95616-8515: third author is extension natural resource specialist, University of California Cooperative Extensioi. Browns Valky, Calg. 95918. Abstract Cattle grazing has been suggested as a principai cause for poor oak recruitment in Caiifornia's hardwood rangebmds. This study evaluated the effects of stock density and season of grazing on blue oak (QuercusdouglasiiH. & A.) establishment. In December 1989, seven hundred and twenty blue oak seedlings were planted on 3-m centers in 30 plots in 3

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... nnual grassland pastures at the Sierra Foothill Research and Extension Center east of Marysviiie, Calif. The treatments consisted of 3 seasons X 3 stock densities plus 1 nongrazed control. During January, April, and July of 1990, steers and heifers @= 318 kg) were aiiowed to graze 1 plot per week at low, medium, and high stock densities (2.5, 7.5, and 15.0 head/ha, respectively). Control plots were used to monitor wildlife browsing. One haif of all seediing sites received an application of glyphosate prior to transplanting to eliminate grass competition. Browsing and trampling damage were estimated at the end of each treatment. Total damage (sum of browsing and trampling damage), browsing damage, trampling damage, and survival to April 1991 were significantly different for the 9 season and stock density treatments wO.05). Spring and summer grazing tended to be most damaging and resulted in the lowest survivai rates. Within each season total damage increased with stock density but survival did not change significantly. Weed control around oak seedlings had no apparent effect on total damage or survival. There were significant differences in browsing damage between seasons but not between control and grazed plots within seasons wO.05). Survival in ungrazed plots was not significantly different wO.05) from the spring and summer grazed plots. Consequently, the contribution of wildlife to reduced blue oak seediing survival in grazed oak woodiands should not be underestimated.