Natural Resources
Conservation Service
Ecological site R041XB202AZ
Clayey Swale
8-12" p.z.
Last updated: 4/09/2021
Accessed: 08/29/2026
-
Search
Major Land Resource Area or ecological site by name and/or ID.
PreviousSectionsNextGeneral 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.
Click to explore map
Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 041X–Madrean Archipelago
AZ 41.2 – Chihuahuan – Sonoran Desert Shrubs
Elevations range from 2600 to 4000 feet and precipitation ranges from 8 to 12 inches per year. Vegetation includes mesquite, palo verde, catclaw acacia, soaptree yucca, creosotebush, whitethorn, staghorn cholla, desert saltbush, Mormon tea, burroweed, snakeweed, tobosa, black grama, threeawns, bush muhly, dropseed, and burrograss. The soil temperature regime is thermic and the soil moisture regime is typic aridic. This unit occurs within the Basin and Range Physiographic Province and is characterized by numerous mountain ranges that rise abruptly from broad, plain-like valleys and basins. Igneous and metamorphic rock classes dominate the mountain ranges and sediments filling the basins represent combinations of fluvial, lacustrine, colluvial and alluvial deposits.Associated sites
R041XB203AZ Clayey Upland 8-12" p.z.
R041XB204AZ Clay Loam Upland 8-12" p.z.
R041XB223AZ Basalt Hills 8-12" p.z.
Similar sites
R041XC302AZ Clayey Swale 12-16" p.z.
R040XA102AZ Clayey Swale 10"-13" p.z.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous (1) Pleuraphis mutica
Physiographic features
This site occurs in the lowest elevations of the Madrean Basin and Range province in southeastern Arizona. It occurs on small floodplains, alluvial fans and swales; usually associated with basalt and andesite mountains. The site benefits on an irregular basis from extra water received as runoff from adjacent uplands.
Table 2. Representative physiographic features
Landforms (1) Flood plain
(2) Alluvial fan
(3) Swale
Flooding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Flooding frequency Rare to occasional Ponding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Ponding frequency Rare to occasional Elevation 2600 – 4000 ft Slope 0 – 6 % Aspect Aspect is not a significant factor Climatic features
Precipitation ranges from 8-12 inches annually. More than half falls during Jul-Sep in brief, but often heavy, thunderstorms. The rest of the moisture comes as light rain or snow that falls slowly for a day or more, but rarely lasts more than a day. May and June are normally the driest months. Humidity is generally very low.
Temperatures are mild throughout most of the year. Freezing temperatures are common at night Dec-Feb; brief 0 F may be observed some nights. During June, July & August, some days may exceed 100 F.
In years of average or greater winter precipitation, annual grasses and forbs occur abundantly in the interspaces.Table 3 Representative climatic features
Frost-free period (average) 240 days Freeze-free period (average) Precipitation total (average) BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
There are no water features associated with this site.
Soil features
These soils are deep and clayey textured. They have thin (1-2 inch) surface horizons that range from clayloam to silty clay in texture. They exhibit strong vertic soil properties. Surface soils (10 inches) are usually non-calcareous, but some soils have calcic horizons below the argillic horizon.
Soil series mapped on areas of this site include: SSA-662 Safford area MU Gy Guest; SSA-664 San Simon area MU's 26 Guest & 27 Guest and Hantz; SSA-666 Cochise county Northwestern part MU's 29, 30, 31, 32 Contention; SSA-671 Cochise county Douglas-Tombstone part MU 35 Contention.Table 4. Representative soil features
Surface texture (1) Clay
(2) Clay loam
(3) Silty clay loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Slow to very slow Soil depth 60 in Surface fragment cover <=3" 0 – 10 % Surface fragment cover >3" 0 – 1 % Available water capacity
(0-40in)9 – 10 in Calcium carbonate equivalent
(0-40in)0 – 10 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 2 Soil reaction (1:1 water)
(0-40in)7 – 8.2 Subsurface fragment volume <=3"
(Depth not specified)0 – 5 % Subsurface fragment volume >3"
(Depth not specified)0 – 1 % Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The historical climax plant community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as grazing, fire, or drought.
Production data provided in this site description is standardized to air-dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity Index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity Index, compare the production (air-dry weight) of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum shown for the group. Divide the resulting total by the total normal year production shown in the plant community description. If rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.
State and transition model
Custom diagramStandard diagram
Figure 4. State and Transition, Clayey Swale 8-12" pz.
More interactive model formats are also available. View Interactive Models
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 5 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe native potential plant community on this site is grassland with a scattering of desert shrubs and cacti. Annual forbs and grasses, of both winter and summer seasons, are very important in the plant community in their respective (wet) seasons. Tobosa is the dominant perennial grass with lesser amounts of vine mesquite.
Figure 5. 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 226 650 935 Forb 5 50 175 Shrub/Vine 0 5 30 Total 231 705 1140 Table 6. Soil surface cover
Tree basal cover 0-0% Shrub/vine/liana basal cover 0-0% Grass/grasslike basal cover 10-10% Forb basal cover 0-0% Non-vascular plants 0% Biological crusts 0-10% Litter 40-70% Surface fragments >0.25" and <=3" 0-20% Surface fragments >3" 0-10% Bedrock 0% Water 0% Bare ground 10-60% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – 0-2% 1-15% 1-15% >0.5 <= 1 – 0-2% 10-35% 1-10% >1 <= 2 – 0-2% 10-20% 0-5% >2 <= 4.5 – 0-2% – 0-1% >4.5 <= 13 – 0-2% – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 6. Plant community growth curve (percent production by month). AZ4121 , 41.2 7-12" p.z. all sites. Growth begins in the late winter to early spring, semi-dormancy occurs during the May through June drought, most growth occurs during the summer rainy season..
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 5 5 10 0 0 25 30 15 5 5 0 State 2
Tobosa - unfloodedCommunity 2.1
Tobosa - unfloodedThis plant community occurs where the site is no longer flooded. The reasons can include the interruption of flood flows by roads, diversions and or floodways. The site acts as Clayey Upland #R041BX203AZ.
State 3
Mesquite, tobosaCommunity 3.1
Mesquite, tobosaThis community occurs where mesquite has invaded and increased to dominate the plant community. Tree canopy ranges from 2 to 20%. Mesquite is well established and sprouts readily after fire to quickly assume dominance. Tobosa cover remains intact and production remains high.
State 4
Annual forbs and grassesCommunity 4.1
Annual forbs and grassesThis community occurs where the tobosa grass cover has been depleted to less than 5% canopy, and is not uniformly dispersed. Causes include the interactions of drought, fire and continuous grazing. In some cases areas of this state occur where the site was cultivated for irrigation and then abandoned. Native and non-native annual forbs and grasses persist to dominate the community.
State 5
ErodedCommunity 5.1
ErodedThis state occurs where the perennial grass cover has been depleted and accelerated erosion has left an imprint of rills and gullies on the site. Flooding is no longer effective as gullies rapidly drain extra water from the site. The plant community is a low production mixture of annuals and shrubs like mesquite and snakeweed. Causes can include the lowering of base levels of larger stream systems causing valley side swales to down-cut. Also in some areas adjacent to the Gila and San Pedro river bottom; these soils have a high percentage of gypsum in the soil profile and erode easily with compaction, trailing and continuous grazing.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Dominant Perennial Grasses 220–700 tobosagrass PLMU3 Pleuraphis mutica 200–600 – vine mesquite PAOB Panicum obtusum 20–100 – 2 Miscellaneous Perennial Grasses 1–35 sideoats grama BOCU Bouteloua curtipendula 0–10 – blue grama BOGR2 Bouteloua gracilis 0–10 – big sacaton SPWR2 Sporobolus wrightii 0–10 – burrograss SCBR2 Scleropogon brevifolius 0–5 – plains bristlegrass SEVU2 Setaria vulpiseta 0–5 – alkali sacaton SPAI Sporobolus airoides 0–5 – black grama BOER4 Bouteloua eriopoda 0–5 – curly-mesquite HIBE Hilaria belangeri 0–5 – green sprangletop LEDU Leptochloa dubia 0–5 – creeping muhly MURE Muhlenbergia repens 0–5 – cane bluestem BOBA3 Bothriochloa barbinodis 0–5 – spidergrass ARTE3 Aristida ternipes 0–2 – poverty threeawn ARDI5 Aristida divaricata 0–2 – Fendler threeawn ARPUL Aristida purpurea var. longiseta 0–2 – whiplash pappusgrass PAVA2 Pappophorum vaginatum 0–2 – squirreltail ELEL5 Elymus elymoides 0–2 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–1 – purple threeawn ARPU9 Aristida purpurea 0–1 – spidergrass ARTEG Aristida ternipes var. gentilis 0–1 – 3 Annual grasses 5–200 mucronate sprangeltop LEPAB Leptochloa panicea ssp. brachiata 1–100 – little barley HOPU Hordeum pusillum 1–100 – Arizona signalgrass URAR Urochloa arizonica 1–50 – Mexican panicgrass PAHI5 Panicum hirticaule 0–30 – sixweeks fescue VUOC Vulpia octoflora 1–25 – sticky sprangletop LEVI5 Leptochloa viscida 0–25 – sixweeks threeawn ARAD Aristida adscensionis 1–25 – needle grama BOAR Bouteloua aristidoides 0–20 – sixweeks grama BOBA2 Bouteloua barbata 0–20 – Rothrock's grama BORO2 Bouteloua rothrockii 0–15 – prairie threeawn AROL Aristida oligantha 1–10 – witchgrass PACA6 Panicum capillare 0–10 – Bigelow's bluegrass POBI Poa bigelovii 0–5 – Mexican sprangletop LEFUU Leptochloa fusca ssp. uninervia 0–5 – Arizona brome BRAR4 Bromus arizonicus 0–5 – feather fingergrass CHVI4 Chloris virgata 0–5 – tapertip cupgrass ERACA Eriochloa acuminata var. acuminata 0–5 – desert lovegrass ERPEM Eragrostis pectinacea var. miserrima 0–5 – tufted lovegrass ERPEP2 Eragrostis pectinacea var. pectinacea 0–5 – delicate muhly MUFR Muhlenbergia fragilis 0–2 – littleseed muhly MUMI Muhlenbergia microsperma 0–2 – Forb4 Perennial Forbs 5–25 dwarf desertpeony ACNA2 Acourtia nana 1–10 – bluedicks DICA14 Dichelostemma capitatum 0–5 – Indian rushpea HOGL2 Hoffmannseggia glauca 1–5 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 1–5 – desert globemallow SPAM2 Sphaeralcea ambigua 1–5 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–5 – slender poreleaf POGR5 Porophyllum gracile 1–5 – Coues' cassia SECO10 Senna covesii 0–1 – silverleaf nightshade SOEL Solanum elaeagnifolium 0–1 – pricklyleaf dogweed THAC Thymophylla acerosa 0–1 – Rocky Mountain zinnia ZIGR Zinnia grandiflora 0–1 – tuber anemone ANTU Anemone tuberosa 0–1 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 0–1 – New Mexico silverbush ARNE2 Argythamnia neomexicana 0–1 – perennial rockcress ARPE2 Arabis perennans 0–1 – dense ayenia AYMI Ayenia microphylla 0–1 – hairyseed bahia BAAB Bahia absinthifolia 0–1 – desert marigold BAMU Baileya multiradiata 0–1 – scarlet spiderling BOCO Boerhavia coccinea 0–1 – desert mariposa lily CAKE Calochortus kennedyi 0–1 – sego lily CANU3 Calochortus nuttallii 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – whitemouth dayflower COER Commelina erecta 0–1 – leatherweed CRPO5 Croton pottsii 0–1 – fingerleaf gourd CUDI Cucurbita digitata 0–1 – Missouri gourd CUFO Cucurbita foetidissima 0–1 – coyote gourd CUPA Cucurbita palmata 0–1 – ragged nettlespurge JAMA Jatropha macrorhiza 0–1 – San Pedro daisy LAPO4 Lasianthaea podocephala 0–1 – Parry's false prairie-clover MAPA7 Marina parryi 0–1 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–1 – plains blackfoot MELE2 Melampodium leucanthum 0–1 – wishbone-bush MILAV Mirabilis laevis var. villosa 0–1 – desert tobacco NIOB Nicotiana obtusifolia 0–1 – spreading fleabane ERDI4 Erigeron divergens 0–1 – desert trumpet ERIN4 Eriogonum inflatum 0–1 – southwestern mock vervain GLGO Glandularia gooddingii 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – poreleaf dogweed ADPO2 Adenophyllum porophyllum 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – largeflower onion ALMA4 Allium macropetalum 0–1 – 5 Annual forbs 0–150 California poppy ESCAM Eschscholzia californica ssp. mexicana 0–25 – western tansymustard DEPI Descurainia pinnata 0–20 – combseed PECTO Pectocarya 0–20 – Arizona popcornflower PLAR Plagiobothrys arizonicus 0–20 – desert Indianwheat PLOV Plantago ovata 0–20 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–15 – intermediate pepperweed LEVIM Lepidium virginicum var. medium 0–15 – coastal bird's-foot trefoil LOSAB Lotus salsuginosus var. brevivexillus 0–15 – tanseyleaf tansyaster MATA2 Machaeranthera tanacetifolia 0–15 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–15 – miniature woollystar ERDI2 Eriastrum diffusum 0–10 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–10 – Arizona poppy KAGR Kallstroemia grandiflora 0–10 – manybristle chinchweed PEPA2 Pectis papposa 0–10 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–5 – slender goldenweed MAGR10 Machaeranthera gracilis 0–5 – Gordon's bladderpod LEGO Lesquerella gordonii 0–5 – longleaf false goldeneye HELOA2 Heliomeris longifolia var. annua 0–5 – camphorweed HESU3 Heterotheca subaxillaris 0–5 – foothill deervetch LOHU2 Lotus humistratus 0–5 – Nuttall's povertyweed MONU Monolepis nuttalliana 0–5 – sorrel buckwheat ERPO4 Eriogonum polycladon 0–5 – Texas stork's bill ERTE13 Erodium texanum 0–5 – wedgeleaf draba DRCU Draba cuneifolia 0–5 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–5 – cryptantha CRYPT Cryptantha 0–5 – pitseed goosefoot CHBE4 Chenopodium berlandieri 0–5 – milkvetch ASTRA Astragalus 0–5 – wheelscale saltbush ATEL Atriplex elegans 0–5 – Coulter's spiderling BOCO2 Boerhavia coulteri 0–5 – carelessweed AMPA Amaranthus palmeri 0–5 – white tackstem CAWR Calycoseris wrightii 0–2 – fringed redmaids CACI2 Calandrinia ciliata 0–2 – brittle spineflower CHBR Chorizanthe brevicornu 0–2 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–2 – Esteve's pincushion CHST Chaenactis stevioides 0–2 – hairy prairie clover DAMO Dalea mollis 0–2 – American wild carrot DAPU3 Daucus pusillus 0–2 – hairy desertsunflower GECA2 Geraea canescens 0–2 – star gilia GIST Gilia stellata 0–2 – green carpetweed MOVE Mollugo verticillata 0–2 – Arizona lupine LUAR4 Lupinus arizonicus 0–2 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–2 – woollyhead neststraw STMI2 Stylocline micropoides 0–2 – sleepy silene SIAN2 Silene antirrhina 0–2 – phacelia PHACE Phacelia 0–2 – desert evening primrose OEPR Oenothera primiveris 0–2 – Florida pellitory PAFL3 Parietaria floridana 0–2 – chia SACO6 Salvia columbariae 0–1 – sawtooth sage SASU7 Salvia subincisa 0–1 – spreading fanpetals SIAB Sida abutifolia 0–1 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – doubleclaw PRPA2 Proboscidea parviflora 0–1 – sand fringepod THCU Thysanocarpus curvipes 0–1 – tumblemustard THELY3 Thelypodiopsis 0–1 – crestrib morning-glory IPCO2 Ipomoea costellata 0–1 – bristly nama NAHI Nama hispidum 0–1 – glandular threadplant NEGL Nemacladus glanduliferus 0–1 – Fendler's desertdandelion MAFE Malacothrix fendleri 0–1 – whitestem blazingstar MEAL6 Mentzelia albicaulis 0–1 – Mexican fireplant EUHE4 Euphorbia heterophylla 0–1 – common woolly sunflower ERLA6 Eriophyllum lanatum 0–1 – scrambled eggs COAU2 Corydalis aurea 0–1 – Canadian horseweed COCA5 Conyza canadensis 0–1 – exserted Indian paintbrush CAEXE Castilleja exserta ssp. exserta 0–1 – yellow tackstem CAPA7 Calycoseris parryi 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – southwestern pricklypoppy ARPL3 Argemone pleiacantha 0–1 – annual agoseris AGHE2 Agoseris heterophylla 0–1 – Shrub/Vine6 Miscellaneous Shrubs 0–10 fourwing saltbush ATCA2 Atriplex canescens 0–5 – western honey mesquite PRGLT Prosopis glandulosa var. torreyana 0–5 – lotebush ZIOB Ziziphus obtusifolia 0–1 – spiny hackberry CEEH Celtis ehrenbergiana 0–1 – longleaf jointfir EPTR Ephedra trifurca 0–1 – American tarwort FLCE Flourensia cernua 0–1 – creosote bush LATR2 Larrea tridentata 0–1 – water jacket LYAN Lycium andersonii 0–1 – pale desert-thorn LYPA Lycium pallidum 0–1 – catclaw mimosa MIACB Mimosa aculeaticarpa var. biuncifera 0–1 – whitethorn acacia ACCO2 Acacia constricta 0–1 – catclaw acacia ACGR Acacia greggii 0–1 – 7 Half shrubs 0–10 bastardsage ERWR Eriogonum wrightii 0–5 – fairyduster CAER Calliandra eriophylla 0–2 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–2 – burroweed ISTE2 Isocoma tenuisecta 0–1 – littleleaf ratany KRER Krameria erecta 0–1 – winterfat KRLA2 Krascheninnikovia lanata 0–1 – rough menodora MESC Menodora scabra 0–1 – turpentine bush ERLA12 Ericameria laricifolia 0–1 – threadleaf snakeweed GUMI Gutierrezia microcephala 0–1 – 9 Succulents 0–10 tulip pricklypear OPPH Opuntia phaeacantha 0–5 – banana yucca YUBA Yucca baccata 0–2 – soaptree yucca YUEL Yucca elata 0–2 – dollarjoint pricklypear OPCH Opuntia chlorotica 0–2 – cactus apple OPEN3 Opuntia engelmannii 0–2 – Christmas cactus CYLE8 Cylindropuntia leptocaulis 0–2 – walkingstick cactus CYSP8 Cylindropuntia spinosior 0–2 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – devil's cholla GRKU Grusonia kunzei 0–1 – buck-horn cholla CYAC8 Cylindropuntia acanthocarpa 0–1 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 11. Community 4.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 12. Community 5.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site produces considerable perennial forage for livestock. Tobosa is very poor quality forage when cured and only fair forage when green. In wet (El Nino) winters the site produces a tremendous amount of annual forbs and grasses, all of which are excellent forage. The site is home to a variety of small mammals and grassland bird species and their associated predators. It is mainly a foraging area for larger mammals like mule deer and javalina.
Hydrological functions
These soils are heavy textured and good producers of runoff.
Recreational uses
Hunting, horseback riding, hiking, wildlife observation, photography, rock hounding and bird watching.
Wood products
None unless the site has been invaded by mesquite.
Other products
Red clay for pot making. Herbs like grass nuts, wild onions and hog potatos.
Supporting information
Type locality
Location 1: Cochise County, AZ Township/Range/Section T17S R21E S19 General legal description Kartchner Ranch, Lonesome Valley, St. David area. Contributors
Dan Robinett
Larry D. EllicottApproval
Curtis Talbot, 4/09/2021
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) Wilma Renken, Dan Robinett, Larry Humphrey, Gwen Dominguez, Clay Stewart Contact for lead author Tucson MLRA Soil Survey Office Date 08/07/2013 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
-
Number and extent of rills:
None -
Presence of water flow patterns:
Water flow paths occupy less than 5% of the surface area. Sheet flow dominates as a process on this site. Sheet flow lengths are 20-40 feet. -
Number and height of erosional pedestals or terracettes:
Pedestals are common on tobosa and about 1 inch high. Terracettes (1-2’ diam x 0.5” ht) are not common on the site making up less than 5% of the area. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is approximately 35-40%. Bare areas, 2’-8’ in diameter, occasionally connected, are common. Bare areas are often masked by annuals and perennial herbaceous overstory. -
Number of gullies and erosion associated with gullies:
None -
Extent of wind scoured, blowouts and/or depositional areas:
None -
Amount of litter movement (describe size and distance expected to travel):
Fine litter size classes are moving a 2-3 feet in sheet flow areas. Coarse litter staying in place. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Values of 2-3 in bare areas and 4-6 within vegetated patches. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
A horizon is a silty clayloam, 0-3 inches thick with weak platy to weak, fine and medium subangular blocky structure. Colors are 10 YR 6/4 dry and 10 YR 4/3 moist. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Aspect is grassland. Perennial grasses (tobosa, burrograss and vine mesquite) dominate the site. Hydrology functions as sheet flow run-off supplementing soil moisture to perennial grass patches. Bare areas contribute to sheet flow and make up approximately 38% of area; vegetated areas are dense and occupy the remaining 62% of the area. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None present, average depth of penetration from an ARS field penetrometer with a 2.2 kg. sliding hammer, set at 20 inches fall height, is 5 cm. The dense (massive structure) silty clay C2 horizon at 3 inches can feel like a compacted layer. -
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:
perennial grasses >Sub-dominant:
annual grasses >> annual forbs > perennial forbs > large shrubs > sub-shrubs > succulentsOther:
large shrubs, sub-shrubs and succulents absent or in minor amountsAdditional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Mortality estimated at about 10% on perennial grasses, as expected for this site. -
Average percent litter cover (%) and depth ( in):
From the ESD, litter cover can be from 35-60% on this site. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
231 lbs/ac. in a below average year; 705 lbs/ac. in an average year; 1140 lbs/ac. in an above average year. Production of summer annual grasses can exceed expected on years with above average seasonal precipitation. -
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:
mesquite, wolfberry, creosotebush, tumbleweed are present and can increase on the site but occur in trace amounts at present -
Perennial plant reproductive capability:
Not impaired.
Print Options
Sections
Font
AAAAOther
PrintThe Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
Accessibility statement
