Summary
A summer highway, Trail Ridge Road in the Rocky Mountain National Park, traverses more than 19 km of alpine tundra, rising to over 3,658 m. The Ridge has been accessible by vehicle for over 50 years and millions of people have visited. Visitor activities are concentrated around parking areas but many hikers walk out along established paths. Excessive trampling destroys the fragile tundra plants and initiates soil erosion. The present study was undertaken to investigate processes and rates of vegetation recovery when protected from further trampling.
Two areas each 100 sq ft (9.24 sq m) suffering trampling damage were protected in spring 1959(subsequentlyenlarged to about twice the size):
Forest Canyon Overlook - An exclosure was erected across the most prominent trail produced by one season of trampling (in 1958).
Rock Cut -An exclosure was installed alongside the prominent trail; the area had been subject to trampling over 26 years, there was a mosaic of bare ground and vegetation patches in various stages of degradation.
In 1960, a third exclosure was added at Fall River Pass in an area by a car park subject to trampling over 38 years. Most vegetation had been lost with just remnants persisting around boulders; most of the area was bare gravel. The exclosure was demarcated by rocks, which greatly reduced rather than eliminated access.
Observations were made every week during spring-autumn (when snow-free) from1959 through 1962. Plants were mapped and photographs taken to record vegetation changes; cover, growth and seedling emergence were monitored.
Forest Canyon - During the first season of protection, all flowering plants (except cushion-plants) exhibited almost normal growth, but total cover was slightly less than undamaged areas; six species of lichens eliminated by trampling remained absent. By the second season the protected area appeared almost natural, except that lichens were still absent and eroded and dead centres of cushion-plants persisted. During 1961 and 1962, a few fragments of soil lichens, the pioneering moss Bryum argenteum, and the grass Poa fendleriana appeared. By the end of the1962 season almost complete vegetation recovery was achieved.
Rock Cut -In the exclosure there was an increase in vegetative growth, but after 4-years the potentially dominant species, bog sedge Kobresia myosuroides, still exhibited reduced vigour and some other important species were absent.
Fall River showed no improvement in the three seasons of observation. The only change noted was that under the reduced trampling, the compacted soil was loosened by needle-ice activity.
This study suggests that badly damaged areas will require many years to recover and that secondary succession back to the climax Kobresia stand appears incredibly slow.
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