Germination and soil seed bank traits of Podocarpus angustifolius (Podocarpaceae): an endemic tree species from Cuban rain forests

Pablo Ferrandis,Marta Bonilla,Licet Del Carmen Osorio

doi:10.15517/rbt.v0i0.3378

Abstract

Podocarpus angustifolius is an endangered recalcitrant-seeded small tree, endemic to mountain rain forests in the central and Pinar del Río regions in Cuba. In this study, the germination patterns of P. angustifolius seeds were evaluated and the nature of the soil seed bank was determined. Using a weighted two-factor design, we analyzed the combined germination response to seed source (i.e. freshly matured seeds directly collected from trees versus seeds extracted from soil samples) and pretreatment (i.e. seed water-immersion for 48h at room temperature). Germination was delayed for four weeks (= 30 days) in all cases, regardless of both factors analyzed. Moreover, nine additional days were necessary to achieve high germination values (in the case of fresh, pretreated seeds). These results overall may indicate the existence of a non-deep simple morphophysiological dormancy in P. angustifolius seeds. The water-immersion significantly enhanced seed germination, probably as a result of the hydration of recalcitrant seeds. Although germination of seeds extracted from soil samples was low, probably due to aging and pathogen effects throughout the time of burial, the study revealed the existence of a persistent soil seed bank (at least short-termed) of approximately 42 viable seeds per m2 in the upper 10cm of soil. Such a record is noteworthy since references to persistent soil seed banks in recalcitrant-seeded species are scarce in the literature. The population consequences derived from the formation of persistent soil seed banks in this endangered species are discussed.

Highlights

Seed germination and seedling establishment are the most vulnerable phases in plants life cycles (Solbrig 1980), and information about them is especially important in understanding the distribution of rare plants. Schemske et al (1994) stressed the importance of compiling information on the stages in the reproductive cycle of endemic, rare, and threatened plant species in order to enhance our understanding of their scarcity, and to design efficient conservation measures
The goals of the present study were to determine the nature of the soil seed bank and germination responses of the endangered Podocarpus angustifolius Griseb., a recalcitrantseeded tree endemic to mountain rain forests in the central and Pinar del Río regions in Cuba
Germination response of P. angustifolius seeds: Germination began about 4 weeks after incubation, both in seeds extracted from soil samples and those collected from trees, regardless of the pretreatment (Fig. 1)

Summary

Introduction

Seed germination and seedling establishment are the most vulnerable phases in plants life cycles (Solbrig 1980), and information about them is especially important in understanding the distribution of rare plants. Schemske et al (1994) stressed the importance of compiling information on the stages in the reproductive cycle of endemic, rare, and threatened plant species in order to enhance our understanding of their scarcity, and to design efficient conservation measures. The ecological significance of soil seeds banks is transcendental since a persistent seed bank can contribute decisively to the resilience of plant populations (Baskin & Baskin 1978), even though no seeds are produced in a given year, and can even facilitate re-colonization after a local extinction (Milberg 1994). Such a point becomes important in the case of threatened plant species. The general aim of the study was to enhance our knowledge of the reproductive traits of P. angustifolius, for which nearly no information is currently available, in order to contribute more effectively to its conservation

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