The Contributions of Nitrogen-Fixing Symbioses to Coastal Heathland Succession

Nutrient availability has been linked to successional change in the extremely Nlimited coastal heathland ecosystem. A study was conducted on Nantucket Island (Massachusetts) to determine if plants with N-fixing symbioses affect nutrient availability and community succession in coastal heathland ecosystems. N-availability was no different in soils collected beneath N-fixing species than in soils collected away from N-fixing species. Furthermore there was no difference in nitrogen content of grasses and soils found in association with N-fixing species than those located away from N-fixers. The 15N content of soils and plants distributed within and without the canopy of N-fixing species was no different. The annual height and weight increments of pines growing within and away from patches of the N-fixing shrub Myrica pensylvanica were not significantly different, indicating that nitrogen derived from N-fixing symbioses did not contribute to the growth of pines. The lack of noticeable effects of N-fixing species on neighboring plants may be the result of leaching in these sandy soils, which would minimize lateral plant-to-plant N transfers via the soil.