellement extraite par les femmes ménopausées et est utilisée dans le traitement d'une dizaine de maladies et en cosmétique. Les feuilles, les écorces et les racines sont également utilisées.

Group ranches (GRs) were established in Kenya in the 1960s and 1970s; their objectives included the increase of pastoral land productivity and the control of land degradation. Since their establishment, GRs have evolved and new trends have emerged in resource management with significant impact on socio-ecological systems (SESs). Little is known about these changes on the GRs in Laikipia County. The central thesis for this study was that GR-level-driven and/or collective action innovations are socio-ecologically more resilient compared to household/individual-level strategies. This study investigated emerging innovations, their drivers and perceived and felt impacts, using Il Motiok GR as a case study. Tools used included semi-structured interviews, key informant interviews, focus group discussions and second order cybernetics. Qualitative analysis using SPSS software was done. The results showed that emerging innovations could be divided into either household/individual- or community-level-driven processes. Some of the innovations in natural capital management included the trading of grazing rights, expansion of traditional enclosures, adoption of ‘new’ livestock species and/or breeds, and crop cultivation. Household-level-driven innovations were influenced by wealth status, age and level of education. Economic returns and to some extent the greater good influenced community-driven initiatives. Formal groupings such as self-help groups and business associations were replacing declining traditional social networks based on clans and age sets/groups. Climate change, development agencies, cultural and technological change and neighbourhood social learning are perceived as having inspired the innovations. Innovations that fragmented natural and social capital were inclined to limit socio-ecological resilience. Implementation of new interventions among communities must factor in the possibilities of transformation and/or emergence of new innovations beyond those initially conceptualised as implementation progresses. Supportive policies that recognise the increasing complexity of common property use are needed to address emerging ‘new’ land use changes. Furthermore, there is need to nurture emergent promising innovations and stop those considered detrimental to the sustainability of SESs.

Tropical forests store 40–50 per cent of terrestrial vegetation carbon 1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests 2. Owing to climatic and soil changes with increasing elevation 3, AGC stocks are lower in tropical montane forests compared with lowland forests 2. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1–164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network 4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane 2,5,6 and lowland 7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa 8. We find that the low stem density and high abundance of large trees of African lowland forests 4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse 9,10 and carbon-rich ecosystems.