Mt. Emily Recreation Area Coalition
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Susan Geer, Plant Ecologist has provided us with the research paper by Cochrane et. al. 1994 that lead to the development of the excellent and unique implementation guide by Dave Powell.
The Cochrane paper drew on many years of research (including research by Boise Cascade) pointing to the value of minimizing insect and disease damage by maintaining high stand vigor. Thinning is the tool for this, and for reducing stand replacing wildfires, and attaining old-growth characteristics (BIG TREES) sooner. The different plant associations (combinations of species) that exist across the natural landscape reflect the characteristics of each site (soil, slope, elevation, precip., past history) and have a certain capacity for tree growth by species. At full occupancy (capacity) there is intense competition between trees, leading to density-related mortality in the understory. The concept of the Management zone is introduced. Beyond the Upper Limit of the Management Zone (ULMZ), trees are subject to density related mortality. The Lower Limit of the Management Zone (LLMZ) was set to still "capture significant site resources in tree growth" and is set at 50% of full occupancy, or 67% of the ULMZ.
Powell's guide expands the concepts and suggestions in Cochrane's paper by providing tables specific to plant association and dominant tree species -- i.e. Through some level of stand exam, one determines quadratic mean diameter of the stand and basal area. One can look that up in a table and see how that stocking level compares to the upper and lower management zones. Powell's guide is a USFS publication extensively used within the FS, and available in print but unfortunately not over the Internet (thus not attached). I suppose that is because it mainly IS tables. Susan Geer and Dave Komlosi have a copy if someone would like to see it.