SPECIES: Sporobolus flexuosus
Taylor, Jennifer L. 1999. Sporobolus flexuosus.
In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).
Available: http://www.fs.fed.us/database/feis/ .
No special status
FRES30 Desert shrub FRES33 Southwestern shrubsteppe FRES35 Pinyon-juniper FRES40 Desert grasslands
AZ CA CO NV NM TX UT
4 Sierra Mountains 5 Columbia Plateau 6 Upper Basin and Range 7 Lower Basin and Range 12 Colorado Plateau 13 Rocky Mountain Piedmont 14 Great Plains
K023 Juniper-pinyon woodland K027 Mesquite bosque K039 Blackbrush K040 Saltbush-greasewood K041 Creosotebush K044 Creosotebush-tarbush K057 Galleta-threeawn shrubsteppe K058 Grama-tobosa shrubsteppe
68 Mesquite 242 Mesquite 239 Pinyon-juniper
211 Creosotebush scrub 408 Other sagebrush types 412 Juniper-pinyon woodland 501 Saltbush-greasewood 504 Juniper-pinyon pine woodland 505 Grama-tobosa shrub 508 Creosotebush-tarbush 701 Alkali sacaton-tobosagrass 702 Black grama-alkali sacaton
Mesa dropseed is a component of desert scrub, shrub, grassland, sagebrush (Artemisia spp.) and pinyon-juniper (Pinus-Juniperus spp.) communities [3,46]. Wolters and others  placed it in the transition zone between desert scrub and desert grassland. Mesa dropseed is also a component of the mesquite-dropseed-broom snakeweed (Prosopis spp.-Sporobolus spp.-Gutierrezia sarothrae) and broom snakeweed-dropseed communities [4,9]. It has become a dominant grass species in fragmented black grama (Bouteloua eriopoda) stands  and is associated with soaptree yucca (Yucca elata) [6,32].
Mesa dropseed is lowest in protein during November to April (5%) and averages 7% during May to October. Calcium is highest from March to December (0.25%), with a peak May through August (0.35-0.45%), and lowest in January and February (< 0.2%) . Mesa dropseed does not provide much forage in the early spring, because the first leaves are short and protected by the culms of previous years .
The nutritional content (%) of fresh mesa dropseed in mid-bloom is as follows :
|Total Digestible Nutrients|
The response of mesa dropseed, measured by total nonstructural carbohydrates (TNC), to the season of defoliation was studied in southern New Mexico. After 3 years, 65% defoliation decreased TNC levels and crown diameter. Productivity during the following year was reduced when plants were clipped during flowering. Mesa dropseed can withstand heavier defoliation prior to flowering than during the rest of the growing season. If it is being continuously grazed, intensity should be < 65% during the growing season . Holechek and others  found that removal of 1/3rd of current year annual growth was practical.
Mesa dropseed usually increases with the control of honey mesquite (Prosopis glandulosa var. glandulosa) [11,17]. Herbel and Gould  found removing at least 40% removal of honey mesquite produced greatest increases in mesa dropseed.
Mesa dropseed survives long droughts with grazing  and can reduce grazing stress on black grama during the growing season . Adjusting grazing regimes to the amount and timing of rainfall can prevent overgrazing of mesa dropseed .
Mesa dropseed is a warm-season, native, perennial bunchgrass. It is short-lived (4-5 years) and sometimes grows as an annual [2,5,7,14,21,36,41,46,49]. Mesa dropseed has long culms (11.8-39.0 inches (30-100 cm)) with many leafy blades and coarse roots [5,7,14]. Dwyer and DeGarmo  found that roots decrease in biomass from top to bottom at 1/3rd field capacity and were better distributed as soil moisture decreased. Sporobolus spp. have small seeds (0.04-0.12 inch (0.1-0.3 mm)) .
Mesa dropseed reproduces from seed [5,15,33,46] that fall from the parent plant and can be wind blown [8,20,34]. The seeds have a hard seed coat that must be punctured before good germination occurs . New culms or tillers originate from basal buds below the ground level and occasionally from a bud at an elevated node . Development is quick during periods of adequate moisture and high night temperatures . There is an almost immediate response to water, especially when soil water is supplied below 3.9 inches (10 cm) . Mesa dropseed usually does not achieve maturity in an unbroken period. During periods of drought, it goes into a dormant stage . New seedlings establish in open areas and under shrubs [30,34].
Mesa dropseed occurs mainly in dry areas with mean annual precipitation of 12 inches (300 mm) or less; it can survive in areas with as little as 6 to 7 inches (150-180 mm) mean annual precipitation [41,46]. It occurs on well-drained sand, sandy loams, loamy sands and gravelly soils [3,7,15,29].
Daniel and others  classified mesa dropseed as a mid- and late-seral species. Bridges  placed it just below the climax stage of black grama and Valentine  included it in the climax vegetation of the sandy soils on the New Mexico State University College Ranch, along with black grama and spike dropseed (Sporobolus contractus).
Mesa dropseed greens up during the spring and again in late fall if moisture is adequate . New culms appear in March and flowering starts 4 to 5 days after inflorescence elongation begins . Mesa dropseed blooms from September to November [8,21,46].
Desert grasslands with mesa dropseed were probably characterized by frequent fire. Kaib and others  studied the fire scar data of Apache pine (Pinus engelmannii) and Arizona pine (P. ponderosa var. arizonica) to determine the historic fire frequency of the Madrean Province in southern Arizona and New Mexico and northern Sonora and Chihuahua. Reconstructing intercanyon fire occurrences provided an estimate of the fire return interval of the adjacent semidesert grasslands. They gave a conservative estimate of every 4 to 8 years, and estimated that the actual fire return interval in semidesert grassland was closer to every 4 years.
Mesa dropseed is found in plant communities characterized by both long and short fire-return intervals. The dominants in plant communities in which mesa dropseed occurs are listed below. Refer to the FEIS species report for information on fire ecology in the following communities:
Fourwing saltbush (Atriplex canescens)
Black grama (Bouteloua eriopoda)
Creosotebush (Larrea tridentata)
Colorado Pinyon (Pinus edulis)
Honey mesquite (Prosopis glandulosa var. glandulosa)
Soaptree yucca (Yucca elata)
Mesa dropseed is damaged by fire , but its susceptiblity relative to other grasses, and its period of recovery, are poorly understood. Research is badly needed on fire's effects on mesa dropseed.
Prescribed fire can be used to control the invasion of broom snakeweed, creosotebush, and young mesquite. Since shrub density in these communities is often low, abundance of mesa dropseed and other grasses must be adequate to carry a fire .
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