Impacts of nineteenth century grazing at Capitol Reef National Park as determined through packrat midden analysis.
Kenneth L. Cole, USGS Colorado Plateau Research Station, Northern Arizona University. 928-523-7767
Norman Henderson, Glen Canyon National Recreation Area, Page, Arizona.
David S. Shafer, U.S. Department of Energy.
Lyndon K. Murray, Anza-Borrego State Park, CA.
Capitol Reef National Park, in southeastern Utah, grants several ongoing grazing leases. The effect of this ongoing grazing on the natural vegetation is not known partly because the natural (presettlement) vegetation was unknown. This study used plant parts collected from fossil and recent packrat middens to reconstruct past grazing impacts on presettlement range vegetation. The results demonstrate that drastic vegetation changes, unprecedented during the last 5,000 years, occurred during the last century. Plant species favored by cattle for grazing and by sheep for browsing were locally eliminated while other less palatable species became more common.
Mid- to Late Holocene vegetation change from a remote high desert site was reconstructed using plant macrofossils and pollen from nine packrat middens ranging from 0 to 5400 years in age. Presettlement middens consistently contained abundant macrofossils of plant species palatable to large herbivores that are now absent or reduced, such as winterfat (Ceratoides lanata) and ricegrass (Stipa hymenoides). Macrofossils and pollen of pinyon pine (Pinus edulis) , sagebrush (Artemisia spp.) and roundleaf buffaloberry (Sheperdia rotundifolia) were also recently reduced to their lowest levels for the 5400 year record. Conversely, species typical of overgrazed range, such as snakeweed (Gutterezia sarothrae), viscid rabbitbrush (Chrysothamnus visidiflorus), and Russian thistle (Salsola sp.) were not recorded prior to the historic introduction of grazing animals. Pollen of Utah juniper (Juniperus osteosperma) also increased during the last 200 years. These records demonstrate that the most severe vegetation changes of the last 5400 years occurred during the last 200 years. The nature and timing of these changes suggest that they were primarily caused by nineteenth century open-land sheep and cattle ranching. The reduction of pinyon and sagebrush concurrent with the other grazing impacts suggest that the effects of cattle grazing at modern stocking levels may be a poor analog for the effects of intense sheep grazing during drought. The reduction of pinyon pine by sheep browsing contradicts the widespread concept of overgrazing causing expansion of pinyon-juniper woodland. Juniper expanded, but pinyon was severely reduced emphasizing the individualistic nature of the two species.
Cole, Kenneth L., Norman Henderson, and David S. Shafer, 1997. Holocene vegetation and historic grazing impacts at Capitol Reef National Park reconstructed using packrat middens. Great Basin Naturalist, 57: 315-326. Full Publication:
Gif Image Comparison (250k): Modern photo of study site and reconstructed presettlement photo. Grass, winterfat, and pinyon pine were formerly more extensive, while snakeweed and rabbitbrush are only present after settlement. Presettlement photo reconstructed via digital editing to add past plant species.
Gif Image (90k): Diagram of plant macrofossil concentration from packrat middens.
Gif Image (70k): Diagram of fossil pollen from packrat middens
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