Growth of thinned and unthinned hardwood stands on a good site in northern California

Abstract

Pacific madrone (Arbutus menziesii Pursh), tanoak (Lithocarpus densiflorus (Hook. & Arn.) Rehd.), and California black oak (Quercus kelloggii Newb.) are three hardwood species commonly found in the Sierra Nevada of California, an area better known for its mixed-conifer forests. Hardwood stands in this region currently are unmanaged and underutilized for commodity production. However, some landowners are now asking "How fast do these hardwoods grow," and "Will thinning increase growth and yield?" Twelve young-growth, mixed-hardwood stands on the Challenge Experimental Forest in north-central California were thinned from an average basal area of 202 ft² per acre to different levels of residual basal area that ranged from 66 to 153 ft² per acre. An additional stand (control) provided information on development in an untreated condition. Tanoak trees grew faster in diameter in thinned plots and control than Pacific madrone, which grew faster than California black oak. In general, having two to four members per clump did not hinder diameter growth in the thinned plots. Tanoak also grew significantly faster both in diameter and volume in a very wet year, but for the other two species a very wet or very dry year did not make a difference. Both diameter and volume growth were best if stands were thinned to less than 75 ft² per acre, and net volume growth (gross growth minus mortality) compared favorably to eastern oak stands on good sites. A future thinning and management regime is suggested.

Citation

McDonald, Philip M.; Vaughn, Nicholas R. 2007. Growth of thinned and unthinned hardwood stands on a good site in northern California. Gen. Tech. Rep. PSW-GTR-204. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station; 23 p