The performance of alternative spatial objective types in forest planning calculations: a case for flying squirrel and moose

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This study examined the characteristics and performance of three different types of spatial objectives in multi-objective forest planning. These types were tested with a case study problem that aimed at improvements in the spatial pattern of the habitats of flying squirrel ( Pteromys volans) and moose ( Alces alces). In the first step, the habitats were determined by using a stand-level habitat suitability index (HSI). Stands in which the HSI exceeded a user-specified limit were considered as habitats. In the forest level problem formulations, the spatial objective types were included in the multi-objective forest-planning model, which was solved by using a heuristic optimization technique. The first type of spatial objective was the proportion of a specified type of stand boundary of the total boundary length. For flying squirrel, the aim was to increase the boundaries between neighboring stands, which were both suitable for breeding and foraging. For moose, the aim was to increase the amount of edge, i.e. the boundary between winter-foraging habitats and other areas. The second spatial objective type was the spatial autocorrelation of HSI. It was maximized for flying squirrel and minimized for moose. Whereas maximization of spatial autocorrelation tends to cluster similar stands, its minimization produces a pattern where neighboring stands often have different characteristics. The third spatial objective type was a weighted mean of the stand-level HSI. The weight depended on the stand location being highest for current habitat patches and decreased as the distance to them increased. This objective, which tends to cluster habitat patches, was applied to flying squirrel only. The spatial objective types were tested in six forest areas located in north Karelia, Finland, ranging from 404.6 to 984.8 ha in area. The first spatial objective resulted in a large area of habitat exceeding the threshold HSI value with a good spatial pattern. The second spatial objective yielded a clearly lower total habitat area but a good spatial pattern, and a good connectivity of the flying squirrels’ habitats. The third objective resulted in a slightly improved spatial pattern of the flying squirrels’ habitats.