Aggregating microsegments into harvest blocks by using spatial optimization and proximity objectives

Abstract

This study analyzed the performance of distance-based objective variables as an alternative to adjacency-based variables in spatial optimization when the aim is to aggregate small forest segments into harvest blocks. Distance-based objective variables maximized harvested volume within a certain distance from a harvested segment. Segments that constituted a harvest block did not have to be adjacent. It was hypothesized that it is more profitable to aggregate harvest blocks by using distance-based objective variables instead of adjacency-based objectives. It was also assumed that distance-based objectives result in harvest areas that correspond better to the harvest blocks of forestry practice. Distance-based objectives were tested with four maximum distances of uncut forest between two segments of the same harvest block. The tested distances were 0, 25, 100, and 300 m. A zero distance means that only adjacent segments form harvest blocks. The results showed that distance-based cutting aggregations improved net present value, as compared with adjacency-based cutting aggregation. Distance-based objective variables also resulted in larger harvest block size than adjacency-based objectives, if the maximum allowed distance of uncut forest between two harvested segments of the same harvest block was 25 m or longer and the average removal of a harvest block was 300 m3 or more. Requirement for adjacency led to small and compact harvest blocks.