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

MethodsThe 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).

PurposeClassification 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 AreaThe 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.

ResultsNMS 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

Community TypeBouteloua-

YuccaBouteloua-

OpuntiaPascopyrum

smithiiBouteloua

OpenMixed Carex-

EleocharisSporobolus- Glycyrrhiza

Bouteloua gracilis

Bouteloua dactyloides

Bouteloua-Yucca 62.5 12.5 12.5 12.5Bouteloua-Opuntia 8.33 41.7 8.33 8.3 25.0 8.3Pascopyrum smithii 100Bouteloua Ridgetop 5.9 94.1Mixed 8.3 16.7 33.3 25.0 16.7Carex-Eleocharis 100Sprobolus- Glycyrrhiza 100Bouteloua gracilis 16.7 8.3 8.3 8.3 50.0 8.3Bouteloua dactyloides 4.8 14.3 4.8 23.8 14.3 38.1

Site 1

Site 2

Site 5

Site 7

Remnant Buffalo Wallow

Site 97

Site 33Site 44Site 11Site 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 CommunityCarex-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

SpeciesBouteloua

OpenBouteloua-

YuccaBouteloua-

OpuntiaBouteloua

gracilisBoutelousa dactyloides

Pascopyrum smithii Mixed

Sporobolis-Glycrrhiza

Carex-Eleocharis

Bouteloua gracilis 2.3 15 10.9 41.7 12.9 13.2 3.2 2.7 0.1Yucca glauca 0.7 6.8 1.3 1.8 2.2 0.2 3.6Bouteloua dactyloides 1.1 4.8 15.6 9.2 40.5 7.2 0.7 tAristida purpurea 0.2 4.5 1.3 1.9 1.5 0.3Elymus elymoides 0.1 2.5 0.2 0.2 0.2 t 0.1Rhus trilobata 0.7 1.9 t t 4.7Opuntia polyacantha 0.2 1.6 8.8 6.1 7.6 0.5 tPascopyrum smithii 2.2 1.1 5.2 2.6 2.6 37.5 0.9 8.2 1.7Artemesia frigida 0.3 0.7 1.5 0.3 0.2 0.2 0.5 tArtemesia filifolia t 0.3 1.8 t t 0.5 tAtriplex canescens 0.1 0.3 1.5 2 1.3 1.4 tSchizochirium scoparium 1.1 0.3 0.5 t 3.3Toxicodendron rydbergii 0.1 0.1 1.7Sporobolus airoides 0.2 0.3 t t 39.2 0.1Glycyrrhiza lepidota 0.2 12.5Distichlis spicata t t t 1.9 2.5 0.9Elymus canadensis 0.4 5.8Juncus balticus 0.1 5.8Taraxacum officinale t t t 0.2 0.1 0.2 1.1Poa spp 0.1 0.1 0.3 2.9 3.1Carex spp 1.1 0.3 t 1.5 0.8 0.2 0.5 t 26Juncus spp 0.5 0.1 t 13.5Eleocharis spp 0.5 7.4Circium arvense t 0.1 t t t 1.7

NMS Axis 1-2 -1 0 1 2

NM

S A

xis

2

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

Bouteloua-YuccaBouteloua-OpuntiaPascopyrum smithiiBouteloua RidgetopMixedCarex-EleocharisSporobolus-GlycyrrhizaBouteloua gracilisBouteloua dactyloides

increasingmoisture

decreasingcover

ClimateMean Max Daily Temp in Summer = 31°C

Mean PPT = 305-380 mm

Slightly increasing moisture from west to east

Geology includes shale, sandstone, sand dunes, and gravel; soils include badlands, mollisols, entisols, and alfisols.

Sedimentary cyclesPhysiography

ResultsA 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 USNVCThe 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 OpenBouteloua-

YuccaBouteloua-

OpuntiaBouteloua

gracilisBoutelousa 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

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.

http://usnvc.org/explore-classification/