SHORT-TERM AND LONG-TERM IMPACTS OF SPATIAL RESTRICTIONS ON HARVEST SCHEDULING WITH REFERENCE TO RIPARIAN ZONE PLANNING

Owing to the significance of shade, wildlife habitat, soil stabilization, and water-filtering effects of streamside vegetation on the riparian zone, spatial restrictions are imposed on both public and private harvesting areas along the stream by state and federal agencies. Analysis of both short- and long-term impacts of the riparian zone spatial restrictions as well as spatial restrictions on harvest units is presented. The heuristic model called SSMART, for spatially constrained harvest scheduling problems, is used to solve the proposed problems. The Green River sub-basin on the Alsea Ranger District, Siuslaw National Forest, Oregon, is used for the analysis. Our computational experiments show that the marginal reduction of the total present net worth in dollars is about 6.2% per 100-foot (1 foot = 0.305 m) width of the riparian management area, and about 6.7% for the average annual harvest flow. It is also shown that increasing the exclusion period to two or three periods could cause major reduction (25-40%) in both the total present net worth and the average annual harvest flow. The linear programming relaxation is revealed to provide a good approximation for impacts of the size of riparian management areas, while it cannot be used for examining impacts of the exclusion period.