Long term results of early density management of a third growth redwood stand

Abstract

Precommercial or early thinning of regenerating redwood forests can support management objectives including maximizing yield, forest structure restoration, and promoting carbon sequestration. We present data collected over 30 years following a precommercial thinning (PCT) in a 19 year-old naturally regenerated and planted coast redwood (Sequoia sempervirens(D. Don) Endl.) and coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stand. The study site is typical of most regenerating redwood forests with spatial variation in tree distribution from stump sprouting (coppice) redwood interspersed with planted and natural regeneration. Three replicates of six density treatments (100, 150, 200, 250, 300 trees per acre (TPA) and unthinned control) were established in 1981 and re-measured repeatedly. Plot size was reassessed in 2011. Postthinning density had a lasting effect. Thirty years after PCT, average diameter at breast height (DBH) and stand density index (SDI) still differed among PCT treatment levels. When focusing on the largest trees (140 TPA), basal area (BA) and cubic foot volume results were significantly affected by post-thin TPA resulting in the highest production from treatments ranging from 120 to 250 TPA. A new method of characterizing site productivity by indexing redwood BA growth revealed that variations in species composition and site quality explained differences in growth and yield between plots. Multiple linear regressions revealed that post-thin TPA, species composition (percent redwood SDI), and site quality in terms of BA growth index all had a lasting influence on redwood productivity monitored over three decades after PCT.

Parent Publication

• Coast redwood science symposium—2016: Past successes and future direction

Citation

Webb, Lynn A.; Berrill, John-Pascal; Lindquist, James L. 2017. Long term results of early density management of a third growth redwood stand. In: Standiford, Richard B.; Valachovic, Yana, tech cords. Coast redwood science symposium—2016: Past successes and future direction. Proceedings of a workshop. Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 267-278.