Question: What are the changes associated with the recent invasion by the non-native legume, Cytisus scoparius?

Location: Subalpine vegetation (1500 m a.s.l.) in Australia.

Methods: We used multivariate techniques and regression analyses to assess vegetation and environmental changes across six study sites. Vegetation and environmental variables were investigated at three different stages of invasion: (1) recent invasion (8–10 yr), (2) mature invasion (15–16 yr) and (3) long-term invasion (25 yr).

Results: Substantial changes in floristic composition and species richness were evident after 15 yr and these changes became more pronounced after 25 yr. Changes due to invasion were associated with a dramatic loss of native species or a reduction in their abundance. No ‘new species’ were evident under invaded stands. Forbs were most affected by the establishment of C. scoparius, although all growth forms responded negatively. Dense canopy shading and an increasingly dense, homogeneous litter layer in the understorey as a result of C. scoparius were strong environmental drivers of vegetation change. Greenhouse studies confirmed the importance of these processes on the germination and growth of two native species.

Conclusions: This study highlights the potential for C. scoparius to alter both vegetation and environmental processes in the subalpine region.

Nomenclature: Ross (2000).