Index of Species Information

SPECIES:  Sporobolus wrightii


SPECIES: Sporobolus wrightii
AUTHORSHIP AND CITATION : Esser, Lora L. 1995. Sporobolus wrightii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [].
ABBREVIATION : SPOWRI SYNONYMS : Sporobolus airodes var. wrightii (Munro) Gould [27,45,54] SCS PLANT CODE : SPWR2 COMMON NAMES : big sacaton sacaton giant sacaton TAXONOMY : The currently accepted scientific name of big sacaton is Sporobolus wrightii Munro (Poaceae) [27,30,45,54]. LIFE FORM : Graminoid FEDERAL LEGAL STATUS : No special status OTHER STATUS : NO-ENTRY


SPECIES: Sporobolus wrightii
GENERAL DISTRIBUTION : Big sacaton occurs from southeastern Arizona east to western Texas and Oklahoma south to northern Mexico [17,30,45].  ECOSYSTEMS :    FRES30  Desert shrub    FRES32  Texas savanna    FRES33  Southwestern shrubsteppe    FRES38  Plains grasslands    FRES40  Desert grasslands STATES :      AZ  CA  HI  NM  OK  TX  UT  MEXICO BLM PHYSIOGRAPHIC REGIONS :     7  Lower Basin and Range    12  Colorado Plateau    13  Rocky Mountain Piedmont KUCHLER PLANT ASSOCIATIONS :    K027  Mesquite bosque    K054  Grama-tobosa prairie    K058  Grama-tobosa shrubsteppe    K060  Mesquite savanna    K065  Grama-buffalograss    K085  Mesquite-buffalograss SAF COVER TYPES :     68  Mesquite    242  Mesquite SRM (RANGELAND) COVER TYPES :    414  Salt desert shrub    502  Grama-galleta    505  Grama-tobosa shrub    706  Blue grama-sideoats grama    707  Blue grama-sideoats grama-black grama    712  Galleta-alkali sacaton    725  Vine mesquite-alkali sacaton    727  Mesquite-buffalograss    729  Mesquite HABITAT TYPES AND PLANT COMMUNITIES : Big sacaton occurs mainly in semidesert grassland and shrubland communities [2,7,15,49].  It is also found in wetland communities such as desert marshes, playa lakes, bolson depressions (enclosed basins), and on floodplains [18,36,50,51]. In southeastern Arizona big sacaton grassland is common in lowland habitats and on floodplains [4,6,12].  Common associates include vine-mesquite (Panicum obtusum), hairy grama (Bouteloua hirsuta), slender grama (B. filiformis), and sand dropseed (Sporobolus cryptandrus) [6,34,43].  In Arizona and New Mexico big sacaton occurs on lower elevation plateaus and mesas with New Mexico feathergrass (Stipa neomexicana) [46].  In New Mexico a giant dropseed (Sporobolus giganteus)-big sacaton-little bluestem (Schizachyrium scoparium) series has been described [19].  In Texas big sacaton is a prominent species in bottomlands and on creek flats of the Rio Grande [33].  At the mouth of the Rio Grande, a big sacaton series has been described [40].  It forms a mosaic with shrublands in the Texas ebony (Pithecellobium flexicaule)-snake eyes (Phaulothamnus spinescens) series, tidal flats in the glasswort (Salicornia bigelovii/S. virginica)-saltwort (Batis maritima) series and cordgrass (Spartina spp.) marshes.  It is also a member of the saltgrass (Distichlis spicata)-Olney threesquare (Scirpus americanus) series [40]. In the Chihuahuan Desert big sacaton grassland communities have been described [25,49,50].  In Arizona a western honey mesquite (Prosopis glandulosa var. torreyana) and big sacaton grassland occurs [49].  Big sacaton is found in bolson depressions surrounded by desert scrub such as honey mesquite; these basins may encircle a saline marsh or playa [50].  Common associates include fourwing saltbush (Atriplex canescens), mound saltbush (A. obovata), tobosa (Hilaria mutica), alkali sacaton (Sporobolus airoides), and seepweed (Suaeda spp.) [25,50].  In north-central Mexico big sacaton is found in stands of prickly-pear (Opuntia spp.) cactus [29].  The following publications list big sacaton as a community dominant or codominant: Habitat relationships of some native perennial grasses in southeastern   Arizona [6] Vegetation and community types of the Chihuahuan Desert [25] Desert grassland [36]


SPECIES: Sporobolus wrightii
IMPORTANCE TO LIVESTOCK AND WILDLIFE : Big sacaton is a valuable forage species for livestock in arid and semiarid regions.  In Arizona new spring growth of big sacaton is readily eaten by livestock [2].  It is grazed throughout the year when preferred grasses or forbs are not available [12,30]. PALATABILITY : NUTRITIONAL VALUE : Big sacaton forage quality is highest in the spring [12].  As plants mature, leaves and stems become coarse and tough [48].  Average percentage of crude protein contained in big sacaton forage harvested from the South Texas Plains near Whitsett from May 1977 to February 1979 was as follows [23]:                             spring      summer      fall      winter defoliation treatments none                         10.1        5.8         6.4        5.4 monthly (spring to fall)     12.3       10.3        12.1       10.9 spring and mid-summer        12.0        9.7        10.9        9.1 spring and early summer      12.3       10.2        10.6        8.9 spring                       12.9        7.5         8.6        8.6 spring/late summer/fall      12.1        7.2        10.9       10.0 mid-summer and fall          12.8        6.4        11.5       10.1 COVER VALUE : Big sacaton stands provide cover for wildlife and cattle in summer [6,12].  In Arizona mature stands of big sacaton provide cover for Botteri's sparrow and other passerines, collared peccaries, diamondback rattlesnakes, and many rodents [2,4,53].  Botteri's sparrow reaches maximum breeding densities in big sacaton grasslands [5]. VALUE FOR REHABILITATION OF DISTURBED SITES : NO-ENTRY OTHER USES AND VALUES : NO-ENTRY OTHER MANAGEMENT CONSIDERATIONS : Big sacaton grasslands favor wildlife [2]; they are utilized by rodents and birds [2,4].  In the Southwest big sacaton grasslands have been severely degraded by channelization, erosion, and overgrazing [4,55]. They are now present in only 5 percent of their original range [14,17]. In southeastern Arizona big sacaton stands produce large green biomass quantities (1,500-3,200 pounds/acre [1,680-3,580 kg/ha]) in the summer that may slow runoff, enhance infiltration, and trap sediments [12]. Big sacaton is important for impeding erosion in areas where flash floods occur [53].  Forage is present throughout the year, but utilization of big sacaton is limited by dead standing foliage; burning or mowing can remove dead foliage, but may decrease forage production of big sacaton for up to 2 years [12,14].  For maximum big sacaton forage production, Cox and others [12] recommend grazing big sacaton in the spring, not grazing in dry summers, and discontinuing fall grazing. Fall defoliation exposes big sacaton crowns to below freezing temperatures; crown exposure may reduce forage production for up to 4 years [14] or kill plants [12].  Managers have traditionally recommended fall and winter burning or mowing big sacaton grassland [14,17].  In southeastern Arizona Cox [14] studied the effect of burning and mowing on big sacaton forage quantity and quality.  Big sacaton plots were mowed to 2-inch (5 cm) stubble height in winter (Feb. 6), summer (July 10), and fall (Oct. 2) in 1980, 1981, and 1982.  Big sacaton forage quality improved for 6 weeks after mowing in all seasons [14,23].  Accelerated growth on summer-defoliated plots supported the hypothesis that summer mowing has the least negative impact on big sacaton production.  Winter and fall mowing had a detrimental effect on production for three summer growing seasons [14]. In another study in southeastern Arizona, Cox and Morton [17] reported that annual winter (February 27) mowing plus spring-summer grazing improved the availability and quality of big sacaton live biomass. However, mowing had a negative effect on growth early in the spring-summer grazing period [17].  See PLANT RESPONSE TO FIRE for information on burning big sacaton grassland.


SPECIES: Sporobolus wrightii
GENERAL BOTANICAL CHARACTERISTICS : Big sacaton is a native, perennial bunchgrass 3 to 6 feet (0.9-1.8 m) tall [5,14,27,47] that grows in dense clumps up to 3 feet (0.9 m) in diameter [47,48].  Leaves are up to 12 inches (30 cm) long [47,48]. Seedheads are open and 1 to 2 feet (0.3-0.6 m) long [48]. RAUNKIAER LIFE FORM :       Hemicryptophyte REGENERATION PROCESSES : Big sacaton reproduces exclusively by seed.  It lacks specialized morphological seed dispersal mechanisms.  In saline habitats of the Chihuahuan Desert, seed may be dispersed by ducks [24].  Big sacaton seed has low germination and establishment rates under high temperatures such as those found in the desert southwest [38].  Establishment of big sacaton seed increased with a reduction of soil temperature from an average of 104 degrees Fahrenheit (40 deg C) to 79 degrees Fahrenheit (26 deg C) [38].  In the laboratory, big sacaton germination was 84 percent under optimum conditions (alternating temperatures of 68-95 degrees Fahrenheit [20-35 deg C] and alternating light and dark periods) [52].  Emergence, average shoot height, average root and shoot weight, and average root length were all less in soils at temperatures of 127 degrees Fahrenheit (53 deg C) than in soils at temperatures of 102 degrees Fahrenheit (39 deg C) [38]. SITE CHARACTERISTICS : Big sacaton grows mainly on low alluvial flats, bottomlands, and arroyos subject to flooding [6,14,23,47,48].  It also occurs in wide floodplains [53].  In southeastern Arizona and southwestern New Mexico big sacaton forms nearly monotypic stands on broad floodplains [4].  It is also found on open, unshaded areas such as rocky slopes, plateaus, and mesas [30,46].  It generally grows on sand, sandy loam, silty clay loam [12,14,36], and saline soils [24,45].  Big sacaton occurs at elevations of 2,000 to 5,000 feet (600-1,500 m) in Arizona and 3,100 to 7,000 feet (930-2,100 m) in New Mexico [30,47]. SUCCESSIONAL STATUS : Big sacaton is shade intolerant [53].  In the early 1900's, the Southwest had extensive stands of big sacaton grassland. Channelization, drought, grazing, and fire suppression have all contributed to the invasion of these grasslands by mesquite (Prosopis spp.) and juniper (Juniperus spp.) [8,28,36,49,55]. SEASONAL DEVELOPMENT : Big sacaton initiates leaf production in both summer and winter; winter leaves form within a protective sheath and expand in early spring [14]. Plants have some green foliage throughout the year [14,23].  Flowering occurs from April to May in California and from July to October in Arizona [32,45].


SPECIES: Sporobolus wrightii
FIRE ECOLOGY OR ADAPTATIONS : Big sacaton sprouts after top-kill [6,53].  Burning may stimulate leaf production.  The ability of big sacaton to recover after fire depends on the extent of root crown removal by fire [14].  The greatest potential for natural fire occurs when lightning strike frequency peaks in early summer [14].  Big sacaton is best adapted to summer fires.  Fall and spring burning may have long-term negative effects [56]. FIRE REGIMES : Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes". POSTFIRE REGENERATION STRATEGY :    Tussock graminoid


SPECIES: Sporobolus wrightii
IMMEDIATE FIRE EFFECT ON PLANT : Many fires probably top-kill big sacaton. In southeastern Arizona a February 1985 wildfire "consumed" all available big sacaton forage [12]. "Hot" early summer fires may kill big sacaton plants.  At the Research Ranch in southeastern Arizona, Bock and Bock [2] studied the impact of fire on an ungrazed sacaton grassland community.  Height and percent cover of big sacaton were reduced until postfire year 2 on sites burned in summer or winter [2]. This study was part of an extensive body of research on fire effects in semidesert grassland, oak savanna, and Madrean oak woodlands of southeastern Arizona. See the Research Project Summary of this work for more information on burning conditions, fires, and fire effects on more than 100 species of plants, birds, small mammals, and grasshoppers. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : Big sacaton sprouts after top-kill by fire [53].  Big sacaton may recover to prefire coverage in 2 to 3 years on ungrazed sites [4]. Postfire recovery is influenced by fire severity [2] and season of burning [14].  In southeastern Arizona in 1975 and 1976 three wildfires occurred in an ungrazed big sacaton grassland community [2].  The first two fires occurred in mid-May and mid-June 1975, and the third in February 1976.  Permanent study sites were established on the two summer burns and on adjacent unburned (control) areas in August 1975.  In February 1976 a wildfire occurred on one of the control sites which then became the winter burn study site.  The summer burns occurred during hot, dry weather and were probably more severe than the winter burn [2]. Big sacaton postfire percent cover on the four study sites is listed below; prefire cover was not reported.                            summer burns             winter burn           control    first year    second year       first year sacaton     74               35            70            50 In postfire year 1, big sacaton percent cover was less on burned than unburned sites, and less on the summer than winter burns.  It was similar to prefire cover in the second year [2].  In southeastern Arizona the impacts of burning on big sacaton forage quality and quantity were studied [14,15].  Plots were burned with a headfire in winter (Feb. 6), summer (July 10), and fall (Oct. 2) 1980, 1981, and 1982.  Plots had been lightly grazed for 5 years prior to burning.  The time from ignition to total forage consumption by fire was recorded by plot.  Fuel moistures and weather conditions were as follows [14]:             fine fuel-moisture     wind speed     air temperature             % oven-dry weight     mi/hr (km/hr)    deg F (deg C) winter           10-30              10 (16)        50-64 (10-18) summer           20-25              8-15 (13-24)   84-86 (29-30) fall             45-55              8-10 (13-16)   66-77 (19-25) Big sacaton green forage at the peak of the summer growing season (Aug. 21) 1,2, and 3 years after treatment was as follows:                    number of growing seasons after treatment                            1              2              3                                                                           kg/ha winter                400-735        690-850         595-695 summer                700-865        850-935         1,375-1,590 fall                  260-725        575-805         745-890 untreated             1,695-1,900    1,365-1,720     1,650-2,000 Green forage availability for the 3 treatment years was consistently greater on untreated plots than on burned plots.  In postfire years 1 and 2, big sacaton green forage was greater on summer than on winter- or fall-burned plots.  By postfire year 3 green forage on summer-burned plots was nearly equivalent to that on unburned plots [14].  At postfire year 1, standing crops were 60 percent less on spring- and fall-burned plots.  At postfire year 2, live biomass on spring-burned plots was 30 percent less than on control plots.  On fall-burned plots, 50 percent of plants failed to produce leaves the following spring.  Removing hte standing dead biomass which insulates against cold temperatures may have killed the plants [56]. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : NO-ENTRY FIRE MANAGEMENT CONSIDERATIONS : Land managers have traditionally recommended burning big sacaton grassland in either fall or winter [7,14].  According to Cox [14], winter and fall burns have a detrimental effect on big sacaton plant production for at least three summer growing seasons [14].  Loss of summer-formed leaves inhibits formation of winter leaves, and root crowns may be damaged by frost.  Winter burning may reduce plant litter, making green foliage more available to livestock but reducing the long-term viability of big sacaton plants [17].  In Arizona seed-eating rodents are abundant on burned big sacaton sites. Bock and Bock [2] propose that ideal wildlife habitat would be mosaic of big sacaton stands in various stages of postfire succession.


SPECIES: Sporobolus wrightii
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