Performance and genetic analysis of coast redwood cultivars for afforestation of converted grassland in California

Abstract

Afforestation of pasture sites results in a net reduction in atmospheric CO2. Coast redwood (Sequoia sempervirens) is well suited to carbon forestry due to its rapid growth and long-lived decay-resistant heartwood. We sought to identify redwood cultivars (clones) suitable for afforestation and rapid growth on pasture sites. Our common garden experiment replicated at three sites tested performance of 32 cultivars and a commercial seedlot. After four growing seasons, the tallest cultivar on the two more productive sites measured 6.1 m and 5.2 m and average heights were 3- and twofold that of the least productive site. Seedling heights ranked intermediate, being outperformed by ≥ 50% of the cultivars. Height growth differed significantly among cultivars. Compared to the seedlings, the top three cultivars averaged 15–18% greater height after four growing seasons at each site. This translated to stemwood volume gains of 106% at the best site and 68% at the second best site. There was relatively low—yet statistically significant—G × E interaction, indicating that redwood cultivars can be expected to rank consistently for growth across a range of different pasture sites. However, there may be minor benefits to specific cultivar-site matching especially under suboptimal conditions such as under partial shade on poorer sites. Overall, our results demonstrate the potential of elite cultivars for rapid afforestation of pasture sites.