Influence of light conditions on the allometry and growth of the understory palm Geonoma undata subsp. edulis (Arecaceae) of neotropical cloud forests.
OBJECTIVE
Knowledge on the growth responses of understory palms to changing light conditions within neotropical cloud forests is limited. The low light regime of these environments, in addition to persistent cloudiness, low ambient temperatures, and slow nutrient cycles, imposes significant constraints on biomass accumulation. Here, we evaluate how changes in the understory light conditions influenced the allometry and growth of G. undata subsp. edulis in two cloud forests in Costa Rica.


METHODS
We examined the structural relationships between stem diameter, stem height, and crown area in reproductive and nonreproductive individuals. We related the variation in stem growth and crown area with allometry, leaf production and longevity, and light conditions that we measured using hemispherical photographs over 1 year.


RESULTS
The allometric and growth pattern of G. undata subsp. edulis was characterized by its investment in crown area, which was strongly and positively related to increments in palm height and reproduction. Growth, measured as the increase in crown area and stem height, was not explained by the variation in the light regime spanning 1 year. However, reproductive individuals were generally taller, more slender, and had larger leaf areas than nonreproductive individuals.


CONCLUSIONS
Our results demonstrated that stem growth responses were mostly controlled by initial crown size rather than by temporal differences in the understory light regimes of cloud forests. These results suggest that cloud forest understory palms have a limited capacity to respond to light changes and rely mostly on an opportunistic strategy for biomass accumulation and reproduction.
Escuela de Biología, Universidad de Costa Rica, 2060, San Pedro, San José, Costa Rica.
Olivia
O
Sylvester
Gerardo
G
Avalos
D000222:Adaptation, Physiological; D028023:Arecaceae / Q000254:growth & development* / Q000502:physiology; D018533:Biomass; D003364:Costa Rica; D017753:Ecosystem; D008027:Light; D018515:Plant Leaves / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development*; D012098:Reproduction; D014197:Trees / Q000254:growth & development / Q000502:physiology; D014329:Tropical Climate
Arecaceae; Geonoma undata subsp. edulis; crown expansion; functional architecture; palm allometry; shade tolerance