Non-native plant species richness adjacent to a horse trail network in seven National Parks in southeast Queensland, Australia

Abstract

Access trails that traverse native vegetation expose these ecosystems to potential invasion by non-native plant species, facilitated by a multitude of vectors that utilise these trails. This study examined the diversity and distribution patterns of non-native plant species occurring adjacent to forest trails that are also designated for horse riding use in National Parks in southeast Queensland. A total of 39 non-native species were recorded within 20 m of the trail edge. Observed species varied among the National Parks with 21 species recorded at Bellthorpe and 16 species at D'Aguilar, compared to one or two species in the rest of the parks. There was a rapid decrease in number of non-native species with increasing distance from the trail edge. Up to 25 species occurred directly adjacent to trails compared to nine species 5 m from the trails. Among the observed non-native species, only Sonchus oleraceus and Plantago major are currently known to be dispersed via horse dung, whereas 15 of the recorded species, including these two, are known to be dispersed by vehicles. These results highlight that disturbed areas beside trails clearly support populations of non-native species in protected areas, but relatively few species seem capable of invading adjacent vegetation.