Montana Department of Natural Resources and Conservation

Sustained Yield Calculation and Habitat Conservation Plan Support

MB&G developed a timber harvest scheduling model and performed a sustained yield calculation for the the  700,000+ state forest trust acres managed byMontana DNRC. MB&G then enhanced that model and performed the forest management modeling to support the DNRC’s effort to develop a habitat conservation plan, which was completed in 2010.

Some years prior, the agency had completed a planning process that established objectives and management guidelines, but had not yet made a harvest calculation. We worked closely with DNRC’s silviculturalist, inventory forester, and fish and wildlife biologists to complete that work.

DNRC had an extensive stand-level inventory – polygons delineated and typed across a wide variety of characteristics. We developed a variety of management regimes for each type, ranging from high-intensity even-aged regimes (plant, PCT, CT, final harvest) to low-intensity uneven-aged regimes designed to create a more complex forest structure. Several regimes were designed to create and maintain old-growth characteristics, or conditions for specific wildlife habitats such as lynx denning habitat, elk winter range, riparian areas, etc.

Using data layers provided by DNRC, MB&G prepared all of the GIS layers needed to represent the land base in the forest management model. There were about 15 layers that were important in various parts of the modeling effort. We helped DNRC select and calibrate a growth model to meet expectations and observations.

MB&G built a timber harvest scheduling model using the USFS Spectrum program. The linear programming-based model used an extensive set of constraints to represent a wide variety of management objectives and regulatory constraints. DNRC was interested in knowing the incremental cost of each set of constraints, and we developed a sensitivity analysis process to report that information.

MB&G prepared a final report that established the 10-year allowable cut for the state trust lands. The report underwent public review and was presented to the State Land Board, which approved and adopted the calculation. Not long after this was completed, the DNRC began work on a Habitat Conservation Plan (HCP). MB&G provided the timber harvest scheduling analytical services to that effort.

Most large-scale planning efforts evolve over time, and this one did that more than most. DNRC started out considering more than 10 species for the HCP, which meant that we had to consider a wide variety of habitat parameters. We took the forest management model developed for the sustained yield calculation, enhanced it to project a wide variety of habitat conditions and allowed constraints and reporting on a variety of different management areas. Further information needs required us to build a post-processor that would link the model results to external databases to make projections for even more parameters. Much of this work was leading edge. For example, we incorporated a snag decay projection into the harvest scheduling model in order to evaluate woodpecker habitat. Ultimately, DNRC successfully obtained an HCP that provides a level of certainty about future habitat requirements.

In 2014 DNRC again contracted the sustained yield calculation to MB&G. Since the prior calculation, DNRC had acquired new tracts, considerably more inventory data, and new managers. We worked closely with DNRC foresters to re-evaluate and revise yield projections, management regimes and plan objectives. At every step it was important to reconcile the new sustained yield calculation with the previous one. For this project MB&G re-calibrated FVS based on the latest inventory data, and rebuilt the harvest scheduling model in Remsoft. We completed all analytical tasks, and produced a final report on data, methods and results for public review.