Contents
The Project Area / Research Design and Methods / Project Results to Date
THE PROJECT AREA Western State College is located in Gunnison, Colorado, in the heart of the Upper Gunnison Basin, a high-elevation (2300-4000 m elevation) ecosystem situated within some of the highest ranges of the Rocky Mountains. This 11,000 km2 basin has no outlet lower than 2650 m (8700 ft) except to the west through the Black Canyon of the Gunnison. This canyon includes a 20 km section that is over 700 m deep and only 400 m across at its narrowest point and acts as a filter for the movement of species in and out of the Basin.
No other large mountain basin in the Rocky Mountain region is enclosed by such high-elevation passes, and it is this feature that we hypothesize has caused the unusual communities now present in the Upper Gunnison Basin.
Ecologically, the flora and fauna in this Basin appear to be depauperate in taxa that should occur here, and the region has been recognized for its unique biogeographic characteristics for plants and animals. For example, piñon trees (Pinus edulis) are notably absent throughout the Basin though juniper, with which piñon normally occurs, is found in numerous areas. Colorado vertebrates that occupy habitats similar to those of the Upper Gunnison Basin, but absent within it, include Woodhouse's toad (Bufo woodhousei), short-horned lizard (Phrynosoma douglassii), collared lizard (Crotaphytus collaris), western rattlesnake (Crotalus viridis), Merriam's shrew (Sorex merriami), sagebrush vole (Lemmiscus curtatus), and thirteen-lined ground squirrel (Spermophilus tridecemlineatus). Fossil evidence indicates that many of these species, including toad (Bufo woodhousei or B. boreas), sagebrush vole, and thirteen-lined ground squirrels, existed in the Gunnison region during the late Pleistocene. This evidence comes primarily from a single fossil site, Haystack Cave, which has produced a rich record of late Pleistocene vertebrates.
Ecological isolation of extant species in the Upper Gunnison Basin also is apparent. A population of sage grouse (Centrocercus urophasianus), for example, has been isolated in the Basin apparently since the Pleistocene and is now being described as a distinct, endemic species. Several plant species are endemic to the Basin as well and there have been suggestions (unpublished) that the Gunnison's prairie dog (Cynomys gunnisoni) may represent a taxon distinct from populations outside the Basin. The development of these ecological anomalies may be the result of the unique topography and climate of the Upper Gunnison Basin that together have caused local extirpations and isolation of species over thousands of years, but this hypothesis remains to be tested.
The purpose of our ongoing research project is to reconstruct the Holocene paleoecology of the Upper Gunnison Basin so that we may test hypotheses on the development of modern communities in this region. Our undergraduate field and laboratory research program gives our students experiences in the design, implementation and completion (including papers and conference presentations) of an advanced research project. We also are stressing the importance of interdisciplinary collaboration in addressing complex research questions in this program. In 1996 and 1997, funding was received from the Colorado Historical Society to investigate the paleoecology and archaeology of the Upper Gunnison Basin. This research, among other things, allows us to search for correlations between climate change and cultural change while reconstructing the history of community development in the Basin.
Our interdisciplinary approach in this project includes studies of ancient packrat middens, palynological investigations of old bog sediments and arroyos, archaeological data from surveys and excavations, and surveys and mapping of modern communities. Radiocarbon analyses are being completed on organic samples using conventional and accelerator mass spectrometry (AMS) techniques to provide absolute ages on paleoenvironmental samples. Geographic Information Systems (GIS) technology is being applied in field surveys using a Global Positioning System (GPS) to locate and map pollen and midden sample points and modern plant communities. All phases of this research are being conducted with undergraduate students who integrate this work with class projects, independent studies, and scholarships obtained from Western State College's unique Thornton Biology Research Program.
In 1996/1997, two undergraduate biology students, Ellen Wambach and Wendelyn Plourde, assisted Dr. Steve Emslie with field and laboratory studies of pollen and midden samples. This research also included collaboration with Dr. Vera Markgraf, University of Colorado Institute of Arctic and Alpine Research, so that the students could be trained in the processing and analysis of pollen samples at this laboratory. In 1997, additional funding was received from the National Geographic Society to support excavations and stabilization of sediments in Haystack Cave, a late Pleistocene site located 22 km WSW of Gunnison that contains a rich vertebrate record. Students from Anthropology classes at Western State have participated in the initial research conducted at this site in fall 1997.
Floral (charcoal, wood, pollen) and faunal data from numerous archaeological sites in the Upper Gunnison Basin are supplementing paleoecological information gathered in this project. The Basin contains a rich archaeological record that spans the Holocene (11,000 to 1000 years before present, B. P.). This record has been the subject of intense investigation by Dr. Mark Stiger and his students for the past six years with funding from the Colorado Historical Society and the City of Gunnison. One Archaic site, the Tenderfoot Site, is being excavated as part the Western State College field school in archaeology that is offered each summer. This site has a temporal range of 8000 to 1000 B. P., as indicated by radiocarbon dates on numerous cultural features (hearths and storage pits). Features, stone tool technology and biological data from this site also indicate that prehistoric humans shifted their methods of environmental exploitation in the Basin over time, perhaps in correlation to climate change, but additional data are needed.
Modern environments in the Upper Gunnison Basin are being mapped using our GIS laboratory and ongoing mapping program. Dr. Allen Stork (geologist) and Dr. John Sowell (botanist) and their undergraduate students have recently produced a land cover map of the Basin through analysis of the four bands provided from Landsat MSS images. Future research will include the analysis of the Landsat TM images, which with their higher resolution and seven-bands, will enable us to produce more accurate and precise land cover maps, particularly in the vicinity of the packrat middens, pollen cores, and archaeological sites that are sampled for paleoecological data. Field surveys of plant communities and indicator species, or those plant and animal species that have unique spatial and temporal distributions as measured by the paleoecological studies, will allow us to produce a map that not only documents current communities but also key species that will facilitate the modeling of past changes in community distribution.
Packrat Midden Studies
Packrat midden analyses have been of considerable importance in paleoecological reconstruction in the Southwest since the early 1960's. These middens, composed of plant remains (including seeds, leaves, and sticks), bone, and other nest debris that often become solidified with dried packrat urine and feces, provide a remarkable record of plant communities that once existed in the immediate vicinity of the midden location (packrats collect plant and bone only within about 50 m of their nest).
Moreover, radiocarbon dates on selected species preserved in the middens give an absolute age for that community. Most midden studies have been conducted in lower elevation regions in the Southwest and on the Colorado Plateau. A recent survey of all radiocarbon-dated middens in western North America indicated that the majority (90%) was collected between 300 to 2200 m elevations.
Though packrats today live in a variety of habitats that extend to timberline (about 3500 m), one reason for the lack of samples from higher elevations and mountain zones is that middens are not as well preserved in these moister areas compared to desert and semi-arid regions. We have found that the dry, interior region of the Upper Gunnison Basin, unlike other montane environments, is ideal for long-term preservation of packrat middens located in sheltered areas (deep crevices and caves), thereby providing a rare opportunity to apply this paleoecological tool in a mountain ecosystem. Surveys conducted in summer 1996 with two undergraduate students from Western State College resulted in the location and collection of 45 midden samples throughout the Basin ranging in elevation from 2350 to 3260 m (7700-10,700 ft). Preliminary analyses of 20 of these middens have been completed. Radiocarbon dates on packrat feces and/or individual plant remains in the middens indicate that they range in age from modern to 3320 B. P. Several middens contain plant remains of species that no longer occur in the vicinity of midden site. The oldest midden at Red Creek, 27 km WSW of Gunnison, produced abundant remains (needles, seeds) of Ponderosa (Pinus ponderosa) and Lodgepole pine (P. contorta) indicating a forested environment where today there is primarily sagebrush and a few scattered juniper and Douglas fir trees. Although Ponderosa pine occur within a kilometer of the site, the nearest Lodgepole pines are at least 14 km north and approximately 600 m higher in elevation from this site. Thus, data from this midden suggest that a cooler, drier environment existed in the Basin over 3300 years ago compared to today, thereby allowing Lodgepole pines to extend to lower elevations. Other middens have indicated similar changes with movement of Bristlecone (P. aristata)/Limber pine (P. flexilis) forests to lower elevations at 240 and 560 B. P.
Given enough sampling points through these long-term investigations, the results will allow us to model past environmental changes with community change and the timing of species extirpations in the Basin. Using multivariate statistical analysis that accounts for shifts in indicator species, as well as the Basin's topography, a temporal sequence of paleoenvironmental maps will be constructed. These maps and data will not only allow us to address specific hypotheses about basin communities and species, but also will provide knowledge on community history and development that can be applied to molecular investigations of endemic species and subspecies with a known history of isolation, ongoing archaeology studies of human cultural adaptations in the Basin, and global change in mountain environments.
Haystack Cave
This cave is a small lava tube in volcanic tuff located on the southern rimrock of Haystack Mesa 22 km WSW of Gunnison. Excavations were first completed in the cave in 1978 by the National Park Service in order to evaluate the cultural significance of the site. A large collection of vertebrate remains, and some cultural remains, were recovered in these excavations and include an extensive late Pleistocene fauna. Two extinct taxa were identified, a cheetah (cf. Acinonyx trumani) and horse (Equus sp.). Later, additional excavations were completed by the University of New Mexico adding to the vertebrate fauna; these data have not yet been published. In 1997, Dr. Steve Emslie received funding from the National Geographic Society to salvage and screen collapsed sediments in an open trench left in the cave from previous investigations, stabilize the remaining in situ sediments, and collect an additional stratigraphic sample of plant and animal remains that span the Holocene in age. In October 1998, Dr. Anna Backer and 10-15 students in her Anthropology class assisted Dr. Emslie in removing and screening collapsed sediments from the cave (see figure).
These efforts produced one new species in the fauna, black-footed ferret (Mustela nigripes), previously unknown from the Upper Gunnison Basin. Identification of the jaw that was recovered of this species was confirmed by Dr. Elaine Anderson, Denver Museum of Natural History.
Cave sediments were stabilized using a new method designed by Dr. Emslie and Tom Verry, a former student from Western State College. Using plywood and wood braces, wooden supports were constructed to match the size of the exposed trench wall in the cave. After covering the in situ sediments with plastic sheeting, the plywood was placed against the trench wall leaving a 5-10 cm gap between the sediments and the plywood. Expanding insulation foam was sprayed into the gap filling the space up to three-quarters to the top of the wall (see figure).
As this foam hardened, it expanded to fill the remainder of
the gap and formed a solid foam layer that fit precisely to the
contours of the trench wall. This foam acts as a semi-permanent
support for the trench wall thereby protecting the in situ sediments
from further collapsing that would cause loss of data and mixing
of sediments. Additional work in the cave was completed in
May/June 1998.
Additional information on this research project can be obtained by contacting Dr. Steve Emslie (paleoecology; Dept. of Biological Sciences, Univ. of North Carolina, Wilmington, NC 28403, Office: (910) 962-3357; emslies at uncw.edu) or Dr. Mark Stiger (archaeology; Anthropology Program; mstiger@western.edu), Western State College, Gunnison, CO 81231. This page was revised in April 1998.