Sheep Grazing as a Tool for Vernal Pool Stewardship

2006 Annual Report for GW06-029

Project Type: Graduate Student
Funds awarded in 2006: $8,813.00
Projected End Date: 12/31/2008
Grant Recipient: Sonoma State University
Region: Western
State: California
Graduate Student:
Major Professor:
J. Hall Cushman
Sonoma State University

Sheep Grazing as a Tool for Vernal Pool Stewardship


I have completed analysis of 2005-06 data on the effects of sheep grazing on vernal pool plant communities. At my experimental site, first-year data indicate that abundance and richness of native or exotic species were not signficantly affected by grazing treatment. I hypothesize that sheep grazing may be best suited to vernal pools that are heavily invaded by non-native forbs in pool bottoms. I also suspect that seedbank limitations may constrain the recovery of native vernal pool species, regardless of grazing treatment. In coming months I plan to discuss possible changes to the grazing regime with the rancher and land manager, which may be more effective at encouraging natives. We are also considering testing sheep grazing at other sites where native seedbanks are more robust.

Objectives/Performance Targets

Our objectives for the first four months of the grant period were to analyze preliminary data, present preliminary results at a grasslands management conference, and begin monitoring vernal pool inundation.


I have completed analysis of preliminary data on the effects of sheep grazing on vernal pool plants at my experimental site. So far, results show that cover and richness of plant species did not differ significantly between grazed and ungrazed plots. However, sheep grazing does show some promise for managing certain problematic invasive species, including pennyroyal (Mentha pulegium). While it is encouraging that grazing did not have a negative effect on natives at the site, we had hypothesized that grazing would actually increase natives. I am discussing possible changes to the timing of grazing with Kerry Williams, the rancher I am working with, that may be more beneficial. Also, the native seedbank at the site may be very limited, and may require supplementation if natives are to increase.

I was not able to present my results at the Bay Area Grasslands Management Conference as anticipated because the conference was not held this year. However, I have accepted an invitation to present my findings at a conference in April 2007 for research on natural systems in the Laguna de Santa Rosa watershed. I will also be presenting this work, along with results of a companion study of cattle grazing on vernal pools, at a public thesis defense on February 2.

I have begun hydrologic monitoring of the vernal pools, as planned.

Impacts and Contributions/Outcomes

My work and partnership with rancher Kerry Williams were featured in a front-page article in the Sonoma West Times, a local newspaper. Link:

Partly as a result of our collaboration and of my research, additional opportunities for sheep and cattle grazing are developing at vernal pool mitigation banks on the Santa Rosa Plain. I have also shared my results with consultants to the Department of Fish and Game, who are developing grazing and monitoring plans for that agency’s vernal pool properties.


J. Hall Cushman

Sonoma State University
1801 E. Cotati Ave.
Rohnert Park, CA 94928
Office Phone: 7076642142