Primary succession pathway of Norway spruce communities on land-uplift seashores

Abstract

The rising Gulf of Bothnia coastlines provide sequences of primary succession. This paper, based on data from transects in northeast Sweden (63º 51’ N, 20º 43’ E), elucidates the pathway of Norway spruce community succession on ground-moraine seashores. We studied spatial and temporal variation in depth of surface organic layer, cover of field layer and bottom layer, density of spruce categories from current seedlings to mature and dead spruce, and diversity changes. We found that field layer declines in cover while bottom layer increases in cover and that field and bottom layers and spruce category diversity show unimodal trends with time of succession. Modal diversity occurred after 100 to 200 years for field- and bottom-layer types and after 200 to 230 years for spruce categories. We also found that spruce seedlings are able to colonize after only 30 to 40 years of succession (25 to 35 cm above mean sea level), that spruce category size increases with time of succession, and that spruce mortality occurs both among small-sized trees at earlier stages and among larger-sized trees at later stages approaching old-growth conditions. We present successional stages of field- and bottom-layer types, and of spruce categories, developed from TWINSPAN analyses and models of organic layer depth development over time.