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

Above-ground biomass and carbon reservoirs in Urabá Gulf mangroves (Colombian Caribbean)

ABSTRACT: Mangroves are the major aboveground biomass (AB) and carbon (C) stocks among the tropical coastal and marine ecosystems. In this study, we estimated the AB and C stocks from the four largest mangrove areas in the Urabá Gulf, by using published allometric equations in combination with eld-obtained forest structure data. The Atrato River Delta exhibited the largest AB and C stocks (165 and 83 t/ha, respectively) due to the dominance of large-diameter Rhizophora mangle trees (> 15 cm), followed by Rionegro Cove (115 and 58 t/ha, respectively), also dominated by the same species. In the Southeastern coast of the Gulf, the largest AB and C stocks were observed in the Puerto César-Punta Coquito sector (85 and 43 t/ha, respectively), followed by the Turbo sector (76 and 38 t C/ha, respectively), both dominated by Avicennia germinans. In the Turbo sector, there was a high density of thin diameter (< 5 cm) R. mangle and Laguncularia racemosa trees, as a consequence of the high logging pressure. The AB and C stocks of these species in the Turbo sector were lower than those observed in the Puerto César-Punta Coquito, located far from the urban area of the Turbo City. The biomass stocks of mangroves in the Urabá Gulf lay within the range observed worldwide, but the Atrato River Delta was one of the largest. This study concluded that mangroves in the Urabá Gulf are signi cant C stocks, mainly those within conservation areas. The size of the stocks is inversely correlated with distance to the two main population centers.RESUMEN: Los manglares son los principales reservorios de biomasa aérea (BA) y carbono (C) sobre el suelo entre los ecosistemas marino-costeros tropicales. A partir de datos estructurales de campo y de ecuaciones alométricas publicadas, se estiman los reservorios de BA y C en la vegetación de las cuatro áreas de manglar más extensas del golfo de Urabá. Los manglares del delta del río Atrato mostraron los mayores reservorios de BA y C (165 y 83 t/ha, respectivamente) concentrados en árboles de Rhizophora mangle, al igual que los de la ensenada de Rionegro (115 y 58 t/ha, respectivamente). En el costado suroriental del Golfo, los mayores valores se obtuvieron en los manglares de Puerto César-Punta Coquito (85 y 43 t/ha, respectivamente), y por último los de Turbo (76 y 38 t C/ha, respectivamente), ambos dominados por Avicennia germinans. En Turbo predominaron árboles de R. mangle y Laguncularia racemosa de diámetros < 5 cm, re ejo de la fuerte intervención antrópica y los reservorios de BA y C son menores que los de Puerto César-Punta Coquito, más alejado de la cabecera urbana. Los reservorios de biomasa de los manglares del Golfo se encuentran dentro del rango observado en todo el mundo, pero los del delta del río Atrato se acercan más al límite superior registrado. Los manglares mejor conservados del golfo de Urabá son reservorios importantes de C en la BA. La magnitud del reservorio está inversamente relacionada con la distancia a los dos principales centros poblados

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

Diversidad e interacciones biológicas en el ecosistema de manglar

Mangroves are trees with special morphological and physiological characteristics to survive the extreme environment between the land and sea boundaries, fulfilling an important function as first line tide barriers. Colombia has great concentration of mangrove forests, 2.09% of the planet’s mangroves, where different species of these trees coexist. Mangrove areas have undergone drastic changes due to an increment in anthropic pressure such as deforestation, pollution, high heavy metal contents in water, among others, creating pressures on the ecosystem and the trees. Several studies have found that in some mangrove areas in Colombia, trees are presenting a disease in the form of galls the exact cause of which is unknown. Being aware of the importance this problem, we need to establish the existing information about biodiversity and biological ecosystem interactions in order to determine the most important components that could be affected by the changes that are taking place in the ecosystem and that could lead to internal imbalances and diseasesLos mangles son árboles que poseen características morfológicas y fisiológicas especiales para sobrevivir en el ambiente extremo que se forma en el límite entre la tierra y el mar, cumpliendo una importante función como primera línea de barrera contra las mareas. En Colombia, se encuentra una gran concentración de bosques de mangle en donde conviven distintas especies de estos árboles, representando el 2,09% del total presente en el planeta. Las zonas de manglar han sufrido cambios drásticos debido al aumento de las presiones antrópicas como la deforestación, la polución, el alto contenido de metales pesados en el agua, entre otros, generando presiones sobre el ecosistema y los árboles. En varios estudios se ha detectado que, en algunas zonas de manglar en Colombia, los árboles están presentando una enfermedad manifestada en forma de agallas y de la cual no se sabe su causa exacta. Conociendo la importancia de esta problemática, se busca establecer que información existe sobre la diversidad e interacciones biológicas en el ecosistema con el fin de determinar los componentes más importantes que pudiesen estar siendo afectados por los cambios que están teniendo lugar en el ecosistema y que podrían llevar a desequilibrios internos y enfermedades

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

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran\u27s eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R$^{2}$ = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R$^{2}$ = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions

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