Natural Resources
Conservation Service
Ecological site R051XY283CO
Foothills 12-16 PZ
Last updated: 12/11/2024
Accessed: 12/22/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 051X–High Intermountain Valleys
This MLRA encompasses the San Luis Valley in south central Colorado and the Taos Plateau and Taos alluvial fans of north central New Mexico. As part of the northern portion of the Rio Grande Rift, the MLRA consists of large, alluvium filled basins washed down from adjacent mountain ranges. The Rio Grande River flows through this MLRA, continuing its long function of carrying mountain sediment down to the basin. Cenozoic volcanism is an extensive characteristic of the MLRA where large basalt flows with volcanic hills and domes are abundant.Ancient Lake Alamosa is a large feature within the MLRA.
Classification relationships
NRCS:
Major Land Resource Area 51, High Intermountain Valleys (United States Department of Agriculture, Natural Resources Conservation Service, 2006).
USFS:
331J – Northern Rio Grande Basin M331Ic > 331Ja - San Luis Valley, 331Jb - San Luis Hills and 331C - Mogotes
EPA:
22 - Arizona/New Mexico Plateau > 22a - San Luis Shrublands and Hills ; 22b -San Luis Alluvial Flats and Wetlands ; 22c - Salt Flats; 22e - Sand Dunes and Sand Sheets and 22f -Taos Plateau (Griffith, 2006).
USGS:
Southern Rocky Mountain Province
Ecological site concept
It is a grassland site that rolling hills, mountains and basalt mesas where alluvium has covered bedrock, creating soils that are deep. The site occurs on the upper end of the slope, on what is considered the mountain-valley fan. This site is associated with volcanic structures and geology.
Associated sites
| R051XY277CO |
Basalt Hill 7-12 PZ The basalt hills site is on soils that are shallow to very shallow, mostly close to the escarpment, and the foothills site is where soil depth becomes deep. |
|---|---|
| R051XY278CO |
Valley Bench 8-12 PZ Along the lower end of the slopes/fans where alluvial soils become very deep the Foothills site grades into the the valley bench. |
| R051XY317CO |
Foothill Loam The Foothills Loam site occurs on what is considered the mountain-valley fan. Component landforms include: alluvial fans, fans, fan remnants, and mountain-slopes. Soils are mostly deep loam formed from alluvium from igneous and metamorphic rock. |
Similar sites
| R051XY317CO |
Foothill Loam The Foothills Loam site occurs on what is considered the mountain-valley fan. Component landforms include: alluvial fans, fans, fan remnants, and mountain-slopes. Soils are mostly deep loam formed from alluvium from igneous and metamorphic rock. |
|---|
Table 1. Dominant plant species
| Tree |
(1) Pinus edulis |
|---|---|
| Shrub |
(1) Artemisia tridentata |
| Herbaceous |
(1) Pascopyrum smithii |
Physiographic features
This site occupies rolling hills, mountains and basalt mesas. The site occurs on the upper end of the slope, on what is considered the mountain-valley fan. The Foothills site is associated with these volcanic structures and geology.
Table 2. Representative physiographic features
| Landforms |
(1)
Mesa
(2) Mountain |
|---|---|
| Runoff class | Low to medium |
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 7,700 – 9,100 ft |
| Slope | 1 – 35% |
Climatic features
Average annual precipitation is 12 to 16 inches. Of this, more than half falls between May 1 and September 1, mostly as hard, spotty thundershowers in July and August. May and June are normally dry. Wide seasonal and yearly variations are common. Snow makes up a slightly higher percent of the total than on some of the nearby ecological sites at lower elevations. Major native plants make most of their growth between early May and mid-July, sometimes extending it through most of August. Some plants normally complete growth by mid-June and may make late regrowth.
Mean annual temperature is 40 degrees to 43 degrees F. Average frost-free period is 80 to 105 days, from late May to early June to September. Summer daytime temperatures are frequently in the low 80's, but rarely exceed 90 degrees F, and nights are cool. Temperatures of -20 degrees to -30 degrees F can be expected each year and are common some winters. Parts of the site are slightly warmer, though than lower valley land because of air drainage. Winds that often reach high velocities are common, especially in spring. Relative humidity is often low. Even so, evaporation rates average lower than those of many dry regions because of the cooler climate. There is usually more snow than at lower elevations, and snow is usually present during the coldest weather. However, snow cover is light through much of some winters.
This climate zone does not have a representative climate station in Colorado. The only station is in Questa ,NM in this zone.
Table 3. Representative climatic features
| Frost-free period (characteristic range) | 80-105 days |
|---|---|
| Freeze-free period (characteristic range) | 60-90 days |
| Precipitation total (characteristic range) | 12-16 in |
| Frost-free period (actual range) | 80-105 days |
| Freeze-free period (actual range) | 60-90 days |
| Precipitation total (actual range) | 12-16 in |
| Frost-free period (average) | 92 days |
| Freeze-free period (average) | 75 days |
| Precipitation total (average) | 14 in |
Figure 1. Monthly precipitation range
Figure 2. Monthly minimum temperature range
Figure 3. Monthly maximum temperature range
Figure 4. Monthly average minimum and maximum temperature
Figure 5. Annual precipitation pattern
Figure 6. Annual average temperature pattern
Climate stations used
-
(1) CERRO [USC00291630], Questa, NM
Influencing water features
This site does not have a water table.
Soil features
The soils are mostly deep loams, occasionally this site will occur on moderately deep soils. The pH is generally 6.6 to 7.8, but in few map units the pH does range from 7.9 to 9.0. Some soils contain varying amounts of gravel and stone through the profile, but not enough to be classified as skeletal. Clay content of the surface layer ranges from 17-25% clay. Soil surface depth ranges from 4 to 15 inches. An argillic horizon starts between 4-15 inches in depth. Typically, the argillic horizon ends around 36 inches.
Potrio series would be a representative soil for this ecological site.
Table 4. Representative soil features
| Parent material |
(1)
Alluvium
–
basalt
(2) Alluvium – volcanic rock |
|---|---|
| Surface texture |
(1) Gravelly silt loam (2) Loam |
| Family particle size |
(1) Fine-loamy |
| Drainage class | Well drained |
| Permeability class | Moderately slow to moderate |
| Soil depth | 40 in |
| Surface fragment cover <=3" | 5 – 30% |
| Surface fragment cover >3" | Not specified |
| Available water capacity (Depth not specified) |
3.5 – 5.5 in |
| Calcium carbonate equivalent (Depth not specified) |
45% |
| Electrical conductivity (Depth not specified) |
2 mmhos/cm |
| Sodium adsorption ratio (Depth not specified) |
Not specified |
| Soil reaction (1:1 water) (Depth not specified) |
6.6 – 9 |
| Subsurface fragment volume <=3" (Depth not specified) |
5 – 30% |
| Subsurface fragment volume >3" (Depth not specified) |
10% |
Ecological dynamics
The site is a productive grass-dominated site. The major gradients that affect the biologic variability of this site include: depth to bedrock; texture, slope; aspect; and elevation. As the site grades toward deeper profiles with thicker argillic horizons it trends towards greater percentage of grass and less for shrubs. Cool and wetter conditions on northern and eastern aspects will favor upper montane bunchgrasses such as mountain muhly and Parry oatgrass at the upper elevations of this site. Warmer and dryer conditions (southern and western aspects and lower elevations) will favor lower montane grasses and shrubs such species as western wheatgrass and needleandthread grass and Wyoming big sagebrush.
State and transition model
More interactive model formats are also available.
View Interactive Models
Click on state and transition labels to scroll to the respective text
Ecosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Grass and Shrub Mix
This site is principally a grassland site with scattered shrubs. Trees are not natural to this site. As the site degrades grasses decrease and big sagebrush becomes more dominant. Blue grama will increase as the site degrades, and it, too becomes sparse under prolonged heavy grazing.
Resilience management. The reference state is most resilient to disturbance. Fire is an important disturbance to keep this site a grassland community. The grasses provide production, cover, annual turnover of fibrous roots and healthy soil microbial communities. Healthy microbial communities improve soil health factors such as water infiltration, retention, and nutrient cycling for plants.
Community 1.1
Grass and Shrub Mix
The reference state is grass dominant with scattered big sagebrush. Cool season grasses such as western wheatgrass, needle-and-thread, muttongrass, and junegrass are common. Minor amounts of forbs and shrubs can be expected. Among them are buckwheats, indian paintbrush, penstemon, lupine, locoweed, prairie sagewort, yellow rabbitbrush, Greene's rabbitbrush, fourwing saltbush, and winterfat. In cooler, wetter areas, mountain muhly and Parry oatgrass are abundant.
Resilience management. Bare ground is minimal and soil health is highest. Resilience to disturbance is greatest with the reference community. To maintain this community, periodic fire must set back the shrubs and trees and rejuvenate the grasses.
Dominant plant species
-
western wheatgrass (Pascopyrum smithii), grass
-
needle and thread (Hesperostipa comata), grass
Figure 7. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (lb/acre) |
Representative value (lb/acre) |
High (lb/acre) |
|---|---|---|---|
| Grass/Grasslike | 525 | 770 | 1050 |
| Shrub/Vine | 150 | 220 | 300 |
| Forb | 75 | 110 | 150 |
| Total | 750 | 1100 | 1500 |
Figure 8. Plant community growth curve (percent production by month). CO5108, Cool-season Dominant Warm-season Subdominant, MLRA 51 Alluvial Fans & fan Remnants. Reference Plant Community for Chico Fan located in LRU 51-5 on fans and fan remnants above valley floor, pre-dominantly in areas surrounding Villa Grove and Saguache, Saguache County..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 3 | 30 | 25 | 20 | 12 | 10 | 0 | 0 | 0 |
Community 1.2
Shrub Dominant
Shrubs constitute the greater percentage of composition and cover. Mainly big sagebrush has expanded with decreased grass cover between shrubs.
Resilience management. The more grass cover that is lost, the closer the site moves toward a threshold. Resilience to disturbance has decreased due to loss of soil, a decrease in infiltration, and a decrease in moisture retention.
Community 1.3
Juniper-Pinyon
This plant community has an increase in oneseed juniper and twoneedle pinyon. Over time, the trees spread from nearby shallow soils to the deep soils that this site occurs on. Grasses and shrubs are still mixed into the composition. As conifers increase, the soil becomes droughted.
Resilience management. Over time juniper and pinyon gain a competitive advantage due to extensive root systems that are both lateral and vertical. Periodic fire is needed to take out tree saplings and improve the vigor of grasses. After a certain percentage of cover becomes juniper and pinyon, a threshold is crossed to a tree state (State 2).
Pathway 1.1A
Community 1.1 to 1.2
The main driver is repetitive, high utilization of palatable species during the growing season without adequate periods of recovery where the plants produce flower and seed.. Palatable grass species decrease, bare ground increases, and shrubs gain a competitive advantage. A decrease in fire is another driver. Periodic fire has been an important disturbance to keep shrubs in check while improving ecological processes which favor grasses and forbs.
Pathway 1.2A
Community 1.2 to 1.1
Adding fire as a disturbance to decrease shrubs and open canopy to improve tillering of grasses. If grazing is to be implemented, then using management that allows for critical cool season grasses to grow and seed.
Pathway 1.2B
Community 1.2 to 1.3
Overtime with lack of fire due to a decrease in fuel load, pinyon and juniper saplings have an opportunity to out-compete shrubs and grasses. The main competitive advantage for pinyon and juniper are extensive root systems, both vertical and lateral. They effectively steal the moisture from everything else, and as they increase, the soil becomes droughted.
Pathway 1.3A
Community 1.3 to 1.1
Improving fuel loads through vegetation management and allowing fire to decrease the trees and shrubs, allowing grasses gain the competitive advantage.
State 2
Degraded
Community 2.1
Pinyon-Juniper
The site has become covered by twoneedle pinyon and oneseed juniper with very little understory. Bareground is high and a few remnant grasses, forbs, and shrubs are scattered between trees.
Transition T1A
State 1 to 2
Over time, with low fuel loads causing a lack of fire in the system, pinon and juniper stands expand from the shallow soils to the deep soils. As trees increase, understory decrease causing erosion and a decrease in ecosystem services. Eventually after a dominant percentage of cover becomes trees a threshold is crossed to the degraded pinon-juniper state.
Restoration pathway R2A
State 2 to 1
Important reference conditions of soil and vegetation need to be met to restore the site. This includes setting the trees back through a combination of mechanical treatment and fire. This also includes re-establishing the natural fire regime for long-term maintenance. And last of all, if grazing is implemented, long term management that promotes adequate fuel loads and encourages the colonization of cool season grasses.
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 600–1000 | |||||
| western wheatgrass | PASM | Pascopyrum smithii | 300–440 | – | ||
| needle and thread | HECO26 | Hesperostipa comata | 75–220 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 75–110 | – | ||
| muttongrass | POFE | Poa fendleriana | 75–110 | – | ||
| mountain muhly | MUMO | Muhlenbergia montana | 0–110 | – | ||
| blue grama | BOGR2 | Bouteloua gracilis | 75–110 | – | ||
| Parry's oatgrass | DAPA2 | Danthonia parryi | 0–110 | – | ||
| squirreltail | ELELE | Elymus elymoides ssp. elymoides | 75–110 | – | ||
| sand dropseed | SPCR | Sporobolus cryptandrus | 0–10 | – | ||
| spike dropseed | SPCO4 | Sporobolus contractus | 0–10 | – | ||
| little bluestem | SCSC | Schizachyrium scoparium | 0–10 | – | ||
| James' galleta | PLJA | Pleuraphis jamesii | 0–10 | – | ||
| littleseed ricegrass | PIMI | Piptatheropsis micrantha | 0–10 | – | ||
| roughleaf ricegrass | ORAS | Oryzopsis asperifolia | 0–10 | – | ||
| ring muhly | MUTO2 | Muhlenbergia torreyi | 0–5 | – | ||
|
Forb
|
||||||
| 2 | 75–150 | |||||
| Wyoming Indian paintbrush | CALI4 | Castilleja linariifolia | 0–10 | – | ||
| redroot buckwheat | ERRA3 | Eriogonum racemosum | 0–10 | – | ||
| hairy false goldenaster | HEVI4 | Heterotheca villosa | 0–10 | – | ||
| pingue rubberweed | HYRI | Hymenoxys richardsonii | 0–10 | – | ||
| scarlet gilia | IPAG | Ipomopsis aggregata | 0–10 | – | ||
| Colorado four o'clock | MIMU | Mirabilis multiflora | 0–10 | – | ||
| scarlet globemallow | SPCO | Sphaeralcea coccinea | 0–10 | – | ||
| lupine | LUPIN | Lupinus | 0–10 | – | ||
| locoweed | OXYTR | Oxytropis | 0–10 | – | ||
| beardtongue | PENST | Penstemon | 0–10 | – | ||
|
Shrub/Vine
|
||||||
| 3 | 175–275 | |||||
| big sagebrush | ARTR2 | Artemisia tridentata | 75–110 | – | ||
| fourwing saltbush | ATCA2 | Atriplex canescens | 0–110 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 0–55 | – | ||
| Greene's rabbitbrush | CHGR6 | Chrysothamnus greenei | 0–55 | – | ||
| skunkbush sumac | RHTR | Rhus trilobata | 0–55 | – | ||
| wax currant | RICE | Ribes cereum | 0–25 | – | ||
| plains pricklypear | OPPO | Opuntia polyacantha | 0–25 | – | ||
| spineless horsebrush | TECA2 | Tetradymia canescens | 0–25 | – | ||
| soapweed yucca | YUGL | Yucca glauca | 0–10 | – | ||
| prairie sagewort | ARFR4 | Artemisia frigida | 0–10 | – | ||
| broom snakeweed | GUSA2 | Gutierrezia sarothrae | 0–10 | – | ||
Interpretations
Supporting information
Inventory data references
Location of Typical Example of Site:
Open areas on top of Sand Pedro Mesa, just southeast of San Luis, Costilla County.
Field Offices in Colorado where the site occurs:
Alamosa, Center, and San Luis
References
-
. 2021 (Date accessed). USDA PLANTS Database. http://plants.usda.gov.
Other references
Chapman, S.S., G.E. Griffith, J.M. Omernik, A.B. Price, J. Freeouf, and D.L. Schrupp. 2006. Ecoregions of Colorado. (2-sided color posterwith map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,200,000.
Cleland, D.T.; Freeouf, J.A.; Keys, J.E.; Nowacki, G.J.; Carpenter, C.A.; and McNab, W.H. 2007. Ecological Subregions: Sections andSubsections for the conterminous United States. Gen. Tech. Report WO-76D [Map on CD-ROM] (A.M. Sloan, cartographer). Washington,DC: U.S. Department of Agriculture, Forest Service, presentation scale 1:3,500,000; colored.
Soil Conservation Service (SCS). August 1975. Range Site Description for Limy Bench #276. : USDA, Denver Colorado.
United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
Contributors
C. Villa, H. Garcia, Scott Woodall
Suzanne Mayne-Kinney
Approval
Kirt Walstad, 12/11/2024
Acknowledgments
Project Staff:
Suzanne Mayne-Kinney, Ecological Site Specialist, NRCS MLRA, Grand Junction SSO
Alan Stuebe, MLRA Soil Survey Leader, NRCS MLRA Alamosa SSO
Program Support:
Rachel Murph, NRCS CO State Rangeland Management Specialist, Denver
Eva Muller, Regional Director, Rocky Mountain Regional Soil Survey Office, Bozeman, MT
B.J. Shoup, CO State Soil Scientist, Denver
Eugene Backhaus, CO State Resource Conservationist, Denver
--Site Development and Testing Plan--:
Future work to validate and further refine the information in this Provisional Ecological Site Description is necessary. This will include field activities to collect low-, medium-, and high-intensity sampling, soil correlations, and analysis of that data.
Additional information and data are required to refine the Plant Production and Annual Production tables for this ecological site. The extent of MLRA 51 must be further investigated.
Field testing of the information contained in this Provisional ESD is required. As this ESD is moved to the Approved ESD level, reviews from the technical team, quality control, quality assurance, and peers will be conducted.
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
| Author(s)/participant(s) | |
|---|---|
| Contact for lead author | |
| Date | 09/25/2023 |
| Approved by | Kirt Walstad |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
-
Presence of water flow patterns:
-
Number and height of erosional pedestals or terracettes:
-
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
-
Number of gullies and erosion associated with gullies:
-
Extent of wind scoured, blowouts and/or depositional areas:
-
Amount of litter movement (describe size and distance expected to travel):
-
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
-
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
-
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
-
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
-
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
-
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
-
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
-
Perennial plant reproductive capability:
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