Land Cover Trends Project

Northern Glaciated Plains Ecoregion Summary

By Roger F. Auch 1

Click to see available downloads for this ecoregion

see caption

Figure 1. Northern Glaciated Plains and surrounding ecoregions. The 30 (and one partial) randomly selected 100 km2 sample blocks are shown along with land cover and land use data from the 1992 National Land Cover Dataset.

Ecoregion Description

The Northern Glaciated Plains is primarily a north to south trending ecoregion across eastern North and South Dakota.  It widens to the west in north-central North Dakota and to the east into west-central Minnesota and covers approximately 141,340 km2 (54,572 mi2) (fig. 1). The climate is considered continental (hot or warm summers and cold winters) and precipitation ranges from approximately 510 to 610 millimeters (20 to 24 inches) in an average year for the main part of the ecoregion but decreases to the northwest and increases in the southeast (Kottek and others, 2006; PRISM Group, 2006). This sub-humid climate makes the Ecoregion "transitional grassland" containing both tall grass and short grass prairie communities (U.S. Environmental Protection Agency, 2002).  Although historically the ecoregion was dominated by grasslands, it has been primarily converted to farmland.  The recent glacial nature of most of the Northern Glaciated Plains’ land forms (less than 25,000 years before present) (Johnson and Higgins, 1997) contributes heavily to the land covers and uses found in the ecoregion.  Drift plains, large glacial lake basins, and shallow river valleys, with level to undulating surfaces and deep soils, provide the basis for crop agriculture.  Where the glaciers left heavy deposits of rock, gravel, and sand, grasslands remained generally more intact and their use became grazing land for livestock. This geologic youth has left an immature drainage system and the ecoregion is dotted with substantial numbers of wetland depressions, ranging in size and permanence. There are also sub-regional concentrations of glacial formed permanent lakes.  Agriculture, grasslands, wetlands, and water form the general mosaic of land cover for the ecoregion. 

 

Agriculture is the canvass on which the other land covers are embedded.  Grain and cattle production is the dominant land use (fig. 2). A majority of the agricultural land cover is cropped.  Farming tends only to be limited by certain soil, topographic, and wetland conditions.  There are latitudinal and longitudinal differences in the combinations of crops grown. Corn and soybeans are the main crops in the southern part of the ecoregion transitioning to soybeans and wheat in the central area and then mostly wheat, other small grains, and canola (rapeseed) in the northern parts (fig. 3). Hay, especially alfalfa, is also a common use of cropland. Pastures of smaller parcel size and more intense use generally fall into the agricultural class. 

 

Grassland cover, land that is more expansive in parcel size and less intensely used in grazing livestock, tends to be more localized.  There are Level IV ecoregions, most notably the Prairie Coteau and the Glacial Lake Deltas, where grassland is a dominant land cover (Bryce and others, 1998) (fig. 4).  Soil and slope conditions are the main reasons for grasslands to persist in these areas, and to a lesser extent the ecoregion in general. The side hills of deeper stream valleys are often used as more expansive pasture. Grassland cover is also found on wildlife habitat areas, such as federally and state owned wildlife refuges and production areas, and other public lands.

 

Wetlands and water are frequent land covers in the Northern Glaciated Plains but their concentration in number and size may be locally dependent. Most wetlands have some sort of herbaceous vegetation but the amount may depend on seasonal and climatic fluctuations. Water is found mostly in permanent lakes, semi-permanent "wetland" lakes (that may be open water in some years and wetland vegetation in others), and a few reservoirs (fig. 5).

 

Minor land covers included forest, development, and mining. Forest land cover is more limited and tends to be sub-regionally concentrated.  The Level IV ecoregions of the Turtle Mountains, the Prairie Coteau, and the northern portions of the Glacial Lake Deltas, have patches of forest (Bryce and others, 1998) (fig. 6).  Larger riparian areas and farm shelterbelts may also have tree cover but may not be wide enough to map continuously (60 or more meters), although exceptions are common. Developed land cover was found within cities and towns and made up a small fraction of the ecoregion. Most small towns in the Northern Glaciated Plains experienced little physical growth during the time period and many are declining in population and economic diversity (fig. 7).  Aggregate mining was also found in the ecoregion because of the glacial geology but tended to be limited in size and frequency.

Results

The overall spatial change from 1973 to 2000 for the Northern Glaciated Plains was 7.5 percent (+/– 1.4 percent) (table 1).  The ecoregion had a moderate amount of change compared to other ecoregions in the Great Plains. The Northern Glaciated Plains had less change than the Northwestern Glaciated Plains to the west but more than either the Lake Agassiz Plain to the northeast or the Western Cornbelt Plains to the south, southeast (fig. 8).  A majority of the change occurred only once during the study period (6.0 percent, +/– 1.1 percent) but some areas (1.5 percent of the ecoregion) experienced multiple changes (table 1).  The multiple changes typically involved wetland land cover conditions that changed back and forth between wetland and open, persisent water with changing climatic cycles or where grassland parcels were convereted to crop production early in the study period and then were enrolled in the Conservation Reserve Program sometime after 1985.  The last two time intervals, 1986-1992 and 1992-2000, had greater amounts of change than the first two time intervals (table 2).  When the uneven time intervals were normalized to an annual rate, the 1992-2000 time interval had the highest rate of change at 0.5 percent (+/–0.1 percent) and the 1973-1980 the lowest at 0.2 percent (+/– <0.1 percent), closely followed by 1980-1986. The rate of change continued to increase after 1986 (fig. 9) but from a combination of drivers and conditions that may diverge in the future.  

 

The agriculture and water land cover classes had the most net change during the study period, followed by wetlands and grassland/shrubland (table 3).   Agriculture land cover had a net loss of 2.0 percent (+/– 0.9 percent), converting primarily to grassland/shrubland, wetland, water, development, and mining.  With the exception of the conversions of agriculture to developed, and possibly some agriculture to mining or water, most of the loss in agricultural land cover was or may be of a limited time.  The most common conversion was agriculture to grassland/shrubland. An estimated 3,386 km2 (+/– 1,180 km2) of agriculture land cover changed to grassland/shrubland (table 4), a majority of it during the last two time intervals (1986-2000) when the Conservation Reserve Program (CRP) was in effect. This program paid farmers to retire marginal cropland to native grasses for specific length contracts, usually ten years in duration. Although some land in the ecoregion may have been in its second CRP contract by 2000, this did not assure a long term change to grassland/shrubland land cover (Leathers and Harrington, 2000) (fig. 10).

 

A more ephemeral change was conversion of agriculture to wetlands, where wetter than normal climatic conditions forced many temporary and seasonal wetlands, that were usually farmed, to stay wet keeping them out of crop production. Many times these formerly farmed temporary and seasonal wetlands became covered in wetland vegetation (Kirby and others, 2002). A series of wetter years in the mid-1980s and mid to late 1990s contributed to most of the agriculture to wetlands change (fig. 11).

 

Water land cover had a net increase of 2.0 percent (+/– 0.7 percent) during the study period (table 3). Water land cover gained mostly from wetland, agriculture, and grass/shrubland. The second most common conversion was wetland land cover converting to water. An estimated 3,244 km2 (+/– 814 km2) of wetland changed to water (table 4), a majority of it during the last time interval (1992-2000).

 

Although water cover gain from wetlands may be more of an ephemeral event based on wetter climatic conditions (table 4), water gain from agriculture and grass/shrubland could represent a longer term but still cyclic change where a number of larger glacial lake basins experienced flooding during the study period. Water bodies such as Lake Thompson and Waubay Lakes in South Dakota, Devil’s Lake in North Dakota, and numerous more minor lakes gained in size from the mid-1980s onwards.  These water bodies may persist at larger surface areas for years (S.D. Game, Fish, and Parks, 2006; Shapely and others, 2005; Todhunter and Rundquist, 2004) (fig. 12).

 

Wetland land cover had a net decrease of 0.9 percent (+/– 0.6 percent) between 1973 and 2000 (table 3), much of it a change to open water conditions. Although this change may reverse itself during drier climatic cycles, the trend from the 1980s onward was wetland conditions transitioning to open water, especially during the last time interval (fig. 13).

 

Grassland /shrubland land cover experienced a net increase of 0.7 percent during the study period and the margin of error was the same at +/- 0.7 percent (table 3).  The high margin of error may reflect that change in grassland/shrubland land cover was quite variable across the ecoregion or that more than one type of conversion affecting grassland/shrubland was canceling out stronger directional trends or a combination of both factors.  

 

Gross change in grassland/shrubland land cover was much higher at 2.7 percent (+/– 0.6 percent) (table 3).  One of the major factors affecting grassland/shrubland was the dynamic between grassland/shrubland and agricultural land cover. If just the estimated changes between agriculture to grassland/shrubland and grassland/shrubland to agriculture are viewed, they show that grassland/shrubland lost to agriculture during the first two time intervals (driven by a period of agricultural economic expansion) and then the trend reversed itself during the last intervals, most notably during the implementation of the Conservation Reserve Program (fig. 14). The grassland/shrubland net gain was much less between 1992 and 2000, as some of the first CRP contracts expired and were not renewed (Leistritz and others, 2002) and formerly unbroken grassland/shrublands were converted to cropland for the first time (Higgins, Naugle, and Forman, 2002).  The trend of native grassland conversion may have been on the increase during the 1990s but masked in the standard Land Cover Trends change statistics that does not distinisuh differences in grassland/shrubland land cover change (i.e. was it grazing land changing to cropland between 1992 and 2000 or was it a CRP field that was no longer enrolled in the federal program?).

Discussion

The three major factors affecting the Northern Glaciated Plains during the study period were the land change dynamics between grassland/shrubland and agriculture (driven mainly by changes in the agricultural economy and federal farm policy), and changes between wetland and water land covers, and changes between agriculture and wetlands (both caused primarily by cyclic climatic conditions).

 

All of these pairings had temporal pulses of change; more grassland/shrubland converted to agriculture during the first two time periods whereas the reverse occurred in the following two with the implementation of the CRP. Wetland transitioning to water was much more dominant during the second half of the study period than what had occurred earlier. A similar pulse was seen in agriculture transitioning to wetland.

 

The changes making up all of these major suites tend to be ephemeral or temporary in nature, depending on the leading factors influencing these changes.  The conversion of native grassland/shrubland and wetlands, however, may be more permanent because restoration efforts can be cost prohibitive and do not result in a version as ecologically complex as the original.

 

[1] U.S. Geological Survey, Earth Resources Observation and Science Center, Sioux Falls, SD 57198

 

 

Figures and tables

Table 1. Percentage of the ecoregion that experienced change and associated error

Number

Percent

Margin

Lower

Upper

Standard

Relative

of

of

of error

bound

bound

error

error

changes

ecoregion

(+/- %)

(%)

(%)

(%)

(%)

1

6.0

 

1.1

 

4.9

 

7.1

 

0.8

 

12.7

 

2

1.2

 

0.3

 

0.8

 

1.5

 

0.2

 

19.0

 

3

0.3

 

0.1

 

0.2

 

0.4

 

0.1

 

20.0

 

4

0.0

 

0.0

 

0.0

 

0.1

 

0.0

 

19.5

 

Overall spatial change

7.5

 

1.4

 

6.1

 

8.9

 

0.9

 

12.5

 

 

 

Table 2. Raw estimates of percent change in the ecoregion computed for each of the four time intervals and associated error at an 85-percent confidence level.
[Estimates of change per interval normalized to an annual rate of change for each of the four time intervals]

Period

Total change

Margin of error

Lower bound

Upper bound

Standard error

Relative error

Average rate

(% of ecoregion)

(+/- %)

(%)

(%)

(%)

(%)

(% per year)

1973-1980

1.4

 

0.3

 

1.1

 

1.7

 

0.2

 

13.0

 

0.2

 

1980-1986

1.4

 

0.3

 

1.1

 

1.7

 

0.2

 

14.4

 

0.2

 

1986-1992

2.4

 

0.5

 

1.8

 

2.9

 

0.4

 

15.2

 

0.4

 

1992-2000

4.1

 

1.0

 

3.1

 

5.2

 

0.7

 

16.8

 

0.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Period

Total change

Margin of error

Lower bound

Upper bound

Standard error

Relative error

Average rate

(km2 of ecoregion)

(+/- km2)

(km2)

(km2)

(km2)

(%)

(km2 per year)

1973-1980

2008

 

386

 

1622

 

2393

 

261

 

13.0

 

287

 

1980-1986

1960

 

418

 

1542

 

2378

 

282

 

14.4

 

327

 

1986-1992

3333

 

749

 

2584

 

4082

 

507

 

15.2

 

556

 

1992-2000

5860

 

1458

 

4402

 

7318

 

986

 

16.8

 

733

 

 

 

 


 

Water

Developed

Mech dist

Mining

Barren

Forest

Grass/Shrub

Agriculture

Wetlands

Nonmech dist

 

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

%

+/-

1973

3.5

2.1

1.4

1.6

0.0

0.0

0.1

0.1

0.0

0.0

3.0

2.6

17.7

4.4

68.5

5.7

5.9

1.0

0.0

0.0

1980

3.3

2.1

1.5

1.6

0.0

0.0

0.1

0.0

0.0

0.0

3.0

2.5

17.5

4.4

68.6

5.7

6.0

1.0

0.0

0.0

1986

3.4

2.1

1.5

1.6

0.0

0.0

0.1

0.1

0.0

0.0

3.0

2.5

17.7

4.5

68.4

5.7

6.0

1.0

0.0

0.0

1992

3.7

2.1

1.6

1.8

0.0

0.0

0.1

0.1

0.0

0.0

3.0

2.5

18.5

4.7

67.5

5.8

5.6

1.0

0.0

0.0

2000

5.5

2.3

1.6

1.8

0.0

0.0

0.1

0.1

0.0

0.0

3.0

2.5

18.4

4.7

66.4

5.8

4.9

1.0

0.0

0.0

Net Change

2.0

0.7

0.2

0.2

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.7

0.7

-2.0

0.9

-0.9

0.6

0.0

0.0

Gross Change

2.9

0.8

0.2

0.2

0.0

0.0

0.1

0.1

0.0

0.0

0.0

0.0

2.7

0.6

3.4

0.8

2.3

0.6

0.0

0.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Water

Developed

Mech dist

Mining

Barren

Forest

Grass/Shrub

Agriculture

Wetlands

Nonmech dist

 

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

km2

+/-

1973

4938

2946

1949

2211

12

18

116

110

0

0

4266

3605

25009

6266

96763

8070

8289

1382

0

0

1980

4651

2930

2080

2271

8

12

82

66

0

0

4256

3591

24787

6283

96972

8061

8507

1419

0

0

1986

4747

2952

2116

2307

0

0

101

86

0

0

4258

3591

24995

6377

96662

8121

8462

1422

0

0

1992

5294

3017

2248

2475

15

14

107

87

0

0

4251

3585

26105

6642

95474

8242

7849

1350

0

0

2000

7760

3241

2283

2491

5

7

140

103

0

0

4238

3574

26035

6698

93917

8135

6956

1477

0

0

Net Change

2822

934

334

297

-7

20

24

30

0

0

-27

34

1026

959

-2846

1245

-1333

854

0

0

Gross Change

4102

1124

334

297

54

43

127

92

0

0

66

33

3790

902

4817

1181

3316

892

0

0

Table 3. Estimated percentage and area for each land cover class between 1973 and 2000

 

 

 

 


Period

From class

To class

Area changed

Margin of error

Standard error

Percent of ecoregion

Percent of all changes

(km2)

(+/- km2)*

(km2)

 

 

1973-1980

Grassland/Shrubland

Agriculture

496

 

204

 

138

 

0.4

 

24.7

 

 

Water

Wetland

478

 

220

 

149

 

0.3

 

23.8

 

 

Agriculture

Grassland/Shrubland

296

 

186

 

126

 

0.2

 

14.7

 

 

Wetland

Agriculture

198

 

78

 

52

 

0.1

 

9.8

 

 

Wetland

Water

193

 

64

 

43

 

0.1

 

9.6

 

 

Other

Other

347

 

n/a

 

n/a

 

0.2

 

17.3

 

 

 

 

2008

 

 

 

 

 

1.4

 

100.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1980-1986

Agriculture

Grassland/Shrubland

564

 

278

 

188

 

0.4

 

28.8

 

 

Wetland

Water

344

 

122

 

83

 

0.2

 

17.6

 

 

Grassland/Shrubland

Agriculture

339

 

204

 

138

 

0.2

 

17.3

 

 

Water

Wetland

255

 

72

 

48

 

0.2

 

13.0

 

 

Agriculture

Wetland

186

 

72

 

49

 

0.1

 

9.5

 

 

Other

Other

272

 

n/a

 

n/a

 

0.2

 

13.9

 

 

 

 

1960

 

 

 

 

 

1.4

 

100.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1986-1992

Agriculture

Grassland/Shrubland

1414

 

558

 

378

 

1.0

 

42.4

 

 

Wetland

Water

791

 

312

 

211

 

0.6

 

23.7

 

 

Water

Wetland

247

 

94

 

63

 

0.2

 

7.4

 

 

Grassland/Shrubland

Agriculture

226

 

130

 

88

 

0.2

 

6.8

 

 

Wetland

Agriculture

211

 

73

 

49

 

0.1

 

6.3

 

 

Other

Other

444

 

n/a

 

n/a

 

0.3

 

13.3

 

 

 

 

3333

 

 

 

 

 

2.4

 

100.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1992-2000

Wetland

Water

1916

 

496

 

335

 

1.4

 

32.7

 

 

Agriculture

Grassland/Shrubland

1113

 

486

 

328

 

0.8

 

19.0

 

 

Agriculture

Wetland

895

 

620

 

419

 

0.6

 

15.3

 

 

Grassland/Shrubland

Agriculture

855

 

344

 

232

 

0.6

 

14.6

 

 

Agriculture

Water

428

 

296

 

200

 

0.3

 

7.3

 

 

Other

Other

654

 

n/a

 

n/a

 

0.5

 

11.2

 

 

 

 

5860

 

 

 

 

 

4.1

 

100.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Overall

 

 

 

 

 

 

 

 

 

 

 

 

1973-2000

Agriculture

Grassland/Shrubland

3386

 

1180

 

798

 

2.4

 

25.7

 

 

Wetland

Water

3244

 

814

 

550

 

2.3

 

24.6

 

 

Grassland/Shrubland

Agriculture

1915

 

602

 

407

 

1.4

 

14.6

 

 

Agriculture

Wetland

1356

 

758

 

513

 

1.0

 

10.3

 

 

Water

Wetland

1107

 

325

 

220

 

0.8

 

8.4

 

 

Other

Other

2152

 

n/a

 

n/a

 

1.5

 

16.4

 

 

 

 

13161

 

 

 

 

 

9.3

 

100.0

 

Table 4. Leading estimated land cover changes for each of the four time intervals and overall study period by area, margin of error, standard error, percentage of ecoregion, and percentage of all changes

 



 

see caption

 

Figure 1. Northern Glaciated Plains and surrounding ecoregions. The 30 (and one partial) randomly selected 100 km2 sample blocks are shown along with land cover and land use data from the 1992 National Land Cover Dataset.

 

see caption

Beef cattle next to a corn field in Miner County, So. Dak. Grain and beef production is the leading land use in the Northern Glaciated Plains. Photo credit: Thomas Loveland.

 

see caption

3a

see caption

3b

see caption

3c

Figure 3. Examples of crops in the Northern Glaciated Plains ecoregion. (3a) Wheat, soybean, and alfalfa fields in northeast South Dakota. (3b) A hay field next to a wetland in south-central North Dakota. (3c) A field of canola (rapeseed) in flower surrounding a wetland in extreme north-central North Dakota. Photo credits: Terry Sohl.

 

 

 

see caption

4a

see caption

4b

Figure 4. Much of the Prairie Coteau Level IV ecoregion’s landscape in northeast South Dakota consists of grasslands and wetlands. (4a) Cattle grazing on a distant grassy hillside in Marshall County, So. Dak. (4b) A common scene of grass and wetlands in Day County, So. Dak. Photo credits: Terry Sohl

 

 

see caption

5a

see caption

5b

Figure 5. Examples of wetlands and water in the Northern Glaciated Plains. (5a) Cattle grazing in a dried up wetland in Codington County, So. Dak. (5b) A more permanent natural lake in Lincoln County, Minn. Photo credits: Terry Sohl

 

 

see caption

Figure 6. A patch of natural forest found in McHenry County, No. Dak. surrounded by grasslands. Cattle ranching is the land use in this part of the ecoregion. Photo credit: Terry Sohl

 

 

see caption

7a

see caption

7b

see caption

7c

Figure 7. Examples of developed land in the Northern Glaciated Plains. (7a) New developed land was almost exclusively limited to the periphery of the region’s cities, such as this area on the outskirts of Minot, No. Dak. (7b) Many small towns in the region experienced little physical growth but appeared economically stable such as the farming community of Menno, So. Dak. (7c) Other developed land may be “hollowing” out as communities decline, as witnessed by this closed post office in a small central North Dakota town. Photo credits: 7a and 7c- Terry Sohl; 7c- Kristi Sayler

 

 

** We won’t have Figure 8 done for this publication until all of the ecoregions in this region are complete.

Figure 8. The overall spatial change in the Great Plains U.S. ecoregions.

 

 

see caption 

Figure 9. This land in south-east North Dakota was cropland that was probably enrolled in the federal Conservation Reserve Program (CRP) during the study period. Many times owners of CRP land can earn additional money by renting the grassland out to state government agencies for public hunting access. Photo credit: Terry Sohl

 

see caption

Figure 10. An example of agriculture and wetland land cover dynamics from Brown County, So. Dak. where more ephemeral wetlands can be farmed in drier years but stay as wetlands in wetter times. Photo Credit: Terry Sohl

 

 

see caption

Figure 11.  A formerly flooded farm shelterbelt (now dead) re-emerges from Lake Thompson in Kingsbury County, So. Dak. in 2005 as water levels receeded from highs experienced during the 1990s. Photo credit: Thomas Loveland

 

 

see caption

Figure 12. Estimated net area gains in wetland and water land covers when only those two land cover classes are compared for the study period.

 

 

see caption

Figure 13. Estimated net area gains in agriculture and grass/shrubland land covers when only those two land cover classes are compared for the study period.

 

 

References Cited

Bryce, S.A., Omernik, J.A., Pater, D.E., Ulmer, M., Schaar, J., Freeouf, J., Johnson, R., Kuck, P., and Azevedo, S.H., 1998, Ecoregions of North and South Dakota (color poster with map, descriptive text, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:500,000).

 

Higgins, K.F., Naugle, D.E., and Forman, K.J., 2002, a case study of changing land use practices in the northern Great Plains, U.S.A.: an uncertain future for waterbird conservation, Waterbirds: The International Journal of Waterbird Biology, v. 25, Special Publication 2: Managing Wetlands for Waterbirds: Integrated Approaches, p. 42-50

.

Johnson, R.R. and Higgins, K.F., 1997, Wetland resources of eastern South Dakota, Appendix A, Brookings, So. Dak.: South Dakota State University and Jamestown, No. Dak.: Northern Prairie Wildlife Research Center, (version July 22, 1999), accessed October 23, 2008 at [http://www.npwrc.usgs.gov/resource/wetlands/sdwet/index.htm].

 

Kirby, D.R., Krabbenhoft, K.D., Sedivec, K.K., and DeKeyeser, E.S., 2002, wetlands in northern plains prairies: benefitting wildlife and livestock, Rangelands, v. 24, no. 2, p. 22-25.

 

Kottek, M.J., Grieser, J., Beck, C., Rudolf, B., and Rubel, F., 2006, world map of the Koppen-Geiger climate classification updated, Meteorologische Zeitschrift v. 15, no. 3, p. 259-263.

 

Leathers, N. and Harrington, L.M.B., 2000, effectiveness of conservation reserve programs and land "slippage" in southwestern Kansas, Professional Geographer, v. 52, no. 1, p. 83-93.

 

Leistritz, F.L., Hodur, N.M., and Bangsund, D.A., 2002, socioeconomic impacts of the conservation reserve program in North Dakota, Rural America v. 17, no. 3, p. 57-65.

 

PRISM Group, Oregon State University, 2006, precipitation: annual climatology (1971-2000), map, accessed August 29, 2008 at [http://prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/ppt/Normals/us_ppt_1971_2000.14.png&year=1971_2000&vartype=ppt&month=14&status=final].

 

S.D. Game, Fish, and Parks, 2006, Lake Thompson recreation area, accessed August 29, 2008 at [http://www.sdgfp.info/parks/regions/GlacialLakes/LakeThompson.htm].

 

 

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