Abstract

FREIBERG, Elke  and  FREIBERG, Martin. Ritmo de crecimiento y longevidad de follaje del estrato arbustivo en la Reserva Biológica A. Brenes, Costa Rica. Rev. biol. trop [online]. 1999, vol.47, n.3, pp.339-349. ISSN 0034-7744.

During one and a half years (February 1991 - July 1992) the growth rhythm and the longevity of leaves of 22 abundant understory species in the tropical premontane rain forest of Reserva Biológica Alberto Ml. Brenes, Alajuela, Costa Rica, were investigated. Three types of growth rhythm were identified. Most species, especially the monocotyledones, produce new leaves in defined intervals throughout the year. Only some have a slower leaf production in the dry season. Other species sprout periodically or only once a year. This interval, which is the time period between the beginning of the shooting of one leaf and the next, varied among the investigated species between 17-22 days (Malvaviscus arboreus, Urera elata, Myriocarpa longipes) and more than half a year (Cyclanthus bipartitus, Iriartea deltoidea, Ocotea gomezii). For some species this interval was longer at dry and dark sites (M. arboreus), but in many cases microclimatical factors such as temperature, relative light intensity, and evaporation varied to such a small extent within the forest that the differences did not lead to significant influences on growth factors of the plants. The mean leaf longevity varied between a half and four years. The maximum leaf age of the palms Cryosophila warscewiczii, I. deltoidea and Calyptrogyne trichostachys was estimated to be more than five years. In some cases leaf age was significantly correlated with microclimatical factors. Leaves of Begonia cooperi growing at higher light intensities in gaps fell earlier than leaves of plants in darker sites in the understory. Generally, the longevity of leaves was lower in plants growing at moister sites, but in most cases this relation was not significant. The data show that even in a rather constant climate in the understory of a very moist premontane rain forest, there is some seasonality in growth rhythm and that plant growth varies between different sites within the forest although climate variations are very small.

Keywords : Costa Rica; growth rhythm; longevity of leaves; microclimate; phenology; seasonality; tropical premontane rain forest; understory.