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INTRODUCTORY

AUTHORSHIP AND CITATION FEIS ABBREVIATION SYNONYMS NRCS PLANT CODE COMMON NAMES TAXONOMY LIFE FORM FEDERAL LEGAL STATUS OTHER STATUS
	Photo © Br. Alfred Brousseau, Saint Mary's College.	Photo courtesy of USGS-NPA, Vegetation Mapping Program.

AUTHORSHIP AND CITATION:
Howard, Janet L. 2003. Descurainia sophia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov/database/feis/plants/forb/dessop/all.html [].

Revisions: On 20 April 2018, the common name of this species was changed in FEIS from:flixweed tansymustard to: herb sophia.

FEIS ABBREVIATION:
DESSOP

SYNONYMS:
None

NRCS PLANT CODE [138
DESO2

COMMON NAMES:
herb sophia
flixweed tansymustard

TAXONOMY:
The scientific name of herb sophia is Descurainia sophia (L.) Webb ex Prantl (Brassicaceae) [32,48,51,64,69,90,106,130,133,142,145,147].

LIFE FORM:
Forb

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Herb sophia is classified as a noxious weed list in Colorado and Minnesota [137,138].

DISTRIBUTION AND OCCURRENCE

• GENERAL DISTRIBUTION
• ECOSYSTEMS
• STATES/PROVINCES
• BLM PHYSIOGRAPHIC REGIONS
• KUCHLER PLANT ASSOCIATIONS
• SAF COVER TYPES
• SRM (RANGELAND) COVER TYPES
• HABITAT TYPES AND PLANT COMMUNITIES

The following biogeographic classification systems are presented as a guide to demonstrate where herb sophia may be found. Precise distribution information is limited. Because it is so widespread, it is difficult to exclude many ecosystems as potential hosts of herb sophia plants or populations; therefore, these lists are speculative.

Herb sophia is ecologically important in most North American desert ecosystems. In Great Basin Desert communities of east-central Nevada, it showed 25-40% frequency in big sagebrush (Artemisia tridentata) communities and 5-66% frequency in singleleaf pinyon-Utah juniper (Pinus monophylla-Juniperus osteosperma) communities [18]. On the Desert Tortoise Research Natural Area in the Mojave Desert, southern California, herb sophia associates with creosotebush (Larrea tridentata), white bursage (Ambrosia dumosa), and other annuals, the most common being cutleaf filaree (Erodium cicutarium), red brome (Bromus madritensis ssp. rubens), and Mediterranean grass (Schismus spp.) [20].

A few vegetation classifications describe plant communities dominated by herb sophia.  A herb sophia-Russian-thistle (Salsola kali) community occurs in Lava Beds National Monument, California, on land with a history of extreme disturbance: 1st by lake drainage, then by cultivation of the lakebed [36]. In east-central Nevada, herb sophia communities occur on highly disturbed winterfat (Krascheninnikovia lanata) habitat types. Halogeton (Halogeton glomerata) codominates, and winterfat is present in trace amounts [18].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

Herb sophia is an exotic, cool-season annual or biennial. It is the type species for the genus [51,64,88,130,134]. The single, 6- to 31-inch-long (15-80 cm) stem is coarse, with basal and cauline leaves. Cauline leaves have a large amount of surface area, being 2 or 3 times pinnately divided. The inflorescence is a raceme of bisexual flowers. The fruit is a 1 × 10- to 71-mm-long silique bearing 10 to 20 small (10-25 mm long), seeds [32,49,51,64,96,106,145]. Tansymustard (Descurainia spp.) fruits and seeds do not have specialized appendages for dispersal [74,76]. Tansymustards have a short taproot [29,153].

Stand structure of herb sophia-dominated communities is sparse immediately after disturbance. Herb sophia stands often become dense and crowded within a few postdisturbance years, and thin as succession advances [16]. For further information on herb sophia's role in succession, see Successional Status below.

Breeding system: Mustards (Brassicaceae) are cross-pollinated. Selfing also occurs [63].

Pollination is insect-mediated. The sepals contain nectaries that attract insect pollinators [63].

Seed production: Herb sophia produces an average of 75-650 seeds per plant [124]. A large plant may produce upwards of 700,000 seeds [114].

Seed dispersal: Wind, water, machinery, and animals transport herb sophia seed, although most seed falls near the parent plant [114]. Animals disperse tansymustard seeds when the mucilaginous seedcoat sticks to feathers or fur [155].

Seed banking: Herb sophia builds up a soil seed bank [2,5,39,149]. The seed bank can be large: Stevens [126] documented a herb sophia seed population of 704,582/m² in North Dakota soil. Herb sophia was an important component of the soil seed pool (all spp.) in big sagebrush-green rabbitbrush (Chrysothamnus viscidiflorus) of southwestern Wyoming [30]. On the Nevada Test Site near Las Vegas, herb sophia was the 2nd most common species to emerge on irrigated and unirrigated test plots; red brome was most common [149]. Long-term viability of herb sophia seed is unknown, but the seed is reported to remain viable for "considerable periods in the soil" [114]. Buried flixweed seed remained viable at least 4 years in Fairbanks, Alaska. Seed viability generally dropped with years of soil storage [26]:

Germination: Herb sophia shows good germination [27], with a mean rate of about 70% [114]. Seed collected in Alberta showed 75% germination after cold storage/stratification. In another aspect of the study, some seeds from the lot survived digestion by ruminant grazers or short-term silage. Three percent of ingested seed germinated after 1 day in a cow's rumen, and seed stored in the bottom of a barley (Hordeum vulgare)-filled silo for 8 weeks showed 2% germination [19].

Herb sophia is adapted to establishing in dry environments. The seedcoat of tansymustards forms a thin layer of mucilage after wetting [64,155]; the mucilaginous layer helps germinating seeds retain water [155].

Seedling establishment/growth: The taproot exploits moisture in the upper soil layer [29,152,153], and uncrowded plants develop rapidly. Plants may develop numerous leaves and up to 15 lateral, fruit-bearing branches at maturity [16].

Elevational ranges of herb sophia are:

A common pattern of succession in disturbed sagebrush steppe begins with Russian-thistle. Herb sophia, western tansymustard (Descurainia pinnata), and/or tall tumblemustard (Sisymbrium altissimum) soon follow successionally. Russian-thistle may in turn reinvade the mustard stands with grazing disturbance, but more commonly, the mustards are succeeded by cheatgrass (Bromus tectorum) [66,101,152]. In desert environments, cheatgrass usually requires litter for successful germination and establishment. Dried skeletons of herb sophia and other annual forbs may facilitate cheatgrass establishment by providing litter [37,38]. For information on the interactions of herb sophia and cheatgrass, see Fire Management Considerations and the FEIS review on cheatgrass.

Herb sophia is uncommon to absent in late seres [115]. In central Saskatchewan, herb sophia occurred in fallow and recently harvested wheat (Triticum aestivum) fields. It was not present, or found in seed bank soil samples, of adjacent undisturbed shortbristle need-and-thread-western wheatgrass (Hesperostipa curtiseta-Pascopyrum smithii) prairie [5]. On strip-mined sites in south-central Alaska, herb sophia volunteered on revegetated reclamation sites, but was absent by posttreatment year 10 [34]. Herb sophia is most likely to persist in communities that retain unlittered soil and open canopies into late succession. In singleleaf pinyon-Colorado pinyon (Pinus edulis)-Utah juniper communities of west-central Utah, where litter build-up can be slow, herb sophia occurred on burns in early to late stages of succession (3-100+ years), but was most common on new burns [13]. On mixed-grass prairies in Wyoming, which are likely to build up litter quickly, herb sophia was common for ~10 years postdisturbance, then became increasing scarce [115].

Herb sophia and the native western tansymustard are apparently equally invasive, and fill similar ecological niches [89].

Herb sophia 1st sheds pollen in mid-May in North Dakota. Average flowering date is May 28th, with flowering ranging from mid-May to early June [125]. Over an 8-year period in western North Dakota, herb sophia began 1st bloom from mid-June to late July. Mean total growth was completed in June [49]. Similarly, May 30th was the mean flowering date over a 7-year period in Saskatchewan. Across years, flowering extended from mid-May to late July [22].

FIRE ECOLOGY

• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

Fire regimes: Introduced species can alter the rate of spread of fire, the probability of occurrence of fire, and the intensity of fire in an ecosystem [31]. Herb sophia has multiple, finely divided leaves [32,51,64,106] and tends to form dense stands that are dead and dry by the fire season [16]; hence, it provides a source of fine surface fuels that can spread fire. If herb sophia stands do not burn, they provide litter that favors establishment of species, including cheatgrass, which are more sensitive to desiccation as germinants and seedlings than herb sophia [37,38].

Herb sophia was absent or unimportant in fire-prone ecosystems when historic fire regimes were functional; however, western and other tansymustards were present. Herb sophia and western tansymustard are morphologically and ecologically similar [89], and herb sophia is filling or sharing the ecological niche of western tansymustard as an initial colonizer and early seral species on burns. The role of both species in facilitating establishment of other weedy species in dry environments by providing litter (and subsequently, more mesic conditions for germination and seedling growth of other species including cheatgrass) needs further investigation. There may be subtle differences in the effectiveness of the 2 species in facilitating postdisturbance succession; this also bears investigation, particularly in areas vulnerable to cheatgrass invasion.

Because herb sophia is widespread, it is difficult to exclude many ecosystems as potential hosts of herb sophia plants or populations. The following table provides some fire return intervals for plant communities where herb sophia may be important. 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".

FIRE EFFECTS

• IMMEDIATE FIRE EFFECT ON PLANT
• DISCUSSION AND QUALIFICATION OF FIRE EFFECT
• PLANT RESPONSE TO FIRE
• DISCUSSION AND QUALIFICATION OF PLANT RESPONSE
• FIRE MANAGEMENT CONSIDERATIONS

In big sagebrush communities that have experienced fire or other disturbance that removes the sagebrush, herb sophia commonly dominates or is an important component of the initial postfire community. Along with herb sophia, Russian-thistle, western tansymustard, and/or tall tumblemustard form the initial plant community, which is dominated by annuals. Cheatgrass may be part of the initial community in mesic environments. On dry sites, it may follow successionally soon after the annual forbs [101], when litter has created a seedbed favorable for cheatgrass germination [37,38].

Although fire creates an open canopy and bare mineral soil, which favors herb sophia establishment, herb sophia is not an obligate "fire follower." Any area with bare ground, open sunlight, and a seed source is vulnerable to herb sophia invasion [60,61].

Grazing: Few studies have focused on the interactive effects of fire and grazing on herb sophia. One study suggests that fire and grazing may reduce postfire cover of annuals more than fire alone, but the results are inconclusive for herb sophia. Russian-thistle, herb sophia, and prickly-lettuce (Lactuca serriola) were the 3 most important annual forbs, respectively, on a Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis)-green rabbitbrush burn in central Utah. The 3 annual forbs showed greatest coverage on ungrazed, burned sites (~50%), slightly less cover on grazed, burned sites (~45%), and least cover on grazed, unburned sites (~27%). (Data are pooled means for the 3 forbs over 12 postfire years) [146]. Further studies are needed to understand how combined fire and grazing affect herb sophia.

Burning may not increase postfire cover of herb sophia. In his classic study of postfire succession of herb sophia and other exotics in big sagebrush, Piemeisel  [100] wrote "the mere statement that a field has been burned is not sufficient information to foretell what the effect will be on the succeeding plant cover." For example, a Gambel oak/common snowberry (Symphoricarpos albus) community in Utah was chained and burned to increase forage production for cattle and elk. Two years after treatment, herb sophia cover showed little change (± 1%) compared to pretreatment levels [79]. Piemesel [100] stated that site grazing history, postfire weather patterns, and level of postfire cheatgrass cover will affect cover and relative abundance of herb sophia and other early successional forbs.

The Research Project Summary Nonnative annual grass fuels and fire in California's Mojave Desert provides information on prescribed fire and postfire response of plant community species including herb sophia.

Interactions with cheatgrass: If present in the seed bank, herb sophia is liable to dominate early postfire communities if the seedbed or the postfire climate are unfavorable for cheatgrass establishment [37,38,100]. Even when cheatgrass dominates the postfire community, herb sophia is likely to be an important forb. The 2 species are frequently found together in the prefire seed bank. In a big sagebrush-rubber rabbitbrush (Chrysothamnus nauseosus) community in Wyoming, cheatgrass dominated the seed bank, but herb sophia was 1 of the most important forbs in the seed bank [93]. Succession after a July 1985 wildfire on the Snake River Birds of Prey Area, southwestern Idaho, followed a typical pattern, with herb sophia showing greater cover than any other plant species except cheatgrass. There was much open ground in the area, especially on sites prepared for postfire rehabilitation. Mean percent cover at postfire year 1 was [54]:

Interactions with western and other tansymustards: Although they are taxonomically and ecologically similar, little is known of possible  growth interference of  exotic herb sophia to western and other native tansymustards in postfire environments. Limited studies are inconclusive, and further research is needed in this area. A review by Wright and others [151] describes herb sophia as more resilient to fall prescribed burning than western tansymustard ("undamaged" vs. "slightly damaged" by fall fire, respectively). Postfire responses of the 2 species probably depend upon their relative abundance in the prefire seed bank and poorly understood differences in germination and seedling establishment requirements. Floyd-Hanna and others [45] noted the presence of both species after the Chapin 5 Wildfire at Mesa Verde National Park in the summer of 1996. Herb sophia was more frequent on study plots than western tansymustard at postfire year 1. Herb sophia was not observed on study plots at postfire year 2, while western tansymustard increased. Tansymustard frequencies (%) on burn sites were as follows [45]:

MANAGEMENT CONSIDERATIONS

• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• OTHER USES
• IMPACTS AND CONTROL

Wildlife use of herb sophia and other tansymustards is poorly documented, and further studies are needed to determine the relative importance of tansymustards in animal communities.

Small mammals: Townsend's ground squirrels graze tansymustards, sometimes in large quantity. Spring use of tansymustard has ranged from 3% on the Snake River Birds of Prey Area in southwestern Idaho to 33% in eastern Washington [71,111,154].

Birds: Sage-grouse in Nevada grazed most of the early spring forbs in a big sagebrush community, but avoided herb sophia [117]. In free-choice trials, chukar preferred western tansymustard seeds to cheatgrass seeds, which form the main staple of their diet [155].

Herb sophia is a larval food for orangetip, white checkered, and white cabbage butterflies [68].

Palatability/nutritional value: Herb sophia is moderately palatable to livestock, although livestock may prefer other tansymustard species. In free-choice trials, cattle in Montana selected western tansymustard more often than herb sophia [99].

Cover value: No information

IMPACTS AND CONTROL:
Impacts: The greatest impact of herb sophia and other tansymustards to wildlands is probably their role in facilitating succession. See Successional Status for further information.

Herb sophia invades rangelands disturbed by heavy grazing [105]. It is a common volunteer on restoration and rehabilitation projects [122,143].

Herb sophia is a crop pest [89] and an alternate host for beet leafhoppers, which transmit curly top virus to sugar beet (Beta vulgaris) crops [65].

Control: Herb sophia does not usually persist in late-seral communities and may not require special control measures. Canopy closure, litter accumulation and/or growth interference from later-successional species tend to exclude tansymustard over time. For example, herb sophia volunteered between rough fescue sod patches on a restoration project in Alberta. As the rough fescue grew and litter accumulated, herb sophia became less abundant [108]. Perhaps because it is largely controlled by succession, there is scant wildland-management interest in using resource monies to control herb sophia with fire, herbicides, or other treatments.

Prevention/Cultural: Since herb sophia is an early seral species, minimizing soil disturbance and seed dispersal and maintaining a healthy plant community is the best way to prevent establishment of herb sophia [25].

Integrated management: Land management practices that promote later-successional species can exclude herb sophia from most plant communities [25]. Some communities, such as sagebrush steppe and salt-desert shrubland, maintain open light and bare ground conditions well into late succession [81]. For these communities, herb sophia is controlled by eliminating seed production until the seed bank is depleted. Mechanical treatment or herbicide application prior to seed set treats established plants [25]. Managers are encouraged to use combinations of control techniques that are appropriate to the site objectives, desired plant community, available resources, and timing of application. For information on integrated weed management without herbicides, see the Bio-Integral Resource Center (BIRC) website.

Physical/mechanical: Small infestations of herb sophia can be controlled by hand pulling rosettes in the fall or early spring [25].

Fire: See Fire Management Considerations.

Biological: There are no biological control organisms reported for herb sophia [25].

Chemical: Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but are rarely a complete or long-term solution to weed management [24]. Herbicides are more effective on large infestations when incorporated into long-term management plans that include replacement of weeds with desirable species, careful land use management, and prevention of new infestations. Control with herbicides is temporary, as it does not change those conditions that allow infestations to occur [157]. See the Weed Control Methods Handbook for considerations on the use of herbicides in natural areas and detailed information on specific chemicals.

Descurainia sophia: References

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