Sowing date, shade, and irrigation affect big-leaf mahogany (Swietenia macrophylla King)

Swietenia macrophylla King (big-leaf mahogany) is one of the most economically important tree species that grows in the Yucatan peninsula. While it is well known that exposure to high levels of light and low levels of competition are necessary for big-leaf mahogany establishment, conditions favoring germination have been little studied. The effect of sowing date, shade, and irrigation on germination were investigated in a nursery in Quintana Roo, Mexico. Three levels of shade (0, 63, and 80%) and two levels of irrigation (non-irrigated and irrigated 20 mm per week) were used. In addition, seed were sown on four different dates, spanning the dry season to the middle of the rainy season. Germination increased linearly with increasing shade. Irrigated seed had significantly higher germination than non-irrigated seed across all three levels of shade. Seed sown in April germinated 10 weeks after sowing, and seed sown in May and June germinated 4-5 weeks after sowing. Most seed sown in August did not germinate. Although shade does not favor establishment and growth, it may contribute to maintaining soil moisture and seed viability during germination of big-leaf mahogany. (C) 2000 Elsevier Science B.V. All rights reserved.