Structure and dynamics of an undisturbed old-growth Norway spruce forest on the rising Bothnian coastline

The ongoing glacial rebound along the Gulf of Bothnia provides continuous exposure of new surfaces for primary succession. On mesic ground moraines the seres terminate in Norway spruce (Picea abies (L.) Karst.) forests. An island in the Gulf of Bothnia, North Sweden (63 degrees 49'N; 20 degrees 41'E) has been the subject of a detailed study. The island emerged from the sea fully 300 years ago and has undergone undisturbed development to an old-growth, climax-like Norway spruce forest. The initial specimens are still present, alive or as deadwood. The oldest living spruce was 106 years old. The forest is dense with a patchy, uneven-sized structure, A total of 365 m(3) ha(-1) (stem volume) of live and 76 m(3) ha(-1) of deadwood has been recorded. The density of spruce seedlings 0.5-1.3 m in height was 8600 ha(-1), and varied from 26,000 to 800 ha(-1) on a 5 m x 5 m quadrate basis. A classification of health stages - live, declining, recently dead, long-time, dead and decomposed - allowed for a dynamic analysis. The ongoing dynamics in the forest as a whole serves to maintain and/or amplify a disorderly structure. A dynamic dichotomy was detected, however. The understorey (less than or equal to5.5 m in height) undergoes a development from contagious towards disorderly structure, while the achieved disorder in the overstorey (>5.5 m) is maintained. The forest provides an excellent reference base for developing management guidelines for multi-sized forests, derived from a firm knowledge base of natural structural development. We conclude that a vertical stratification approach to structural description may provide relevant ecological insight for practical application, and we elaborate on the apparent rapidity with which old-growth conditions can be obtained. (C) 2001 Elsevier Science B.V. All rights reserved.