Pacific Southwest

Title: Size Class Distribution of Quercus engelmannii (Engelmann Oak) on the Santa Rosa Plateau, Riverside County, California

Author: Lathrop, Earl W.; Osborne, Chris; Rochester, Anna; Yeung, Kevin; Soret, Samuel; Hopper, Rochelle

Date: 1991

Source: In: Standiford, Richard B., tech. coord. 1991. Proceedings of the symposium on oak woodlands and hardwood rangeland management; October 31 - November 2, 1990; Davis, California. Gen. Tech. Rep. PSW-GTR-126. Berkeley, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; p. 371-376

Station ID: GTR-PSW-126

Description: Size class distribution of Quercus engelmannii (Engelmann oak) on the Santa Rosa Plateau was studied to understand whether current recruitment of young oaks is sufficient to maintain the population in spite of high natural mortality and impacts of development in some portions of the plateau woodland. Sapling-size oaks (1-10 cm dbh) made up 5.56 pct, 4.17 pct and 6.58 pct of total trees sampled at hill (N=252), mesa (N=216) and valley (N=228) sites respectively where cattle were removed in 1986. Approximately 22.5 pct out of 200 trees sampled in an adjacent oak woodland (estimated to have been non-grazed for 20 years) were of sapling size. Peak abundance of Quercus engelmannii was in the 46-50 and 51-55 cm dbh size classes on hill, valley and mesa sites and in the 36-40 and 46-50 cm dbh size classes in an adjacent oak woodland. Trees in size classes larger than the 46-50 cm dbh increment declined in abundance at all four sites. Only 17.1 pct of total trees (N=896) were in sizes classes beyond 66-70 cm dbh and only two trees in size class 131-135 cm dbh. Despite the high numbers of young oaks at one of the four sites sampled, current stand size structure of Quercus engelmannii on the Santa Rosa Plateau indicates that reproduction is insufficient to maintain the present occurence and abundance of older age classes in the future.

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Citation

Lathrop, Earl W.; Osborne, Chris; Rochester, Anna; Yeung, Kevin; Soret, Samuel; Hopper, Rochelle  1991.  Size Class Distribution of Quercus engelmannii (Engelmann Oak) on the Santa Rosa Plateau, Riverside County, California .   In: Standiford, Richard B., tech. coord. 1991. Proceedings of the symposium on oak woodlands and hardwood rangeland management; October 31 - November 2, 1990; Davis, California. Gen. Tech. Rep. PSW-GTR-126. Berkeley, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; p. 371-376.