Density Effects on Giant Sequoia (Sequoiadendron giganteum) Growth Through 22 Years: Implications for Restoration and Plantation Management

Abstract

Giant sequoia were planted at various densities and tracked for 22 years to quantify the effect of growing space on diameter, height, stem volume, branch diameter, and branch density. Beginning after just 4 years and continuing through year 22, both stem diameter and height growth were highly sensitive to initial planting density (expressed in this case as horizontal growing space per tree) within the tested range of 3.7 to 28.4 m 2. Through 22 years, treatments allocating the greatest growing space per tree had greater volume per tree with no tradeoff yet observed in stand level volume growth. Branch diameter along the stem generally increased with growing space, but branch density did not change. To meet objectives, this study demonstrates that management strategies should be tailored to species' specific growth strategies. Giant sequoia is characterized by rapid early growth coupled with exceptionally low mortality, which has relevance in both native grove restoration as well as plantation management contexts. The measurements in this study suggest either planting at low density or thinning giant sequoia very early in dense stands if the objective is to increase individual tree growth rates without a corresponding reduction in stand volume. Young stands developing following high-severity fires may benefit from low-severity prescribed burns if objectives are to increase average stem growth or the rate of canopy recruitment.

Tamm Review: Reforestation for resilience in dry western U.S. forests

“…While the application of prescribed burning in young conifer stands has traditionally been associated with a risk of high stand mortality (Smith et al, 1997), emerging research suggests prescribed fire can effectively treat young stands with relatively low levels of stand mortality while supporting other management objectives, including: (1) reduction of surface fuels (Lyons-Tinsley and Peterson, 2012;Stevens et al, 2014); (2) maintenance of evolutionary selection for fire-resistant trees; (3) introduction of stand heterogeneity (Kobziar et al, 2009); (4) cost-effectiveness compared to mechanical treatments (Kobziar et al, 2009); (5) reducing activity fuel following mechanical treatments such as mastication (Reiner et al, 2012;Bellows et al, 2016); and (6) stand density management (York et al, 2013) (Fig. 7).…”

Emerging Stress and Relative Resiliency of Giant Sequoia Groves Experiencing Multiyear Dry Periods in a Warming Climate

“…A warmer temperature can extend the growing season and thus enhance SEGI growth; however, wildfire frequency within SEGI groves is also higher as temperature warms (Mutch, ). Gaps created by wildfires are beneficial to the SEGI recruitment (Meyer & Safford, ; van Mantgem et al, ; York et al, ; York, Battles, & Heald, ; York, Louen, & Thomson, ; York, O'Hara, & Battles, ). It is suggested that a minimum of ~0.1 ha gap is required for significant SEGI recruitment (Stephenson, ).…”

Giant sequoia ( Sequoiadendron giganteum ) in the UK: carbon storage potential and growth rates

“…allocating more biomass to branch materials than to trunk materials with reduced light [55]. York et al [56] found that DBH was more sensitive to growing space than height, with a sharp reduction in the DBH growth rate where forest stands are more dense. The trees at Wakehurst are the most widely spaced, followed by Benmore, with Havering trees being closest together.…”