Hierarchy for Ecological Sites
(LRR, MLRA, LRU, Soil-Landscape
Properties)
Interagency Ecological Site Applications Workshop
Winnemucca, NV
June 5-7, 2012
Herman B. Garcia
Ecological Site Inventory Specialist
USDA-NRCS Phoenix AZ
What are
Land Resource Regions?
Land Resource Regions (LRRs ) are a group of geographically
associated major land resource areas.
There are 28 LRRs described across the conterminous United States,
Alaska, Pacific Basin Region, Hawaiian Region,
and the Caribbean Region.
United States Department of Agriculture Handbook 296
Land Resource Regions and Major Land Resource Areas of the United States, the
Caribbean, and the Pacific Basin
LRR - D
Western Range and Irrigated Region
D
This is a semidesert or desert region of plateaus, plains,
basins, and many isolated mountain ranges.
549,725 square miles
average annual precipitation 6 – 42 inches
average annual temperature 40-60 degrees F
SE receive warm summer rains … elsewhere in the region, however,
most of the precipitation falls during the cool season.
freeze-free period ranges from 105-260 days
soils are dominantly Aridisols, Entisols,
and Mollisols
dominantly mesic soil temperature regime
aridic soil moisture regime
and mixed mineralogy
What are
Major Land Resource Areas (MLRAs)?
Major land resource areas are geographically associated land
resource units.
Over 300 MLRAs are currently described
23 MLRAs are identified within LRR D
Nevada MLRAs
24—Humboldt Area
Area is in Nevada and Oregon
-12,680 square miles.
-Winnemucca Nevada
Physiography…the Great Basin Section
of the Basin and Range Province of the
Intermontane Plateaus
Elevation 3,950-5,900 feet to 8,850
feet mountain peaks
Geology… wide valleys , N to S
trending isolated ranges are uplifted
fault-block mountains
Climate…average annual precipitation
is 6-12 inches as much as 40
inches…Summers are dry. The average
annual temperature is 38-53 degrees
F… freeze-free period averages 135
days and ranges from 100 to 175
days…
Soils… dominant soil order is Aridisols
Torriorthents (Boton series) in loess
and alluvium over lacustrine
sediments…
Biological Resources… Shrub-grass veg
Nevada MLRAs
25—Owyhee High Plateau
Area is in Nevada, Idaho, Oregon, and Utah
-28,930 square miles
-Elko, Nevada,
Physiography…within the Intermontane
Plateaus... separated by narrow, aggraded
Desert … N. half within the Columbia
Plateaus Province...NE corner has deep,
narrow canyons draining into the Snake
River…. Elevation ranges 3,000 -7,550 feet
…9,840 feet on some steep mtns.
Geology… dominant rock types in the
area are volcanic - andesite, basalt, and
rhyolite… Cretaceous granitic rocks occur
in the mountains. Only a few narrow
valleys occur in this area .
Climate… AAP is 7-16 inches and exceed 50
Inches…Ppt evenly - fall, winter, and spring
The average annual temperature is 35-53
degrees F… freeze-free period avg 135 days
Soils… dominant order are Aridisols and
mollisols
Biological Resources… Shrub-grass veg- high
plateaus support juniper and mahogany
What are
Land Resource Units (LRUs)?
Land resource units (LRUs) are the basic units
from which major land resource areas (MLRAs) are
determined.
LRUs are generally several thousand
acres in size
Synonymous with Common Resource Areas (CRAs) in 2005
Ecological Sites are the building blocks for LRUs
Regions with similar climate, land use
Geographic areas with similar soils
Similar landscape patterns
Groups of Ecological Sites -share landscapes
Intermingled ecological sites or single site
One individual representative of the site
An observation of plant-soil relationships
Ecological Cross-References
MLRA
Forest Service Section
EPA Level III Ecoregion
% of
MLRA
24 Humboldt Area
341E Northern Mono
13 Central Basin and Range
67
24 Humboldt Area
M341D W Great Basin
and Mtns
13 Central Basin and Range
17
24 Humboldt Area
342B Northwestern
Basin and Range
80 Northern Basin and Range
10
24 Humboldt Area
341G Northeastern
Great Basin
13Central Basin and Range
6
25 Owyhee High
Plateau
342C Owyhee Uplands
80 Northern Basin and Range
43
25 Owyhee High
Plateau
341G Northeastern
Great Basin
80 Northern Basin and Range
13
25 Owyhee High
Plateau
341G Northeastern
Great Basin
13 Central Basin and Range
13
25 Owyhee High
Plateau
342J Eastern Basin and
Range
80 Northern Basin and Range
11
25 Owyhee High
Plateau
M341A East Great Basin
and Mtns
13 Central Basin and Range
7
Source: USDA Ag Handbook 296;Appendix I