Natural Resources Conservation Service Ecological site R041XC316AZ Sandy Wash 12-16" p.z. Accessed: 09/23/2021 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. 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–Southeastern Arizona Basin and Range AZ 41.3 – Chihuahuan – Sonoran Semidesert Grasslands Elevations range from 3200 to 5000 feet and precipitation ranges from 12 to 16 inches per year. Vegetation includes mesquite, catclaw acacia, netleaf hackberry, palo verde, false mesquite, range ratany, fourwing saltbush, tarbush, littleleaf sumac, sideoats grama, black grama, plains lovegrass, cane beardgrass, tobosa, vine mesquite, threeawns, Arizona cottontop and bush muhly. The soil temperature regime is thermic and the soil moisture regime is ustic 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 R041XC306AZ Shallow Hills 12-16" p.z. R041XC308AZ Limy Slopes 12-16" p.z. R041XC309AZ Limy Upland 12-16" p.z. R041XC313AZ Loamy Upland 12"-16" p.z. R041XC318AZ Sandy Loam 12-16" p.z. Deep R041XC319AZ Sandy Loam Upland 12-16" p.z. R041XC322AZ Shallow Upland 12-16" p.z. R041XC330AZ Volcanic Hills 12-16" p.z. Clayey Similar sites R041XB213AZ Sandy Wash 8-12" p.z. R040XA115AZ Sandy Wash 10"-13" p.z. Table 1. Dominant plant species Tree (1) Prosopis (2) Acacia greggii Shrub (1) Celtis pallida Herbaceous Not specified Physiographic features This site occurs in the middle elevations of the Madrean Basin and Range province in southeastern Arizona. It occurs on floodplains, low stream terraces; in canyons and on alluvial fans. It benefits on a regular basis from extra moisture received as over-bank flooding of channels and as runoff from adjacent upland areas. It does not benefit from shallow water tables. Table 2. Representative physiographic features Landforms (1) Flood plain (2) Stream terrace (3) Canyon Flooding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Flooding frequency Occasional to frequent Ponding duration Very brief (4 to 48 hours) Ponding frequency None to rare Elevation 3,200–5,000 ft Slope 0–3% Aspect Aspect is not a significant factor Climatic features Precipitation in this common resource area ranges from 12-16 inches yearly in the eastern part with elevations from 3600-5000 feet, and 13-17 inches in the western part where elevations are 3300-4500 feet. Winter-Summer rainfall ratios are 40-60% in the west and 30-70% in the east. Summer rains fall July-September, originate in the Gulf of Mexico and are convective, usually brief, intense thunderstorms. Cool season moisture tends to be frontal, originates in the Pacific and Gulf of California, and falls in widespread storms with long duration and low intensity. Snow rarely lasts more than one day. May and June are the driest months of the year. Humidity is generally very low. Temperatures are mild. Freezing temperatures are common at night from December-April; however temperatures during the day are frequently above 50 F. Occasionally in December-February, brief 0 F temperatures may be experienced some nights. During June, July and August, some days may exceed 100 F. Cool season plants start growth in early spring and mature in early summer. Warm season plants take advantage of summer rains and are growing and nutritious July-September. Warm season grasses may remain green throughout the year. Table 3. Representative climatic features Frost-free period (average) 220 days Freeze-free period (average) 0 days Precipitation total (average) 16 in Influencing water features There are no water features associated with this site. Soil features These are very young soils on gravelly and sandy alluvium of mixed origin. They are deep and well drained. Surface textures range from gravelly sand to loamy fine sand. Sub-soils are sandy loam and loamy sands with various amounts of gravel and/or cobbles. Although course textures make for low available water holding capacities, plant- soil moisture relationships are very good due to extra moisture the site receives. Soil surfaces, outside of channel areas, are dark colored. Soils mapped on this site include: SSA-661 Eastern Pinal & Southern Gila counties MU 6 Bodecker; SSA-663 Gila- Duncan area MU's 7 Camoro & Santo Tomas, 36 Santo Tomas; SSA-664 San Simon area MU 36 Santo Tomas; SSA-666 Cochise county Northwest part MU's 7 Bodecker and 52 Keesto; SSA-667 Santa Cruz area MU's CtB & GbB Comoro; SSA-669 Pima county Eastern part MU's 19 & 68 Comoro; SSA-671 Cochise county Douglas- Tombstone part MU's 9 Bodecker & Comoro, 10 Bodecker GrVSL, 11 Bodecker GrVSL saline-sodic, 33 Comoro SL, 34 Comoro SL saline-sodic, 94 Keysto and 127 Bodecker; SSA-703 Tohono O'odham Nation MU 38 Keesto. Table 4. Representative soil features Family particle size (1) Sandy Drainage class Excessively drained to well drained Permeability class Very rapid to moderately rapid Soil depth 60 in Surface fragment cover <=3" 10–25% Surface fragment cover >3" 0–10% Available water capacity 2.4–6 in (0-40in) Calcium carbonate equivalent 0–5% (0-40in) Electrical conductivity 0–2 mmhos/cm (0-40in) Sodium adsorption ratio 0–2 (0-40in) Soil reaction (1:1 water) 7.4–8.4 (0-40in) Subsurface fragment volume <=3" 5–45% (Depth not specified) Subsurface fragment volume >3" 0–10% (Depth not specified) 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 fire, grazing, 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 amount shown for each group. Divide the resulting total by the total normal year production shown in the plant community description. If the 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. The potential plant community on this site is a diverse mixture of native perennial grasses, shrubs, vines, trees and annual forbs and grasses. Smaller drainage-ways are dominated by desert trees like mesquite, desert willow and catclaw acacia. Larger washes and canyons will have a higher percentage of broadleaf trees like ash, walnut and netleaf hackberry. State and transition model Figure 4. State and Transition, Sandy Wash 12-16" pz. State 1 Historic Climax Plant Community Community 1.1 Historic Climax Plant Community The potential plant community of this site is a diverse mixture of perennial grasses, forbs, vines, trees and shrubs. Annual forbs and grasses of both the warm and cool seasons are well represented in the plant community. The major grass, forb and shrub species on the site are well dispersed throughout the plant community. The aspect is savannah. Periodic natural fires were important in maintaining a balance between woody species and herbaceous species. With continuous heavy grazing, palatable mid-grasses decline and species such as Rothrock grama, dropseed and threeawns increase. With severe deterioration, woody species increase to dominate the plant community. Mesquite, with lesser amounts of catclaw acacia and desert willow, form the over-story and burroweed dominates the under- story. Actively eroding areas become dominated by shrubs like burrobrush, rubber rabbitbush, batamote and desert broom. The site is very susceptible to gully, channel and bank erosion, especially where it has deteriorated to shrubby conditions and where depleted watershed areas are contributing larger than normal amounts of runoff. The lowering of the base level of the axial stream of a watershed will eventually cause channeling of the site. Deeply channeled areas will no longer flood the stream terraces of this site. Due to deep, course textured soils and extra moisture received as flooding, trees grow to maximum size on the site. This site can produce effective herbaceous covers with tree canopies up to 25%.