Plant Community and Soil Variation Within a Northern Indiana Prairie

Abstract

The community pattern of an area of prairie vegetation in Lake County, Indiana, is described using data obtained by sampling various stands with 1 x 2 m quadrats. In each stand, soil profile descriptions were made, and samples obtained for analyses of pH, organic content, texture, available K and P, soil moisture and bulk density. Five community types were recognized: 1) Big Bluestem community (Andropogon gerardi) on gentle slopes with soils having a deep A-horizon, high availability of soil moisture, high organic content, and good internal drainage; 2) Little Bluestem community (Andropogon scoparius) on soils with a thinner A-horizon, lower availability of soil moisture, and less organic matter; 3) Prairie Dropseed community (Sporobolus heterolepis) on soils with a relatively thin A-horizon, a plastic, highly mottled B-horizon, and low availability of soil moisture; 4) Cordgrass community (Spartina pectinata) on bottomland soils with a very deep A-horizon, high moisture level throughout much of the year, and high organic content; and 5) Poverty Grass-Bluegrass community (Danthonia spicata, Poa com pressa) on disturbed sites with a thin A-horizon, low soil moisture, and low nutrient availability. Floristically, the Big Bluestem community was richest and the Cordgrass community poorest. The distribution of these communities forms a mosaic pattern which is closely correlated with soil differences, particularly depth of A-horizon, availability of soil moisture, and internal drainage. It is of special interest that these grassland communiity types are probably developed on timber soils rather than on true prairie soils.