Natural Areas Journal . to advance the preservation of natural diversity A publication of the Natural Areas Association - www.naturalarea.org © Natural Areas Association Sixty-seven Years of Landscape Change in the Last, Large Remnant of the Pacific Northwest Bunchgrass Prairie Anne M. Bartuszevige1 1Playa Lakes Joint Venture 2575 Park Lane, Suite 110 Lafayette, CO 80026 USA Patricia L. Kennedy2,4 Robert V. Taylor3 2Oregon State University Eastern Oregon Agricultural Research Center – Union P.O. Box E Union, OR 97883 USA 3The Nature Conservancy Northeast Oregon Field Office 906 S River St. Enterprise, OR 97828 USA 4 Corresponding author: [email protected] Natural Areas Journal 32:166–170 R E S E A R C H N O T E ABSTRACT: The Zumwalt Prairie in northeastern Oregon is the last large remnant of the Pacific Northwest Bunchgrass Prairie. Compared to other prairies in North America, relatively little is known about these arid temperate grasslands as the majority disappeared quickly after Euro-American settlement. In this paper we describe the landscape history of the Zumwalt Prairie through interpretation of historical aerial photos. Beginning with photos taken in 1938, we examined photos for area of cultivation and woody vegetation and number of buildings and stock ponds. Using data collected in 1976 and 2001, area of • woody vegetation was further classified as aspen (Populus tremuloides, Michx.), conifers, and shrubs for analysis of trends. Area in cultivation and number of buildings decreased over the 67 years we examined. In contrast, the number of stock ponds increased. Overall, the area of woody species increased over the Sixty-seven Years of period of study; area of aspen declined while acreage of conifers and shrubs increased. The land cover and land-use changes observed on the Zumwalt Prairie reflect the complex social and economic changes Landscape Change that have occurred since Euro-American settlement began in the late nineteenth century. Index terms: aspen, cattle grazing, cultivation, grassland, historic aerial photos, private lands, shrub in the Last, Large encroachment, stock ponds, tree invasion Remnant of the INTRODUCTION versity of forbs (The Nature Conservancy, Pacific Northwest unpubl. data). Shallow rooted species such The Zumwalt Prairie (hereafter “Zumwalt”) as Sandberg’s bluegrass (Poa secunda, J. Bunchgrass Prairie is located in Wallowa County in northeast Presl) and one-spike oatgrass (Danthonia Oregon and is the last large (approximately unispicata,(Thurb.) Munro ex Macoun) 64,000 ha) relict of the Pacific Northwest share dominance with dwarf-shrubs and 1 Bunchgrass Prairie. The prairie is situated forbs such as Douglas’ buckwheat (Eriogo- Anne M. Bartuszevige on a rolling basalt tableland (elevation num douglasii, Benth), hoary balsamroot 1Playa Lakes Joint Venture 1060 – 1680 m) deeply incised by several (Balsamorhiza incana, Nutt.), and dwarf 2575 Park Lane, Suite 110 tributaries of the Grande Ronde and Imnaha yellow fleabane (Erigeron chrysopsidis, A. Lafayette, CO 80026 USA rivers. Annual precipitation for the area is Gray) in areas with more shallow, rocky approximately 49 cm/year, as measured by soils (The Nature Conservancy, unpubl. Patricia L. Kennedy2,4 the nearest long-term weather station in data). Robert V. Taylor3 Enterprise, Oregon (data from 1965 – 2005; Western Regional Climate Center 2009). Historically, shrub and forest vegetation are 2Oregon State University Winters are cold and relatively moist; mean localized and restricted to areas with deeper Eastern Oregon Agricultural Research daily minimum temperatures were -7 ºC soils, cooler micro-climates, or higher soil Center – Union (December – March). Summers are very moisture such as valleys, swales, slopes P.O. Box E warm and relatively dry, though June’s with northerly aspects, and riparian areas. Union, OR 97883 USA average precipitation of 4.9 cm exceeds The streams of the Zumwalt are mostly that of any winter month. Daily maximum first- and second-order and ephemeral, 3The Nature Conservancy temperatures during June – September running only during spring and early sum- Northeast Oregon Field Office average 27 ºC. mer. Riparian vegetation includes black 906 S River St. hawthorn (Crataegus douglasii, Lindl.), Enterprise, OR 97828 USA Soils on the Zumwalt are predominantly mockorange (Philadelphus lewisii, Pursh), Xerolls. Plant productivity and species and common snowberry (Symphoricarpos • composition vary strikingly as a function albus, (L.) S.F. Blake). In areas where of slope, aspect, and soil characteristics soils are saturated throughout the grow- (Loy et al. 2001; U.S. Department of Ag- ing season, willow-dominated (Salix spp.) riculture 2010; Schmalz 2011). Because of communities occur. 4 Corresponding author: its dry climate and mostly shallow soils, [email protected] the majority (> 90%) of the Zumwalt The Nez Perce and other indigenous historically supported steppe vegetation peoples hunted game and gathered plant dominated by bunchgrasses, forbs, and foods on the Zumwalt for thousands of sub-shrubs. Shallow to moderately deep years. After acquiring livestock in the soils are dominated by Idaho fescue (Fes- 1700s, the area was also used for grazing tuca idahoensis, Elmer), prairie junegrass of their horses (Equus ferus) and cattle (Koeleria macrantha, (Ledeb.) Schult), and (Bos taurus) during spring and summer. Natural Areas Journal 32:166–170 bluebunch wheatgrass (Pseudoroegneria Indigenous people were removed from spicata,(Pursh) A. Lӧve), and a high di- the area in 1877, shortly after the arrival 166 Natural Areas Journal Volume 32 (2), 2012 of Euro-American settlers. These settlers METHODS AND MATERIAL distinguish aspen canopy from other types brought large herds of cattle and horses of tree canopy. and acquired lands through the Homestead The study area was stratified based on Acts of 1862 and 1909. Title to land was habitat suitability as part of another inves- Between May and July 2005, we ground- granted to applicants who “proved up,” tigation designed to examine the influence truthed the data in the 2001 DOQQ. These which generally required evidence of farm- of landscape factors on territory occupancy field observations were used to validate fea- ing. Zumwalt homesteaders were, thus, of prairie nesting raptors (Bartuszevige et ture identifications on photos from previous compelled to plow land even though lands al., unpubl. data). We used this stratified years. In 2006, we made notes regarding were often unsuitable or marginal for this random sampling approach for the land- the type of woody vegetation found in the activity. The extreme weather and unpro- scape examination we report here. Based plots. We used three categories: conifer ductive soils of the prairie forced many on historic data (1979 – 80: Cottrell 1981) [mostly ponderosa pine (Pinus ponderosa, homesteaders to sell off their lands. Lands and published habitat literature, the major- C. Lawson) and Douglas fir (Pseudotsuga were thus consolidated into larger holdings, ity (~75%) of the study area was deemed menziesii, (Mirb.)Franco)], aspen, and and cultivated lands were re-seeded using suitable habitat. Areas deemed unsuitable shrubs [mostly black hawthorn and a few exotic pasture grasses. When severe winters were flat, high elevation ridge tops with willows and cottonwoods (Populus sp.)]. resulted in catastrophic die-offs of cattle little woody vegetation. We assume the in the 1880s, many ranchers switched to land-use changes we document in our RESULTS AND DISCUSSION raising sheep (Ovis aries)). By the 1940s, random samples of suitable habitat are low prices for sheep resulted in a return applicable to these regions but we cannot Based on our examination of the aerial to cattle as the favored choice of stock evaluate this assumption. Historical land- photos, several profound changes have oc- (Rowley 1985; Williams and Melville scape data were collected on 102, 800-m curred on the Zumwalt between 1938 and 2005, unpubl. data). These ranches utilized x 800-m plots. Because we sampled plots 2001 (Table 1). The number of buildings on a pastoral system of grazing where animals randomly, we extrapolate our observations the Zumwalt declined over time from 83 in were wintered in low-elevation canyons to the entire prairie remnant. 1938 to 30 in 2001 in the examined plots and moved to the prairie only during sum- (Table 1). This likely represents a decrease mer and fall. Currently, over 95% of the Historical aerial photographs were ob- in both dwellings and farm-related build- Zumwalt is privately owned and is utilized tained for the following years: 1938, ings and may reflect demographic changes primarily for the production of beef cattle, 1947, 1956, 1971, 1976, 1984, and 1994. that were taking place in the region. The which are grazed from summer to fall. To represent the current landscape, we population of Wallowa County declined Because of this history, the Zumwalt still obtained 2001 Digital Ortho Quarter Quad consistently during this period – from a supports a mostly native flora with low photographs (DOQQs) – the most recent maximum of nearly 10,000 to just over cover of invasive exotic species (Johnson aerial dataset available during the study 6000 in 1970 (U.S. Census Bureau 1995). and O’Neil 2001; Anonymous 2005; Kagan period. A complete set of aerial photos Population declines were likely even more et al. 2008; Kennedy et al. 2009). for 1947 was unavailable (approximately pronounced on the Zumwalt as homestead- 25% of the study area was missing, 18 ers left to re-settle in other parts of the Although certain portions of the Zumwalt plots); therefore, landscape descriptions county, which provided greater economic (i.e., “Leap”) have and continue to sup- for this year are incomplete. The photos opportunity. port significant agricultural activity, the were georeferenced to the 2001 DOQQs northern portion of this area has experi- using ArcMap (version 9.x, ESRI 2007). Between 1938 and 2001, there was a 90% enced minimal conversion and includes a Important landscape features were digitized reduction in the area cultivated on the high diversity of native vegetation types. from these photos.