New and old invaders in forests in eastern Austria: The role of species attributes and invasion history

Recent studies have shown that temperate forests are susceptible to the invasion of alien species. However, it is less known how species attributes such as functional traits, invasion success on large scales (e.g. globally or in Europe), residence time and pathways of introduction interact in shaping the distribution of alien species in forests. Here, we analyse the distribution of alien species species introduced long ago (i.e. archaeophytes, introduced before 1492) and of more recently introduced aliens (i.e. neophytes, i.e. introduced after 1492) in 43 study sites (5 ha size) in forest remnants in a cultural landscape in eastern Austria. We recorded 167 alien species (112 neophytes, 55 archaeophytes). There was a significant, yet moderate correlation between number of neophyte and archaeophyte species per site. Life form composition of archaeophytes differed substantially from that of neophytes: archaeophytes mostly were short-lived (76%) and long-lived (22%) herbs. For neophytes, life-form composition was much more even, with long-lived herbs being most abundant (36%), and all other life forms being similarly represented (21-23%). While the dominant pathway for archaeophytes was unintentional introduction (51 species), neophytes were mostly introduced by horticulture (90 species). Year of first record in Austria, and the number of European regions a species has invaded highly significantly explain local invasion success, i.e. the number of invaded study sites. Further, the number of short-distance dispersal mechanisms highly significantly explained the number of invaded sites, while the number of long-distance dispersal mechanisms was insignificant. The maximum height of a species had also a significant positive influence on the number of invaded sites. Our results show that the composition of old and more recently introduced alien species in forests differs substantially in terms of regions of origin, life-form and pathways, and that basic species attributes contribute to local invasion success. © 2021