Visitors 173
Modified 16-May-11
Created 16-May-11
8 photos

Stanford Professor Rodolfo Dirzo is leading an ongoing study at Jasper Ridge of the impact of herbivory -- primarily from deer and rabbits -- on oak reproduction. He and collaborators have identified 75 pairs of oak seedlings of each of 3 species of oaks -- Coast Live Oaks (Quercus agrifolia), Valley Oaks (Q. lobata), and Blue Oaks (Q. douglasii). They caged one member of each pair and left the other, nearby plant unprotected. See <>

A question arose -- are the observed differences between the two due to herbivory, or to trampling by the deer? (The cages prevent both.) This question has been taken up by Tess Morgridge, a Stanford sophomore majoring in Biology with a concentration in Ecology and Evolution. She is making this her project for Bio 105, the Jasper Ridge docent class <>. She made some "artificial seedlings" out of wire, wood, and plastic, which would be bent over by deer trampling. So the artificial seedlings can test the impact of trampling alone, independent of browsing.

On 5/15/2011, Dan & Helen Quinn assisted Tess & Rodolfo, placing approx. 150 artificial seedlings near the pairs of young Blue Oaks & Coast Live Oaks. (The 75 Valley Oaks were already done.) There was only a little rain, and no hail while we were out in the field.
Tess Morgridge Places Artificial SeedlingRodolfo Dirzo and Assistant Place Artificial Seedling near Caged Blue Oak Seedling (Quercus douglasii)Placing the Artificial Seedling (Detail)Placing the Artificial Seedling (Detail)Uncaged Oak Seedling (Quercus douglasii)Uncaged Oak Seedling (Quercus douglasii)WorkersCow Parsnip (Heracleum lanatum or H. maximum)