A model and tabu search method to optimize stand harvest and road construction schedules

An important function of tactical planning in forest management is to choos e spatially and temporally explicit schedules for both harvesting and road construction activities. In addition to maintaining consistency with goals of the strategic planning process, harvesting decisions are subjected to sp atial, environmental constraints. At the same time, planning and cost of ro ad access over the medium-term planning horizon must be considered. This article presents a model and heuristic solution methodology to address stand level harvest scheduling and the associated road construction schedu ling problem, The model is formulated to determine minimal cost schedules, for stand harvests and road construction, that achieve recommended timber h arvest volume targets and that comply with environmental regulations. The h arvest decisions are made at the stand level of resolution. Graph structure s are used to formulate the spatial restrictions on clearcut opening size a nd location. Road construction projects are scheduled to create a feasible road network at minimum net present capital cost. The optimization problem is solved using a Tabu search heuristic, which inc ludes special constructs to cope with the complexity of this problem. An ef ficient frontier of solutions is produced, which may be utilized to analyze tradeoffs between lost forest productivity, due to timing of harvests, and the capital cost of road construction.