PARENT SESSION
Oral Session #8: Plant Ecology: Nutrient Uptake, Movement, Use.
Presiding: V. Gutschick
Monday, August 5. 8:00 AM to 11:30 AM. Grand Ballroom West, Radisson.
Generation of microhabitats by a nitrogen-fixing shrub: the only good shrub is a dead shrub.
Alpert, Peter*,1, Abare, Nathan1, Benson, Jennifer1, Blanchard, Jonathan1, Giggey, Joanne1, Stevens, Andrew1, 1 Biology Department, Amherst, MA
ABSTRACT- Nitrogen-fixing shrubs can create a spatial separation between light and nitrogen availabilities to smaller plants: high nitrogen under shrubs but high light away from shrubs. However, availabilities of both resources might be high at the edge of shrub canopies and under dead shrubs. To test whether canopy edges and dead canopies of nitrogen-fixing shrubs provide favorable microsites for herbaceous plants, we transplanted a common native perennial herb, Fragaria chiloensis, under and around shrubs of the most abundant native nitrogen-fixer, Lupinus arboreus, on coastal sand dunes at the University of California Bodega Marine Reserve in two successive years. We measured light, plant-available nitrogen, and accumulation of biomass by transplants. On average, transplants grew more than twice as much under shrubs that had been dead for <1 year than on open sand, at the edge of live shrubs, under live shrubs, or under shrubs that had been dead for 1-2 years. Newly dead shrubs were also the only microsites in which both light and nitrogen levels were high. Results suggest that Lupinus arboreus provides favorable microsites for herbs in this system only when shrubs die, and then only for one growing season. This should make the habitat highly unpredictable in both time and space for the herbs.
KEY WORDS: coastal sand dunes, nitrogen-fixing shrub, light and nitrogen availability, northern California