Browsing by Autor "Teresa Schwarzkopf"

Now showing 1 - 2 of 2

Ambiente de luz del sotobosque de una selva nublada andina: efectos de la estructura del dosel y la estacionalidad climática.
(Vicerractoría Investigación, 2016) Ana Mercedes Rojas; Teresa Schwarzkopf; Carlos García; Mauricio Jeréz
The light environment in the understory of cloud forests is highly heterogeneous and determined by species composition, canopy structure, site conditions, and seasonality. This study was carried out at San Eusebio cloud forest, Venezuela (2 300 - 2 500 masl). The impact of canopy structure variations on understory light availability was estimated in the dry (December-February) and rainy (March-November) seasons, in sites under continuous canopy cover and gaps of various sizes. Hemispherical photographs were taken to estimate the percentage of canopy openness, leaf area index, percentages of transmitted direct and diffuse light, and duration and frequency of sunflecks. A light index was calculated from the relative proportions of direct and diffuse light transmitted to the understory. For most variables, there were significant differences between seasons, as well as among different gap sizes and under closed canopy. The light index was low (0.25 to 26 of a maximum = 100), even for the largest gaps, indicating a highly shaded light environment, especially beneath closed canopy in the rainy season. Patterns and interactions among factors were analyzed (gaps vs. continuous canopy, gap sizes, location within the gaps, and seasonality) with a mixed effects repeated measures Anova design. Results showed that the amount of light reaching the understory is low in both gaps and closed canopy. However, small but significant differences in light availability existed for both seasonality and magnitude of the perturbations. These differences could contribute to explain the dynamics of tree species regeneration in this forest. The knowledge of the factors conditioning light availability in the understory where tree regeneration begins is crucial in cloud forests because of energetic limitations in this ecosystem, and might be essential for future restoration and conservation plans concerning the preservation of the diversity and integrity of these forests.
Estructura de la vegetación en la zona de transición bosque-páramo en La Sierra Nevada de Mérida: implicacionespara analizar la dinámica del límite forestal
(2018) Lirey Ramírez; Luis D. Llambí; Teresa Schwarzkopf; Luis E. Gámez; Nelson Márquez
El limite altitudinal del bosque continuo corresponde en los Andes del Norte a una compleja zona de transicion entre el bosque paramero y el paramo, y es considerado un ambiente clave para el monitoreo de los efectos del cambio climatico global. Se analizo comparativamente la estructura de la vegetacion en el limite superior del bosque continuo, en pequenas islas de bosque y en paramos abiertos en una transecta altitudinal desde 3260 hasta 3550 m s.n.m. en la vertiente noroeste de la Sierra Nevada de Merida. Se incluyeron tambien parcelas ubicadas en el ecotono bosque-paramo a lo largo del gradiente. La diversidad del estrato superior lenoso disminuyo con el aumento de altitud mientras que en el estrato inferior sucedio lo contrario. Se observo un claro patron de cambio en la composicion y abundancia de las plantas lenosas en el gradiente altitudinal. En los bosques continuos por debajo de 3300 m predominaron elementos propios de la selva nublada montana alta y del bosque paramero (ej. Psammisia penduliflora, Libanothamnus nerifolius), los cuales estuvieron ausentes en las islas de bosque y los paramos mas altos. En las islas de bosque y en los bordes bosque-paramo dominaron las plantas lenosas Diplostephium venezuelense y Cybianthus marginatus. Aun cuando D. venezuelense estuvo ausente en los paramos a mayor altitud, fue predomiante en el componente lenoso del paramo a menor altitud. Esto la senala como una posible especie pionera en escenarios de ascenso altitudinal del limite del bosque por efecto del calentamiento global.