Phytoliths in plants and soils of the interior Pacific Northwest, USA Mikhail S. Blinnikov T Department of Geography, St. Cloud State University, St. Cloud, MN 56301-4498, USA Received 13 July 2004; received in revised form 14 February 2005; accepted 23 February 2005 Abstract Phytoliths are a useful paleoproxy in the arid environments. This modern analog study assessed variability of silica phytoliths in 38 species of plants and 58 modern soil samples from 24 locations in the interior Pacific Northwest. Phytoliths were grouped into 20 broadly defined morphotypes based on their 3D shapes under light microscope and presumed anatomical origin within the plant. Grasses (all C 3 ) have most diverse forms. Most examined conifers, sedges and some shrubs produce identifiable phytoliths as well. Eight different community types can be distinguished based on their modern phytolith record in soils, including shrublands, four regional grassland types, and three forest types. Low percentages of grass phytoliths and high incidence of non-grass forms correspond to forest vegetation in the region today, while certain grass phytoliths allow further differentiation among different grasslands. Phytolith assemblages were further compared to 5 environmental variables, including elevation, mean annual temperature, mean annual precipitation, a moisture index and a growing-degree days index. Some morphotypes tend to occur within relatively narrow environmental windows, which could enable direct paleoenvironmental inferences from phytoliths in geological sediments from the region. D 2005 Elsevier B.V. All rights reserved. Keywords: climate; modern analogs; Oregon state; plant opal; vegetation; Washington state 1. Introduction Phytolith analysis is a powerful, yet relatively underutilized, method of paleoenvironmental recon- struction that can be used to supplement pollen and macrofossil analyses (Piperno, 1988; Pearsall, 2000). In North America, both archaeologists (Rovner, 1971; Mulholland, 1993) and paleoecologists (Kurman, 1985; Fredlund and Tieszen, 1997a,b; Kearns, 2001; Blinnikov et al., 2002) used phytoliths to infer a range of paleoenvironmental conditions. Despite some early applications of phytoliths in paleoenvironmental and paleopedological work (Smithson, 1958; Witty and Knox, 1964; Twiss et al., 1969; Rovner, 1971; Norgren, 1973), the use of phytoliths in paleoecology remains uncommon (Piperno and Persall, 1993). Recent studies suggest that any paleoenvironmental reconstructions using phytoliths must begin with analyzing modern phytoliths distribution in plants and soils in the given region (Bowdery, 1998; Carnelli et al., 2001; Lu and Liu, 2003). 0034-6667/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2005.02.006 T Tel.: +1 320 308 2263; fax: +1 320 308 1660. E-mail address: mblinnikov@stcloudstate.edu. Review of Palaeobotany and Palynology 135 (2005) 71 – 98 www.elsevier.com/locate/revpalbo