(1) The department shall manage old growth to meet biodiversity and fiduciary objectives.  The department shall consider the role of all stand age classes in the maintenance of biodiversity when designing harvests and other activities. Stand age distributions, including old growth, shall be evaluated and managed as described in ARM 36.11.407 through 36.11.416 based on the patterns historically present on the landscape as a result of natural disturbances.  Amounts and distributions of all age classes will shift and change over time.  No stands would be permanently deferred from management, although some stands may not be entered for relatively long time periods.

(a) The department shall identify old growth that occurs in a project area.  Old growth stands shall be managed to achieve biodiversity objectives, including possible harvest.  The department shall consider site-specific concerns and other legal criteria regarding the harvest of old growth.  Interdisciplinary teams shall work to meet overall objectives to generate revenue for the trust, while also meeting biodiversity goals across the landscape, which shall entail project-level harvesting decisions.

(b) Designation of old growth set-asides, or networks, may be made as long as the trust secures full market value.

(c) When managing old growth the department shall apply restoration, maintenance, or removal treatments consistent with the range of natural disturbances.

(i) When utilizing old growth restoration treatments, the department shall retain sufficient large live trees to meet the old growth definition as defined in ARM 36.11.403. Such treatments shall be applicable on sites that historically had non-lethal frequent fire regimes.  The department shall target shade tolerant species for removal and overall stand density shall be reduced.  The department shall treat stands with periodic re-entry, and prescribed under-burning when practicable, to maintain relatively low densities, open understories and dominance by shade-intolerant species.  The department shall determine specific prescriptions at the project level.

(ii) When utilizing old growth maintenance treatments, the department shall retain sufficient large live trees to meet the old growth definition as defined in ARM 36.11.403.  The department shall apply such treatments on sites that historically had mixed severity fire regimes, either relatively frequent or infrequent.  In some cases, the department may apply these treatments to stand replacement regimes when determined reasonable at the project level. The department shall target shade tolerant species for removal and reduce stand density.  For residual stands, the department shall incorporate canopy gaps of sufficient size to encourage regeneration of shade-intolerant tree species.  The department shall treat stands with periodic re-entry at less frequent intervals than for restoration.  Densities and representation of shade-tolerant species will be higher than in restoration treatments.  Fire shall be less frequently applied than in restoration treatments.  The department shall determine specific prescriptions at the project level.

(iii) The department shall consider old growth removal treatments on sites that historically had stand replacement fire regimes.  The department shall make selection of this treatment at the project level after considerations for biodiversity and forest health.  Post treatment stands shall no longer qualify as old growth.  The department shall determine specific prescriptions at the project level.

(d) The department shall maintain the option to apply or to not apply old growth removal treatments, regardless of disturbance regime, when determined reasonable at the project level.