Lichens of Anaktuvuk Pass, Alaska, with Emphasis on the Impact of Caribou Grazing

Abstract

Anaktuvuk Pass in the central Brooks Range of northern Alaska provides a major migration route for the western arctic caribou herd. A por- tion of the herd overwintered in the Anaktuvuk Pass area 8 years prior to sampling. Caribou grazing resulted in the almost complete removal of mac- rolichens in grazed areas and this has been followed by the invasion of crus- tose and squamulose species. An analysis by species biomass composition for grazed and nongrazed areas on both north and south slope exposures revealed a lichen composition of 31 species, with Cladonia stellaris, C. rangiferina, C. arbuscula and C. mitis being the most common and present in almost equal abundance on both exposures. In addition, 288 species in 71 genera are re- ported for the Anaktuvuk Pass area. Aspicilia plicigera (Zahlbr.) Thoms. is reported as a new combination and new to North America. Tundra occupies approximately 15% of the earth's land surface, principally con- fined to the northern portion of the Northern Hemisphere (Bliss, 1971). These vast treeless expanses are dominated by prostrate shrubs, short-stemmed herbaceous pe- rennials, lichens and mosses (Billings, 1973). The lichens are particularly important in upland portions of tundra systems where they form extensive mats (Thomson, 1972) that are utilized by caribou and reindeer as a winter food source (Hanson, 1966a; White et al., 1975). Although lichens are more diverse than higher plants in the arctic, most ecological studies have been conducted on higher plants. Lichens are capable of existing in this heat deficient ecosystem, in part because they are highly resistant to frost injury and can survive long periods of inactivity while in a frozen state (Kap- pen, 1973). Consequently, lichens are opportunistic species which are capable of efficiently using favorable conditions present during the brief summer period for pro-