Logging damage in thinned, young-growth true fir stands in California and recommendations for prevention.

Logging-damage surveys and tree-dissection studies were made in commercially thinned, naturally established young-growth true fir stands in the Lassen National Forest in northern California. Significant damage occurred to residual trees in stands logged by conventional methods. Logging damage was substantially lower in stands thinned using techniques designed to reduce injuries from felling and skidding. A total of 243 wounded white and red firs in 11 stands were felled, dissected, and analyzed for decay. All wounds were infected by decay fungi. Decay losses associated with wounds were 6.8 and 14.0 percent of the gross merchantable Scribner board-foot volume of the red and white firs sampled, respectively. Wound area and age were most closely related to extent of decay. Volumes of cubic- and board-foot decay are given for wounds of various sizes and ages. Recommendations are made for reducing logging damage to residual trees during thinning operations.