Changes in the invasion level, and impact of alien plants in Finnish semi-natural agricultural habitats

Miia Jauni,Juha Helenius,Terho Hyvönen

doi:10.23986/afsci.5136

Abstract

Using dataset of 508 transects of 50 m2, we assessed changes in the invasion level of alien plant species in semi-natural agricultural habitats in three study years (2001, 2005 and 2010) in four geographical regions of Finland. In addition, the impact of environmental factors on the occurrence of the most common neophytes (alien species introduced after the 17th century) and the impact of neophytes on native species diversity were studied. In total, 37 neophyte species were detected, but neophytes regarded as highly invasive were rare and occasional. We detected spatio-temporal variation in the invasion level, but it changed according to the measure used. For instance, alien species diversity was lower in south-western Finland than in other years in 2005, and the relative alien species richness was highest in southern and lowest in eastern Finland. Preferences for environmental conditions (disturbance, habitat type and geographical location) and the impact on plant diversity varied among the most common neophytes. The most common neophytes were positively rather than negatively associated with native and alien species diversity. The results suggest that alien species management and control methods should be species-specific and considered case-by-case. Neophytes do not yet cause severe problems, but regular monitoring is needed to detect changes in their invasion levels.

Highlights

An alien plant is one whose presence in a region is due to intentional or accidental introduction as a result of human activity (Richardson et al 2000)
We observed strong spatio-temporal variation in invasion level, which was enhanced by environmental, geographic and climatic variation and depended on the measure used for invasion level
When invasion level of an alien plant was measured as relative alien species richness, no temporal variation was detected across the country

Summary

Introduction

An alien plant is one whose presence in a region is due to intentional or accidental introduction as a result of human activity (Richardson et al 2000). Invasion level refers to both the extent and severity of an alien plant invasion (e.g. Chytrý et al 2008, Catford et al 2012). In Europe, the invasion level of alien plants is considered to be lower in the boreal region than in central and southern Europe, but in highly disturbed habitats, such as agricultural habitats, the invasion level may be similar throughout the continent (e.g. Chytrý et al 2008, Chytrý et al 2009, Pyšek et al 2009, Jauni and Hyvönen 2010). Agricultural habitats should be the primary focus when considering alien plant invasions in the boreal region

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