Presettlement Vegetation of Southern Beaverhead County, Montana
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PRESETTLEMENT VEGETATION OF SOUTHERN BEAVERHEAD COUNTY, MONTANA Peter Lesica & Stephen V. Cooper Montana Natural Heritage Program P.O. Box 201800 1515 East Sixth Avenue Helena, Montana 59620-1800 © 1997 Montana Natural Heritage Program Prepared for: USDI Bureau of Land Management State Office P.O. Box 36800 Billings, MT 59107-6800 (Assistance Agreement No. 1422-E950-A1-0006; Task Order # 32) and USDA Forest Service Beaverhead-Deerlodge National Forest 420 Barrett Street Dillon, MT 59725 (Challenge Cost-Share Agreement No. 11-01-02-95-36) This document should be cited as follows: Lesica, P. and S. V. Cooper. 1997. Presettlement vegetation of southern Beaverhead County, Montana. Unpublished report to the State Office, Bureau of Land Management and Beaverhead-Deerlodge National Forest. Montana Natural Heritage Program, Helena, MT. 35 pp. CONTENTS INTRODUCTION............................................................................................................. 3 METHODS ...................................................................................................................... 3 RESULTS........................................................................................................................ 6 Hypothesis 1. Bison were common in southern Beaverhead County .................. 6 Hypothesis 2. Livestock grazing was common in the later part of the 19th Century ................................................................................................................ 7 Hypothesis 3. Palatable bunch grasses had a higher density, and unpalatable forbs had a lower density...................................................................................... 7 Hypothesis 4. Coniferous forests were less extensive, and densities of coniferous trees were lower.................................................................................. 8 Hypothesis 5. Aspen (Populus tremuloides) forests were more extensive .......... 9 Hypothesis 6. Sagebrush (Artemisia spp.) steppe was less extensive, and density of sagebrush was lower............................................................................ 9 Hypothesis 7. Basin big sagebrush (A. tridentata ssp. tridentata) was more common along many streams............................................................................. 12 Hypothesis 8. Basin wildrye (Elymus cinereus) was more common along many streams..................................................................................................... 13 Hypothesis 9. Willows (Salix spp.) were more common along many streams ... 14 Hypothesis 10. Mountain mahogany (Cercocarpus ledifolius) woodland was less extensive ............................................................................................................ 15 Hypothesis 11. Cottonwood (Populus trichocarpa, P. angustifolia) forests were more extensive ................................................................................................... 16 DISCUSSION................................................................................................................ 18 Agriculture .......................................................................................................... 18 Fire suppression ................................................................................................. 18 Grazing............................................................................................................... 19 1 ACKNOWLEDGMENTS................................................................................................ 21 LITERATURE CITED .................................................................................................... 22 APPENDICES ............................................................................................................... 27 A. Observations of bison made by early trappers in Beaverhead and adjacent Madison counties................................................................................................ 27 B. Comparison of vegetation dominated by Elymus cinereus or Artemisia tridentata ssp. tridentata inside and outside livestock exclosures in southern Beaverhead County............................................................................................ 29 C. Number of willow plants along steam banks inside and outside of livestock exclosures on three stream reaches in southern Beaverhead County ............... 33 TABLES: 1. Hypotheses on presettlement vegetation of southern Beaverhead County 4 2 INTRODUCTION Individual species have evolved with and adapted to landscapes that remain relatively stable for thousands of years. In a comparativley short time Europeans have radically changed many of these systems through fire suppression, water diversion and livestock grazing. Knowing how landscapes have changed during the past century allows managers to better understand what conditions plants and animals are adapted to and to develop hypotheses regarding changes in their abundance and distribution. Unfortunately, there is little systematically collected information on presettlement vegetation. Nonetheless, much can be learned about presettlement vegetation from accounts of early explorers and travellers and early photographs (Dorn 1986, Gilkerson 1980, Gruell 1983, Vale 1975). Our study uses historical evidence to describe presettlement vegetation in various parts of southern Beaverhead County and adjacent areas. We then compare these descriptions to current vegetation to determine how it has changed in the interim. Finally, we infer the causes of observed changes using information from the ecological research literature. METHODS Our study area is Beaverhead County south of the lowest reach of the Big Hole River, just north of the town of Dillon. We have also included information from adjacent northern Beaverhead County, Madison County and Lemhi County, Idaho. At the start of our study we proposed a set of hypotheses suggested to us by previous studies or our personal experience (Table 1). We collected information relating to these hypotheses from three sources. Primary sources of information are journals of explorers and early settlers that traveled through or lived in the area (Knowles and Knowles 1993). We collected descriptions of vegetation from these sources and revisited the described areas in August 1996 to determine how vegetation 3 Table 1. Hypotheses on presettlement vegetation of southern Beaverhead County. We found no information for hypotheses 12-15. 1. Bison were common in southern Beaverhead County. 2. Livestock grazing was common in the later part of the 19th Century. 3. Palatable bunch grasses had a higher density, and unpalatable forbs had a lower density. 4. Coniferous forests were less extensive, and densities of coniferous trees were lower. 5. Aspen (Populus tremuloides) forests were more extensive. 6. Sagebrush (Artemisia spp.) steppe was less extensive, and density of sagebrush was lower. 7. Basin big sagebrush (A. tridentata ssp. tridentata) was more common along many streams. 8. Basin wildrye (Elymus cinereus) was more common along many streams. 9. Willows (Salix spp.) were more common along many streams. 10. Mountain mahogany (Cercocarpus ledifolius) woodland was less extensive. 11. Cottonwood (Populus trichocarpa, P. angustifolia) forests were more extensive. 12. Relative abundance of three-tip sagebrush (Artemisia tripartita) compared to big sagebrush has declined. 13. Toxic forbs have increased and palatable forbs have decreased 14. Tufted hairgrass (Deschampsia cespitosa) has decreased in wetlands and riparian areas. 15. Baltic rush (Juncus balticus) has increased in wetland areas. 4 had changed. These are the most reliable sources of information because many of the descriptions predate livestock grazing in the study area. Meriwether Lewis and William Clark led an exploratory expedition for the U.S. Government in 1804-06. Warren A. Ferris was a fur trapper in Montana in 1831-34. John Work was a British fur trader in Montana in 1831-32. Osborne Russell was a fur trapper in Montana in 1834-43. John Mullan led a survey party for the Stevens Railroad Survey in Montana in 1853-54. William Raynolds led a U.S. Army expedition exploring Montana in 1859-60. Granville Stuart was a rancher and businessman in Montana from 1857-1919. Albert Brackett was a colonel in the U.S. Army in Montana in 1869. Ferdinand Hayden led expeditions for the U.S. Geological Survey in Montana in 1871 and 1872. Secondary sources are compilations of old/modern comparison photography (Gilkerson 1980, Gruell 1983). The earliest photographs examined date from the 1870's. However, most are from near the turn of the century or later, well after livestock grazing was common in the 1870's. We did not use photographs taken after 1910 to examine the effects of grazing. Tertiary sources are data gathered from intentional or unintentional experiments conducted in the study area; i.e., livestock exclosures or fence line grazing contrasts. 5 RESULTS Hypotheses, stated in bold print, are considered below in order in which they appear in Table 1. 1. Bison were common in southern Beaverhead County. Bison were generally commented on and reported to be common by the early explorers and trappers. However, it also appears that the herds moved frequently and could not always be found. Forage for livestock was minimal in areas recently grazed by bison. Bison were common in the broad valleys below Dillon. Ferris described the Jefferson River Valley just south of Whitehall as "alive with