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Abstract
The relative importance of livestock grazing in limiting or enhancing oak recruitment remains unclear because results from previous studies have been contradictory. In Santa Barbara County, we have replicated large-scale planting experiments from 1997 to 2001 to determine the effects of cattle and other factors on seedling establishment of valley oak (
Quercus lobata) and coast live oak (
Q. agrifolia). We manipulated cattle grazing (ungrazed vs. winter-spring rotational grazing) and protection from small and large mammals. Rainfall and seed predation and herbivory by small mammals—most likely gophers and ground squirrels–significantly impacted rates of seedling recruitment. Exclusion of cattle alone has not significantly increased establishment of either valley or coast live oak. However, protected seedlings in pastures with cattle have higher survival and growth rates than protected seedlings in plots excluding cattle. Our results suggest that winter-spring livestock grazing can have indirect positive effects on oak establishment, by reducing herbaceous biomass and associated small mammals adjacent to protected seedlings. Contrary to expectations based on the relative abundance of natural oak seedling recruits, establishment and survival of coast live oak planted in our experiments has been significantly and consistently lower than that of valley oak.
Parent Publication
Citation
Tyler, Claudia M.; Mahall, Bruce E.; Davis, Frank W. 2008. Influence of winter-spring livestock grazing on survival and growth of Quercus lobata and Q. agrifolia seedlings. In: Merenlender, Adina; McCreary, Douglas; Purcell, Kathryn L., tech. eds. 2008. Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: pp. 105-114.
