Abstract
Sorbus aucuparia L. is a short-lived tree species very common throughout Europe, often occurring as a pioneer tree in open habitats as well as forest. Its life history traits are discussed on the basis of a case study in the Solling Mts (northwest Germany), with special regard to germination, establishment and growth. Investigations covered an old-growth spruce stand and a birch-rowan pioneer forest, the latter having developed spontaneously after storm damage in 1982. To emphasize the specific character of S. aucuparia among short-lived tree species it is compared with Betula pendula Roth, a short-lived tree species also very common in Europe, which is well studied biologically and ecologically. In its early life history, rowan should be considered a very shade-tolerant tree species, able to germinate in old-growth spruce forests under poor light and on thick layers of raw humus. There is no evidence that germination of rowan is slowed down or impeded by dense cover of Deschampsia flexuosa (L.) Trin. For birch the most suitable site conditions for germination and establishment are provided by moist sites with high relative light intensities and naturally or anthropogenously loosened topsoil layers. Once established, rowan is able to build up a ramet bank through a ‘guerrilla’ type of clonal growth in the organic layer and can thus successfully penetrate into closed vegetation cover. Whereas rowan acts as a ‘stresstolerant competitor’ in its early life history, birch tends to have a more ruderal strategy by very successfully colonizing severely disturbed habitats and growing rapidly.