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These four aerial photos of McKnight Prairie were taken over50 years, and it is possible to see changes in the prairie landscapeover that time. For example, the large white areas in the center ofthe 1940 image are probably open sand. The 1930s were a time ofextreme drought and it is likely that the vegetative cover was greatlyreduced then. The sandy areas steadily decrease in size after 1940.Also visible is the changing amount of woody vegetation, seen as adark band on the north slope of the east hill. Rows of farm cropscan be seen in the images from 1940 and 1964, before purchase byCarleton College.

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Legal description:The south 34 rods of the W1/2 of the SE1/4 and thesouth 34 rods of the E1/2 of the SW1/4 all in section18, township 112 north, range 18 west. And part ofthe NE1/4 of Section 19, township 112 north, range18 west, Goodhue County, Minnesota.

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McKnight Prairie is a rarity, one of the few prairie fragmentsleft in southern Minnesota. It was purchased by Carleton Collegein 1968, funded by a grant from the Sumner T. McKnight Foundation.Paul Jensen, a professor of biology at Carleton, was responsible foridentifying the site, procuring the funding for its purchase, andmanaging the prairie until his retirement in 1986.SITE DESCRIPTION

The 33.5 acres (13.5 hectares) of McKnight Prairie containdiverse soils and topography. The soils at McKnight are derivedfrom the St. Peter sandstone (explaining the high content of sand),from older glacial tills, and from a mantle of silty wind-blown materialwhich was deposited throughout this area during more recentglaciations. The Ordovician St. Peter sandstone can be seen inexposures east of the saddle between the two main hills. This friable,fine-grained sandstone disaggregates readily into individual grainsunder the influence of water and wind. At one time, the McKnighthills undoubtedly retained the cap of resistant Platteville limestonethat forms the caprock of the “Stanton mesas” to the south andwest. After the Platteville was breached hundreds of thousands ofyears ago, erosion must have proceeded rapidly to reduce the elevationof the summits to their present height.

There are some relatively large rocks scattered throughout theprairie. These are glacial erratics, and are of types more commonlyfound in northern Minnesota and Canada. This site is well east andsouth of the glacial moraines of the last 20,000 years, so these rockswere deposited here by an older glacial advance (perhaps thewidespread one dated to 600,000 - 700,000 years ago).

At the time of European settlement of the region in the mid-19th century, land survey records show that the entire surroundingarea was prairie (except for the floodplain forest along the CannonRiver to the north). The exact land use history since Europeansettlement is poorly known, but a significant proportion of the lowareas were at one time cultivated; see approximate boundaries ofcultivation on the map. The hilltops were never plowed, thoughthey were used for some livestock grazing. There has been nocultivation since Carleton purchased the prairie in 1968, and thedisturbed areas have slowly been colonized by native prairie species.Some of the cultivated areas have been planted with seedlings ofnative plants from here or from nearby prairie remnants.MANAGEMENT

The primary purpose of McKnight Prairie is scientific educationand research. Classes from Carleton College and other educationalinstitutions use the prairie as an outdoor classroom. Researchersinvestigating prairie ecology often make use of this site, since thereare so few prairie remnants remaining in southern Minnesota. Thegoal of management is to maintain the species and communities ofnative tallgrass prairie.

Controlled burns are an essential part of prairie management.Without such fires, woody plant species would quickly invade andshade out the prairie plants. The fire does not kill the native prairieplants, since they have buds below the soil surface. During thegrowing season following a spring burn, prairie plants grow fasterand flower more than plants on adjacent unburned areas. This seemsto be mainly because the fire removes the buildup of litter from thesoil surface, which allows the sun to warm the soil more quicklyand give the plants a head start on the growing season. Often thesoil on burned prairies is several degrees warmer than unburned soilfor weeks after a burn.

McKnight Prairie has been burned periodically since 1971.There are currently three burn units (see map), and they are burnedin rotation so that a unit is burned approximately every four years.The burning has only been partially effective in setting back treesand shrubs. Particularly on the north slopes of the hills, there isconsiderable invasion by aspen (Populus tremuloides) and sumac(Rhus glabra). These are occasionally removed by hand to checktheir spread across the prairie.SPECIES DIVERSITY

The vegetation of McKnight Prairie is highly diverse. Over 240species of vascular plants have been identified, and new species arestill being discovered. Most of the prairie plants are now uncommonin the area, and several are on the Minnesota list of Threatened orSpecial Concern species.

Grasses (Family Poaceae) dominate many areas of the prairie.The tallgrass species include Indian grass (Sorghastrum nutans), bigbluestem (Andropogon gerardii), and switchgrass (Panicum virgatum).There are also fine stands of midgrasses such as little bluestem(Schizachyrium scoparium) and needlegrass (Stipa spartea).

Wildflowers are in bloom on the prairie from April throughSeptember. The legumes (Family Fabaceae) are important becausethey are able to fix atmospheric nitrogen by means of symbioticbacteria that live in their root nodules. There are over 20 legumespecies here, including characteristic prairies species such as leadplant(Amorpha canescens), prairie clover (Dalea spp.), and bush clover(Lespedeza spp.). Members of the composite family (Asteraceae) areespecially common in late summer; look for the yellow goldenrods(Solidago spp.) and sunflowers (Helianthus spp.), and both purpleand white asters (Aster spp.).

Many animal species live in or regularly visit McKnight Prairie.Grassland birds are common, including declining species such asdickcissels (Spiza americana). Loggerhead shrikes (Lanius ludovicianus),listed as Threatened in Minnesota, are occasionally sighted and atone time nested here. The mammals include diverse species of rodents,most notably prairie voles (Microtus ochrogaster, listed as a species

of Special Concern in Minnesota). Plains pocket gophers (Geomysbursarius) are abundant underground herbivores, and their moundscan be seen throughout the prairie. Gopher mounds are importantlocations for recruitment of prairie plants from seed. The gophersare preyed upon by badgers (Taxidea taxus), which are rarely observedbut leave characteristic large disturbances in the soil when diggingfor prey.

The process of documenting McKnight’s large number of insectspecies has begun with surveys of ants and butterflies. See the Arbweb pages at www.carleton.edu/campus/arb for the latest lists ofinsect survey results.VISITORS

Visitors are welcome, but care must be taken to avoid damagingthe prairie or interfering with ongoing scientific work. Please do notremove any animal or plant material (including seeds), and stay awayfrom areas that are flagged. Groups of visitors larger than 10 arerequired to register their use with the Carleton Arboretum office(507-646-5413).

Mark McKone, Director of McKnight PrairieMyles Bakke, Manager of McKnight Prairie

ACKNOWLEDGEMENTSPaul Jensen (Professor Emeritus of Biology) and Mary Savina

(Professor of Geology) contributed to the text. Preparation of thismap was made possible by funding from the Richard S. Cole MemorialFund.

100m50m25m0m

SCALE: 1:2000 1cm = 20m 31.7 inches = 1 mileMcKnight Prairie • Carleton Collegelocated in Stanton Township, Goodhue County, Minnesota

McKnight Prairie • Carleton Collegelocated in Stanton Township, Goodhue County, Minnesota

Approximate areanever farmed

Elevation contours(dark= 1m, light=.5m)

Survey markerOld wooden post

Property lineCurrent fence lineRoadBurn unit boundary

Selected trees

©2000 Carleton College.Cartography and layout by Nat Case ’88,Hedberg Maps, Inc., Minneapolis, MN.

Text by Mark McKone, Carleton College.

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Getting to McKnight Prairie

McKnight Prairie Map

Carleton CollegeNORTHFIELD, MINNESOTA