The Rannells Flint Hills Prairie Preserve is located near Manhattan, KS (39 12N, 96 35W, 324 m above msl). Vegetation on the site is a mixture of C3 and C4 species, dominated by the C4, warm-season grasses, Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash., and Andropogon scoparius Michx. (C4 warm-season grass). Total perennial grasses make up 85% of the plant composition. Members of the Cyperaceae- grasslike plants, (C3 cool-season monocots) made up 5-7%. Principal perennial forbs (all C3 warm-season) also make up 5-7 % of the stand and include Vernonia baldwinii var. interior (Small) Schub., Ambrosia psilostachya DC., Artemesia ludoviciana Nutt., and Psoralea tenuiflora var. floribunda (Nutt.) Rydb. The principal cool-season grass was Poa pratensis L.. At this site, average peak aboveground biomass (dry wt.) of 425 g m² usually occurs in early August, of which 35 g m² is from forbs. The 30-year average annual precipitation is 840 mm, with 520 mm occurring during the growing season. Soils at the site are primarily silty clay loams (Argiustolls). The upper 10-cm of the soil profile had a bulk density of 1.0 to 1.2 g C m³ and an organic matter content of 4 to 6%. The area has been grazed by yearling steers during the summer and annually burned in spring for the past century or more. Below is a schematic depicting the range sites on the area.