Seasonality of weather and tree phenology in a tropical evergreen mountain rain forest

Abstract

Flowering and fruiting as phenological events of 12 tree species in an evergreen tropical mountain rain forest in southern Ecuador were examined over a period of 3-4 years. Leaf shedding of two species was observed for 12 months. Parallel to the phenological recordings, meteorological parameters were monitored in detail and related to the flowering and fruiting activity of the trees. In spite of the perhumid climate of that area, a high degree of intra- and inter-specific synchronisation of phenological traits was apparent. With the exception of one species that flowered more or less continuously, two groups of trees could be observed, one of which flowered during the less humid months (September to October) while the second group started to initiate flowers towards the end of that phase and flowered during the heavy rains (April to July). As reflected by correlation coefficients, the all-time series of meteorological parameters showed a distinct seasonality of 8-12 months, apparently following the quasi-periodic oscillation of precipitation and related cloudiness. As revealed by power spectrum analysis and Markov persistence, rainfall and minimum temperature appear to be the only parameters with a periodicity free of long-term variations. The phenological events of most of the plant species showed a similar periodicity of 8-12 months, which followed the annual oscillation of relatively less and more humid periods and thus was in phase or in counter-phase with the oscillations of the meteorological parameters. Periods of unusual cold or dryness, presumably resulting from underlying longer-term trends or oscillations (such as ENSO), affected the homogeneity of quasi-12-month flowering events, fruit maturation and also the production of germinable seeds. Some species show underlying quasi-2-year-oscillations, for example that synchronise with the development of air temperature; others reveal an underlying decrease or increase in flowering activity over the observation period, influenced for instance by solar irradiance. As Ecuador suffers the highest rate of deforestation in South America, there is an urgent need for indigenous plant material for reforestation. A detailed knowledge of the biology of reproduction in relation to governing external factors (mainly climate) is thus required.

Impact of elevation and weather patterns on the isotopic composition of precipitation in a tropical montane rainforest

“…amounts to 1500 mm a −1 , whilst at the lowest point (ECSF, 1800 m a.s.l.) it is 2176 mm a −1 (Bendix et al, 2006;Emck, 2007). This demonstrates the high spatial variability of precipitation amounts occurring in the study area.…”

Diverging temperature response of tree stem CO2 release under dry and wet season conditions in a tropical montane moist forest

“…However, an extremely wet period (April-July) is followed by several months with less frequent rainfall (September-December) (Bendix et al 2006). Mean annual precipitation at 1,960 m a.s.l.…”

Fenología de Schizolobium parahyba y Vochysia guatemalensis en una selva alta perennifolia de Oaxaca, México

“…En Vochysia guatemalensis no hay asociación entre la floración y la precipitación, pues se desfasa de los meses con menor lluvia. Este hecho se ha observado en otras selvas perennifolias y se atribuye a mecanismos endógenos llamados "síndromes de dispersión" o aspectos como la radiación solar y duración del día (Morellato et al, 2000;Hamann, 2004;Bendix et al, 2006). Wright y Cornejo (1990) comprobaron experimentalmente que el estrés hídrico en algunas especies arbóreas tropicales no está necesariamente asociado con la periodicidad de la aparición de flores, aún cuando se proporcione agua de forma ininterrumpida durante la época más seca.…”

“…Varios trabajos señalan que la fructificación se correlaciona con la precipitación ya que frutos de Leguminosas tuvieron su mayor pico de fructificación durante la época lluviosa (Bendix et al, 2006), al igual que Vochysia guatemalensis (Vilchez et al, 2004) y V. pyramidalis (Silveira et al, 2002) maduraron sus frutos en la época de mayor disponibilidad de agua edáfica y en la planta. Se sabe que la humedad del sitio influye en la cantidad y tamaño de las estructuras reproductivas, ya que es fundamental en el transporte de minerales y carbohidratos para la formación de frutos (Kramer y Boyer, 1995), la mayor humedad encontrada en los sitios de Vochysia se favorece por la textura arcillosa del suelo que posee una mayor cantidad de microporos donde el agua es retenida con más fuerza que en la arena o el limo (Aguilera, 1989;Lamber et al, 2008).…”

“…También se reportan correlaciones significativas negativas entre la precipitación con la floración y positivas con la fructificación en Norte (Carabias y Guevara, 1985;Ibarra et al, 1991), Centro (O'Brien et al, 2008;Solis et al, 2009) y Sudamérica (Bendix et al, 2006;Zarate et al, 2006), África (Bollen y Donati, 2005) y Asia (Van Shaick, 1986).…”