Forest Types and Fire Regimes (Appendix B)
This appendix, which expands upon principle five, is included because the issue of fire is one of the most contentious issues related to forest ecosystem restoration. It is therefore significant that our diverse group has agreed to include this appendix.
The following briefly describes major forest ecotypes in Montana and ascribes to each an approximate historical fire regime and a very general picture of historical stand structure. Because there is overlap between each ecotype and no black and white distinctions in historical fire regimes or stand structures, these elements should be considered in the planning and design of restoration projects.
Restoration by Forest Type
Low-to-mid elevation ponderosa pine, Douglas-fir, and western larch forests typify the low- and mixed-severity fire regime with average fire return intervals of 5 to 30 years.
- Pure ponderosa pine experienced frequent, low-severity fires and primarily exhibited an open stand structure across the landscape.
- Mixed ponderosa pine/Douglas-fir/western Larch (in all combinations) forests exhibited less frequent fire, more variable stand structures across the landscape, and variable fire intensity and severity.
- Historically, these low elevation forests were subject to the greatest amount of timber management and fire suppression activities and thus are likely the furthest from their natural range of variability.
- These forest types are the most likely and appropriate candidates for restoration activities to re-establish natural fire return intervals, but especially in the case of mid-elevation mixed-fire severity forests, restoration activities should be taken on a case-by-case basis.
Mid-elevation lodgepole pine, Douglas-fir, and subalpine fir forests exhibit dense stand structures and historically experienced mixed and stand replacing fire regimes.
- Mixed fire regimes may be more widespread than stand replacement regimes in the Inland Northwest and have fire intervals averaging between 30 and 100 years. Stand replacement regimes have average natural return intervals of about 100 – 200 years.
- Mixed severity forest types were likely historically dominant and may not require any specific management activity to allow them to maintain function within their historic range of variability, but again they would have to be considered on a case by case basis.
High-elevation subalpine fir, lodgepole pine and Englemann spruce forests historically experienced fire on a 200 - 300 year fire return interval where subalpine forests of whitebark pine historically experienced fire on a mean fire return interval of 50 – 300 years. These forest ecotypes are likely the closest to their natural range of variability and likely require minimal restoration efforts.