Douglas D. McCreary

Effects of cattle grazing on blue oak seedling damage and survival

Cattle grazing has been suggested as a principal cause for poor oak recruitment in Californias hardwood rangelands. This study evaluated the effects of stock density and season of grazing on blue oak (Quercus douglasii H. & A.) establishment. In December 1989, seven hundred and twenty blue oak seedlings were planted on 3-m centers in 30 plots in 3 annual grassland pastures at the Sierra Foothill Research and Extension Center east of Marysville, 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 (mean = 318 kg) were allowed 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 half of all seedling 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 (P < 0.05). Spring and summer grazing tended to be most damaging and resulted in the lowest survival 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 (P < 0.05). Survival in ungrazed plots was not significantly different (P < 0.05) from the spring and summer grazed plots. Consequently, the contribution of wildlife to reduced blue oak seedling survival in grazed oak woodlands should not be underestimated.

Predicting field performance of Douglas-fir seedlings: comparison of root growth potential, vigor and plant moisture stress

Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were evaluated- by three measurements of seedling quality — root growth potential or RGP, vigor, and plant moisture stress or PMS — and the results were correlated with subsequent field performance. Measurements made by each method were significantly (p≤ 0.05) correlated with first- and second-year survival and terminal height growth. Seedlings from lots that grew many new roots during a 28-day interval in a growth room (RGP evaluation) or that survived for 6 weeks in the growth room and initiated rapid budburst (vigor evaluation) or whose plant moisture stress values remained fairly constant during 1 week after potting (PMS evaluation) had the greatest field survival and height growth.The RGP evaluation was the best predictor of first-year height growth, while the vigor evaluation was the best predictor of first- and second-year survival. All evaluations predicted second-year height growth equally well.These results demonstrate that all three evaluations can be successfully used to predict field performance of Douglas-fir seedlings. Each has its advantages and limitations, and none can be considered “best”. The one used should be selected on the basis of time constraints, equipment and resources available, and specific objectives, such as whether it is considered more important to estimate field survival or growth.

Lifting and storing bareroot blue oak (Quercus douglasii) seedlings

In California today, several species of native oaks are not regenerating adequately. Artificial regeneration is a means of ensuring sufficient recruitment to replace trees that die or are harvested, and restoring areas where trees have been cleared. Until recently, however, no bareroot oak seedlings were being produced in the state and there was little information to guide nursery operators. This study evaluated the potential of bareroot blue oak seedlings to survive and grow after outplanting. Results indicated that 1-0 nursery stock performed well in the field as long as seedlings were planted early enough in the season to take advantage of a favorable growing environment. Late lifting and long storage resulted in planting at a time when soils were already becoming dry and temperatures were hot. As a result, seedlings grew slowly or even died. Seedlings lifted early in the season (December) grew best. Either one or two months of storage had little effect on seedlings lifted at this time of year. However, seedlings lifted in January, February, and even early March performed adequately as long as they were in the ground by early March. In this study, root growth capacity was not a good predictor of subsequent field performance.

Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities

The Sixth Oak Symposium provided a forum for current research and outstanding case studies on oak woodland science and sustainability in California. This symposium was the latest in a series of conferences on this subject held every 5 years since 1979. The proceedings from this conference series represent the most comprehensive source of scientific and management information on a wide range of subjects including oak ecology, hardwood rangeland management, oak restoration and conservation, woodland land-use change and planning. The conference was attended by academics, planners, conservation practitioners, foresters, arborists, and people just interested in oaks and oak-woodland conservation. Together we form a community of researchers and practitioners working toward maintaining and restoring Californias oak woodlands. The findings reported here recognize: (1) the rich history and current interest that Native American communities have for oaks, (2) the inherent complexity of wildlife relationships with woodland resources, (3) the need for greater understanding of belowground processes, and (4) that the land conservation tools and policies evolving rapidly to protect and restore oak woodlands need to be evaluated. Although progress has been made, continued emphasis on research and extension is required to further California oak conservation.