SGER: Determining Seed Bank Age Structure with Tandem Accelerator Mass Spectrometry C14 Dating

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9520888 Venable There are many questions in both pure and applied ecology for which an understanding of seed bank dynamics and seed age structure is critical. These include an understanding of succession, extinction and colonization dynamics, revegetation policies, and weed management. Traditionally, the only way to determine seed bank age structure has been to follow seed cohorts for many years. This project will use new techniques involving Tandem Accelerator Mass Spectrometry (TAMS) to date modern seed banks with 14C. This technology, in conjunction with the variable levels of atmospheric 14C as a result of nuclear bomb testing which peaked in 1963, should permit accurate estimates of the ages of seeds produced over the last 30 years. This procedure will be tested with seeds of a Sonoran Desert annual plant. The dating procedure will be calibrated with seed of known age and then utilized to age a carefully sampled seed bank of this desert annual. It is widely believed that long-lived seed banks play an important role in the ecology of desert annuals and desert annuals have played an important role as model organisms in the development of our understanding of adaptation to environmental variability and community dynamics in variable environments. Long-term demographic data are available for desert annuals at the study site. The long-term data will aid in the interpretation of the 14C dates, because differences in production of seeds over the last 14 years can be compared to their incorporation into the seed bank. Likewise, the 14C dates will aid in the interpretation of the long-term data by permitting estimation of the role of seed retention in population dynamics. The research in this Small Grant for Exploratory Research proposal will lead to important breakthroughs in the development of technology that will permit in-depth understanding of long-term community dynamics and diversity. Seed bank age structure is critical in many habitats for many ecological questions, and TAMS 14C aging of seeds for up to 30 years of age would constitute a major methodological breakthrough.