Seed production, seed dispersal, and seedling ecology of mahogany (Swietenia macrophylla King) in Quintana Roo, Mexico.

摘要

The ecology of Swietenia macrophylla and three associated tree species in seasonal tropical forests in Quintana Roo, Mexico were studied to improve the design of sustainable forest management methods.; Seed production of 82 Swietenia trees from 15 to >100 cm diameter at breast height (DBH) was estimated by counting fruit pericarp segments beneath the tree crowns. The number of fruits/tree increased with DBH size and was related to increasing tree crown. Trees >75 cm DBH had significantly greater fruit production than smaller trees, and had a larger median seed dispersal distance (38 m) that was skewed to the west of the trees. Fruit production varied among the six-years, but did not reach the population variability or tree synchronicity that is found in masting species.; The effect of 7%, 22%, and 45% sunlight and two soil moisture types on seedlings of Swietenia, Cedrela odorata, Cordia dodecandra, and Manilkara zapota were studied in shade houses in Quintana Roo, in order to examine plasticity of physiology, morphology, and biomass allocation as a background to understanding growth and competition in forest conditions.; Some expected trends occurred in all species: leaf area ratio (LAR), specific leaf area (SLA), and foliar biomass allocation all increased with decreasing light. Good soil moisture increased height, diameter and biomass, therefore greater photosynthesis rates may be explained by more water availability. However, comparisons among species did not always show trends expected to be associated with different levels of shade tolerance. Shade tolerant Manilkara had the lowest total biomass, and the highest foliar biomass allocation, but did not have the expected high SLA because of its thick evergreen leaves. Shade intolerant Cedrela had the lowest foliar allocation, but compensated with the highest SLA, foliar nitrogen content, and photosynthetic rate. Intermediate/intolerant Swietenia had the highest biomass production of all species; it had high plasticity in foliar allocation such that there was little difference in total biomass among light levels. Intermediate/intolerant Cordia had lower plasticity in foliar allocation than Swietenia , so a lower LAR and substantially less total biomass in low light. It had thicker leaves and higher foliar nitrogen-area in high light.