Managing cultivated plants of rare tree species presents challenges because inadequate species-specific horticultural knowledge is available, and seed collections are often highly regulated and limited. Decision makers and researchers recognize the need to effectively confront the data deficiency that is inherent to rare species research and management. Deciding how to allocate limited resources to achieve maximum conservation benefit within recovery plans, for example, cannot accurately proceed in the absence of species-specific research. Moreover, the value of each individual specimen in conservation research mandates the employment of the most accurate horticultural protocols. This restriction may hinder the inclusion of some treatments in traditional horticultural experimental approaches if death or compromised plant health is predicted to result from those treatments.
These and other restrictions to effectual management of rare plant nurseries are magnified by the fact that the skill level required by horticulturists to maintain a specialized conservation nursery is highly dependent on the requirements of each taxon. An understanding of the species-specific requirements is needed to effectively manage human resources by assigning highly capable horticultural technicians to care for the most problematic species. Therefore, empirical research results are a prerequisite to managing this aspect of a conservation nursery.
Several tree species that are native to the Mariana Islands are characterized by limited regeneration potential and extensive habitat loss, and the need for formal conservation has become paramount. Elaeocarpus joga, S. nelsonii, and T. rotensis are three of these species. Informal information that was generated in the absence of scientific rigor is often available for propagation and nursery care of seedlings, even for rare species such as these. For example, several writings discuss anecdotal observations on S. nelsonii seed germination (Richardson and Marutani, 1997; USFWS, 1994) or E. joga germination (Ritter and Naugle, 1999). However, to date, we know of no published reports that used an experimental approach to accurately increase knowledge on the specifics of nursery protocols for any rare species in the Mariana Islands. Nurseries positioned to pursue recovery plans or respond to conservation efforts are hindered by this lack of information.
We have conducted conservation projects on these three species, which included nursery research. The initial objective herein was to determine the influence of a wide range of ambient light exclusion levels on seedling emergence and early seedling growth traits of these three species. The secondary objective was to determine the influence of 9 months of seed storage on seedling emergence percentage. The results will inform management decisions for conservation nurseries.
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