Threatened Native Trees in Guam: Short-term Seed Storage and Shade Conditions Influence Emergence and Growth of Seedlings

Seedling emergence and growth traits of three rare and threatened tree species in the Mariana Islands were studied within a range of incident light levels and up to 9 months of seed storage. Seedling emergence percentage and velocity were maximized in moderate shade for Elaeocarpus joga Merr., deep shade for Serianthes nelsonii Merr., and full sunlight for Tabernaemontana rotensis (Kaneh.) P.T. Li. Seedling height was increased by shade for E. joga and S. nelsonii. Height of T. rotensis seedlings was not influenced by incident light from 25% to 100%. Nine months of seed storage at ambient temperature did not influence emergence percentage of E. joga or S. nelsonii seeds. In contrast, seeds of T. rotensis began declining in seedling emergence percentage between 2 and 3 months of storage, and seedling emergence was nil by 4 months. This study represents the first experimental approach to determining the influences of light and storage on seed and seedling behavior for any rare and threatened taxa from the Mariana Islands. Our findings that revealed highly contrasting responses among the species provide a valuable start to building the knowledge base needed to respond to formal recovery or conservation plans by defining horticultural protocols for managing a conservation nursery.