Economic gain of genetically-selected coastal Douglas-fir: Timber, log and carbon value at varying planting densities

Substantial investments in tree breeding for coastal Douglas-fir in British Columbia are projected to lead to significant volume gain at rotation age. Recent research shows growth gains are accumulating as expected, but it is less clear to what degree and when these volume gains translate into economic gains. We use discounted cash flow analysis techniques to quantify economic gains and determine optimal rotation ages expected from planting three levels of genetic gain in tree volume (a 0 % control, +10 % and + 18 %) at four initial densities (625, 1189, 1890 and 3906 stems/ha). Valuations were estimated for a variety of economic conditions for timber volume and log grades, with and without carbon pricing. These analyses rely on a growth and yield model simulating data from a 21-year coastal Douglas-fir realized gain trial, installed on five sites differing in productivity. Simulations show that planting selectively-bred coastal Douglas-fir trees reliably led to significant economic gains relative to unselected control stands, across initial planting densities, sites and varied economic scenarios. Highest financial returns are projected for genetically-selected seedlings at the most productive sites. Lower initial planting densities were associated with higher economic gains but also reduced important wood quality metrics that were not captured by the financial analyses, suggesting that operational planting densities (1189–1890 stems/ha) could offer a suitable compromise. Incorporating carbon prices led to larger economic returns and longer rotations. Altogether, these simulations suggest that a reliably higher return on investment can be achieved by deploying selectively-bred planting stock.