Migration of vascular plants to secondary woodlands in southern Sweden

Abstract

1 We studied the migration of field layer plants across ecotones between ancient woodlands and recent deciduous woods on former arable land varying in age between 30 and 75 years. 2 Number and percentage cover of woodland species in recent woods decreased with increasing distance to the ancient woods, and increased with the age of the recent woods, indicating dispersal limitation during secondary succession. 3 Colonization by typical woodland plants was observed in 183 of 200 species × site combinations. In 72 combinations, a colonization front was characterized by logarithmic or linear decrease in species cover, indicating establishment of isolated individuals and gradual infill of gaps. This pattern was most common in ant‐dispersed species and less frequent in species with adhesive or ingested seeds. 4 Migration rates were calculated for 49 woodland species. Mean migration rates based on maximum cover in recent woods varied from 0.00 to 1.00 m year −1 between species, with a median migration rate of 0.30 m year −1 . Migration rates calculated on occurrence of the farthest individual ranged from 0.00 to 1.25 m year −1 , with a median rate of 0.53 m year −1 . 5 Ant‐dispersed species had lower migration rates based on maximum cover compared with species with adhesive or ingested seeds. No differences between dispersal modes were found when comparing migration rates based on the farthest individuals. Most of the calculated migration rates (84%) exceeded the rate of possible vegetative spread of woodland species. 6 Establishment of a field layer vegetation in secondary woods comparable to that of the adjacent ancient stands proceeded at a rate of c. 0.3–0.5 m year −1 . We conclude that scale and intensity of temperate forest management should be adjusted to the relatively slow migration of the field layer flora in order to enable complete recovery during a management cycle.