PARENT SESSION
Oral Session #64: Plant Population Ecology.
Presiding: S. Collins
Wednesday, August 7. 1:00 PM to 4:45 PM. Gila Meeting Room, TCC.
Dynamics of granivory in a California grassland forb.
Espeland, Erin*,1,2, Carlsen, Tina1, 1 Lawrence Livermore National Laboratory, Livermore, CA2 UC Davis, Davis, CA
ABSTRACT- Granivory of Amsinckia grandiflora (Boraginaceae) seeds was examined in California grasslands over five years. Because this forb does well in a perennial grasslands, often achieved through fire, the influence of fire on granivory of A. grandiflora seeds may be important for population maintenance of this rare annual plant. Effects of burning and bird exclusion were examined in multiple years. Granivory was highly variable, ranging from 4% to 99%. Nearly all plots were discovered (>10% predation) by granivores, but plot decimation (>75% predation per plot) appeared correlated with total granivory. Rodents appeared to be the primary granivore in 1998 and 1999 and were equally effective in burned and unburned areas with bird exclusion making no difference in total granivory. Granivory was lower in 1995, 2000 and 2001 (no burns were conducted in 1995 and 2000). In 2001, burned plots experienced higher granivory than unburned plots, and burned plots that excluded birds had similar granivory rates to unburned plots. These results indicate that burning has little effect on total granivory of A. grandiflora seeds when granivory rates are high. But in low seed predation years, creating open areas through burning may increase total granivory on A. grandiflora seeds. The results of this study indicate that factors such as rodent population cycling may have strong interactions with other external effects on plant populations and that these interactions may be difficult to determine in short-term studies. Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
KEY WORDS: granivory, predation, Amsinckia grandiflora, fire