Targeted Grazing Deer Brush for Fuel Suppression

Deer brush (Ceanothus integerrimus.), is a prevalent shrub in the Sierra Nevada foothills, especially within the mixed conifer belt. This plant typically grows in elevations ranging from 2,000 to 6,000 feet, and is characterized by its bushy, spreading form, which can reach heights of up to 10 feet. In the mixed conifer belt, deer brush often becomes dominant in areas where the forest canopy is open, such as after logging, fires, or other disturbances. It plays an essential role in the ecosystem by fixing nitrogen in the soil, which benefits the surrounding vegetation. However, its thick growth can also create competition for resources with young conifers and other desirable species, potentially hindering forest regeneration.

Cattle grazing has deep historical roots in the Sierra Nevada as a strategic land management tool to control the growth of deer brush. The leaves are a good source of protein, and the stems and leaves have been found to contain a high amount of calcium. When managed correctly, grazing can reduce the density and spread of deer brush, promoting the establishment and growth of young conifers. Cattle feed on the tender shoots of deer brush during the summer before they lose their leaves. This browsing action suppresses the shrub's growth, reducing its competitive advantage over tree seedlings and other vegetation.

Additionally, grazing helps maintain a more open understory, reducing the fuel load and potential fire hazards. Another significant benefit of cattle grazing is its role in preventing brush encroachment along forest roads. By grazing on the young shoots of deer brush and other shrubs, cattle keep the vegetation in check, ensuring that forest roads remain accessible and free of overgrown brush, which can otherwise become a fire hazard and obstruct crucial access routes for both fire management and recreational purposes.

Virtual fencing (VF) has the potential to enhance the effectiveness of cattle grazing on deer brush by targeting cattle to the exact locations where land managers need to control deer brush the most. Many summer grazing allotments span hundreds to thousands of acres, and while cattle naturally migrate to areas with deer brush, they don't always graze in the specific spots that align with land management objectives. In July 2024, we initiated a VF trial in collaboration with Sierra Pacific Industries. We selected a 2-mile-long logging road with encroaching deer brush and abundant natural water sources. Using Gallagher eShepherd collars, 35 cattle were driven into the VF zone on horseback. Although the trial is ongoing, the impact is already noticeable, with many deer brush shoots along the road stripped of their leaves.

In this trial we have also observed a limitation of VF. A VF’s ability to successfully contain livestock in the desired area is heavily influenced by external pressures, and where those pressures are in relation to the VF boundary. For instance, cattle are strongly influenced to stay in a herd. If the herd is within the VF boundary, then individuals are encouraged to stay in bounds. In this trial other cattle without VF collars sometimes wander into the trial area. When they leave the VF, which they have no awareness of, this entices cattle with VF collars to follow. At present, 9 of the 35 cows have left the VF boundary.