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Mortalidad y reclutamiento de árboles en un bosque nublado de la cordillera de Los Andes, Venezuela

Tree mortality and recruitment was studied in a Tropical lower montane moist forest (sensu Holdridge) located in the Venezuelan Andes (8o39’N; 71o24’O). Data from six 0,25 ha permanent plots, with 23 successive measurements (1968 – 2000) were used to analyze tree mortality in individuals with a breast height diameter (dbh) = 10 cm. Fifty five tree species were recorded, including palms, with 622 individuals ha -1 , and a mean basimetric of 46 m 2 ha -1 . Among the most abundant species are found Myrcia fallax, Graffenrieda latifolia and Beilschmeidia sulcata, with more than 100 trees ha -1 . Annual tree recruitment and mortality rates averaged 1.64 and 1,59%, respectively. Significant differences among periods were found for both rates. Tree density increased in 12”%. Similarly, estimation of average tree half life varied among plots and averaged 43.1 years. Apparently forest dynamics is not affected by human pressure. However, some forest conservation actions are suggestedSe estudió la mortalidad y el reclutamiento de los árboles con un diámetro a la altura de pecho (dap) = 10 cm, en un bosque húmedo montano bajo (sensu Holdridge) situado en la Cordillera de los Andes (8o39’N; 71o24’O), entre 2200 y 2500 m.s.n.m. El análisis se realizó con datos provenientes de seis parcelas permanentes de 0,25 ha, con 23 mediciones sucesivas (1968 – 2000). Se registraron 55 especies arbóreas incluyendo palmas, con 622 individuos ha -1 y un área basal promedio de 46 m 2 ha -1 . Entre las especies más abundantes se encuentran Myrcia fallax, Graffenrieda latifolia y Beilschmeidia sulcata, con más de 100 ind ha -1 . Las tasas anuales de reclutamiento y mortalidad de los árboles fueron de 1,64 y 1,59%, respectivamente, con diferencias estadísticas entre parcelas solo para el reclutamiento. En cuanto a la variación entre periodos, se encontraron diferencias significativas para ambas tasas. Se observó un incremento en la densidad arbórea de un 12%. Así mismo, las estimaciones de vida media proyectadas varían entre parcelas para un promedio de 43,21 años. Se concluye que aparentemente el bosque no está siendo afectado en su dinámica; sin embargo, se sugieren algunas acciones que podrían contribuir a su conservación

Diametric tree growth in functional groups species in a seasonal forest of the venezuelan western plains

Se estudiaron las tasas de crecimiento de especies arbóreas que pertenecen a diferentes grupos funcionales y que ocupan distintas posiciones fisiográficas en un bosque estacional de la Reserva Forestal Caparo, Venezuela. Los grupos fueron conformados de acuerdo con sus requerimientos de luz y la altura máxima que pueden alcanzar los individuos. Se utilizaron datos de parcelas permanentes, con mediciones continuas durante 18 años del diámetro a la altura del pecho (DAP) a partir de 10 cm de DAP. Los mayores diámetros corresponden a los grupos de tolerantes intermedias grandes (>30 m de altura) y de tolerantes grandes. En general, los valores de crecimiento diamétrico encontrados están en el intervalo reportado en la zona tropical. La densidad total difirió significativamente entre grupos funcionales, pero no entre posiciones fisiográficas. Las mayores tasas anuales de crecimiento por categoría diamétrica correspondieron a las categorías intermedias. Se hallaron diferencias significativas de las tasas de crecimiento para los grupos, mas no entre posiciones fisiográficas. Las palmas son las especies que presentaron la mayor tasa de crecimiento, seguidas por las intolerantes medianas y las intolerantes pequeñas; las tolerantes intermedias y las tolerantes pequeñas presentaron las tasas menores. Estos resultados coinciden con lo esperado, considerando las características propias de cada uno de esos grupos.Tree species diametric growth rates were studied for different functional groups and in several physiographic positions in theExperimental Area of Caparo Forest Reserve, Venezuela. Functional groups were defined according to light requirements and maximum tree heights. We used a data set from permanent plots where diameter at breast height (DBH) was measured during a period of 18 years for all trees with DBH ≥ 10 cm. The largest DBH values were found for large (>30 m in height) intermediate tolerant species and large tolerant species. In general, growth rates estimated in this study are within the range reported for the tropical zone. Regarding tree total density significant differences were found among functional groups, but not between physiographic positions. The highest values of tree growth rate per diametric category were recorded for the intermediate categories. Moreover, highly significant differences were found between tree growth rates of functional group species, but not between physiographical positions. The group of palms showed the highest growth rates followed by small intermediate tolerant species. Intermediate tolerant species and small tolerant species showed the lowest tree growth rates. These results are in agreement with expected patterns regarding the traits of these functional groups

Reciclaje, Reutilización y Ecodiseño en la Facultad de Ciencias Forestales y Ambientales, Universidad de Los Andes, Mérida Venezuela

Es reconocida, con enorme preocupación, la insostenibilidad que se presentan en territorios urbanos donde la huella ecológica es negativa. El área metropolitana de Mérida no escapa a esa realidad. Se denota en su escala ecosistémica bioregional la perdida, entre otros, de la cobertura forestal, emisiones, vertidos y residuos que contaminan sus fuentes de agua, aire y suelos. Los residuos sólidos urbanos se han transformado en un problema que distrae buena parte de la atención de la gestión de las administraciones municipales, especialmente del municipio Libertador, más cuando el vertedero municipal está a punto de colapso. La Universidad de Los Andes, y todo el conjunto de facultades que la conforman en la ciudad de Mérida, presentan igual realidad. Es una sinergia técnica desarticulada entre Comunidad-Universidad-Administración local/regional-Medio Ambiente-Disposición de residuos sólidos. Ante esta realidad, el presente trabajo se enmarca dentro de las actividades ya iniciadas en el edificio central de la Facultad de Ciencias Forestales y Ambientales de la ULA, con la Implantación de un sistema de gestión ambiental para el reciclaje y reutilización de residuos no peligrosos y peligrosos. Es una manera de aportar soluciones a este problema, sirviendo de vitrina expositiva al conjunto de instituciones que le conforman; trasmitir y desarrollar acciones conjuntas con otras facultades; servir de puente sensibilizador y de capacitación para comunidades adyacentes; y trabajar como apoyo a los esfuerzos de la municipalidad merideña por instaurar la cultura del reciclaje y reutilización hasta lograr la minimización de los impactos ambientales. Palabras clave: reciclaje, reutilización, sistema de gestión medio ambiental, desechos sólidos.Abstract Recycling, reuses and ecodesign at the Faculty of Forestry Science and Environment, University of the Andes, Merida, Venezuela At our Faculty, we have initiated a project called Environmental Management System for Recycling and Reuses of non-dangerous and dangerous urban wastes, with an intension of becoming a showcase, firstly at the University and then on to the metropolitan area of Merida, Venezuela. We envision three basic phases in implementing the project. First phase is to introduce and establish the program, the second is to confirm the effectiveness, and the third is to examine and revise the program. We have placed classified containers on campus for collecting used papers, carton boxes, glass, plastic containers, PET bottles, metal objects, and organic matters that come out from class rooms, offices, and laboratories. We have at our disposition a center for stock-piling solid wastes. We also organize awareness programs such as local meetings, participatory conferences, training workshops, as well as forming motivational brigades, placing bulletin and publicity boards on campus, among other activities. Keywords: environmental management system, solid wastes, recollection and classification of urban wastes

Use and misuse of trait imputation in ecology: the problem of using out‐of‐context imputed values

Despite the progress in the measurement and accessibility of plant trait information, acquiring sufficiently complete data from enough species to answer broad‐scale questions in plant functional ecology and biogeography remains challenging. A common way to overcome this challenge is by imputation, or ‘gap‐filling' of trait values. This has proven appropriate when focusing on the overall patterns emerging from the database being imputed. However, some applications force the imputation procedure out of its original scope, using imputed values independently from the imputation context, and specific trait values for a given species are used as input for computing new variables. We tested the performance of three widely used imputation methods (Bayesian hierarchical probabilistic matrix factorization, multiple imputation by chained equations with predictive mean matching, and Rphylopars) on a database of tropical tree and shrub traits. By applying a leave‐one‐out procedure, we assessed the accuracy and precision of the imputed values and found that out‐of‐context use of imputed values may bias the estimation of different variables. We also found that low redundancy (i.e. low predictability of a new value on the basis of existing values) in the dataset, not uncommon for empirical datasets, is likely the main cause of low accuracy and precision in the imputed values. We therefore suggest the use of a leave‐one‐out procedure to test the quality of the imputed values before any out‐of‐context application of the imputed values, and make practical recommendations to avoid the misuse of imputation procedures. Furthermore, we recommend not publishing gap‐filled datasets, publishing instead only the empirical data, together with the imputation method applied and the corresponding script to reproduce the imputation. This will help avoid the spread of imputed data, whose accuracy, precision, and source are difficult to assess and track, into the public domain

The pace of life for forest trees.

Tree growth and longevity trade-offs fundamentally shape the terrestrial carbon balance. Yet, we lack a unified understanding of how such trade-offs vary across the world's forests. By mapping life history traits for a wide range of species across the Americas, we reveal considerable variation in life expectancies from 10 centimeters in diameter (ranging from 1.3 to 3195 years) and show that the pace of life for trees can be accurately classified into four demographic functional types. We found emergent patterns in the strength of trade-offs between growth and longevity across a temperature gradient. Furthermore, we show that the diversity of life history traits varies predictably across forest biomes, giving rise to a positive relationship between trait diversity and productivity. Our pan-latitudinal assessment provides new insights into the demographic mechanisms that govern the carbon turnover rate across forest biomes

Water table depth modulates productivity and biomass across Amazonian forests

Funding: This work was part of the PhD thesis of the first author, developed at the Graduate Program in Ecology of the National Institute of Amazonian Research (INPA), with a fellowship funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES), Finance Code 001, (88887.141433/2017-00). The authors are also grateful for the financial and research support of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Amazonas State Research Foundation (FAPEAM), the Newton Fund via the Natural Environment Research Council (NE/M022021/1 to O.L.P. and F.R.C.C.), PPBio Manaus, Centro de Estudos Integrados da Biodiversidade Amazônica and RAINFOR. We also thank Karina Melgaço, Aurora Levesley and Gabriela Lopez-Gonzalez for curating and managing ForestPlots.net. This was ForestPlots.net Project 26 led by Thaiane Sousa. This is publication number 832 of the Technical Series of the Biological Dynamics of Forest Fragments Project (BDFFP, INPA/STRI).Aim : Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location : Lowland Amazonian forests. Time period : 1971–2019. Methods : We used 344 long-term inventory plots distributed across Amazonia to analyse the effects of long-term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil-water and edaphic properties. Results : Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth <5 m) had 18% less above-ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit < −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. Main conclusions : We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra-firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.Peer reviewe

The number of tree species on Earth.

One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness

Tropical forests in the Americas are changing too slowly to track climate change

Understanding the capacity of forests to adapt to climate change is of pivotal importance for conservation science, yet this is still widely unknown. This knowledge gap is particularly acute in high-biodiversity tropical forests. Here, we examined how tropical forests of the Americas have shifted community trait composition in recent decades as a response to changes in climate. Based on historical trait-climate relationships, we found that, overall, the studied functional traits show shifts of less than 8% of what would be expected given the observed changes in climate. However, the recruit assemblage shows shifts of 21% relative to climate change expectation. The most diverse forests on Earth are changing in functional trait composition but at a rate that is fundamentally insufficient to track climate change

The number of tree species on Earth.

One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness