Examining alternative landscape metrics in ecological forest planning: a case for capercaillie in Catalonia

Abstract

This study examined the performance of four different landscape metrics in a landscape ecological forest planning situation in Catalonia: (1) proportion of suitable habitat (non-spatial) (%H); (2) spatial autocorrelation; (3) the proportion of habitat-habitat boundary of the total compartment boundary (H-H) and (4) the proportion of habitat-non-habitat boundary (H-nonH). They were analysed in a case study problem that aimed at the maintenance and improvement of capercaillie habitats in two simulated forests of 14,400 hectares consisting mainly of Pinus uncinata, P. sylvestris and P. nigra stands. The habitats were determined by using a stand-level habitat suitability index (HSI). Stands in which the HSI exceed a specified threshold value were considered as habitats. Then, four different planning problems were formulated to test the four landscape metrics as one of the management objectives. The objective functions of the problems were written in the form of an additive utility model, and the problems were solved using heuristic optimization techniques. Before this, five different heuristic optimization techniques: random ascent; Hero, simulated annealing (SA), tabu search and genetic algorithms (GA), were compared in a non-spatial and a spatial planning problem. Based on these comparisons, GA was selected for solving the spatial planning problems while SA was used for non-spatial problems. The spatial pattern of habitat patches was comparable when using the %H, H-H or spatial autocorrelation as a management objective. However, the limitations of using the non-spatial %H objective were clear in the second forest landscape with lacking trends in forest features. H-H and spatial autocorrelation yielded a more clustered landscape with larger habitat patches. The largest proportions of habitat and habitat–habitat boundaries were created when using the H-H as the ecological management objective. The use of spatial autocorrelation as a management objective resulted in a smaller habitat area and shorter habitat-habitat boundary than when %H and H-H were used as objectives, but the proportion of large habitat patches was rather high. H-H was very suitable for connecting habitat patches. When H-nonH was used as the ecological management objective a very fragmented landscape was generated.