Land Cover Trends Project

Northern Basin and Range

By Christopher E. Soulard 1

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map of Northern Basin and Range<

Figure 1. Northern Basin and Range ecoregion and surrounding ecoregions. Information shown includes land-use/land-cover data from the 1992 National Land Cover Dataset (Vogelmann and others, 2001) and the 32 randomly selected 100 km² sample blocks used to create estimates of change for the entire ecoregion. Click to enlarge.

 

Ecoregion Description

 

The Northern Basin and Range Level III ecoregion is generally oriented from east to west, and is in essence defined by the northern extent of the hydrographic Great Basin (Grayson, 1993). Most of the region is located in Oregon (58.7 percent), with parts of the region in Nevada (20.6 percent), Idaho (14.8 percent), and California (5.9 percent). In all, the Northern Basin and Range ecoregion encompasses 109,400 km² of land bordered on the west by the Eastern Cascades Slopes and Foothills ecoregion, on the east by the Middle Rockies ecoregion, on the north by the Blue Mountains ecoregion and Snake River Plain ecoregion, and on the south by the Central Basin and Range ecoregion (fig. 1). Much like the other basin and range provinces of the western United States (for example, Central Basin and Range, Mojave Basin and Range, and Sonoran Basin and Range), the Northern Basin and Range ecoregion is characterized by basin and range topography. The ecoregion contains several wide basins bordered by scattered low mountains. The Northern Basin and Range ecoregion also is similar to some of the other basin and range ecoregions in the sense that sagebrush is the predominant vegetation. Most of the Northern Basin and Range ecoregion is dry and receives very little precipitation, but springs and wetlands scatter the landscape and sustain much of the regional wildlife (Oregon Department of State Lands, 2000).

 

Since most of the Northern Basin and Range ecoregion is arid and soil development is generally poor, viable economic land uses are limited. Livestock grazing is the predominant land use (cattle and sheep), and tends to occur in the grassland/shrubland landscapes (fig. 2). However, some agriculture (mostly hay farming) has been made possible following the construction of reservoirs along regional waterways. Finally, mining and recreation account for small, yet notable fragments of local economies in the Northern Basin and Range ecoregion. Ultimately, the scarcity of economic activity within the Northern Basin and Range ecoregion explains the absence of any large municipalities and the general lack of developed land across the region’s landscape.

 

Although human land uses are limited within the Northern Basin and Range ecoregion, activities such as grazing have significantly changed the contemporary fire regime, ultimately contributing to the loss of native plant communities in the region (Miller and others, 2001) (fig. 3). Historic land management practices such as unregulated grazing and fire suppression has led to fuel build up and invasion of rangelands by nonnative species (Oregon Department of State Lands, 2000). The most notable of these invasive species is cheatgrass (Bromus tectorum), which was introduced by settlers intending to feed domestic livestock by filling areas left void by native plants (Pellant and others, 2004). Cheatgrass and other introduced annuals not only outcompete native plants, but also alter the Northern Basin and Range ecoregion’s fire regime by providing a dense and continuous source of fuel that extends the fire season (Pyke, 2002). Frequent fires not only eliminate native sagebrush in the short term. Following wildfire events, the competitiveness and prolific seed production of cheatgrass allows it to reestablish before sagebrush (Keeley, 2006, Pellant and others, 2004). Cheatgrass has ultimately created a positive feedback mechanism that favors frequent fires and early reestablishment in landscapes formerly occupied by sagebrush.

 

Contemporary Land Cover Change (1973 to 2000)

Between 1973 and 2000, the footprint (overall areal extent) of LU/LC change in the Northern Basin and Range ecoregion was 5.8 percent, or 6,392 km². This change can be interpreted as the amount of the Northern Basin and Range ecoregion that experienced LU/LC change during at least one of the four intervals that make up the entire 27-year study period. This footprint of change translates to an estimated 3,577 km² that changed during one period, 2,435 km² that changed during two periods, 162 km² that changed during three periods, and 217 km² that changed throughout all four periods (table 1).

 

The average annual rate of LU/LC change in the Northern Basin and Range ecoregion from 1973 to 2000 was 0.3 percent per year. This measurement, which normalizes the results for the 27-year study period to an annual scale, means that the region averaged 0.3 percent (363 km²) of change each year from 1973 to 2000. However, this annual change varied between each of the four periods. Between 1973 and 1980, the annual rate of change in the Northern Basin and Range ecoregion was 0.1 percent per year, while the annual rate of change increased to 0.3 percent per year from 1980 to 1986 and 0.6 percent from 1986 to 1992. The normalized annual rate dropped from 1992 to 2000 to 0.3 percent per year (table 2).

 

In 2000, our results illustrate the estimated prevalence of five of the eleven LU/LC classes in the Northern Basin and Range ecoregion: grassland/shrubland (88.3 percent), forest (4.8 percent), nonmechanically disturbed (2.5 percent), agriculture (2.3 percent), and wetland (1.1 percent). Five other LU/LC classes cumulatively made up the remaining one percent of the Northern Basin and Range ecoregion landscape in 2000 (table 3). Between 1973 and 2000, the LU/LC types that experienced a measurable net change in relation to the total Northern Basin and Range ecoregion area include, in descending order, grassland/shrubland (3.6 percent decrease), nonmechanically disturbed (2.3 percent increase), and forest (1.0 percent increase).

 

The "from-to" information afforded by a post classification comparison allowed us to identify LU/LC class conversions and rank these conversions according to their magnitude. Table 4 illustrates the most frequent conversions for each period and from 1973 to 2000 in the Northern Basin and Range ecoregion. Although field work confirmed the presence of many of the conversions listed in Table 4, our ability to report these changes based on our interpretations was accomplished with varying degrees of uncertainty (as illustrated in the errors contained within the table). In general, higher uncertainty arose where sampled changes were clustered within certain parts of the Northern Basin and Range ecoregion rather than evenly across the region.

 

Four of the top ten most prominent conversions are connected to nonmechanical disturbance of land cover by fire. Cumulatively, the effect of nonmechanical disturbance on grassland and shrubland resulted in an estimated 5,007 km² of vegetated land-cover loss (fig. 4). However, much of this land experienced ecological succession, or regrowth, after each disturbance event. This regrowth accounts for 2,527 km² of vegetated land-cover gain (areas that experienced fires in consecutive periods account for an additional 1,491 km² of change). The transitions to and from the water class represent other common conversions in the Northern Basin and Range ecoregion during the study period (992 km²). Less common conversions consisted of the transitions from grassland/shrubland to land uses such as agriculture and mining.

 

References

 

Grayson, D.K., 1993, The desert's past; a natural prehistory of the Great Basin: Washington, D.C., Smithsonian Institution Press, 356 p.

 

Keeley, J.E., 2006, Fire management impacts on invasive plants species in the Western United States: Conservation Biology, v. 20, p. 375-384.

 

Miller, R., Baisan, C., Rose, J., and Pacioretty, D., 2001, Pre- and post-settlement fire regime in mountain big sagebrush steppe and aspen: the northwestern Great Basin: Corvallis, Oregon, National Interagency Fire Center.

 

Oregon Department of State Lands, 2000, Chapter 4.8: Northern Basin and Range, in, Oregon State of the Environment Report: Salem, Oregon: [http://egov.oregon.gov/DAS/OPB/docs/SOER2000/Ch4_8.pdf (last accessed January 3, 2008)]

 

Pellant, M., Abbey, B., and Karl, S., 2004, Restoring the Great Basin Desert, U.S.A.; integrating science, management, and people: Environmental Modeling and Assessment, v. 99, p. 169-179.

 

Pyke, D.A., 2002, Born of fire-restoring sagebrush steppe: U.S. Geological Survey Forest and Rangeland Ecosystem Science Center, Fact Sheet 126-02, 2 p.

 

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., Wylie, B.K., and van Driel, N., 2001, Completion of the 1990s National Land Cover Data Set for the conterminous United States from Landsat Thematic Mapper data and ancillary data sources: Photogrammetic Engineering and Remote Sensing, v. 67, p. 650-662.

 

 

 

Figures and Tables

 

Refer to caption

 

Figure 1. Northern Basin and Range ecoregion and surrounding ecoregions. Information shown includes land-use/land-cover data from the 1992 National Land Cover Dataset (Vogelmann and others, 2001) and the 32 randomly selected 100 km² sample blocks used to create estimates of change for the entire ecoregion.

 

Table 1. Footprint of Change in the Northern Basin and Range ecoregion. Estimated percentage of ecoregion that experienced change within the study period. 

 

 

 

 

 

 

 

 

 

 

 

 

 

85% CONFIDENCE INTERVAL

 

 

 

 

FOOTPRINT of CHANGE

% of ECOREGION

 +/- (%)

LOWER

UPPER

STANDARD ERROR

RELATIVE ERROR

ECOREGION AREA (km²)

 +/- (km²)

 (1973-2000)

ALL CHANGE

5.8%

3.9%

2.0%

9.7%

2.6%

44.7%

6391.8

4220.1

1 Change

3.3%

3.2%

0.0%

6.5%

2.2%

67.0%

3577.6

3537.1

2 Changes

2.2%

2.1%

0.1%

4.4%

1.5%

65.3%

2434.9

2345.9

3 Changes

0.1%

0.1%

0.0%

0.3%

0.1%

52.7%

162.3

126.2

4 Changes

0.2%

0.3%

-0.1%

0.5%

0.2%

97.7%

217.0

312.8

 

 

 

 

 

 

 

 

 

 

 

 

Table 2. Overall change in the Northern Basin and Range ecoregion. Overall change estimates by interval, 85% confidence interval, standard error, relative error, and normalized average annual change.

 

 

 

 

 

 

 

 

% stratum

 

85% Confidence Interval

 

 

 

 

Change Estimate

+/-

Lower Bound

Upper Bound

Standard Error

Relative Error

Average Annual %

1973 to 1980

0.8%

0.5%

0.3%

1.2%

0.3%

42.8%

0.1%

1980 to 1986

1.6%

1.0%

0.6%

2.6%

0.7%

43.3%

0.3%

1986 to 1992

3.9%

2.7%

1.2%

6.5%

1.8%

47.2%

0.6%

1992 to 2000

2.8%

2.1%

0.7%

4.8%

1.4%

50.2%

0.3%

 

 

 

 

 

 

 

 

km²

 

85% Confidence Interval

 

 

 

 

Change Estimate

+/-

Lower Bound

Upper Bound

Standard Error

Relative Error

Average Annual %

1973 to 1980

823.5

520.1

303.5

1343.6

1.0%

17.1%

117.6

1980 to 1986

1717.4

1097.2

620.2

2814.6

0.6%

17.6%

286.2

1986 to 1992

4224.4

2940.2

1284.1

7164.6

0.8%

27.5%

704.1

1992 to 2000

3037.8

2249.8

788.0

5287.6

0.9%

22.4%

379.7

 

 


Table 3. Land-cover trends in the Northern Basin and Range ecoregion. Percentages and amounts of each land cover class for each of the five mapped dates and associated margins of error.


 

1973

1980

1986

1992

2000

 

 

Estimate

85% CI

Estimate

85% CI

Estimate

85% CI

Estimate

85% CI

Estimate

85% CI

Change

Water

0.50%

0.36%

0.34%

0.20%

0.56%

0.35%

0.28%

0.19%

0.34%

0.20%

-0.16%

Developed

0.06%

0.04%

0.06%

0.04%

0.06%

0.04%

0.06%

0.04%

0.07%

0.05%

0.02%

Mech. Disturbed

0.05%

0.07%

0.24%

0.31%

0.00%

0.00%

0.34%

0.30%

0.03%

0.02%

-0.03%

Mining

0.07%

0.05%

0.07%

0.05%

0.09%

0.05%

0.17%

0.10%

0.20%

0.12%

0.13%

Barren

0.42%

0.16%

0.42%

0.16%

0.42%

0.16%

0.41%

0.16%

0.41%

0.16%

-0.01%

Forest

3.78%

2.53%

3.78%

2.53%

3.78%

2.53%

3.78%

2.53%

4.78%

2.85%

1.00%

Grass/Shrub*

91.92%

2.64%

91.91%

2.67%

90.65%

2.70%

89.39%

3.20%

88.30%

4.01%

-3.63%

Agriculture

1.98%

0.87%

2.18%

0.97%

2.26%

1.02%

2.25%

1.02%

2.31%

1.07%

0.33%

Wetland

1.05%

0.47%

0.99%

0.47%

1.04%

0.47%

0.98%

0.47%

1.10%

0.49%

0.05%

N.M. Disturbed

0.18%

0.25%

0.00%

0.00%

1.14%

0.96%

2.35%

2.37%

2.47%

3.24%

2.29%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1973

1980

1986

1992

2000

 

 

(km²)

85% CI

(km²)

85% CI

(km²)

85% CI

(km²)

85% CI

(km²)

85% CI

Change

Water

547.8

393.8

371.6

218.8

615.2

382.9

304.7

207.9

376.1

218.8

-171.7

Developed

61.9

43.8

63.3

43.8

67.8

43.8

69.0

43.8

79.3

54.7

17.4

Mech. Disturbed

59.1

76.6

265.3

339.1

0.6

0.0

369.3

328.2

29.8

21.9

-29.3

Mining

72.7

54.7

78.5

54.7

96.8

54.7

186.6

109.4

217.6

131.3

144.9

Barren

460.8

175.0

458.1

175.0

455.5

175.0

446.6

175.0

448.5

175.0

-12.3

Forest

4132.2

2767.8

4133.5

2767.8

4133.2

2767.8

4132.7

2767.8

5229.4

3117.9

1097.3

Grass/Shrub*

100562.8

2888.2

100552.0

2921.0

99172.4

2953.8

97790.4

3500.8

96595.6

4386.9

-3967.2

Agriculture

2164.0

951.8

2387.3

1061.2

2477.3

1115.9

2459.8

1115.9

2522.8

1170.6

358.8

Wetland

1145.7

514.2

1085.1

514.2

1138.1

514.2

1071.5

514.2

1203.3

536.1

57.6

N.M. Disturbed

193.1

273.5

5.4

0.0

1243.0

1050.2

2569.4

2592.8

2697.6

3544.6

2504.5

 

 

 

 

 

 

 

 

 

 

 

 

Note: Only the Water, Wetland, and Grassland/Shrubland classes had Wilcoxon pairs (N) ≥10.

 

 

 

 

* Denotes classes with statistically significant trends and N>10

 

 

 

 

 

 

 


 

Table 4. Common land-cover conversions in the Northern Basin and Range ecoregion. Top five land cover conversions, margin of error, standard error, and as a percentage of all changes.

 

 

 

 

 

 

 

 

 

 

 

Area changed

Standard Error

85% CI

% of ecoregion

% of all

Period

From class

To class

(km²)

+/- (km²)

changes

1973-1980

Water

M.Disturbed

255.6

230.6

340.4

0.2%

31.1%

 

Grass/Shrub

Agriculture

225.1

123.7

182.5

0.2%

27.4%

 

N.M.Disturbed

Grass/Shrub

192.2

189.4

279.6

0.2%

23.4%

 

M.Disturbed

Water

59.3

57.1

84.3

0.1%

7.2%

 

Wetland

Grass/Shrub

43.8

33.8

49.9

0.0%

5.3%

 

Other classes

Other classes

46.0

n/a

n/a

0.0%

5.6%

 

 

 

822.1

 

 

0.8%

100%

 

 

 

 

 

 

 

 

1980-1986

Grass/Shrub

N.M.Disturbed

1247.9

716.8

1058.0

1.1%

73.5%

 

M.Disturbed

Water

237.0

213.0

314.4

0.2%

14.0%

 

Grass/Shrub

Agriculture

94.8

65.0

95.9

0.1%

5.6%

 

Grass/Shrub

Wetland

33.8

27.0

39.8

0.0%

2.0%

 

Grass/Shrub

Mining

21.4

19.1

28.2

0.0%

1.3%

 

Other classes

Other classes

62.0

n/a

n/a

0.1%

3.7%

 

 

 

1697.0

 

 

1.6%

100%

 

 

 

 

 

 

 

 

1986-1992

Grass/Shrub

N.M.Disturbed

2477.4

1709.4

2523.0

2.3%

58.6%

 

N.M.Disturbed

Grass/Shrub

1137.3

649.7

959.0

1.0%

26.9%

 

Water

M.Disturbed

312.6

223.3

329.6

0.3%

7.4%

 

N.M.Disturbed

N.M.Disturbed

102.3

100.8

148.7

0.1%

2.4%

 

Wetland

Grass/Shrub

69.7

45.9

67.7

0.1%

1.6%

 

Other classes

Other classes

130.6

n/a

n/a

0.1%

3.1%

 

 

 

4229.8

 

 

3.9%

100%

 

 

 

 

 

 

 

 

1992-2000

N.M.Disturbed

N.M.Disturbed

1388.8

1368.3

2019.6

1.3%

31.8%

 

Grass/Shrub

N.M.Disturbed

1276.4

1053.5

1555.0

1.2%

29.2%

 

N.M.Disturbed

Forest

1146.8

1129.9

1667.8

1.0%

26.3%

 

M.Disturbed

Wetland

151.5

148.9

219.8

0.1%

3.5%

 

M.Disturbed

Grass/Shrub

143.8

86.1

127.1

0.1%

3.3%

 

Other classes

Other classes

259.6

n/a

n/a

0.2%

5.9%

 

 

 

4366.8

 

 

4.0%

100%

Overall:

 

 

 

 

 

 

 

1973-2000

Grass/Shrub

N.M.Disturbed

5006.9

2869.4

4235.2

4.6%

45.4%

 

N.M.Disturbed

N.M.Disturbed

1491.2

1368.8

2020.3

1.4%

13.5%

 

N.M.Disturbed

Grass/Shrub

1379.1

810.2

1195.9

1.3%

12.5%

 

N.M.Disturbed

Forest

1148.2

1129.9

1667.7

1.0%

10.4%

 

Water

M.Disturbed

568.2

447.8

660.9

0.5%

5.2%

 

Grass/Shrub

Agriculture

406.4

233.4

344.5

0.4%

3.7%

 

M.Disturbed

Water

353.5

233.4

344.6

0.3%

3.2%

 

M.Disturbed

Wetland

167.8

164.9

243.4

0.2%

1.5%

 

M.Disturbed

Grass/Shrub

156.1

89.6

132.3

0.1%

1.4%

 

Grass/Shrub

Mining

147.0

78.3

115.5

0.1%

1.3%

 

Other classes

Other classes

199.9

n/a

n/a

0.2%

1.8%

 

 

 

11024.1

 

 

10.1%

100%

 

Refer to caption

 

Figure 2. Area undergoing livestock grazing and hay farming. Land-use/land-cover types shown are grass/shrubland and agriculture.

 

 

Refer to caption

 

 

Figure 3. Shrubland being used as open rangeland for cattle. Charred shrubs illustrate the presence of nonmechanical disturbance of land cover by fire. Land-use/land-cover types shown are grass/shrubland and nonmechanically disturbed.


Refer to caption

 

Figure 4. Area experiencing active nonmechanical disturbance of land cover by fire. Land-use/land-cover types shown are grass/shrubland, forest, and nonmechanically disturbed.

 

[1] U.S. Geological Survey, Western Geographic Science Center, Menlo Park, CA 94025

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