Backcountry Huts as Introduction Points for Invasion by Non-native Species into Subalpine Vegetation

Abstract

The role of backcountry huts as introduction points for the establishment and spread of non-native plants into remote natural areas has received little attention. We surveyed soil and vegetation around 25 backcountry huts in the subalpine landscape of the Australian Alps to examine the role that such huts play in acting as foci for invasion by non-native species into remote mountain areas. We found that the hut surroundings were characterized by greater soil compaction, lower vegetation height, and more bare ground relative to the native plant community located 100 m from huts. At the landscape-scale, a total of 32 non-native species were recorded within 100 m of huts. Seven species were found at greater than 50% of huts (Hypochoeris radicata, Taraxacum officinale, Acetosella vulgaris, Trifolium repens, Cerastium glomeratum, Agrostis capillaris, Poa annua), and these tended to be the species that have (a) been long-established (>50–100 yrs) and (b) are the most frequent in the broader landscape. Hence, huts act to promote these ruderals by providing opportunities for their establishment, but such opportunities are not confined to hut surroundings. Several other non-native species, however, were common around huts but largely absent from the wider landscape (e.g. Anthoxanthum odoratum, Plantago major, Polygonum aviculare, Stellaria media). This suggests that some species are advantaged by the disturbance and dispersal opportunities provided by hut recreational activities in a way that is not catered for elsewhere in the Australian Alps. A weak negative relationship between non-native species richness and increasing altitude was found, but native species richness and distance of hut from access road were poor predictors of non-native species richness. Our study highlights that recreational activities may provide opportunities for the establishment of non-native plant species in remote high mountain areas, some of which are novel to the landscape, and that these may form the basis for further invasion into adjoining native vegetation.