We incorporated a robust snag dynamics submodel into SORTIE-ND. We found that Mountain Pine Beetle (MPB) killed pine snags block considerable light for at least 10 years after their death. Light levels in the understory of recently killed lodgepole pine stands is too low for survival of regenerating pine seedlings. This is a very different regeneration environment for pine than found after wildfire. We used data from the BC Ecological Classification program to identify four major stand types found in MPB damaged forests. Three of the four stand types identified had variable levels of residual spruce either in the overstory, the understory, or both. After pine mortality, the spruce in these stand types released and grew well resulting in well-stocked stands with good basal areas 100 years after disturbance. Planting these stand types with spruce shortly after MPB attack resulted in higher basal areas at 100 years, but increases were moderate and varied depending on starting stand type. In pine dominated stands with few live residual trees either salvage and planting or under planting is required. Delaying under planting until pine snags transmit greater light to the understory (5-15 years after initial MPB attack) may result in much higher plantation survival and subsequent volume development. SORTIE-ND predicted growth of pine or spruce plantations after total salvage were very similar to TASS predictions (based on TIPSY v3.2 runs). SORTIE-ND subalpine fir plantations grew slower than those projected by TASS. Lastly, we were unable to predict the extent of natural regeneration in the four stand types due to lack of data to parameterize the recruitment submodel, however, we have a 2005/07 FSP funded study to address this short coming. None-the-less, shading by MPB killed snags are severe in the first few years after MPB attack and may greatly limit regeneration success.
K. David Coates and Erin C. Hall.
Coates, K. David, Hill, Erin C.. 2005. Growth and yield implications of alternate silvicultural strategies in Mountain Pine Beetle damaged stands. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report