Using Multivariate Techniques to Quantitatively Estimate Ecological Stages in a Mixed Grass Prairie

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Abstract
Cluster analysis followed by stepwise discriminant analysis was used to delineate ecological stages on a mixed grass prairie in western South Dakota. Forty-seven variables were analyzed for 48 sites ranging from potential vegetation to early seral stages. A cover-frequency index for western wheatgrass (Agropyron smi- thii), blue grama (Bouteloua gracilis), and buffalograss (Buchloe dactyloides) was the most valuable in identifying 4 different (P<0.0001) ecological stages. Ecological stage classification was estimated to be 95% accurate. The methods presented are quantita- tive, precise, easy, time-efficient, and meet the goals of resource managers with a minimum of bias. is 40 cm, based on 20 years of climatological data from Cedar Pass Visitor Center in the Badlands National Park, 21 km from the study area. Most precipitation occurs as rain during the growing season (April-September). Precipitation (October I to September 30) for plant growth during this study was 46 cm. The study area is within the wheatgrass-grama-buffalograss (Agropyron-Bouteloua-Buchloe) vegetation type (Kuchler 1975). Dominant grasses on the study area are western wheatgrass (Agropyron smithii Rydb.), blue grama (Boutelouagracilis (H.B.K.) Lag.) buffalograss (Buchloe dactyloides (Nutt.)), and needleleaf sedge (Carex eleocharis Bailey). Dominant forbs are scarlet globemallow (Sphaeralcea coccinea (Pursh) Rydb.), prostrate ver- vain (Verbena bracteata Lag. & Rodr.), Patagonian plantain (Plantago patagonica var. spinulosa (Dene.) A. Gray), and dog- weed (Dyssodia papposa Vent.)). Plant nomenclature follows McGregor et al. (1986). Soil textures of the study sites in the Badlands National Park and Conata Basin are clayey, and range sites included dense clay, silty clay, and shallow clay (SCS, unpub- lished Pennington Co. Soil Survey, in prep. Wall, S. Dak.).

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