Graduate Thesis Or Dissertation
 

Subalpine revegetation on backcountry campsites near Tuolumne Meadows, Yosemite National Park, California : third year results

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  • The National Park Service initiated a backcountry campsite restoration project in 1987 to restore native vegetation on severely degraded campsites in three subalpine lake basins in Yosemite National Park. Restoration treatments included soil scarification, transplanting, manual seeding and site protection. Eight of the treated campsites were monitored in 1990 to evaluate changes in percent vegetation cover, species richness and volunteer establishment that had occurred over the three year period beginning prior to treatment application in the summer of 1987, and ending in the summer of 1990. Percent vegetation cover increased slightly across all sampled quadrats ([mean] = 0.71; N = 214) with mean percent cover changes ranging from -0.37 to 4.36 on individual campsites. Three sites had a loss of cover. Percent cover changes differed most among campsites within lake basins. Changes in percent cover did not differ among lake basins or impact strata (barren core, moderately trampled, and peripheral). Transplanting did not appear to be an important influence on changes in percent cover, as cover changes did not differ between planted and unplanted areas. Survival of transplants planted in 1987 was poor (19.2%), but survival of transplants planted in 1988 was higher (70.5%). Species richness increased slightly across all sampled quadrats ([mean] = 0.54 species per quadrat), with species richness changes on campsites ranging from -0.13 to 1.75 species per quadrat. One site had a mean decrease in species richness. Species richness changes differed among campsites, with the largest increases occurring on those campsites that also had the greatest increases in percent cover. Changes in species richness also differed among impact strata, with the largest increases occurring on barren core areas. There were small differences among lake basins, and species richness changes did not differ between planted and unplanted areas. Volunteer establishment occurred on all treated sites. The number of volunteers per site ranged from one to 45, and 29 species were represented. Individual quadrats had from one to four volunteers. Approximately 50% of the volunteers were producing seed, and overall vigor among volunteers was good. Numbers of volunteers per quadrat differed most strongly among campsites. Slight differences were detected among lake basins and impact strata, with numbers decreasing from barren core to peripheral quadrats. Differences in numbers of volunteers per quadrat between planted and unplanted areas were not detected. Soil scarification may enhance increases in cover, species richness and numbers of volunteers. However, the influence of scarification was tested on two sites only, and further study is recommended. The recovery process appeared to be strongly affected by factors operating at the campsite level. For example, sites with the greatest increases in percent cover also had the greatest increases in species richness and the most volunteers. These sites had coarse soils, relatively abundant sunlight and moisture, and were effectively protected from trampling after site treatment. Results indicate revegetation prescriptions should be made on a site-by-site basis. The performances of eleven species used in transplanting or occurring as volunteers were evaluated. Five species, Agrostis humilis, Calamagrostis breweri, Muhlenbergia filifonnis, Trisetum spicatum, and Calyptridium umbellatum show potential as colonizers in unassisted revegetation and may be useful in manual seeding treatments; three species, Calamagrostis breweri, Carex rossii, and Juncus panyi show potential for transplanting and nursery propagation; and two species, Carex spectabilis and Carex straminiformis, require further study to determine their effectiveness in subalpine revegetation treatments.
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