. A descriptive analysis of Montana's forest resources. Forests and forestry Montana Statistics; Timber Montana Statistics. 120+ 85-120 50-84 20-49 Levels of Management Stocking control plus commercial thinnings Stocking control only Nonstocked (custodial) Productivity classes (cubic feet per acre per year) Column width proportionate to acreage Figure 23.—Achievable mean annual increments under alternative management regimes by -productivity classes (Northern Region Office data3 1972 ). The potential gains in growth from regeneration and thinning are shown in figure 23. Adequate stocking contr
. A descriptive analysis of Montana's forest resources. Forests and forestry Montana Statistics; Timber Montana Statistics. 120+ 85-120 50-84 20-49 Levels of Management Stocking control plus commercial thinnings Stocking control only Nonstocked (custodial) Productivity classes (cubic feet per acre per year) Column width proportionate to acreage Figure 23.—Achievable mean annual increments under alternative management regimes by -productivity classes (Northern Region Office data3 1972 ). The potential gains in growth from regeneration and thinning are shown in figure 23. Adequate stocking controls alone would, on the average, double growth over that in wild stands. If, in addition, three commercial thinnings were carried out on the best sites, merchantable wood production could be tripled. Two commercial thinnings on the medium sites and one thinning on the poorest sites also promise substantial increases. Tree improvement through the planting of genetically superior stock also will lead to increased growth rates and the production of a superior product. Trees being planted now are expected to increase timber yields by about 15 percent in 30 or 40 years (Howe 1973). Net growth in Montana's old-growth timber varies from 60 to about 150 board feet per acre per year. Forestwide, annual yields under intensive management are expected to exceed 400 board feet per acre on the Flathead, Kootenai, and Lolo National Forests and to exceed 200 board feet on other Forests. The ability to replace the old growth with second-growth forests, and to achieve the higher growth rates, is dependent upon rates of road develop- ment and operating budget levels. These items are also critical when we consider the assumptions basic to allowable harvest calculations. For the National Forests in Montana, present planning assumes that all stands undergoing regeneration harvests will then have stocking control and commercial thinning (fig. 23). As a result, the 38. Please note that these images
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