Effects of precommercial thinning on structural development of young coast redwood – Douglas-fir forests

Knowledge of stand development patterns and stand responses to treatments allow managers to silviculturally manage forests and achieve management objectives sooner. In the coast redwood (Sequoia sempervirens) region, the development of effective silvicultural treatments is inhibited because documentation and quantification of mixed species stand dynamics and stand responses to treatments are currently lacking. This study documented stand development and stand responses to precommercial thinning in dense, young (50 years old), even-aged, second-growth coast redwood – Douglas-fir (Pseudotsuga menziesii) stands. A significant portion of the northern range of coast redwood is currently in this dense, young condition and in need of management. To assess the effects of precommercial thinning on species dominance patterns, I compared adjacent precommercially thinned and unthinned stands, 12-17 years post thinning. Precommercially thinned stands displayed enhanced vigor, growth, and tree stability. Dominant tree diameter and mean maximum branch diameters were larger in thinned stands than in unthinned stands. The potential for redwood dominance was improved as redwood responded more positively to thinning than Douglas-fir in all measures of this study and the proportion of redwood in the dominant crown class increased by 45%. Stand reconstruction allowed the comparison of height development patterns between thinned and unthinned stands. The height:age curves illustrated that thinning improved redwood height growth relative to Douglas-fir and the patterns of height stratification in these stands may be influenced by stand density. Precommercial thinning postponed declines in vigor, growth, and stability, thereby improving response to future thinnings and broadening the range of potential stand conditions. Precommercial thinning is recommended as an initial stand treatment at this stage of stand development because it accomplishes a wide range of management goals while maintaining sufficient tree stocking to buffer against future small-scale disturbances.