Demonstration
Spruce-fir Alternative Silviculture
Group selection and single tree selection systems are the most common silvicultural systems for managing spruce-fir in the Central Rocky Mountains. While effective at regenerating desired shade-tolerant species, they are somewhat limited. A project to showcase and research both of these systems, alongside an unconventional shelterwood-with-reserves, was initiated in the early 1990s by Dr James N. Long. The overriding goal of the three silvicultural systems was to maintain Engelmann spruce on the landscape in the face of mounting spruce beetle pressure.
The silvicultural elements of the three prescriptions were: a) shelterwood-with-reserves, uniform shelterwood with retention of reserve trees beyond the regeneration period, underplanted with Engelmann spruce seedlings, b) small group selection, ¼ acre regeneration openings planted with Engelmann spruce seedlings, 20-year cycle and thinning in the matrix to 120-150 feet squared per acre, c) single tree selection, structural stocking control with a maximum diameter of 24 inches, 20-year cutting cycle, and residual relative density of 33% of maximum stand density index.
Natural Disturbance-Based Landscape-Scale Silviculture
Contemporary silviculture has its roots in emulating natural disturbance regimes. The most common disturbance in the forests of the Central Rocky Mountains was fire, but it typical occurred at spatial scales bigger than desirable by managers. The Slideout and Bear Hodges timber sales were designed to emulated the behavior of a lightning-caused fire that started low in elevation and burned upslope through an entire drainage. Remnant beaver dams in the Slideout drainage suggested that previous fires had denuded large areas of the drainage in the past, enough to support beaver populations.
The reference condition for the lodgepole pine type within the analysis area is based on a mixed and and variable severity fire regime with a fire-free interval between 100-200 years. Fires were of various sizes, but generally > 600 acres. Mixed-severity fires produced variation in pattern resulting from low to high severity burning. Differences in fire behavior created a range of density of surviving trees, a range of regeneration density, and a range of post-fire tree species diversity (i.e., pure lodgepole pine to mixed conifer and aspen).
The silvicultural elements intended to capture this reference condition included: a) uniform shelterwood simulating a low severity burn (surface fire behavior) and leaving many surviving trees (10% of the unit) at the low elevation end of the unit, b) clearcut-with-reserves with reserves ranging from single trees up to 1 acre patches, simulating medium severity burn (mix of surface fire, torching, and crowning fire behavior, 80% of the unit), and c) traditional (complete) clearcut simulating a high severity burn without surviving trees (10% of the unit).
Lodgepole Pine Alternative Silviculture
Early clearcutting in lodgepole pine on the School Forest resulted in substantial regeneration. So much so, that subsequent intermediate treatments (pre-commercial thinning) were necessary to maintain adequate growing stock for a reasonable end-of-rotation mean tree size. With this experience in mind, a shelterwood-with-reserves in the adjacent lodgepole pine was conducted in the late 1980s. The goal of leaving lodgepole pine reserves was to provide enough shade to reduce the regeneration response. Post-harvest enrichment planting of Engelmann spruce was done to increase diversity in the stand.
