Soil as a critical component of vegetation restoration on a sub-alpine mountain summit in Acadia National Park

Aims Recreational use on mountain summits has caused severe degradation of
soils and vegetation, and climate change is exacerbating these impacts.
Best practices for restoration of these important ecosystems are unknown.
Here we examine the effectiveness of different treatments for restoring
native vegetation (plant cover and native species richness) in degraded
areas on a mountain summit through an experimental restoration approach.
Location Cadillac Mountain, Acadia National Park, Maine, USA. Methods We
tested six restoration-method treatments: control, planting modules, coir
erosion control, seed and coir, soil and coir, and soil, seed, and coir.
We established four replicates of each restoration-method treatment in
2016 and monitored percent cover and species richness twice per year from
2017-2022. In 2017, we established four more plots for each of three
soil-depth treatments (2.5 cm soil, seed, and coir, 13 cm soil and coir,
and 13 cm soil, seed, and coir), and monitored percent cover. Results Six
years after restoration began, native vegetation cover was highest in
treatments with added soil. Seeding (502 seeds/m2) had no effect on
percent cover. Planting seedlings added vegetative cover initially, but
did not increase over time. Cover was equally high in treatments with
shallow soil (2.5 cm deep) and deep soil (13 cm deep). Treatments with
added soil also had the highest native species richness. Adding a small
amount of soil (2.5 cm soil depth) with erosion control (i.e., coir
matting) successfully restored vegetation to previously degraded areas of
the Cadillac Mountain summit. Conclusions Mountain ecosystems will
continue to experience degradation from human recreation and climate
change. Restoration of degraded areas is critical to maintain these rare
ecosystems. Our results suggest that restoring and maintaining soil is key
to restoring degraded areas. However, more research is needed to
understand the long-term implications and success of mountain summit
restoration. Our study provides an example of how this work can be done
without delaying restoration using an experimental restoration approach.