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Soil seed bank from lowland rain forest in Singapore:canopy-gap and litter-gap demanders

Published online by Cambridge University Press:  01 January 1998

DANIEL J. METCALFE
Affiliation:
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
I. M. TURNER
Affiliation:
School of Biological Sciences, National University of Singapore, Lower Kent Ridge Road, Singapore 0511

Abstract

The vast array of species found in the humid lowland tropical forests of the world are frequently divided into two general groups, light-demanders and shade-tolerators (Denslow 1980, Swaine & Whitmore 1988). In this dichotomy the characteristics of the gap-demanders are often given to include small seed size, dormancy mechanisms, potentially rapid growth, and requirement of direct sunlight for germination and establishment. Conversely, shade-tolerators are considered to have large, short-lived seeds, the potential to germinate in canopy shade and an ability to grow slowly in deep shade (Swaine & Whitmore 1988). Failing to conform to either general pattern, small-seeded shade-tolerant species have been documented from both the Central American and South-east Asian tropics (Ellison at al., Metcalfe & Grubb 1995). Some of these small-seeded species have been shown to be able to germinate in filtered light approximating to canopy shade (Metcalfe 1996), and seedlings of other small-seeded species have been recorded growing under a closed canopy (Grubb 1996, Kiew 1988, Raich & Gong 1990). Several taxa shown by Metcalfe (1996) and Metcalfe & Grubb (1997) to be small-seeded and shade-tolerant were found in considerable numbers in the soil seed bank in Sabah by Kennedy (1991), and one (Urophyllum glabrum) by Putz & Appanah (1987) in Peninsular Malaysia. Species with small seeds (less than about 1-10 mg) do not have the resources to emerge from underneath a covering of leaf litter, and require litter-free sites for successful establishment (Guzmán-Grajales & Walker 1991, Molofsky & Augspurger 1992, Putz 1983).

Type
SHORT COMMUNICATION
Copyright
© 1998 Cambridge University Press

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