PARENT SESSION
Oral Session #99: Grazing.
Presiding: T. Arredondo
Friday, August 9. 9:00 AM to 12:00 PM. Graham Meeting Room, TCC.
The relative importance of grazing and topography on oak performance since 1928.
ANDERSON, SEAN1, SCHINSKE, JEFF*,1, KLUSE, JENNIE1, 1 Center for Conservation Biology, Stanford, California
ABSTRACT- California has lost at least 1 million ha of oak woodland in the last 200 years. Cattle grazing was a major factor in the conversion of oak woodland to grassland and continues to dominate land use decisions in oak regions. Quantifying the impact of grazing within topographically complex coastal foothill landscapes is non-trivial. We assembled a 70-year time series of aerial photographs of our study site at Stanford University to evaluate the relative importance of grazing and topography upon oak distributions. We characterized the slope, aspect, and insolation within each 30m x 30m grid across 310 ha of heavily grazed and 393 ha of lightly grazed land with a Digital Elevation Model. Oak cover, recruitment, and survivorship all changed through time. The effect of grazing was significant even after controlling for the effects of slope, aspect, and insolation. Grazing generally had the effect of restricting oak performance to a narrower range of abiotic conditions. Insolation and aspect usually interacted with grazing, suggesting grazing benefits oak performance in certain settings. The results of this study are currently being evaluated with more extensive monitoring and a series of restoration experiments.
KEY WORDS: oak woodland, cattle grazing, habitat loss, recruitment