PERSISTENCE OF VASCULAR PLANTS IN A NORWEGIAN BOREAL CONIFEROUS FOREST

Persistence, the tendency of a species to remain in its original posit ion and not to colonize new sites, is studied for the most abundant fo rest vascular plants (25 species in spruce forest and 7 in pine forest ) in Solhomfjell, Gjerstad, S Norway. Data sets included presence/abse nce in 199 meso plots (1 m(2)) and 3184 subplots (1/16 m(2)), analyzed over a 5 yr interval, and a subset of 50 meso plots and 800 subplots, analyzed for six consecutive years. Relationships between species var iables (seedling frequency and mobility rate compiled from the literat ure, and cover and abundance means in the study area) are studied, and related to species optima along ecologically interpreted DCA ordinati on axes. Vascular plant mobility may increase towards nutrient-poor si tes. Dominance in the boreal forest floor is mostly by clonal species. Persistence was calculated for different temporal (1-5 yr) and spatia l (1/16 and 1 m(2)) scales. Persistence patterns in the spruce and pin e forests were similar, but persistence decreased towards the xeric pi ne forests. One main component of variation in persistence was demonst rated by PCA analyses: the absolute level of persistence, which is rel ated to seedling recruitment vs clonal growth, and within clonal speci es to ramet longevity, abundance, mobility, growth pattern and mode of surviving the infavourable season. Minor components of variation in p ersistence were related to spatial scale and temporal scale. Persisten ce characteristics were species-specific and varied little between yea rs. Numerous species characteristics were relevant to interpretation o f variation in persistence, indicating a continuous, multidimensional variation in life history characteristics.