PARENT SESSION
Oral Session #19: Plant Competition. Presiding: N. Slade.
Monday, August 6, 2001. 1:00 PM to 5:15 PM. Hall of Ideas J.
Effects of competition, spatial variability, and timing of germination on Mimulus nudatus, a rare serpentine endemic plant.
Brigham, Christy1, Schwartz, Mark1, 1
ABSTRACT- Although studies of plant competition abound, few authors have studied competition for more than one year or incorporated spatial and temporal variability into studies of competition. Similarly, few studies of rare plant biology have assessed the effects of more than a single factor on plant performance. Here we evaluate the effects of competition and spatial and temporal variability on the survivorship, growth, and reproduction of a rare annual plant, Mimulus nudatus. We used naturally germinating seedlings at three sites and two different time periods (early and late in the season) and applied two competitive intensities (neighbors removed from a 10-centimeter radius and neighbors present). Competition treatments were applied in two different years (1998 and 2000). Survivorship was significantly affected by site and timing of germination but not by competition. Site, timing, and competition all had significant effects on growth and reproduction. There were also significant interactions between site and timing of germination and competition and site on growth and reproduction. The least productive site showed the smallest effects of competition on plant traits. Similarly, late in the season, when resources were lowest, competitive effects declined. Our results support the hypothesis that the importance of competition declines as abiotic stress increases. Additionally, for this rare plant factors such as site and timing of germination may be more important than competition in determining survivorship and reproduction.
KEY WORDS: competition, plants, rare, Mimulus