LAUSR

Abstract Comprehensive description and quantification of stand structure is needed for managing or maintaining forests as complex systems. The tree position and diameter based structural complexity index SCI was used to quantify the structural heterogeneity of forest stands in Estonia. The aims of the study were to determine if SCI is related to the conventional stand characteristics used for forest management planning and to assess the direct impact of silvicultural treatments on stand structural heterogeneity. The SCI for hemiboreal forests in Estonia ranged from 1.36 to 10.78, being highest in conservation forests on fertile sites (7.42 ± 1.20), followed by managed forests on fertile sites (4.74 ± 1.44), managed forests on poor sites (4.00 ± 1.02), conservation forests on poor sites (3.85 ± 0.87), and lowest in rehabilitation forests (2.64 ± 0.69). The mean SCI between forest groups and site types differs significantly, except in managed and protected forests growing on poor sites. The SCI is positively associated with commonly measured stand characteristics, indicating that stand structural heterogeneity reflected in SCI is higher for older stands with larger trees, higher deadwood quantity and biomass. The results also show that species diversity promotes stand structural diversity. SCI is a promising method for providing quantitative assessments of multidimensional forest stand structure in Estonia.