Sixty-seven Years of Landscape Change in the Last, Large Remnant of the Pacific Northwest Bunchgrass Prairie

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 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 that have occurred since Euro-American settlement began in the late nineteenth century.