Graduate Thesis Or Dissertation
 

LMSCHED.BAS

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Abstract
  • A land management scheduling model is developed that uses a Tabu search procedure to schedule timber harvests and road management activities, while simultaneously meeting (over time and space) two aquatic goals, and also providing for an even-flow of timber harvest volume. Decision variables include land units and roads, and they are considered to take on integer (0-1) solutions. Decision choices include those that involve land allocation issues (harvest and road obliteration), and those that involve changes in management practices (using lower tire pressures on certain roads to reduce the amount of sediment produced). The scheduling model included provisions for estimating stream sediment and temperature impacts as a result of the spatial location of management activities, and provisions for projecting the growth and yield of timber stands over time using growth rates derived from yield tables. The model uses Tabu search procedures to guide the selection of land management activities, and was applied to a 14,643 acre case study watershed in eastern Oregon. Twenty independent solutions were generated, of which 80 percent were within 10 percent of an estimated global optimum net present value, and all were within 15 percent. Although the limitation to using Tabu search is that one is not assured of obtaining the global optimum solution to a particular problem, the model developed here is an important contribution to forest planning for problems which have 100,000+ integer variables and spatial goals. An analysis of model results showed significant negative correlation between equivalent clearcut acres (ECA), a commonly used measure of cumulative watershed effects, and a stream temperature index. No correlation was observed between ECA, a stream sediment index, and timber harvest volume levels. These results suggest that sediment and temperature index levels may not be good proxies for ECA (or vice versa). Finally, the sensitivity of model results was examined using three different representations of the landscape: (a) vegetation units, (b) soils units, and (c) a combination of vegetation and soils units. Results show significant differences exist in terms of net present value, length of road assigned to central tire inflation use per period, stream sediment and temperature indices, ECA, and timber harvest volume levels.
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