Environmental controls over forest succession of a former oak savanna, Jim's Creek, Willamette National Forest, Oregon

Abstract

Oak savanna is believed to have existed in North America for 20-25 million years (Barry and Spicer 1987). When Euro-Americans began settling the Midwestern United States, oak savanna was found from Minnesota to Texas and had been relatively stable there for thousands of years (Nuzzo 1986). Approximately 12,000,000 ha of oak savanna were found in the upper Midwestern United States when settlement of the region began in the early nineteenth century (Nuzzo 1986). In the Pacific Northwest, oak savanna is estimated to have covered 500,000 ha prior to Euro-American settlement around 1850 (Vesely and Tucker 2004). Today, oak savanna is considered critically endangered in both the Midwestern United States and Oregon's Willamette Valley (Noss et al. 1995).