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2018 Regional Interpretation - Intermountain West

Introduction | Regional Interpretation | Rangeland Health | Non-Native Plant Species | Invasive Plant Species | Bare Ground, Inter-Canopy Gaps, and Soil Aggregate Stability | About the Data | Index of Tables | Index of Maps

Great Plains | Intermountain West | Southwest | Texas and Oklahoma | Other

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Intermountain West

The Intermountain West includes the Columbia River Basin and Snake River Plateau in the northwest, the Great Basin in Nevada and western Utah, and the Colorado Plateau in the Four Corners area of Utah, Arizona, New Mexico and Colorado (Figure 1). In addition to large areas of forest, this region has the highest proportion of Federal lands (Figure 2). Much of the rangeland in the Intermountain West is characterized by plant communities that were historically dominated by bunchgrasses and shrubs (Cronquist, Holmgren, Holmgren, Reveal, & Holmgren, 1977). Typical bunchgrasses include bluebunch wheatgrass [(Pseudoroegneria spicata), Idaho fescue (Festuca idahoensis, Sandberg's bluegrass (Poa secunda, various needlegrass spp., (Stipa spp.), dropseed spp. (Sporobolus spp.), and prairie junegrass (Koeleria macrantha). Sagebrush (Artemisia spp.) and juniper (Juniperus spp.) with pinyon pine (Pinyon spp.), mountain mahogany (Cercocarpus spp.), salt desert shrub (Atriplex spp and others), and greasewood (Sarcobatus spp.) are found throughout various shrub vegetation types. In Intermountain West vegetation, a shrub canopy zone often exists with a dominant shrub, an understory and interspace area consisting of smaller shrubs, bunchgrasses, forbs, and biological soil crusts (lichens, mosses and cyanobacteria at the soil surface). Intermountain West plant communities are especially susceptible to non-native exotic plants due to a combination of disturbances such as heavy grazing, frequent wildfires, and vehicular traffic. Exotic annual grasses can negatively impact biotic integrity, ecosystem stability, composition and structure, natural fire cycles, diversity, soil biota, vegetation production, forage quality, wildlife habitat, soil physical properties, organic matter dynamics, carbon balance, nutrient and energy cycles, and hydrology and erosion dynamics (Chapin III, et al., 2000; Evans, Rimer, & Belnap, 2001; Pierson, Calrson, & Spaeth, 2002; Ehrenfeld, 2003; Ogle, Reiners, & Gerow, 2003; Brooks, D’Antonio, & Richardson, 2004; Norton, Monaco, Norton, Johnson, & Jones, 2004; Belnap, Welter, Grimm, Barger, & Ludwig, 2005; Hooper, et al., 2005; Boxell & Drohan, 2008; Herrick, et al., 2010; Davies, 2011).

Figure 1. Broad Regions Described in the Interpretations

map showing broad regions

Figure 2. Acres of Non-Federal Rangeland, 2012

Map showing distribution of rangeland

Dramatic soil variability, driven by geology (soil parent material) and subsequent landscape formation, contribute to large differences in potential plant community composition. Soil-driven differences in plant communities are particularly evident in many parts of Utah, where salt-affected soils cover large areas (e.g., Bonneville Salt Flats). Large precipitation gradients and differences in potential evaporation and transpiration associated with aspect and elevation (lower on north-facing slopes and higher on south- and west-facing slopes) also contribute to variability in ecological potentials in this region. There are some significant localized areas of irrigated agriculture. Where cropland fields have been abandoned, they revert to rangeland, often with a predominance of non-native invasive plants.

Results in this report are based on NRI rangeland on-site data collected over two periods, 2004-2010 and 2011-2015. Drought impacted the area during the second period (Figures 3-14). While this region was abnormally dry or moderate drought during the early period (2004-2010), much of this region experienced severe to extreme drought during the more recent period (2011-2015). The figures provide context for subsequent summary results.

Water is the limiting resource throughout this region and droughts are common. Extended droughts may impact plant communities and result in increases in exposed bare ground. During the 2004 through 2010 sampling period Nevada and Oregon had all or portions of their land in the region with at least 25 percent of the land area in severe to extreme drought for four of the seven years, but that portion tended to change location annually and it never extended beyond two years. During the second sampling period (2011 – 2015), Nevada and Oregon had portions or all of their land in the region with severe to exceptional drought for four of the five years (2012 – 2015). The surrounding states only had two of the five years with severe to extreme drought and only ID and WA had years with repeated drought (2013-14 and 2014-15). For states on the periphery of the region (northern AZ, northwestern NM, western CO, WY and MT), the latter time period tended to have more years of drought. Northern AZ and northwestern NM had severe to extreme drought for three of the five years (2011-12 and 2014). None of these peripheral locations had extended droughts in the 2005 to 2010 period.

Figures 3-4. Maps of Average Drought Monitor Rating (0 to 4 scale, where 0 is mild drought and 4 is extreme) Across the Two NRI Sampling Periods

Figure 3. NRI Period 1: 2005-2010
Map showing dought conditions during 2005-

2010
Figure 4. NRI Period 2: 2011-2015
Map showing dought conditions during 2011-

2015
Map legend showing the 5 drought categories  
Figure 5. Average drought severity in the Washington portion of the Intermountain West region
Chart showing dought conditions in Washington
Figure 6. Average drought severity in the Oregon portion of the Intermountain West region
Chart showing dought conditions in Oregon
Figure 7. Average drought severity in the Idaho portion of the Intermountain West region
Chart showing dought conditions in Idaho
Figure 8. Average drought severity in the Nevada portion of the Intermountain West region
Chart showing dought conditions in Nevada
Figure 9. Average drought severity in the Utah portion of the Intermountain West region
Chart showing dought conditions in Utah
Figure 10. Average drought severity in the Montana portion of the Intermountain West region
Chart showing dought conditions in Montana
Figure 11. Average drought severity in the Wyoming portion of the Intermountain West region
Chart showing dought conditions in Wyoming
Figure 12. Average drought severity in the Colorado portion of the Intermountain West region
Chart showing dought conditions in Colorado
Figure 13. Average drought severity in the Arizona portion of the Intermountain West region
Chart showing dought conditions in Arizona
Figure 14. Average drought severity in the New Mexico portion of the Intermountain West region
Chart showing dought conditions in New Mexico

Rangeland Health Attributes

Within the Intermountain West region, there were increases in area where all three attributes showed moderate or greater departure from reference conditions in Arizona (from 6.7 ±2.7 percent to 22.3 ±8.0 percent) and New Mexico (from 23.0 ±6.2 percent to 50.5 ±9.9 percent) between the earlier and later periods. Figures 15-20 show these departures were especially evident in the Colorado Plateau, generally comprising northeast Arizona, southwest Utah, western Colorado, and northwest New Mexico. In the Colorado Plateau there was an increase in area between the two periods with at least one Rangeland Health attribute showing moderate or greater departure (Figures 15-16). In the same region, areas with all three Rangeland Health attributes having a moderate departure also increased (Figures 17-18). Parts of these states experienced severe to exceptional drought during the both periods and the years prior.

Utah was the only state in the region to report a statistically significant reduction (from 21.2 ±4.2 percent to 8.2 ±4.1 percent) in the non- Federal rangeland area where all three rangeland health attributes were at least a moderate departure from reference condition between the two sampling periods (Figures 15-17). In 2004-2010, 21.3 (±4.3) percent of the land exhibited at least moderate departures from reference condition, while in the 2011 -2015 period only 8.2 (±4.1) percent of the land showed the same departures (Rangeland Health Table 2, Table 3, and Table 4). During the same two periods Utah also had a reduction in non-Federal rangeland area with at least one rangeland health attribute with moderate or greater departure from reference conditions, declining from 41.2 (±5.8) percent to 29.5 (±6.3) percent between the two sample periods (Figures 18-20). The figures, however, show most of the improvements were on the west side of the state, but not in the portion that is part of the Colorado Plateau. Utah never had two years adjacent with severe or greater drought conditions relative to the other states, but in years prior to the first period much of the state experience extreme to exceptional drought. These factors may have contributed to the improved rangeland health results between 2004-2010 and 2011-2015.

Figures 15-16. Non-Federal Rangeland Where All Three Rangeland Health Attributes Show at Least Moderate Departure from Reference Conditions (Source: Rangeland Health Table 2, Table 3)

Figure 15. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where All Three Rangeland Health Attributes Show at Least Moderate Departure from Reference Conditions
Figure 16. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where All Three Rangeland Health Attributes Show at Least Moderate Departure from Reference Conditions

Figure 17. Non-Federal Rangeland Where All Three Rangeland Health Attributes Show at Least Moderate Departure from Reference Conditions. Error bars represent margins of error.

bar chart showing Non-Federal rangeland Where All Three Rangeland Health Attribute Shows at Least Moderate Departure from Reference Conditions 

by state

Figures 18-19. Non-Federal Rangeland Where at Least One Rangeland Health Attribute Shows at Least Moderate Departure from Reference Conditions (Source: Rangeland Health Table 2, Table 3)

Figure 18. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where at Least One Rangeland Health Attribute Shows at Least Moderate Departure from Reference Conditions
Figure 19. 2011-2015
Map showing 2011-2015 Non-Federal 

RangelandWhere at Least One Rangeland Health Attribute Shows at Least Moderate Departure from Reference Conditions

Figure 20. Non-Federal Rangeland Where at Least One Rangeland Health Attribute Shows at Least Moderate Departure from Reference Conditions. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where at Least One Rangeland Health Attribute Shows at Least Moderate Departure from Reference 

Conditions by state

Soil and Site Stability

Most states in this region did not show a statistically significant change between the two time periods in the amount of area with Soil and Site Stability having a moderate or greater departure. Utah was an exception where the amount of area with moderate or greater departure reduced from 25.2 (±4.7) percent to 12.4 (±4.9) percent. This improvement was not reflected in any quantitative measurement for Utah (see bare ground, soil aggregate stability below). The New Mexico and Arizona portions of the Colorado Plateau both increase the percent non-Federal rangeland area with moderate or greater departure for this attribute (Figures 21-23).

Figures 21-22. Non-Federal Rangeland Where Soil and Site Stability Shows at Least Moderate Departure from Reference Conditions (Source: Rangeland Health Table 2, Table 3)

Figure 21. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland Where 

Soil and Site Stability Shows at Least Moderate Departure from Reference Conditions
Figure 22. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland Where 

Soil and Site Stability Shows at Least Moderate Departure from Reference Conditions

Figure 23. Intermountain West Non-Federal Rangeland Where Soil and Site Stability Has Moderate or Greater Departure from Reference Conditions. Error bars represent margins of error.

bar chart showing Non-Federal rangeland where soil site stability ratings show at least moderate departure from reference conditions by state

Hydrologic Function

Similar to Soil and Site Stability, the amount of non-Federal rangeland area with moderate or greater departure in Hydrologic Function remained roughly the same between the two time periods in all states in the region except Utah, where the percent area was reduced from 30.4 (±5.3) to 16.2 (±4.5) between the two periods. In the Colorado Plateau, straddling the borders between AZ, UT, NM and CO along with the northwestern NM, there were increases in the areas of moderate or greater departure (Figures 24-26).

Figures 24-25. Non-Federal Rangeland Where Hydrologic Function Shows at Least Moderate Departure from Reference Conditions (Source: Rangeland Health Table 2, Table 3)

Figure 24. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland Where 

Hydrologic Function Shows at Least Moderate Departure from Reference Conditions
Figure 25. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland Where 

Hydrologic Function Shows at Least Moderate Departure from Reference Conditions

Figure 26. Intermountain West Non-Federal Rangeland Where Hydrologic Function Has Moderate or Greater Departure from Reference Conditions. Error bars represent margins of error.

bar chart showing Non-Federal rangeland where hydrologic function shows at least moderate departure from reference conditions by state

Biotic Integrity

Although there were some changes between the two time periods in the amount of non-Federal rangeland area that had moderate or greater departures in Biological Integrity within smaller areas (Figures 27-28), most states within the region had very little change (Figure 29). Within the Intermountain West, New Mexico was the exception with an increase from 33.0 (±6.8) to 69.2 (±9.2) percent.

Figures 27-28. Non-Federal Rangeland Where Biotic Integrity Shows at Least Moderate Departure from Reference Conditions (Source: Rangeland Health Table 2, Table 3)

Figure 27. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland Where 

Biotic Integrity Shows at Least Moderate Departure from Reference Conditions
Figure 28. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland Where 

Biotic Integrity Shows at Least Moderate Departure from Reference Conditions

Figure 29. Intermountain West Non-Federal Rangeland Where Biotic Integrity Has Moderate or Greater Departure from Reference Conditions. Error bars represent margins of error.

bar chart showing Non-Federal rangeland where biotic integrity shows at least moderate departure from reference conditions by state

Specific Indicator Discussion

Bare Ground

In the Intermountain West there was very little change in the amount of bare ground on non-Federal rangeland between 2004-2010 and 2011-2015 (Figures 30-32), but is highest in New Mexico (43.4 ±6.0 percent) and Arizona (41.7 ±5.9 percent). Similarly, there was no change in the percent of non- Federal rangeland where at least 50 percent of the land was bare ground (Figures 33-35). Within the Intermountain West the states with the highest percent non- Federal rangeland with at least 50 percent bare ground are New Mexico (40.9 ±13.0 percent) and Arizona (37.1 ±13.3 percent).

Figures 30-31. Bare Ground on Non-Federal Rangeland (Source: Bare Ground, Inter-Canopy Gaps, and Soil Aggregate Stability Table 111, Table 112)

Figure 30. 2004-2010
Map showing 2004-2010 Bare Ground on Non-Federal 

Rangeland
Figure 31. 2011-2015
Map showing 2011-2015 Bare Ground on Non-Federal 

Rangeland

Figure 32. Average Bare Ground on Non-Federal Rangeland in the Intermountain West. Error bars represent margins of error.

bar chart showing bare ground on non-Federal rangeland in the Intermountain West by state

Figures 33-34. Non-Federal Rangeland That is at Least 50% Bare Ground (Source: Bare Ground, Inter-Canopy Gaps, and Soil Aggregate Stability Table 114, Table 115)

Figure 33. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

that is at Least 50% Bare Ground
Figure 34. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

that is at Least 50% Bare Ground

Figure 35. Non-Federal Rangeland That Is At Least 50 Percent Bare Ground in the Intermountain West. Error bars represent margins of error.

bar chart showing Non-Federal rangeland in the Intermountain West that is at least 50 percent bare ground by state

Soil Aggregate Stability

Soil aggregate stability is a measure of resistance to water erosion and an indicator of soil quality and rangeland health. In this procedure soil peds are repeatedly immersed in water and rated 1 to 6 based on their ability to resist breaking apart during the process. Values of 4 or less indicate less stable aggregates. Within the Intermountain West region, there was little change in areas of non-Federal rangeland with soil aggregate stability values of 4 or less (Figures 36-38). However, within the region the pervasiveness of non-Federal rangeland with soil aggregate stability values of 4 or less in several states including New Mexico (91.3 ±4.6 percent), Arizona (90.7 ±7.0 percent), and Nevada (75.1 ±6.8 percent) is a concern. Without knowledge of the potential soil aggregate stability value for the site it is difficult to interpret this result.

Figures 36-37. Non-Federal Rangeland Where Soil Aggregate Stability is Rated 4 or Less (Source: Bare Ground, Inter- Canopy Gaps, and Soil Aggregate Stability Table 120, Table 121)

Figure 36. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland Where 

Soil Aggregate Stability is Rated 4 or Less
Figure 37. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland Where 

Soil Aggregate Stability is Rated 4 or Less

Figure 38. Intermountain West Non-Federal Rangeland Where Soil Aggregate Stability1 is Rated 4 or Less. Error bars represent margins of error.

bar chart showing Intermountain West Non-Federal Rangeland Where Soil Aggregate Stability is Rated 4 or Less by state

1 Soil aggregate stability ratings:
1 = 50% of structural integrity lost, (melts) within 5 seconds of immersion in water and less than 10% remains after 5 dipping cycles or soil too unstable to sample (falls through the sieve).
2 = 50% of structural integrity lost (melts) 5–30 seconds after immersion and less than 10% remains after 5 dipping cycles.
3 = 50% of structural integrity lost, (melts) 30–300 seconds after immersion or less than 10% remains on the sieve after five dipping cycles.
4 = 10–25% of original soil material remains on the sieve after five dipping cycles.
5 = 25–75% of original soil material remains on the sieve after five dipping cycles.
6 = 75–100% of original soil material remains on the sieve after five dipping cycles.

Gaps Greater than 2 Meters

Within the region there was little change between the two periods in non-Federal rangeland area where 2 meter of greater inter-canopy gaps account for at least 20% of the land. Arizona (45.9 ±10.9 percent), Nevada (39.5 ±8.1 percent), New Mexico (38.1 ±11.0 percent), and Utah (31.1 ±8.1) had the highest proportions of non-Federal rangeland with these large and numerous inter-canopy gaps (Figures 39-41). Within the region these same states, Arizona (30.7 ±10.3 percent), New Mexico (29.4 ±10.9 percent), Nevada (20.1 ±7.1 percent), and Utah (14.6 ±6.4 percent), had high proportions of non-Federal rangeland where 2-meter canopy gaps account for at least 20 percent of the land and inter-canopy gaps are at least 50% bare ground (Figures 42-44).

Figures 39-40. Non-Federal Rangeland Where 2-Meter Canopy Gaps Account for at Least 20 Percent of the Land (Source: Bare Ground, Inter-Canopy Gaps, and Soil Aggregate Stability Table 117, Table 118)

Figure 39. 2004-2010
Map showing 2004-2010 Where 2-Meter Canopy Gaps 

Account for at Least 20 Percent of the Land
Figure 40. 2011-2015
Map showing 2011-2015 Where 2-Meter Canopy Gaps 

Account for at Least 20 Percent of the Land

Figure 41. Intermountain West Non-Federal Rangeland Where 2-Meter Canopy Gaps Account for at Least 20 Percent of the Land. Error bars represent margins of error.

bar chart showing Non-Federal rangeland Where 2-Meter Canopy Gaps Account for at Least 20 Percent of the Land by state

Figures 42-43. Non-Federal Rangeland Where 2-Meter Canopy Gaps Account for at Least 20 Percent of the Land and Inter-Canopy Gaps Are at Least 50% Bare Ground (Source: Bare Ground, Inter-Canopy Gaps, and Soil Aggregate Stability Table 117, Table 118)

Figure 42. 2004-2010
Map showing 2004-2010 Where 2-Meter Canopy 

Gaps Account for at Least 20 Percent of the Land and Inter-Canopy Gaps Are at Least 50% Bare Ground
Figure 43. 2011-2015
Map showing 2011-2015 Where 2-Meter Canopy 

Gaps Account for at Least 20 Percent of the Land and Inter-Canopy Gaps Are at Least 50% Bare Ground

Figure 44. Intermountain West Non-Federal Rangeland Where 2-Meter Inter-canopy Gaps Account for at Least 20 Percent of the Land and the Inter-canopy Gaps are at Least 50 Percent Bare Ground. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where 2-Meter Inter-canopy Gaps Account for at Least 20 Percent of the Land and the Inter-canopy Gaps 

are at Least 50 Percent Bare Ground by state

Invasive Plants

The Intermountain West fire regimes on rangelands have changed because of the spread and dominance of annual grasses including annual bromes [for example, cheatgrass (Bromus tectorum) and red brome (Bromus rubens)], medusahead (Taeniatherum sp.) and North Africa grass (Ventenata dubia). Dominance of annual bromes (Bromus spp.) in the Intermountain West is widespread (Figures 45-47). Areas of non-Federal rangeland dominated by annual bromes having at least 50 percent relative cover of those species is 20.0 (±5.6) percent in Nevada, 15.5 (±5.4) percent in Oregon, 14.0 (±8.5) percent in Idaho, 11.5 (±7.2) percent in Washington, and 8.2 (±3.8) percent in Utah.

Medusahead and North Africa grass are also invasive within the region. Medusahead is widespread and now present on 24.3 (±6.5) percent of non- Federal rangeland in Idaho, 22.6 (±9.3) percent in Oregon, and 8.8 (±6.3) percent in Washington (Figure 48-50). Although not statistically significant, it is important to note the new presence of medusahead on lands in Nevada (0.2 ±0.4 percent), Utah (0.1 ±0.2 percent) and Wyoming (0.6 ± 1.3 percent) during the latter period. Presence of North Africa grass (ventenata) remained the same between the two time periods (Figures 51-53). It is present in Oregon on 8.1 (±4.4) percent of non-Federal rangeland and detected on trace amounts of land in Idaho and Washington.

Figures 45-46. Non-Federal Rangeland Where Annual Bromes Cover at Least 50% of the Soil Surface (Source: Invasive Plant Species Table 17, Table 18)

Figure 45. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where Annual Bromes Cover at Least 50% of the Soil Surface
Figure 46. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where Annual Bromes Cover at Least 50% of the Soil Surface

Figure 47. Intermountain West Non-Federal Rangeland Where Relative Cover of Annual Bromes is at Least 50 Percent. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where Annual Brome Species Cover at Least 50% of the Soil Surface by state

Figures 48-49. Non-Federal Rangeland Where Medusahead is Present (Source: Invasive Plant Species Table 33, Table 34)

Figure 48. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where Medusahead is Present
Figure 49. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where Medusahead is Present

Figure 50. Intermountain West Non-Federal Rangeland Where Medusahead is Present. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where Medusahead is Present by state

Figures 51-52. Non-Federal Rangeland Where Ventenata is Present (Source: Table 36, Table 37)

Figure 51. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland Where 

Ventenata is Present
Figure 52. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland Where 

Ventenata is Present

Figure 53. Intermountain West Non-Federal Rangeland Where Ventenata is Present. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where Ventenata is Present by state

Conifer Presence

Pacific junipers (Juniperus occidentalis and Juniperus californica) exist in the Intermountain West region as trace amounts in Idaho, Montana and Utah (Figures 54-56). However, in Oregon they were present on 17.9 (±4.4) percent of non-Federal rangeland during 2004-2010 and 13.1 (±7.7) percent during 2011-2015 (5 percent or greater relative cover on 12.2 (±3.1) vs 9.1 (±6.2) percent of non-Federal rangeland and 15 percent or greater relative cover on 6.5 (±2.7) vs. 5.1 (±4.8) percent of land between the earlier vs the later period). Although the difference was not significant between the periods, the direction of change was moving toward a reduction which may be a reflection of removal treatments.

Presence of Montane/intermontane junipers (Juniperus osteosperma and Juniperus scopulorum) did not change significantly in most states within this region (Figures 57-59). The exception is Arizona. In Arizona, their presence declined from 10.4 (±4.1) percent in 2004-2010 to 0.3 (±0.7) percent during 2011-2015. Pinyon pine (Pinus edulis and Pinus monophylla) presence did not change in Utah, Colorado, New Mexico, Arizona, and Nevada where they were detected (Figures 60-62).

Figures 54-55. Non-Federal Rangeland Where Pacific Juniper Species are Present (Source: Invasive Plant Species Table 81, Table 82)

Figure 54. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where Pacific Juniper species are Present
Figure 55. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where Pacific Juniper species are Present

Figure 56. Intermountain West Non-Federal Rangeland Where Pacific Juniper species are Present. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where  Pacific Juniper species are Present by state

Figures 57-58. Non-Federal Rangeland Where Montane/Intermontane Juniper Species are Present (Source: Invasive Plant Species Table 84, Table 85)

Figure 57. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where Montane/Intermontane Juniper species are Present
Figure 58. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where Montane/Intermontane Juniper species are Present

Figure 59. Intermountain West Non-Federal Rangeland Where Montane/Intermontane Juniper species are Present. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where  Montane/Intermontane Juniper species are Present by state

Figures 60-61. Non-Federal Rangeland Where Pinyon Pine Species are Present (Source: Invasive Plant Species Table 90, Table 91)

Figure 60. 2004-2010
Map showing 2004-2010 Non-Federal Rangeland 

Where Pinyon Pine Species are Present
Figure 61. 2011-2015
Map showing 2011-2015 Non-Federal Rangeland 

Where Pinyon Pine Species are Present

Figure 62. Intermountain West Non-Federal Rangeland Where Pinyon Pine Species are Present. Error bars represent margins of error.

bar chart showing Non-Federal Rangeland Where Pinyon Pine Species are Present by state

Summary and Conclusions

Within the Intermountain West region, the high desert Colorado Plateau which surrounds the four corners of northeast Arizona, northwest New Mexico, southwest Colorado, and southeast Utah had increased area of non-Federal rangeland where all three rangeland health attributes had at least moderate departure from reference conditions. This area also has high percentages of bare ground, numerous large (greater than two meters) inter-canopy gaps, and large inter-canopy gaps with at least 50 percent bare ground in the interspaces. Those openings in the plant canopy provide opportunities for erosion and invasion by weedy plant species. Although native to the region, Montane/intermontane junipers (Juniperus osteosperma and Juniperus scopulorum) and pinyon pine (Pinus edulis and Pinus monophylla) are common in this area. In places where they form dense stands, they can alter nutrient and water cycles, and energy flow through the ecosystem, affect hydrology, and reduce wildlife habitat and forage for domestic animals and wildlife (DiTomaso, 2000; Archer, Schimel, & Holland, 1995).

In the northwest area of the Intermountain West region, biotic integrity is the rangeland health attribute of most concern. Non-native annual bromes (Bromus spp.) are widespread and dominate areas of non-Federal rangeland in this part of the U.S. Medusahead and North Africa grass are also invasive within the region. These species are not only highly invasive in shrub communities often outcompeting native grasses and forbs, but they can be highly flammable, thus changing the fire regime in areas they invade (Brooks, D'Antonio, & Richardson, 2004).

About the Maps

The maps are constructed with NRI rangeland data collected in the field on rangeland during the periods 2004 to 2010 and 2011 to 2015. The regions are based on level IV ecoregion boundaries defined by the U.S. Environmental Protection Agency Western Ecology Division. In some cases level IV ecoregions were combined to include more sample sites. An additional category, referred to as "Insufficient data", represents areas where there were too few data points. Regions without non-Federal rangeland are described as "No data". Areas of Federal land are depicted with cross-hatching.

The rangeland health maps represent various levels of departure from the reference state as described in the ecological site description for that land area based on the indicators listed in Table 1. Note that some indicators are associated with more than one attribute while others are specific to a single attribute; this is intentional and is part of the evaluation process. Although these maps portray percentages of non-Federal rangeland with specific attribute ratings, not all of the indicators associated with that attribute may will have that rating. For example, one map displays non-Federal rangeland where soil and site stability shows at least moderate departure from reference conditions. Although some of the indicators associated with soil and site stability may have been rated on a scale representing none-to-slight and slight-to-moderate departure, the median rating was at least moderate. Rangeland health assessments evaluate the function of ecological processes for rangeland sites relative to their ecological site descriptions, which define expected ecological processes based on climate and soil. For some rangeland sites, no soil survey exists and no ecological site description has been developed. For those areas the no rangeland health data are reported. Maps exclude rangeland health estimates for mapping regions where at least 10 percent of non-Federal rangeland does not report rangeland health data. Rangeland health attribute assessments in the maps are based on percentages of non-Federal rangeland where rangeland health evaluations are reported.

Line point intercept data are utilized in summaries of non-native plant species, invasive plant species, and bare ground. Line point intercept data are collected along two intersecting 150-foot transects centered on each sample location. Data collectors record plant species, litter, lichen, moss, rock fragment, bedrock, and/or bare soil present at each 3-foot interval (mark).

Canopy gap data are used to identify areas with large foliar inter-canopy gaps which have more exposure to erosion and may provide opportunity for invasive plants to become established. Data collectors record lengths of plant inter-canopy gaps along the two intersecting 150-foot transects.

Soil aggregate stability is a recognized indicator of soil quality and rangeland health. Data collectors water immerse soil surface peds collected at the sample site and subject the soil peds to five dipping cycles. Soil stability is rated based on the outcomes of these water exposure techniques. Ratings range from 1 (very unstable) to 6 (very stable).

The source data used to construct the drought figures are from the National Drought Mitigation Center, and follow the drought monitor categories: https://droughtmonitor.unl.edu/About/AbouttheData/DroughtClassification.aspx. The weekly drought monitor data were converted to a 1/8-degree grid, and the state and broad region polygons were used to clip out the grid cells within each region for the two time periods. Both the stack plots show the distribution of 1/8-degree grid cells of each drought monitor class for each year.

Map legend showing the 5 drought categories

More Information

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Belnap, J., Welter, J., Grimm, N., Barger, N., & Ludwig, J. (2005). Linkages between microbial and hydrologic processes in arid and semiarid watersheds. Ecology, 86(2), 298-307.

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