Lichens of the Mendenhall Valley, Southeastern Alaska

Abstract

Ninety-three species are reported from the Mendenhall Valley near Juneau and 35 species from nunataks in the Juneau ice field. The lichens of Alaska still present a challenge because the area is so large and until recently so little had been done with the flora. The present paper reports collections from a limited area in southeastern Alaska. During the summer of 1963, from June to August, I was temporarily employed by the U.S. Forest Service and worked in the Mendenhall Glacier area of the North Tongass National Forest. During that time the Forest Service provided me the 6pportunity to collect in the area. 1 I thank Dr. Aino Henssen who checked many of the determinations, Dr. I. M. Lamb who identified my Stereocaula, Dr. Grace Howard who identified the Ochrolechia, Dr. John W. Thomson for some determinations including those of the crustose lichens from the nunataks, and Drs. Hildur Krog and Teuvo Ahti for several identifications or verifications. 2 Department of Biology, Howard College, Birmingham, Alabama 35209. This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 06:23:49 UTC All use subject to http://about.jstor.org/terms 222 THE BRYOLOGIST [Volume 68 The Mendenhall Glacier is located about 13 miles northwest of Juneau. The study area included the region from immediately adjacent to the terminus of the glacier outward to sea level. The collection areas more distant from the glacier were outside the boundaries of the National Forest. Physiographically, the area is dominated by the Mendenhall Glacier which extends from the Juneau ice field southward 12 miles, to its terminus in the Mendenhall Valley. The maximum of the present glacier is considered to have been reached about 200 years ago and to have extended about two miles beyond its present terminus. Numerous evidences of recession are present in the valley. Morainal ridges and flats are fairly well covered by successional vegetation stages, depending upon their age. Glacial erratic bouldels are scattered throughout the area. The terminus of the glacier is bounded on the east by Bullard Mountain (4,225 ft) and on the west and northwest by McGinnis Mountain (4,228 ft) and Stroller White Mountain (5,150 ft). South of the glacier, Mendenhall Lake, a meltwater body, covers an area approximately one mile square. An outcropping of a schist bedrock crosses under the lake and is exposed on each side immediately adjacent to the glacier, as well as at one point on the glacial face. This bedrock is the material most recently exposed by the recession of the glacier. From here the valley gradually broadens out toward the southwest to terminate in the Gastineau Channel. Extending northwestward from the main valley is the Montana Creek area which provided muskeg and mature forest collecting sites. Elevation in the region of study varied from about 500 feet to sea level. Most collections were made at about 100 feet (Fig. 1). The climate of the Mendenhall Valley is under the maritime influences which prevail along all of the coastal areas of southeastern Alaska. Thus, the area has abundant precipitation, little sunshine, and generally moderate temperatures. Comparison of weather records from the Juneau airport at the end of the Mendenhall Valley and from the city of Juneau itself indicate that there can be considerable climatic difference in locations only a few miles apart. The average length of the growing season in the city of Juneau is 177 days while at the airport it is 146 days. Total precipitation at the Juneau airport has reached a high of 64.06 inches while at Juneau yearly amounts have reached 119.48 inches. The mean precipitation at the airport over the period 1943-1961 is 54.56 inches. Snowfall is frequently heavy in the Juneau area varying from 32 inches in 1940-41 to a record of 246.3 inches as the annual total for the year 1917-1918 (Anderson 1955; Weather Bureau, U.S. Dept. of Commerce 1961). Four successional stages are evident in the Mendenhall Valley. The natural vegetation is a hemlock-spruce forest with the dominant plants being Tsuga heterophylla and Picea sitchensis. Successional stages leading toward this climax originate with an initial lichen-moss community. As evidenced on the most recently exposed bedrock, This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 06:23:49 UTC All use subject to http://about.jstor.org/terms 1965] MCCULLOUGH: LICHENS FROM ALASKA 223 I -;??/ \,? ?~p~ a r