Lichens of Granitic Rocks in Rocky Mountain National Park Larimer County, Colorado, U.S.A.

Henson, Ann; Lea, Christopher; Bates, Scott

Rocky Mountain National Park is located in north central Colorado in the Front Range Mountains. Within the Park, areas of high elevation experience intense solar radiation and extreme climates that impose formidable challenges to plant life and lichens growing on exposed rock surfaces. The Alpine zone occurs from 3,505 to 4,345 m in elevation (Beidleman et al. 2000), has a very short frost-free period (10 to 30 days), and receives 76 to 102 cm of precipitation per year. The Subalpine zone occurs from 2,895 to 3,505 m in elevation, has a slightly longer frost-free period (10 to 50 days), and receives 61 to 102 cm of precipitation per year. The Montane zone has an elevation range of 2,285 to 2,895 m, a frostfree period of 40 to 100 days, and receives 41 to 76 cm of precipitation per year. Most rainfall occurs from April to September on the eastern side (Soil survey, NRCS). The National Park Service completed the Park’s “Vegetation Inventory” which classified, described, and mapped the park’s vegetation communities (Salas et al. 2005). This information provides a wide variety of resource assessment, park management, and conservation needs (NPS), but focuses primarily on vascular plant communities. While constructing the inventory map, many areas were mapped as “rock,” “talus,” or “cliff face.” These areas, which constitute more than 9% of the map area, might be considered devoid of life, if we follow the vascular plant-centric view of the inventory results. But the rocks of the Park are encrusted with copious amounts of lichens, mosses, and scattered lithophilic vascular plants. Until now, lichen communities have been omitted from the NPS inventory process, primarily because of a general lack of field identification skills in inventory team members. Yet lichens represent an important measure of the community biodiversity. Lichens also play an important part in nutrient and mineral cycling; contributing to pedogensis; providing food, shelter, and nest building material for micro- and mega-fauna; and serve as bio-indicators of ecosystem health (Nash 2008). We propose that communities dominated by these organisms be included in future vegetation inventories and mapping projects whenever the identification skills and ecological knowledge can be recruited. Our goal was to quantitatively define the lithomorphic lichen communities. The methodology also yielded abundance and environmental data for individual species. These data are not often provided but are useful complements to traditional “species list” floristic surveys, such as those of Kleiner, Weber, Sushan, Imshaug, Anderson, Egan and Wetmore (NPLichen). We will present the community inventory Evansia 30(1) 18 and mapping results in another paper. Time and travel constraints limited our observations to Proterozoic crystalline rock substrates east of the Continental Divide in Rocky Mountain National Park. These rock substrates comprise more than 90% of the mapped bedrock geology of the park (Braddock and Cole 1990). Our sites were at locations mapped as Silver Plume Granite, Hagues Peak Granite, or biotite schists (Braddock and Cole 1990)