Klemow, K.M. 1986. PERSISTANCE OF MELILOTUS ALBA IN A TEMPORALLY VARIABLE HABITAT: WHEN DOES A BIENNIAL BEHAVE LIKE AN ANNUAL? Contributed paper: Pennsylvania Academy of Science meeting. Abstract: Proceedings of the Pennsylvania Academy of Science 60:85.
Plants colonizing a 50-year-old abandoned limestone quarry near Syracuse, New York are subjected to substantial year-to-year variability in rainfall. Cohorts of seedlings that emerge during years of drought often suffer complete pre-reproductive mortality. Such complete mortality would cause populations of monocarpic annuals and biennials to go extinct on the site, unless they possessed life-history attributes that enabled persistance. An annual species (Erucastrum gallicum) persists by a pool of seeds that remain dormant for two or more seasons. Conversely, seeds of two facultative biennial species (Picris hieracioides and Echium vulgare) do not have long term dormancy. Instead, populations persist by individuals that delay flowering for two or more seasons. The purpose of this study was to determine the importance of seed dormancy as a characteristic that enables population persistance in Melilotus alba (white sweet clover). Germination and survival of M. alba seeds were assessed in a field experiment that lasted one year . The results showed that a large fraction (25-45%) of the seeds remained dormant and viable. Thus, the mechanism of persistance of this biennial species was more similar to that of the annual species than of the other two biennials.
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