Browsing by Autor "Pablo R. Stevenson"

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A New Species Of Dichaea (Orchidaceae: Zygopetalinae) From The Andes Of Colombia
(2026) Yasmin A. Alomía; Aurélien Sambin; J. Tupac Otero; Pablo R. Stevenson
Demography and Biomass Productivity in Colombian Sub-Andean Forests in Cueva de los Guácharos National Park (Huila): A Comparison Between Primary and Secondary Forests
(Multidisciplinary Digital Publishing Institute, 2025) Laura Isabel Ramos Velásquez; Cecilia M. Prada; Pablo R. Stevenson
Understanding species composition and forest dynamics is essential for predicting biomass productivity and informing conservation in tropical montane ecosystems. We evaluated floristic, demographic, and biomass changes in eighteen 0.1 ha permanent plots in the Colombian Sub-Andean forest, including both primary (ca. 60 y old) and secondary forests (ca. 30 years old). Two censuses of individuals (DBH ≥ 2.5 cm) were conducted over 7–13 years. We recorded 516 species across 202 genera and 89 families. Floristic composition differed significantly between forest types (PERMANOVA, p = 0.001), and black oak (Trigonobalanus excelsa Lozano, Hern. Cam. & Henao) forests formed distinct assemblages. Demographic rates were higher in secondary forests, with mortality (4.17% yr), recruitment (4.51% yr), and relative growth rate (0.02% yr) exceeding those of primary forests. The mean aboveground biomass accumulation and the rate of annual change were higher in primary forests (447.5 Mg ha−1 and 466.8 Mg ha−1 yr−1, respectively) than in secondary forests (217.2 Mg ha−1 and 217.2 Mg ha−1 yr−1, respectively). Notably, black oak forests showed the greatest biomass accumulation and rate of change in biomass. Annual net biomass production was higher in secondary forests (8.72 Mg ha−1 yr−1) than in primary forests (5.66 Mg ha−1 yr−1). These findings highlight the ecological distinctiveness and recovery potential of secondary Sub-Andean forests and underscore the value of multitemporal monitoring to understand forest resilience and assess vulnerability to environmental change.
Determinantes de la Composición Florística y Efecto de Borde en un Frangmento de Bosque en el Guaviare, Amazonía Colombiana
(District University of Bogotá, 2007) Pablo R. Stevenson; M. Elizabeth Rodríguez‐Ronderos
La revista Colombia Forestal publica manuscritos originales en temáticas del campo forestal y diversos aspectos de los recursos naturales y del medio ambiente, los cuales se discriminan en las categorías de artículo de investigación, de revisión, de reflexión y notas técnicas de acuerdo con lo estipulado por COLCIENCIAS para las publicaciones científicas. De acuerdo a la clasificación de áreas científicas de la Organización para la Cooperación y el Desarrollo Económico (OCDE), la revista Colombia Forestal pertenece al gran área de Ciencias Agrícolas(4), área de Agricultura, Silvicultura y Pesca(4A) y a la disciplina Forestal (4A02).
Determinants of Plant Community Assembly in a Mosaic of Landscape Units in Central Amazonia: Ecological and Phylogenetic Perspectives
(Public Library of Science, 2012) María Natalia Umaña; Natalia Norden; Ángela Cano; Pablo R. Stevenson
The Amazon harbours one of the richest ecosystems on Earth. Such diversity is likely to be promoted by plant specialization, associated with the occurrence of a mosaic of landscape units. Here, we integrate ecological and phylogenetic data at different spatial scales to assess the importance of habitat specialization in driving compositional and phylogenetic variation across the Amazonian forest. To do so, we evaluated patterns of floristic dissimilarity and phylogenetic turnover, habitat association and phylogenetic structure in three different landscape units occurring in terra firme (Hilly and Terrace) and flooded forests (Igapó). We established two 1-ha tree plots in each of these landscape units at the Caparú Biological Station, SW Colombia, and measured edaphic, topographic and light variables. At large spatial scales, terra firme forests exhibited higher levels of species diversity and phylodiversity than flooded forests. These two types of forests showed conspicuous differences in species and phylogenetic composition, suggesting that environmental sorting due to flood is important, and can go beyond the species level. At a local level, landscape units showed floristic divergence, driven both by geographical distance and by edaphic specialization. In terms of phylogenetic structure, Igapó forests showed phylogenetic clustering, whereas Hilly and Terrace forests showed phylogenetic evenness. Within plots, however, local communities did not show any particular trend. Overall, our findings suggest that flooded forests, characterized by stressful environments, impose limits to species occurrence, whereas terra firme forests, more environmentally heterogeneous, are likely to provide a wider range of ecological conditions and therefore to bear higher diversity. Thus, Amazonia should be considered as a mosaic of landscape units, where the strength of habitat association depends upon their environmental properties.
Dietary preferences and feeding strategies of Colombian highland woolly monkeys
(Nature Portfolio, 2022) Manuel L. Fonseca; Marcela A. Ramírez-Pinzón; Kaylie N. McNeil; Michelle Guevara; Laura M. Gómez-Gutiérrez; Klaus Harter; Alvaro Monguí; Pablo R. Stevenson
Dispersión de semillas de la palma útil (Astrocaryum chambira Burret) en tres bosques amazónicos con diferente grado de intervención humana
(District University of Bogotá, 2008) Beatriz H. Ramírez; Ángela Parrado-Rosselli; Pablo R. Stevenson
La revista Colombia Forestal publica manuscritos originales en temáticas del campo forestal y diversos aspectos de los recursos naturales y del medio ambiente, los cuales se discriminan en las categorías de artículo de investigación, de revisión, de reflexión y notas técnicas de acuerdo con lo estipulado por COLCIENCIAS para las publicaciones científicas. De acuerdo a la clasificación de áreas científicas de la Organización para la Cooperación y el Desarrollo Económico (OCDE), la revista Colombia Forestal pertenece al gran área de Ciencias Agrícolas(4), área de Agricultura, Silvicultura y Pesca(4A) y a la disciplina Forestal (4A02).
Dispersión de semillas por murciélagos en un borde de bosque montano
(2007) Sergio Estrada‐Villegas; Jairo Pérez‐Torres; Pablo R. Stevenson
Seed dispersal by bats has been overlooked and the effects of different vegetation types in this process are still unknown. We measured abundance and diversity of seeds dispersed by bats and other dispersal agents in a forest edge next to a young eucalyptus plantation in the Santuario de Fauna y Flora Otun-Quimbaya, Risaralda, Colombia. We compared seed shadows generated by bats and birds. We found that the habitats in the edge have significant effects on seed dispersal. Dispersal was more abundant and diverse in the mature forest compared to the first meters of the plantation and inside the plantation. Even though few seeds where dispersed by bats outside the forest, these are pioneer species with a higher probability of establishment. Ornithochory outside the forest was almost absent. We believe that bats face a cost-benefit choice: to fly over areas without plant cover and increase their risk of predation, or to fly through dense plant cover and reduce their predation risk. Any choice ultimately has an influence in the seed dispersal processes in these habitats.
DISPERSIÓN DIFERENCIAL DE SEMILLAS DE HOBOS (SPONDIAS SPP.J POR MICOS CHURUCOS (I.AGOTHRIX I.AGOTHRICHAJ Y SU RELACIÓN CON U MORFOLOGÍA DE lOS FRUTOS
(LA Referencia, 2013) Pablo R. Stevenson; María Clara Castellanos; Juan Orrantia
We determined the seed dispersa] rate of two species of Spondias (S. mombin and S. venulosa) by woolly monkeys at Tinigua National Park, Colombia. Focal sampling was used to quantify the dispersa] pattems during one year. Woolly monkeys disperse seeds of S. mombin more frequently than seeds of S. venulosa (11.2 vs. 0.4 seeds per hour of fruit consumption). In order to find out if differences in shape were correlated with the differences in dispersa] rates of the two species of seeds, we compared severa] morphological features of a sample of 587 seeds and 65 whole fruits, belonging to a total of 23 individualtrees. As seed. width was differerit in the two species; on average, seeds of S. venulosa were wider thanS. mombin seeds. Additionally, a sample of seeds collected frorn the rnonkey's feces indlcated that, on average, seeds dispersed by the rnonkeys are ·srnaller than those available in the forest. The rnorphological differences between the fruits and seeds of the two species of Spondias. are rtpt Iikely to be dlie to .allornetric relationships. The interspecific variation was srnaller than that found between trees of the same species, suggesting a high heritable cornponent in the rnorphological cháracteristics Then, it is possible that woolly rnonkeys in this cornrnunity put a significant selective pressure on the fruit rnorphology of Spondias species. Given their dispersa! patterns, probably they are affecting also the population densities of the plants. Further work on the effect of woolly rnonkeys and other dispersa! agents on the reproductive success of the dispersed is necessary to conf"mn our interpretations.
Dispersion of seeds at night and day in sub-Andean forests, Cueva Los Guacharos Park, Colombia
(Vicerractoría Investigación, 2023) Sebastiàn Bautista Plazas; Pablo R. Stevenson
Introduction: Much has been argued about the importance of the role that different types of frugivores play as seed dispersers in plant communities, but few studies have been actually carried out. Objective: We evaluated and compared diurnal and nocturnal seed dispersal in a primary and secondary sub-Andean forest in Southern Colombia. Methods: We estimated number and biomass (kg/ha) of seeds dispersed over one year (2017) using 60 fruit traps that were checked before sunrise and before sunset for 10 continuous days every two months. Results: We found that from 1 874 dispersed seeds, 55.8 % (10.9 kg/ha) were collected during the day and 44.2 % (6.39 kg/ha) at night. There were no significant differences between diurnal and nocturnal seed dispersal in number of seeds or biomass. We also found no difference in between seed dispersal that in the primary forest and secondary forest over time. Within diurnal organisms, primates and fruit-eating birds appear to be primarily responsible for this ecosystem service during the day; while bats, birds (e.g. oilbirds), and probably primates did so during the night. Conclusions: Diurnal and nocturnal dispersal seem to be equal in terms of number and weight of seeds, but not in the similarity of dispersed plant species. It remains a challenge to recognize the relative importance of different fruit-eating organisms as seed dispersers using fruit trap methods.
Diversidad florística en la Serranía de Quinchas, Colombia
(2024) María Fernanda Millán; Pablo R. Stevenson; Pablo R. Stevenson; Universidad de Los Andes
La Serranía de Quinchas es una de las zonas más diversas en el Magdalena Medio, sin embargo, aún hace falta registrar más de su diversidad, estructura y composición florística. Especialmente en una zona que ha estado expuesta a altas presiones antropogénicas. Es por esto que, el objetivo fue cuantificar la diversidad y describir la composición florística en términos de índices de importancia para familias y especies. Para esta finalidad se levantó una parcela de vegetación de una hectárea en un bosque de tipo várzea, en la Serranía de Quinchas, específicamente en la Reserva ProAves el Paujil, ubicada entre los municipios de Puerto Boyacá y Cimitarra. Se incluyeron todas las plantas leñosas de mínimo 10 cm de diámetro a la altura del pecho (DAP). Las familias más importantes de la parcela fueron Anacardiaceae, Boraginaceae y Fabaceae. Y, siendo las especies con el mayor índice de importancia (IVI) Cordia gerascanthus, Anacardium excelsum y Hura crepitans con valores de 39.21, 36.61 y 27.91, respectivamente. Finalmente, se encontró una diversidad relativamente baja (α Fisher= 19.21) en comparación con otros tipos de bosque en la zona.
DIVERSIDAD Y COMPOSICIÓN FLORÍSTICA DE TRES TIPOS DE BOSQUE EN LA ESTACIÓN BIOLÓGICA CAPARÚ, VAUPÉS
(District University of Bogotá, 2008) Ángela Cano; Pablo R. Stevenson
La revista Colombia Forestal publica manuscritos originales en temáticas del campo forestal y diversos aspectos de los recursos naturales y del medio ambiente, los cuales se discriminan en las categorías de artículo de investigación, de revisión, de reflexión y notas técnicas de acuerdo con lo estipulado por COLCIENCIAS para las publicaciones científicas. De acuerdo a la clasificación de áreas científicas de la Organización para la Cooperación y el Desarrollo Económico (OCDE), la revista Colombia Forestal pertenece al gran área de Ciencias Agrícolas(4), área de Agricultura, Silvicultura y Pesca(4A) y a la disciplina Forestal (4A02).
Elementos arbóreos de los bosques de un plano inundable en el Parque Natural Tinigua, Colombia
(1999) Pablo R. Stevenson; María Clara Castellanos; Alicia del Pilar Medina
Se realizó un análisis de la composición arbórea de un plano de inundación del Río Duda, Departamento del Meta, Colombia, con base en un muestreo de 0.9 ha en donde se censaron los individuos de 10 o más cm de DAP. Se encontraron dos comunidades principales, una dominada por Guarea guidonia-Cecropia membranacea y otra por Laetia corymbulosa. Estas comunidades están fuertemente relacionadas con la duración en el tiempo de inundación de diferentes zonas del plano inundable. Los análisis florísticos revelan marcadas afinidades con los bosques del Río Manú al sur del Perú. Estos resultados apoyan las ideas de Gentry, quien argumentó que las mayores afinidades florísticas se dan por similitudes ecológicas (v. gr. fertilidad de suelos y regímenes de lluvias), más que por otros factores (refugios pleistocénicos o barreras geográficas).
EVIDENCIA EN LA DIRECCIONALIDAD DEL PROCESO DE SUCESIÓN TEMPRANA DEL BOSQUE ALTOANDINO
(District University of Bogotá, 2016) Manuel E. Lequerica Támara; M. Carmen Pacheco Bernal; Pablo R. Stevenson
Los bosques secundarios han aumentado su extensión en las últimas décadas; a su vez, han sido propuestos como elementos de conservación. El propósito de este estudio fue evaluar la composición vegetal y la diversidad en potreros y bosques (Granada, Cundinamarca, Colombia), para comprobar si los procesos sucesionales demuestran direccionalidad. Se ubicaron seis parcelas de 0.1 Ha del borde del bosque hacia el potrero y hacia el bosque. Para cada parcela se determinó la estructura de la vegetación, diversidad y composición florística. Se encontró que la diversidad de los bosques es significativamente superior a la de los potreros en etapas tempranas de sucesión. Por medio de ordenaciones, el estado sucesional de cada una de las parcelas y se caracterizó observando que la vegetación tiende a agruparse según su edad, evidencia de que la sucesión es un proceso direccional. Dibujando perfiles de vegetación y calculando la densidad de plántulas a lo largo del gradiente bosque-potrero se encontró que el reclutamiento de plántulas no es significativamente diferente entre el borde y el interior del bosque. Por último, se encontró una relación inversamente proporcional entre distancias florísticas y geográficas de las parcelas, señalando la discontinuidad como una barrera a la sucesión del bosque.
Forest dynamics in different scenarios: Selective logging in the middle Magdalena (Colombia)
(2021) Isabel Cristina Restrepo; Ana M. Aldana; Pablo R. Stevenson
Selective logging is a frequently used forest use activity that has been shown to have less impact on biodiversity than clear-cutting. However, both the magnitude and direction of ecological change after logging depend on its intensity and subsequent forest dynamics. Therefore, it is important to conduct studies to understand the functioning of different ecosystems after selective logging. This study analyzed forest dynamics in the El Paujil reserve (Middle Magdalena, Colombia) in terms of demography, regeneration, clear-cutting dynamics, biomass accumulation and floristic composition by comparing two one-hectare plots in a fragment of the little disturbed (primary) forest and two one-hectare plots in a fragment of the forest that was selectively logged in the past. As expected, forest structure and biomass accumulation are altered by selective logging, but it did not have a significant impact on the other aspects mentioned, since it seems that the steep slopes of the area cause high mortality and promote the formation of clearings in both logged and lightly disturbed forests.
Forestación de bosques en sabanas de la altillanura colombiana: relevancia de las condiciones ambientales para el establecimiento de plántulas
(Alexander von Humboldt Biological Resources Research Institute, 2017) Pablo R. Stevenson; Mónica A. Ramírez; Luisa Fernanda Casas; Francisco Henao-Díaz
One way to counteract climate change is to plant forests with high carbon storage capacity. In this study we report the results of a reforestation project in savannas of the Tomogrande Reserve, in Vichada Department, Colombia. We restricted fire in six one-hectare plots: in two seasonally inundated and two highland savannas we planted seedlings of trees found in the Orinoco Basin and nearby gallery forests and in two of them we did not plant seedlings (control plots). Out of 200 seedlings planted in well-drained savannas, only 17 % survived after two and a half years (33 % came from nearby forest and 12 % from other areas). None of the 182 seedlings planted in flooded savannas survived at the end of the study. The main mortality cause in well-drained savannas was wilting. We concluded that in addition to the control of fire, seedling establishment of forest trees in savannas is highly affected by climatic and light conditions and for this reason the trees with highest potential for restoration are the ones already found at the site in the same ecological conditions (e.g. forest edge).
Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates
(Wiley, 2022) Diego F. Correa; Pablo R. Stevenson; María Natalia Umaña; Luiz de Souza Coêlho; Diógenes de Andrade Lima Filho; Rafael P. Salomão; Iêda Leão do Amaral; Florian Wittmann; Francisca Dionízia de Almeida Matos; Carolina V. Castilho
Abstract 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.
New ecological information for the Black Tinamou (<i>Tinamus osgoodi hershkovitzi</i>)
(Oxford University Press, 2015) Pablo José Negret; Oscar Garzón; Pablo R. Stevenson; Oscar Laverde-R.
The Black Tinamou (Tinamus osgoodi) is a rare and endangered bird with two geographically disjunct subspecies. Very little pertinent information exists due to its secretive habits and cryptic coloration. Observations from a one-year study at Alto Fragua Indi Wasi National Park in southern Colombia have provided new ecological information for T. o. hershkovitzi. This subspecies vocalizes mostly between March and April, suggesting that the breeding season occurs during the first half of the year. Detections by camera traps indicate that this tinamou is more active in late morning, a pattern also found in other lowland tinamous. The subspecies was found in the entire study area, but more commonly at middle altitudes (1,400-1,600 m). We estimated a density of 13.47 birds km 2 , which is relatively high compared with the abundance of other tinamous of similar size. Despite the locally observed high density of this subspecies of Black Tinamou, high rates of logging and hunting in the area make this population vulnerable to rapid decline in the future.
Nutrient transport within and between habitats through seed dispersal processes by woolly monkeys in north‐western Amazonia
(Wiley, 2010) Pablo R. Stevenson; Diana C. Guzmán‐Caro
The contribution of vertebrate animals to nutrient cycling has proven to be important in various ecosystems. However, the role of large bodied primates in nutrient transport in neotropical forests is not well documented. Here, we assess the role of a population of woolly monkeys (Lagothrix lagothricha lugens) as vectors of nutrient movement through seed dispersal. We estimated total seed biomass transported by the population within and between two habitats (terra firme and flooded forests) at Tinigua Park, Colombia, and quantified potassium (K), phosphorus (P) and nitrogen (N) content in seeds of 20 plant species from both forests. Overall, the population transported an estimated minimum of 11.5 (±1.2 SD) g of potassium, 13.2 (±0.7) g of phosphorus and 34.3 (±0.1) g nitrogen, within 22.4 (±2.0) kg of seeds ha(-1) y(-1). Approximately 84% of all nutrients were deposited in the terra firme forest mostly through recycling processes, and also through translocation from the flooded forest. This type of translocation represents an important and high-quality route of transport since abiotic mechanisms do not usually move nutrients upwards, and since chemical tests show that seeds from flooded forests have comparatively higher nutrient contents. The overall contribution to nutrient movement by the population of woolly monkeys is significant because of the large amount of biomass transported, and the high phosphorus content of seeds. As a result, the phosphorus input generated by these monkeys is of the same order of magnitude as other abiotic mechanisms of nutrient transport such as atmospheric deposition and some weathering processes. Our results suggest that via seed dispersal processes, woolly monkey populations can contribute to nutrient movement in tropical forests, and may act as important nutrient input vectors in terra firme forests.
Patterns of frequency and abundance of plant dispersal systems in Colombian forests and its relationship with the geographical regions of the country
(2013) Diego Felipe Correa Gómez; Pablo R. Stevenson; Esteban Álvarez‐Dávila; Ana M. Aldana; María Natalia Umaña; Ángela Cano; Juan Adarve; Doris Benítez; Alejandro Castaño; Álvaro Cogollo
The study of plant dispersal systems allows to go in depth in aspects that define the regeneration of forests, being essential to understand not only the population dynamics of plants but also the ecological relationships that emerge within ecosystems. In Colombia there is not a broad scale study showing the patterns of frequency and abundance of dispersal systems in different geographical regions (Amazonian, Andean, Caribbean, Upper Magdalena, Middle Magdalena, Orinoco, Pacific). Based on information of the identity and abundance of plants found in 101 vegetation plots of 1-ha, we explored the differences and associations in the frequency and abundance of dispersal systems between geographic regions. Additionally, we explored the importance value of families and genera per dispersal system, and the association between genera and geographic regions. The results show that environmental factors would be more important than the biogeographic history of the region in determining patterns of dispersal systems, reinforcing the importance of seed dispersal mediated by animals in tropical forests of different biogeographic regions.
Plant Diversity Reduces the Length of Food Scarcity Periods for Frugivorous Animals
(RELX Group (Netherlands), 2024) Pablo R. Stevenson; Maria Paula Obregón