Estimating Large Snag Recruitment Needs in Regeneration Timber Harvests

Retaining snags after timber harvest is now a common silvicultural practice. However, little is known about silvicultural practices necessary to ensure timber-rotation length equilibrium of snag densities (existing snags all fall eventually). Large diameter snags in particular are important to many wildlife species and require long time periods to develop. Where timber harvest removes most of the existing stand, estimates of required retention density must be made ahead of time if long-term equilibrium in snag abundance is desired.A simple simulation model was used to investigate potential dynamics of snags for 80-120 yr following timber harvest. Parameters resulting in recovery of the initial number of snags at rotation length are presented. Whether or not equilibrium was achieved depended on three parameters usually beyond management control: annual mortality rate of live trees; snag fall rate; and transition rate from smaller to larger retention trees. At the time of timber harvest, managers can most easily adjust the density and size-class of live retention trees. I recommend erring on the side of retaining more, rather than fewer live trees to prevent long-term declines in the abundance of large snags. West. J. Appl. For. 15(3):140-146.