The Intermountain Region contains a diverse array of landscapes, from rich alpine meadows to dry salt flats, isolated subalpine bristlecone forests on "forest islands" and much more in between. Across these landscapes an equally diverse array of fungi and plants can be found.
Many collections provide on-line access to specimen data, but organisms do not exist in isolation. Information (summarized data) rather than raw data is needed if we are to understand the factors responsible for species distributions and be able to predict where a species will be found. We have taken a regional approach because the flora and mycoflora in the Intermountain Region share a common geological history and climate. Our approach is two-pronged. Direct access to label data for specialists, the norm among herbaria. In addition the distribution of many of the specimens can be mapped over satellite photos. The result is a visual representation of the distribution of taxa in relation to topography. We hope to incorporate a Geographic Information System that will let us map distributions in relation to a number of factors, e.g., land cover, ownership, etc.
Our partners in this effort include the University of Michigan Fungus Collection (MICH) and the New York Botanical Garden (NY). Both herbaria have shared specimen records from their databases.
The floristic Intermountain Region (IMR) as defined by Cronquist et al. covers 267,000 square miles in Utah, most of Nevada, plus portions of southern Idaho, southeastern Oregon, the Arizona strip and California. The IMR consists of the dry land region between the Sierra Nevada on the west and the Rocky Mountains on the east and between the wetter Pacific Northwest to the north and the warmer dry lands to the south.
The Region contains four distinct floristic divisions: the floristic Great Basin, Wasatch Mountains, Uinta Mountains and Colorado Plateau. The area selected is a bit arbitrary since it includes all of Utah "a priori"and the Utah-Colorado state line is used for the eastern boundary. Despite these arbitrary decisions, the Region shares a common history and geology. The naturalness of the IMR is reflected in the names of a number of businesses, e.g., Intermountain Health Care, Intermountain Farmers Association, Intermountain Geothermal, etc.
The IMR lies wholly within the arid and semiarid areas of the United States. About 75% is covered by plant communities dominated by shadscale (Atriplex confertifolia), sagebrush (Artemisia tridentata), or pinyon-juniper woodland (Pinus monophylla or P. edulis and Juniperus osteosperma).
Discontinuous mountain ranges rise above a large number of dry pluvial lake basins filled with unconsolidated alluvium. The Middle Rocky Mountains extend southwest from eastern Idaho into Utah and Colorado. The Wasatch and Uinta ranges are probably the most visited portions of the Middle Rocky Mountains. The Wasatch Range with peaks up to 12,000 ft. trends north-south for nearly 200 miles in Utah and southeastern Idaho. The Uinta Range, located mainly in northeastern Utah below the Wyoming border, is the largest east-west trending mountain range in the western hemisphere.
The Great Basin Division of the IMR contains numerous parallel north-south trending isolated mountain ranges separated by nearly level basins. These ranges vary in elevation between 7,000 and 12,000 ft. The mountains are mesic enough to support woodlands, forests and alpine communities.
The distribution of plants is extremely heterogeneous reflecting the 12,000 ft. difference in elevation in the IMR, frontal storms in winter and summer monsoons in the south, soils derived from a variety of parent materials and geological history. The parent materials range from Precambrian quartzite in the Uinta Range to lava outflows less than a thousand years old in the Snake River Plains Division. Other parent materials include sedimentary shales, mudstones, sandstones, metamorphic granite and limestone, alkaline lake deposits and aeolian sand dunes.
Locally, lead concentrations can be high enough to restrict the vegetation to tolerant species. The resulting "burned" areas are used by prospectors to locate silver deposits in central Nevada. The interaction of parent material and climate has produced soils ranging from caliches rich in calcium carbonate to acidic soils derived from the Uinta Range quartzite.
The present vegetation of the IMR is a result of the heterogeneous distribution of habitats and history of the region, especially climatic changes during the Quaternary. Presently, two alternate hypotheses explain the distribution of plants in the Great Basin Division. Wells, based on fossil packrat midden research, suggested that during the last glacial-pluvial 9,000 yr-BP, the montane conifers were contiguous while subalpine conifers survived at higher elevations in refugia.
Axelrod and Raven, on the other hand, suggested that the montane and subalpine conifers have not formed a contiguous population since the Miocene and have persisted at mid elevations in refugia. Other refugia existed at mid-altitude sites in the southern Rocky Mountains, the Mohave Desert, and the southern reaches of the Great Basin. As the climate warmed during the early Holocene, plants spread north rapidly, with some rates of migration as fast as 2000 m./yr. Some of the rapid dispersal was due to aerial transport by jays and Clark's nutcracker. Assisted by these corvid birds, single-needle pinyon dispersed from Late Pleistocene refugia in the what is now the Mohave desert to its modern range from southern California to the Idaho-Utah border in a few thousand years during the middle Holocene.
The results of the interaction between suitable habitats, local extinction for many species during glaciation, and reinvasion from refugia are locally depauperate communities. Some of the subalpine forests in the Great Basin Division, for instance, contain Englemann spruce but lack its common associate, subalpine fir. Another result is very small numbers of some species. Ponderosa pine, for instance, is represented by only five individuals in the Schell Creek Range, Nevada.
Very little is known about the distribution of fungi in the IMR, either because label data has not been summarized or a paucity of collecting. Truffles and false-truffles in general are found, as expected, where their plant associates are found. It appears, however, that the truffle mycoflora in the Great Basin Division is depauperate compared to that in the Uinta and Wasatch Mountain Divisions. Local populations may produce a large number of truffles, but the same species may be absent in adjacent forest islands.
This site uses data from the Intermountain Herbarium, New York Botanic Garden, and fungal collections from the University of Michigan herbarium.
Slightly more than a third of the collection in the Intermountain Herbarium has been databased so far; about 14% of the records are georeferenced, many retrospectively. Major contributors to its vascular plant collection, as reflected in the herbarium's database, are Bassett Maguire, Noel Holmgren, Leila Shultz, and Art Holmgren. Its mushroom and truffle specimens come primarily from collections by Brad Kropp and Michael Piep plus exsiccatae specimens. The records of fungi contributed by the University of Michigan Fungus Collection are primarily those of Robert Fogel, Alexander H. Smith, Jack States, and Ellen Trueblood.
References
Axelrod, D.I., and Raven, P.H. 1985. Origins of the Cordilleran Flora. J. Biogeography 12:21-47.
Betancourt, J.L., T.R. Van Devender and P.S. Martin. 1990. Packrat middens: The last 40,000 years of biotic change. Univ. Arizona Press, Tucson.
Charlet, D.A. 1996. Atlas of Nevada conifers: A phytogeographic reference. Univ. Nevada Press, Reno.
Cronquist, A., A.H. Holmgren, N.H. Holmgren and J.L. Reveal. 1972. Intermountain flora: Vascular plants of the Intermountain West, U.S.A., vol. 1. Hafner Publ. Co., New York.
Heusser, L. 1998. Direct correlation of millennial scale changes in western North American vegetation and climate with changes in the California current system over the past similar to 60K yr. Paleoceanography 13:252-262.
Hockett, B.S. 2000. Paleobiogeographic changes at the Pleistocene-Holocene boundary Near Pintwater Cave, Southern Nevada. Quaternary Research 53:263-269.
Huntley, B., Bartlein, P.J., and Prentice, I.C. 1989. Climatic Control of the Distribution and Abundance of beech (Fagus L) in Europe and North America. Journal of Biogeography 16:551-560.
Madsen, D.B., Rhode, D., Grayson, D.K., Broughton, J.M., Livingston, S.D., Hunt, J., Quade, J., Schmitt, D.N., and Shaver, M.W. (2001) Late Quaternary Environmental Change in the Bonneville Basin, Western USA. Palaeogeography, Palaeoclimatology Palaeoecology 167:243-271.
Rhode, D., and Madsen, D.B. 1995. Late Wisconsin Early Holocene vegetation in the Bonneville Basin. Quaternary Research 44:246-256.
Tidwell, W.D. 1972. Physiography of the Intermountain West. pp. 10-18. In: Cronquist, A., A.H. Holmgren, N.H. Holmgren and J.L. Reveal. Intermountain flora: Vascular plants of the Intermountain West, U.S.A., vol. 1. Hafner Publ. Co., New York.
Thompson, R.S. 1990. Late Quaternary vegetation gradients through the Great Basin. pp. 200-239. In: Betancourt, J.L., T.R. Van Devender and P.S. Martin. Packrat middens: The last 40,000 years of biotic change. Univ. Arizona Press, Tucson.
Wells, P.V. 1983. Paleobiogeography of montane islands in the Great Basin since the last glaciopluvial. Ecological Monographs 53:341-382.
Wilkinson, D.M. 1998. Mycorrhizal fungi and Quaternary plant migrations. Global Ecology and Biogeography Letters 7:137-140.
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Utah Extension Service and the Intermountain
Herbarium.
Last Update: 23 Nov 2005.
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