Phytosociological and Environmental Characteristics of Some Plant Communities in the Umiat Region of Alaska

Churchill, Ethan

1. The general aspect of the Umiat area, located between the Brooks Range and Barrow, Alaska, results from the presence of gently rolling hills with dense vegetation generally 6 to 12 inches high consisting of dwarf heath shrubs, dwarf birches and willow, intermingled herbaceous species and, in places, alders and willows from 3 to 8 feet high. The tall alders and willows occasionally form thickets, especially on slopes and on the flood-plain. 2. The environment of the Umiat area is rigorous, annual precipitation is very low, the winters are long and severe, and the summers are cool and short. No freeze-free season can be expected, and permanently frozen ground underlies the area at usually shallow depths. 3. Eighty stands of various plant communities were investigated during the summer of 1951 in the Umiat area of Alaska. Quadrat analysis and soil profile descriptions were made in each stand. 4. Aerial photographs were found to be useful in differentiating, delineating, and selecting stands for detailed analysis since differences were more readily detected on aerial photographs than on the ground. 5. Frequency is one of the most important phytosociological characteristics because the cover of each component species of a stand is usually low to an equal degree. 6. Association tables and phytosociological indices are useful in analyzing stands, in comparing stands, in determining relationships of stands and in evaluating the phytosociological importance of species. 7. The stands are grouped into 5 types. The most widespread type, the Dwarf Shrub Heath, is divided into 4 subtypes, Eriophorum Tussock-Dwarf shrub Heath, Eriophorum spissum-Carex Lugens-Arctagrostis latifolia-Dwarf Shrub Heath, Carex-Dwarf Shrub Heath and Grass-Dwarf Shrub Heath. The Frost-Scar Collective Type is divided into the Dryas integrifolia (var. canescens?) and the Dwarf Shrub Heath Subtypes. The other three types are the Salix, the Alnus crispa and the Carex aquatilis-Marsh Types. Microhabitats, and therefore the microcommunities which they determine, are characteristic of the first 2 types so that these types could be considered as mosaics of microcommunities. These types display a homogeneity which results from the uniformity of distribution of microcommunities within the stand. 8. The most important vascular species with regard to cover and frequency are Alnus crispa, Arctostaphylos alpina, Betula nana ssp. exilis, Cassiope tetragona, Dryas integrifolia (var. canescens?), Empetrum nigrum, Ledum decumbens, Vaccinium uliginosum, V. vitis-idaea, Salix glauca, Carex aquatilis, C. lugens, Eriophorum spissum, Arctagrostis latifolia, Lupinus arcticus, Polygonum bistorta ssp. plumosum, Pyrola grandiflora and Stellaria laxmannii.

Phytosociological and Environmental Characteristics of Some Plant Communities in the Umiat Region of Alaska

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