Impact of broom, Cytisus scoparius (Fabaceae), in naturally treeless sub-alpine frost-hollow vegetation communities at the Barrington Tops, south-eastern Australia.

Abstract

The exotic shrub Cytisus scoparius (L.) Link (family Fabaceae), known as broom, is having a major impact on native vegetation in naturally treeless sub-alpine frost-hollow areas (c. 32 o 01' 37 S, 151 o 26' 12 E', 1440 m elevation) at the Barrington Tops, New South Wales, in south-eastern Australia. This vegetation is of limited extent and has significant biogeographical and ecological importance. Nine paired 10 m line transects were compared, with one of the pair in areas of almost 100% Cytisus scoparius and the other in adjacent areas without Cytisus scoparius. Results were compared with species recorded from this area in the 1930s. There are obvious differences in native vegetation in areas with and without Cytisus scoparius. On average there were 5.1 (range 2-10) species per 10 m in areas of almost 100% Cytisus scoparius cover and 17.0 (12-25) species per 10 m in areas adjacent to infested areas but without Cytisus scoparius. Other than Cytisus scoparius, the area surveyed had little in the way of exotic species and these were only present at low densities. Native species present in 2008 are similar to those recorded in the 1930s; there were no records of Cytisus scoparius in the area in the 1930s. The study suggests that control of Cytisus scoparius in naturally treeless areas at the Barrington Tops should be a priority to prevent a decline in the distribution and abundance of many plant species, many of which only occur in treeless areas of the Barrington Tops.