Recreational trails as a source of negative impacts on the persistence of keystone species and facilitation

Abstract

Hiking trails, which are among the most common forms of infrastructure created for nature-based tourism, can alter key ecological processes. Trails can damage plants that facilitate the establishment and growth of other species leading to changes in community and functional composition. This can be a particular concern in harsh alpine ecosystems where plant communities are often dominated by one or two keystone species that provide shelter to a suite of beneficiary species. We analysed how a hiking trail affects interspecific facilitation by a dominant trampling-sensitive nurse shrub in the highest National Park in Australia. First we assessed the effects of the trail on the abundance, size and density of the nurse shrub at different distances from the trail. We then compared species richness and composition between areas in, and out, of the nurse shrub's canopy at different distances from the trail. To better understand why some species may benefit from facilitation and any effects of the trail on the quality of facilitation we compared functional composition between quadrats using community trait weighted means calculated by combining plant composition with species functional traits (canopy height, leaf area, % dry weight of leaves and specific leaf area). The abundance, size and density of nurse shrubs was lower on the trail edges than further away, particularly on the leeward edge, where there was more bare ground and less shrub cover. There were differences in species richness, cover, composition and functional composition in and outside the nurse shrub canopy. The shrubs appeared to facilitate species with more competitive, but less stress tolerant traits (e.g. taller plants with leaves that were larger, had high specific leaf area and low dry matter content). However, despite reductions in nurse shrubs near the trail, where they do exist, they appear to provide the same 'quality' of facilitation as nurse shrubs further away. However, longer-term effects may be occurring as the loss of nurse shrubs alters the wind profile of the ridgeline and therefore succession. The use of a steel mesh walkway along the trail may facilitate the regeneration of nurse shrubs and other plants that require protection from wind. Our results highlight the importance of diversifying recreation ecology research to assess how trails affect important ecological processes.

Local trampling disturbance effects on alpine plant populations and communities: Negative implications for climate change vulnerability

“…Although other studies have showed that disturbance can negatively affect nurse plant abundance, size, and density (e.g., Ballantyne & Pickering, ,), we are not aware of other studies that have examined responses in cushion plant size structure and reproduction to relatively high disturbance levels. However, past studies also point to changes in abundance and percent cover.…”

The impacts of trail infrastructure on vegetation and soils: Current literature and future directions

“…Additional structural studies could look at the effects of trails on the density of trees, loss of key resources such as hollow-bearing and mature trees, and changes in litter layers. Functional studies could assess how trails affect fire regimes, competition, facilitation, dispersal, pollination and plant-soil feedback loops (Ballantyne and Pickering, 2015b).…”

Impact of biotic interactions on biodiversity varies across a landscape

“…In negative interactions, one species may reduce the survival, growth and/or reproduction of another through, for example, competition or allelopathy, whereas in positive interactions, the presence of a species facilitates other species through the provisioning of resources or amelioration of stresses or disturbances (Jones et al ., , ; Tilman, ; Aerts, ; Bruno et al ., ; Brooker et al ., ; Filazzola & Lortie, ). Such interactions may significantly affect the composition of communities (Cavieres & Badano, ; le Roux et al ., ; McIntire & Fajardo, ) and thus also potentially alter spatial biodiversity patterns (Araújo & Luoto, ; Meier et al ., ; Cavieres et al ., ; Ballantyne & Pickering, ; Michalet et al ., ; Mod et al ., ).…”