Community Classification of the Pawnee National Grasslands, Shortgrass Steppe, USA Scott B. Franklin 1, Michael Schiebout 2, & Amber Brandt 1 1 School of Biological Sciences, University of Northern Colorado, Greeley, CO USA; 2 Department of Biology, Union University, Jackson, TN USA But from these immense prairies may arise one great advantage to the United States, viz., the restriction of our population to some certain limits, and thereby a continuation of the union. Our citizens being so prone to rambling, and extending themselves on the frontiers, will, through necessity, be constrained to limit their extent on the west to the borders of the Missouri and the Mississippi, while they leave the prairies, incapable of cultivation, to the wandering and uncivilized Aborigines of the country. Zebulon Pike Methods The initial phase of this project used GIS map layers to develop an ecological land type classification that was used to stratify field plots, including geology, soils, elevation, and landscape location (Kupfer & Franklin 2000; see Figures below). Purpose Classification of vegetation provides an inventory to assess change, a common language to compare communities among regions, and a baseline for land stewardship decisions. Several initial efforts toward mapping and vegetation data collection are available for the Pawnee National Grasslands, but not a structured community analysis and subsequent mapping for the entire area. The goal of this study is to provide such a local community analysis and relate community types to environmental conditions. Subsequently, local types will be related to The National Vegetation Classification (USNVC) developed as a standard for the United States. Study Area The Pawnee National Grasslands is located in northeastern Colorado with the Shortgrass Steppe Ecoregion, and part of the Colorado Piedmont and High Plains physiographic regions. The fragmented area is gently rolling with few outcrops; 78,128 ha. Results NMS ordination revealed clear significant patterns of community types, and subsequent discriminant analyses differentiated community types mainly by Euclidean Distance Clustering using Ward’s Method Community Type Bouteloua- Yucca Bouteloua- Opuntia Pascopyrum smithii Bouteloua Open MixedCarex- Eleocharis Sporobolus- Glycyrrhiza Bouteloua gracilis Bouteloua dactyloides Bouteloua-Yucca Bouteloua-Opuntia Pascopyrum smithii100 Bouteloua Ridgetop Mixed Carex-Eleocharis100 Sprobolus- Glycyrrhiza100 Bouteloua gracilis Bouteloua dactyloides Site 1 Site 2 Site 5 Site 7 Remnant Buffalo Wallow Site 97 Site 33 Site 44Site 11 Site 4 Cottonwood riparian Bouteloua-Yucca Small Rock Outcrop Community Bouteloua-Opuntia Slope Community Pascopyrum smithii Community Bouteloua Open [low cover] Community Mixed Community Bouteloua gracilis Community Bouteloua dactyloides Community Sprobolis airoides-Glycyrrhiza lepidota Community Carex-Eleocharis Wet Community Plot sampling utilized the Carolina Vegetation Sampling method modular plots (Peet et al. 1998); ten 10X10 modules = 20X50 m plots. A total of 102 plots were collected. Cover of taxa was recorded in four of the ten modules using a modified Daubenmire cover scale. Trees were measured in all ten modules. Various multivariate techniques were used to classify the local community types and relate those types to abiotic parameters. Community Types Species Bouteloua Open Bouteloua- Yucca Bouteloua- Opuntia Bouteloua gracilis Boutelousa dactyloides Pascopyrum smithiiMixed Sporobolis- Glycrrhiza Carex- Eleocharis Bouteloua gracilis Yucca glauca Bouteloua dactyloides t Aristida purpurea Elymus elymoides t0.1 Rhus trilobata0.71.9tt4.7 Opuntia polyacantha t Pascopyrum smithii Artemesia frigida t Artemesia filifoliat0.31.8tt0.5t Atriplex canescens t Schizochirium scoparium t3.3 Toxicodendron rydbergii Sporobolus airoides0.20.3tt Glycyrrhiza lepidota Distichlis spicatattt Elymus canadensis Juncus balticus Taraxacum officinalettt Poa spp Carex spp1.10.3t t26 Juncus spp0.50.1t13.5 Eleocharis spp Circium arvenset0.1ttt1.7 Climate Mean Max Daily Temp in Summer = 31°C Mean PPT = mm Slightly increasing moisture from west to east Geology includes shale, sandstone, sand dunes, and gravel; soils include badlands, mollisols, entisols, and alfisols. Sedimentary cycles Physiography Results A total of 299 species (~430 known) were witnessed in the 102 plots scattered throughout the Pawnee National Grasslands. Eights distinct (one mixed) community types were distinguished through clustering analysis. Discriminant Analysis accuracy table; values are percent of plots correctly classified percent cover and site type (an index of the moisture gradient). The mixed community included everything from dry riparian to rock outcrops harboring mixed prairie species, Pinus flexilis, and shrubs. Fitting the Local Community Types to the USNVC The local Community types provided above are just that, local, and represent variations on concepts of wider distribution. However, it is important to place our local community types into the national classification concepts to fully describe the types. Most of the communities are part of the Great Plains Shortgrass Prairie Group. Community Types USNVC Bouteloua Open Bouteloua- Yucca Bouteloua- Opuntia Bouteloua gracilis Boutelousa dactyloides Pascopyrum smithii Sporobolis- Glycyrrhiza Carex- Eleocharis Great Plains Shortgrass Prairie & Shrubland MG Great Plains Shortgrass Prairie Group Bouteloua gracilis- Buchloe dactyloides Xeric Soil Herbaceous Vegetation Gutierrezia sarothrae – Yucca glauca Dwarf-shrub Artemesia frigida- Boutleloua gracilis Dwarf- shrub Bouteloua gracilis-Buchloe dactyloides Herbaceous Vegetation ?? Great Plains Mixedgrass Prairie & Shrubland MG Central Great Plains Mixed Grass Prairie Group Pascopyrum smithii- Bouteloua gracilis Great Plains Sand Grassland & Shrubland MG Artemesia filifolia- Bouteloua gracilis Shrubland Take-home Messages  A vegetation gradient was found from open rock communities to wet prairies.  Local communities were related to environmental factors, but also typical disturbances (i.e., prairie dogs, grazing).  The relation of these local types to the USNVC is clear for most of the area and common vegetation, but the USNVC is lacking mesic prairie association descriptions.