Reconstrucción de la sucesión en bosque de "Guandal"(Pacífico colombiano) durante el holocoeno reciente

Se presenta la reconstrucción, por medio del anúlisis palinológico, de la sccuencia sucesional de una sección de sedimentos tomada en el valle del río Sanquianga en cl departamento de Nariño, Pacifico sur colombiano. A partir de la formación de una playa colonizada por herbáceas y vegetación pionera, principalmcnte Tetrapteris, Cyperaceae y Cecropia, se da lugar a la formación de un bosque dc diquc alrededor de 2080 años A.P., cuando prcdominaron Moraceac-LJrticaeeae, Euterpe, Melastomataceae-Combretaeeae y Campf10sperma elemcntos típicos de los humedales turbosos actualcs. En esta fecha se presentaron desccnsos en los niveles de inundación coincidentes con los registrados en otras zonas bajas de la Amazonia y el Pacifico. Posteriormente, se prescntó un aumento cn los niveles de inundación dcl valle, de corta duración, representado por la alta dominancia de Euterpe y Pterocarpus (taxones típicos de bosques con altos niveles de inundación permanente). Cuando los niveles de inundación descendieron alrededor de 690 años A.P se estableció el bosque de Campnosperma, época en la clla!, estudios arqueológicos registraron actividad humana en esa zona del territorio e idcntificada como la probable causa de perturbación que se registra en los bosques de guandal presentes en la última zona del diagrama y que dominan desde entonces en el área estudiada./ ABSTRACT: The reconstruction 01' a forest sllcccssiol1 was achieved by means of pollen analysis in a sediment core obtained from (he Sanquianga valley in Nariño, southern Colombian Paeific. Starting from a bcach sand colonized by hcrbs ane! pioncer vegetation, mainly Tetrapteris, Cyperaceac and Cecropia, the formation of a levcc forest took place around 2080 years B.P., wherc typical elements from the present swamp forest dominated sueh as Moraccae-LJrticaceac, Euterpe, MelastomataceaeCombretaeeae, and Campnmperma. In this date, decrease in the inundation level was presented, eoinciding with those registered in other Amazonia and Pacific lowlands. Later (subsequently), a sho!'t term increase in the flooding level ofthe valley oecurred, represente

Ecosystem-Wide Impacts of Deforestation inMangroves : the Urabá Gulf (Colombian Caribbean) Case Study

ABSTRACT: Mangroves are ecologically important and extensive in the Neotropics, but they are visibly threatened by selective logging and conversion to pastures in the Southern Caribbean. The objective of this paper was to summarize the impacts of both threats on forest structure, species composition, aboveground biomass and carbon reservoir, species introgressions, and benthic fauna populations by collating past and current data and by using an interdisciplinary approach in the Urab´a Gulf (Colombia) as a case study. Mangroves in the Eastern Coast have been decimated and have produced unskewed tree-diameter (DBH) distributions due to the overexploitation of Rhizophora mangle for poles (DBH range: 7–17 cm) and of Avicennia germinans for planks and pilings (DBH > 40 cm). Selective logging increased the importance value of the light-tolerant whitemangrove Laguncularia racemosa, also increasing biomass and carbon storage in this species, thus offsetting reductions in other species. Introgressions (cryptic ecological degradation) by L. racemosa and Acrostichum aureum (mangrove fern) and low densities of otherwise dominant detritivore snails (Neritina virginea) were observed in periurban basin mangroves. Finally, basin mangroves were more threatened than fringing mangroves due to their proximity to expanding pastures, villages, and a coastal city

Expedición Caribe sur : Antioquia y Chocó costeros

RESUMEN: Hasta el momento el conocimiento que se tenía de la región Darién-Urabá-Caribe antioqueño era fragmentario: los estudios no se habían realizado de manera simultánea a lo largo del litoral, y así había poca interacción entre las disciplinas de las ciencias del mar. El objetivo de este estudio fue construir una base de datos sobre las características geomorfológicas, oceanográficas, forestales y faunísticas de los manglares, a lo largo del litoral comprendido entre cabo Tiburón (Acandí-Chocó) y quebrada Peñoncito (Arboletes, Antioquia). Se realizó una expedición en la que participaron científicos de diferentes ciencias del mar, para recolectar información de campo sobre diferentes componentes temáticos, a lo largo de los 609 km del contorno costero (...

Estimating the global conservation status of more than 15,000 Amazonian tree species

Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Unraveling Amazon tree community assembly using Maximum Information Entropy: a quantitative analysis of tropical forest ecology

In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics