This description provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [42,49,64,101]).
Small burnet is a perennial forb. Stems are erect [49], ranging from 0.8 inch (2 cm) in height on droughty sites to 28 inches (70 cm) on moist sites [49,64,119]. There are 12 to 17 pinnately compound basal leaves that are 2 to 8 inches (4-20 cm) long, egg-shaped, and sharply toothed. Cauline leaves become few and much reduced up the stem. The inflorescence is a terminal spike with dense, mostly imperfect, sessile flowers. Lower flowers are often staminate, with upper flowers pistillate or perfect. Flowers have 4 broad, petal-like sepals; true petals are lacking. The fruits are achenes, paired in a persistent, usually winged, 3- to 5-mm-long hypanthium [18,42,49,64,101,117,119,155]. Hypanthia are sometimes wingless [101]. The seeds are small, with about 50,000 seeds/lb [58,106,117]. The stem base ends in a usually branched caudex, with a long, stout taproot beneath [18,42,89,119,120,127]. Roots of plants in southern England were estimated at more than 16 inches (40 cm) in length [11], while small burnet roots in New Zealand were traced to 3-foot (1 m) depths [117]. Small burnet sometimes has short rhizomes [42,64,115,116,119].
Small burnet is drought tolerant [11,157]. Drought resistance is partially attributable to its long, stout taproots, which have high water-storing capacity [38,133]. Small burnet can also adjust its water-use efficiency as environmental conditions change [37,38].
Age classes: Small burnet may live as long as 20 years on western rangelands, although life spans of 7 to 12 years are typical [89,99]. On chalk grasslands in southern England, 7 of 21 small burnet rosettes that emerged from plots in spring survived to flower. An additional 5 plants died after flowering, so total mortality rate from spring through summer averaged 57% [77].
Small burnet is native to Europe, western Asia and Siberia, and northern Africa [41,109,112]. It is nonnative in North America, South America, Australia, and New Zealand. Most North American small burnet populations originated in Europe [49,50,89,132,155]. A few small burnet accessions came from the Middle East [127]. Small burnet was deliberately introduced as a pasture and rehabilitation forb. It is very rarely invasive [7,78,119,156], typically occurring in small populations in only a few counties of the states in which it grows (for example, see [74,78,101,132]). In western North America, small burnet occurs sporadically from British Columbia east to Montana and south to California, New Mexico, and Nebraska [18,60,64]. It is also sporadically distributed to the east [42,110] from Ontario east to Nova Scotia and south to Tennessee and North Carolina [60,110]. Plants Database provides a distributional map of small burnet.
Subspecies: Nearly all small burnet populations in North America are Sanguisorba minor subsp. muricata. The North American distribution of Sanguisorba minor subsp. muricata overlaps that of the species, given above [109,143]. Sanguisorba minor subsp. minor occurs in northwestern Washington and southwestern British Columbia, with very small, widely scattered populations in Alberta, Saskatchewan, and Ontario [85]. Sanguisorba minor subsp. magnolii is native to the Mediterranean region [112] and was introduced in North America from Spain and Portugal in the 2000s. It is grown experimentally and is rare in North America [41].
Fire adaptations: Although small burnet is native to fire-adapted ecosystems such as Kermes oak maquis [139,141], little is known regarding small burnet's adaptations to fire. It is anecdotally noted as fire resistant because its foliage remains green through the fire season [89,116,129]. Little fire research has been conducted on small burnet where it is native. Research in North America has focused on postfire establishment of small burnet from seed mixes sown soon after fires have passed, not postfire self-regeneration of small burnet. Further research is needed on the fire ecology of small burnet in both its native lands and in areas where it is nonnative.
FIRE REGIMES: It is difficult to predict how small burnet may respond to various FIRE REGIMES because its response to fire is not well documented. Since small burnet seed accessioned for North America came mostly from northern and western Europe, fire histories there best reflect the FIRE REGIMES under which North American small burnet plants evolved. The grasslands of Europe have been managed for so long that their natural fire regime is unknown. In the historical period of Europe (750 BC on), most grassland fires were set for pastoral and agricultural purposes (review by [138]). The chaparral-like maquis of Europe experiences a fire regime similar to that of chaparral in southwestern Oregon and California: moderate (10-50 years) to long (>50 years) fire-return interval, stand-replacement fires that are difficult to suppress (review by [138]), [63]. This literature review found only 1 study on small burnet's response to fire in Europe (see Plant Response to Fire), so discussions of small burnet's fire ecology in this review are largely speculative.
The fire regime in the Intermountain West, where small burnet is most commonly seeded, is probably unlike FIRE REGIMES under which small burnet evolved in Europe because the climates are so different. Intermountain West plant communities in which small burnet is commonly seeded include pinyon-juniper woodlands, big sagebrush steppes, and mountain grasslands. FIRE REGIMES for those communities range from mixed-severity and long return interval, stand-replacement fires in pinyon-juniper [40,62], moderate return interval, mixed-severity fires in big sagebrush [4,161], and frequent fires in mountain grasslands [2,3]. Cheatgrass (Bromus tectorum) population expansions have dramatically changed FIRE REGIMES and plant communities in the Intermountain West by creating flammable, continuous fuels that ignite easily and produce fires that spread rapidly, cover large areas, and occur frequently [130,158,159,160].
Since small burnet is seeded in after fire and is noninvasive, its response under various FIRE REGIMES of the Intermountain West may be less important than its rate of seedling establishment in postfire seedings, which is discussed in Plant Response to Fire. Some of the other nonnative species in seed mixes with small burnet may become invasive, however, particularly crested wheatgrass and desert wheatgrass [33].
For further information on FIRE REGIMES of plant communities where small burnet is often seeded in after fire, see the small burnet Fire Regime Table. The expanded version of the Fire Regime Table provides information on FIRE REGIMES of plant communities in which small burnet is less common.
Fuels: Small burnet leaves stay green and maintain a relatively high moisture content in the fire season [119]. Monsen [79] rates small burnet foliage as moderately flammable and its litter as low in flammability. Because of its high moisture content, small burnet is often seeded onto greenstrip fuelbreaks [79,93,94] (see Greenstrips for further information).
Native species recovery after seeding: Reestablishment of native species is critical in maintaining and restoring genetic and ecological function in native systems of the Intermountain West [108]. The rapid growth, broad adaptability, and longevity of many of the nonnative species used in seed mixes have made it difficult for native species to establish on some rehabilitation sites in the Intermountain West [81,150]. Although postfire rehabilitation is mandated [91,108], few studies compare postfire plant community composition on seeded vs. unseeded plots, so it is difficult to assess the cost- and ecological effectiveness of postfire seedings [91]. Nonnative seedings may reduce plant community diversity in the long term. For example, a 20-year study of rehabilitation projects in big sagebrush communities of northwestern Colorado found total plant species richness was greater on plots seeded with either native or combination native-nonnative mixes than on plots seeded with nonnative species alone (P=0.05) [86].
Two other studies [20,34] found seeding made little difference in native species recovery on seeded plots compared to native species recovery on unseeded plots. After wildfires on Wyoming big sagebrush communities in the Snake River Plains of southern Idaho, there was no significant difference in species composition on seeded vs. unseeded plots. Thirty-four burns, all seeded during postfire year 1, were inventoried. Time-since-seeding ranged from 2 to 17 years across the burned sites. The seed mixes contained small burnet, other nonnative species, and native species including Wyoming big sagebrush. Across sites, native plants were establishing or recovering as well on unseeded as seeded plots. Coverage of nonnative species was similar on seeded and unseeded plots [20].
A study in Grand Staircase-Escalante National Monument, Utah, had similar findings. Three Buckskin Mountain sites burned by summer wildfiresÂ1 in 1966 and 2 in 1997Âwere studied. The burned plant community was primarily Utah juniper woodland, with patches of big sagebrush-Stansbury cliffrose (Purshia mexicana var. stansburiana) steppe. Burned areas were seeded with native-nonnative mixes the fall or spring after the fires. Small burnet was included in the seed mix used on 1 of the burned sites. The study found that whether seeded or not, burned plots had significantly higher diversity and cover of nonnative species and lower diversity and cover of native species compared to unburned plots (P<0.001). Coverage of small burnet alone was not provided. Cheatgrass dominated both burned and unburned plots. Comparing the two 1997 burns, which were on west and east slopes, the east-slope burn had significantly higher coverage of native plants than the west-slope burn (P<0.01). The authors concluded that site factors were at least as important in determining postfire recovery of the native species as rehabilitation seedings [34]. Further studies are needed to assess the effectiveness of postfire rehabilitation seedings that include small burnet and the ecological impacts of such seedings on native species.
Postfire rehabilitation: Despite the potential interference of nonnative species with native species' establishment and growth, seed mixes with small burnet and other nonnative, noninvasive plants are widely used in the Intermountain West to prevent postfire erosion and slow postfire spread of invasive nonnative plants [108,128]. Stevens and Monsen [128] recommend against using nonnative species to restore native communities when possible. However, nonnative seedings will likely continue until native plant materials become more widely available [128]. Seed mixes that include nonnative species can be effective where rapid plant establishment and coverage are desired. Nonnative species in commercial seed mixes usually grow quickly and have wide ecological amplitudes. Compared to native seed mixes, nonnative seed mixes are less expensive, and species in nonnative seed mixes selected for the Intermountain West may establish more easily than species native to the area [6,128]. Further, seeds of many native species may be unavailable [96,102,128]. Small burnet, dryland alfalfa, Siberian wheatgrass, and desert wheatgrass were among the most frequently seeded species in a study of 50 burned-area rehabilitation sites on the Battle Mountain, Elko, Ely, and Winnemucca Districts of the US Department of Interior, Bureau of Land Management in Nevada. In contrast, most species sown on mine reclamation sites were native grasses [108]. Small burnet provides only spotty cover when planted alone, but shows good establishment when included in seed mixes [79].
Postfire control of invasive species: Seed mixes with nonnative species can help control spread of invasive species on some sites [128]. Small burnet is often included in seed mixes used to reduce postfire establishment of cheatgrass in sagebrush and pinyon-juniper ecosystems [13,17]. Species selected for cheatgrass control show rapid seedling establishment and growth, have broad adaptability and high forage value, and are resistant to grazing. Small burnet is usually blended with Lewis flax, dryland alfalfa, forage kochia, Russian wildrye, and/or nonnative wheatgrasses (Agropyron spp.) in mixes formulated for cheatgrass control. Native grasses are often included in the mix [81,94,121,128]. See Cultural control for further information on this subject.
Greenstrips are long, narrow bands of vegetation that maintains relatively high moisture contents during the fire season. They are used to disrupt fuel flammability, accumulation, and continuity [23,79,93,94]. Seed mixes used on greenstrips usually include nonnative and native species. Small burnet, forage kochia, dryland alfalfa, and Lewis flax are forbs commonly used in greenstrip seedings; crested or desert wheatgrass, bottlebrush squirreltail, and bluebunch wheatgrass are commonly used grasses [48]. Small burnet's long, stout taproot enables it to store water and maintain high moisture levels under drought, so small burnet is well suited for greenstrip seedings. During an extreme drought in southern England, small burnet maintained a higher relative water content than 30 associated species [11].
Interference with conifers: Small burnet and other seeded species may interfere with postfire conifer seedling growth. On the Fort Valley Experiment Station near Flagstaff, Arizona, ponderosa pine (Pinus ponderosa var. scopulorum) seedlings on seeded plots gained significantly less height and stem diameter growth than ponderosa pine seedlings on plots where other vegetation was hand-pulled (P<0.05 for all study measures). The study site had been severely burned by a wildfire that removed all aboveground vegetation. Burned areas were planted in postfire year 1 with 2-year-old ponderosa pine seedlings and herbaceous species including small burnet, yellow sweetclover, crested wheatgrass, desert wheatgrass, orchardgrass (Dactylis glomerata), bottlebrush squirreltail, and blue grama (Bouteloua gracilis). Soils on burned sites had significantly higher nitrogen levels compared to unburned plots. The authors suggested that small burnet and ponderosa pine were competing for nitrogen and water on burned plots [32].Small burnet is frost, cold, and drought tolerant [11,157]. In the Great Basin small burnet is most common on relatively mesic sites [71]. It does not establish well on xeric sites in either the Great Basin [10] or the Mojave Desert [71]. Small burnet establishes best in areas receiving 18 or more inches (>457 mm) of mean annual precipitation [120], although it can establish in areas receiving as little as 10 inches (255 mm) of annual precipitation [127]. It does not generally persist with less than 12 inches (305 mm) of mean annual precipitation [10,51,119,127]. Small burnet occurs mostly on moist slopes and in moist woodlands in New Mexico [74].
In the East, small burnet is reported mostly on disturbed sites [101,110,132,149] and "waste places" [101]. It grows on cliffs in the Carolinas [101].
Soils: Small burnet accessions in North America are adapted to relatively infertile, well-drained soils [120,157]. Small burnet is most productive on slightly acidic to mildly alkaline soils [119,156], although small burnet tolerates soils up to 8.0 in pH [51]. It also tolerates mildly saline soils [89]. 'Delar' small burnet, a cultivar widely seeded in the Intermountain West, does not grow on sites that are poorly drained, flooded, or have a high water table [119,152].
Parent materials and soil textures: Small burnet is restricted mostly to calcareous soils in Europe [76,113], growing, for example, on limestone- and chalk-derived soils in Great Britain grasslands [76,118,141,147]. It also grows on siliceous soils in Spain (Salmeron 1966, cited in [117]), [142]. Small burnet grows on calcareous soils in North America but is not restricted to them. Soil types supporting small burnet in Michigan, for example, include rocky, calcareous streambanks and lakeshores, but small burnet also grows on gravels and sands in Michigan [149]. Small burnet is most productive on silty or loamy soil textures, although it grows on sandy and clayey soils [117,152]. It is reported on sands in eastern New Jersey [137]. Small burnet's near-restriction to calcareous soils in Europe may help explain its inability to spread on most North American sites. Further studies on soil preferences of small burnet in North America are needed.
Elevation: Small burnet grows on mid- and low-elevation sites in the Intermountain West. It does not establish well on low-elevation, xeric sites in the Great Basin. The mountain big sagebrush zone, which is higher in elevation than the basin big sagebrush zone, favors small burnet growth there [10]. Small burnet does not establish well in high-elevation Sierra Nevada locations [71].
Small burnet elevational ranges in the western United States
California 100-5,200 feet (30-1,600 m) [49] Nevada 6,500-7,500 feet (2,000-2,300 m) [61] Utah 5,000-7,005 feet (1,525-2,135 m) [155] New Mexico 6,000-7,500 feet (1,800-2,300 m) [74] Intermountain West 5,200-8,900 feet (1,600-2,700 m) [18]Elevational ranges in Eurasia
Europe sea level-4,600 feet (0-1,400 m) Iran and Afghanistan 5,900-6,600 feet (1,800-2,000 m) (review by [29])Wildlife: Small burnet provides good wildlife forage. Elk, deer, pronghorn, eastern cottontails, and birds utilize the foliage and/or seeds [89,123,137], (McLain 1959, cited in [137]). On Utah juniper-Colorado pinyon sites near Ephram, Utah, mule deer use increased from pretreatment levels after chaining to reduce tree density, then seeding with a nonnative-native mix of small burnet, other forbs, and grasses [22]. Deer use of small burnet may be slight when many other green plant species are available. Mule deer on the Kaibab Plateau, Arizona, grazed small burnet only lightly in summer (0.33% of total summer diet) [55]. White-tailed deer in New Jersey fed heavily on small burnet rosettes in May and June but grazed small burnet moderately in other times of the year [137]. Greater sage-grouse also graze small burnet. Pellant and Lysne [95] recommend planting small burnet on crested wheatgrass-dominated sites to provide forage for greater sage-grouse and break up crested wheatgrass stands.
Northern bobwhite and mourning doves eat small burnet seeds (McLain 1959, cited in [137]).
Livestock: Small burnet is planted in pastures and rangelands [49,120]. It provides high-value forage for livestock in general [157] and is especially valuable as domestic sheep forage [24,26]. Livestock use is generally highest in early spring, late fall, and winter, when other forage is sparse [127].
Small burnet's utility as a honeybee food in New Zealand is rated moderate [157].
Palatability/nutritional value: Small burnet has good to excellent forage value for wildlife and livestock in all seasons. It generally stays green and palatable throughout the growing season and into winter until heavy snows [26,119]. Small burnet is often added to rangeland seed mixes because it is so palatable to grazing wildlife [9]. Domestic sheep and mule deer prefer it, and small burnet is "very palatable" to ungulates in general [120].
Small burnet seed is palatable to granivorous rodents, lagomorphs, and upland game birds. Ungulates graze small burnet seedheads [127]. Deer mice preferentially selected small burnet seeds in 2 cafeteria trials. In 1 trial, small burnet seeds were their primary food choice, forming 20.5% of the total deer mouse diet. Deer mice selected small burnet 3rd in the other trial, comprising 14.3% of their total diet [36].
Small burnet is high in protein and carotene [97,117,120]. Its in vitro digestibility is ranked just below that of alfalfa [117]. Welch [154] found protein content of small burnet on western rangelands dropped from 17.4% in spring to 9.8% in summer and 6.6% in winter. For nutritional analyses of small burnet in Europe and the Middle East, see these sources: [1,5,117,145,148].
Grazing tolerance: Small burnet tolerates moderate grazing [152], showing good compensatory growth in response to moderate utilization. Small burnet regrowth after domestic sheep grazing in New Zealand was termed "splendid" (review by [29]). In a New Zealand pasture, small burnet showed mean regrowth rates of 46 kg dm/ha/day after 3 repeated domestic sheep defoliations down to 2.8- to 3.2-inch (7-8 cm) heights [26]. Small burnet typically tolerates severe grazing as long as grazing is not continuous [29]. In the greenhouse, repeated severe defoliation (80-100% topgrowth removal) slowed 3- and 4-month-old small burnet seedling growth greatly [28]. Well established small burnet in New Zealand tolerated "depleting and severe" domestic sheep grazing for 5 years [30]. After 2 years of rest, Small burnet in Oregon made a "remarkable" recovery from 10 years of moderate to intense domestic sheep grazing [145]. When repeated over many years, early spring, late summer, and/or late winter grazing may reduce small burnet abundance [129]. Livestock often graze small burnet heavily in spring and early summer, and that use is often followed by heavy wildlife grazing in late fall and winter. Livestock utilization may need to be controlled to avoid overgrazing of small burnet in areas where small burnet is desired as a forage species [127].
Cover value: Small burnet provides cover for small birds [89].
Small burnet grows in grasslands and shrublands in Europe. It is most common on
chalk grasslands in England [44,72,76,118,141,147]. In France, it occurs on
alluvial meadows [147] and chaparral-like,
Kermes oak (Quercus coccifera) maquis (sclerophyllous shrubland on
siliceous soil) and garrigue (sclerophyllous shrubland on calcareous soil)
in the southern part of the country [139,141,142].
Small burnet is most common on western rangelands in North America.
It is usually planted in pinyon-juniper (Pinus-Juniperus spp.) woodlands [21,31,127,128],
ponderosa pine (P. ponderosa) forests [128], relatively dry quaking aspen (Populus tremuloides)
parklands [19,127], mountain grasslands [95], chaparral [9,135], mountain brushlands [98,127,128], desert shrublands
[116,127,128], and sagebrush (Artemisia spp.) steppes [98,127,128]. In sagebrush ecosystems,
it is most abundant in the relatively mesic types such as Wyoming big
sagebrush (A. tridentata subsp. wyomingensis) and mountain big sagebrush
(A. t. subsp. vaseyana) [10,127,128], although it persists in some basin big sagebrush
(A. t. subsp. tridentata) communities [127].
Seed mixes applied on western rangelands contain a fairly consistent blend of
recommended species. The mix often contains both nonnative and native species, selected to help ensure no
one species interferes greatly with development of the other species [54,75,80,89].
Because they are regenerated artificially and establish together, the seeded species are often associated across a
broad array of plant communities. Nonnative species most often included in seed mixes with
small burnet include dryland alfalfa (Medicago sativa), forage
kochia (Kochia prostrata), yellow sweetclover (Melilotus officinalis),
Russian wildrye (Psathyrostachys juncea),
Siberian wheatgrass (Agropyron fragile), crested wheatgrass (A.
cristatum), and desert wheatgrass (A.
desertorum). Native species often included in the mix are Lewis flax (Linum lewisii), bottlebrush
squirreltail (Elymus elymoides), and bluebunch wheatgrass (Pseudoroegneria
spicata) [17,48,81,94,108,121].
In the East, small burnet is associated more closely with
disturbance than with particular plant communities (see Site Characteristics).
Cultural control:
Small burnet may provide cultivation control of invasive nonnative
herbs. When grown with rush skeletonweed (Chondrilla juncea) in a greenhouse pot
study, small burnet was rated "most competitive" against rush skeletonweed
among 5 herbaceous species tested. Compared to other herbs tested, small burnet showed highest productivity rates
when grown with rush skeletonweed [100]. Small
burnet is rated moderate in ability to control nonnative hawkweed (Hieracium
spp.) in New Zealand [157].
A mix of small burnet, other forbs, and bunchgrasses is often planted for control of
cheatgrass, red brome (Bromus rubens), and/or medusahead (Taeniatherum
caput-medusae) [128]. Stevens and Monsen [127] report that small burnet competes "fairly well" with
cheatgrass once small burnet has established. Seed mixes
with small burnet do not always effectively control cheatgrass, however.
On burned sites where a seed mix was drilled in near Pocatello, Idaho, cheatgrass mean
cover was greater on seeded than unseeded sites (P<0.35). Small burnet
seed comprised 16% of the mix by weight [103].
Few long-term studies were available on the effects of introduced herbs on
establishment of native plant species (as of 2008). A study in a Utah juniper-Colorado pinyon
community in Sanpete County, Utah, found introduced, seeded species were
somewhat more competitive (had higher mean coverages) than native species 23
years after seeding. Sites had been chained to reduce tree density, then seeded with a mix of
nonnative and native grasses and forbs, including small burnet, and native big
sagebrush and rubber rabbitbrush. Twenty-three years after seeding, nonnative
grasses had significantly greater densities than native grasses on ungrazed
sites (P<0.05 for all treatments). Grazing pressure from cattle, mule deer, and
black-tailed jackrabbits lowered the ratio of nonnative:native grass species,
however. On grazed plots, nonnative grasses had lower mean densities
(x=11,459
plants/ha) compared to native species (x=14,887 plants/ha),
with a significant increase in mean native grass density over
23 years [151]. See Fire Management Considerations
for further information on the effects of nonnative seedings on native species.
Culinary: As the alternative common names garden burnet and salad burnet imply, small burnet is used in the kitchen, more often in Europe than in North America. The cucumber-flavored leaves are used in iced drinks, salads, and other foods [97,119].
Medical: Small burnet extracts have shown positive physiological effects in laboratory studies. A Spanish study found small burnet extracts exhibited anti-HIV activity in vitro [8]. In Germany, small burnet extracts significantly lowered blood sugar levels of laboratory mice treated with the extracts compared to control mice [107]. In a Turkish study, small burnet extracts gave significant protection against gastric ulcers in laboratory mice (P<0.001) [45]. In an Iranian study, crude extracts from small burnet collected in Iran and Canada showed fungicidal activity [114]. Small burnet is used as a folk medicine in Europe and the Middle East. The roots and leaves are astringent and are used to stop bleeding. An infusion of the plant is used to treat gout and rheumatism [97].
Small burnet phenology
Area Event and seasonUnited States
California flowers May-July [84] North and South Carolina flowers June-July [101] Illinois flowers May-July [78] Nevada flowers June-Aug. [61] New Mexico flowers June-Aug. [74] Utah seed ripens from early Aug.-late Sept. [99] West Virginia flowers May-June [132] Intermountain West flowers May-June [18,127]Europe
England flowers June-July; aboveground biomass peaks in August [133]Small burnet response to fire is not well documented. Since it is known to sprout from a thick caudex [79,117] that is attached to a large, storage taproot [18,42,89,119,120,127], sprouting is likely important to small burnet's postfire recovery. Rhizomatous plants may also sprout from the rhizomes after fire. Monsen [79] rates small burnet's sprouting ability as "good". Barnes [144] collected a small burnet plant that had sprouted from the caudex and produced a single flowerhead the year following fire in a pinyon-juniper community in the Beaver Dam Mountains of Utah. The specimen can be viewed online at Utah Valley State College's Virtual Herbarium.
As the flowering herbarium specimen suggests, small burnet can establish from seed after fire [139]. Top-killed plants that sprout and produce seed after fire provide on-site seed sources for small burnet regeneration. Since small burnet has long-lived seed that is stored in soil [67,141,147,147], the seed bank is another likely source of postfire establishment for small burnet.
Excluding sites seeded after fire, only one study was found for this literature review that documented small burnet presence after fire in North America. Small burnet was present in small numbers after prescribed fires in blackbrush (Coleogyne ramosissima) communities of southwestern Utah [12]. Method of regeneration (from seed or by sprouting) was not noted in the study.
Mean small burnet cover across 8 burned blackbrush communities in Utah. Values are means (SD) [12]. Postfire year Cover (%) 1 0.0 (0.0) 2 0.7 (0.9) 6 0.0 (0.0) 12 1.9 (0.4) 17 0.0 (0.0) 19.5 0.0 (0.0) 37 0.0 (0.0) unburned plots 0.0 (0.0)A single study was found of small burnet response to fire in Europe. A study in a Kermes oak community near Montpellier, France, found small burnet established only from seed after single or repeated prescribed fires. Trabaud [140] noted that small burnet was present in trace amounts before summer or fall prescribed burning. In postfire year 4, small burnet frequency was low on all plots, but was higher on burned than on unburned plots [139,140,142]. Repeat-burn sites were burned every other spring or fall, with a total of 5 fires in 9 years. Small burnet established in low numbers in some years and failed to establish in others on repeat-burn plots [139]. Small burnet flower production was similar on burned and unburned plots [141].
Small burnet seedling frequency (%) after spring or fall prescribed burning in southern France [139] Year Spring fires Fall fires 1969* 0 1 1970 0 1 1971* 0 0 1972 3 0 1973* 1 0 1974 2 0 1975* 0 0 1976 0 0 1977* 0 1 1978 0 1 *Burn year.Postfire seedings: Small burnet usually establishes the year after seeding, then declines rapidly [43,98]. Quantitative studies documenting small burnet presence after postfire seedings are few. In Wyoming big sagebrush and Utah juniper-Colorado pinyon (Juniperus osteosperma-Pinus edulis) communities of central Utah, small burnet was mixed with other nonnative herbs and native fourwing saltbush (Atriplex canescens) and seeded on burned sites the fall after an August wildfire. Small burnet's mean frequency 1 and 2 years after the wildfire was 25%; its frequency dropped to 19% in postfire year 3. Small burnet was not present on unburned plots [91,92]. It was also included in a nonnative seed mix used after wildfire in a threetip sagebrush (Artemisia tripartita)-basin big sagebrush-mountain big sagebrush community near Pocatello, Idaho. In postfire year 2, small burnet had 0.20% cover on seeded plots and 0% cover on unseeded plots [103]. In central Utah, a nonnative-native mix was seeded in the fall after July wildfires on pinyon-juniper and big sagebrush communities. In postfire year 3, small burnet was present in only trace amounts in both communities [15].
Small burnet was used in a mostly nonnative seed mix that included mountain big sagebrush after a prescribed fall fire in Daggett County, Utah, shrublands. Colorado pinyon and junipers (Juniperus spp.) were encroaching onto 2 shrub communities: a north-slope alderleaf mountain-mahogany (Cercocarpus montanus var. montanus)/bluebunch wheatgrass community and a south-slope rubber rabbitbrush (Chrysothamnus nauseosus)-mountain big sagebrush community. The fire was used to remove the conifers, and both communities were seeded soon after the fire. Moisture the year after fire was "favorable for establishment and growth of plants". Small burnet frequencies on south-slope sites were 23% in postfire year 6 and 0% in postfire year 11. Small burnet did not establish on north-slope sites [43].
Small burnet may not establish on harsh, high-elevation burned sites. It was included in a seed mix sown on a burned lodgepole pine (Pinus contorta var. latifolia) site on the Colville National Forest, Washington. The site experienced a stand-replacement wildfire in the summer of 1929, was burned under prescription in the fall of 1949 to prepare the site as a lodgepole pine plantation, then seeded with a grass-forb mix that fall. The effect of the double burning was to remove all standing live vegetation and much organic material from the soil. Four years later, small burnet showed no establishment on southwest-facing slopes. It had "good vigor" and a density of 0.2 plant/foot² on the moister, northeast-facing slopes [35].
Small burnet establishes from seed [127,156] and by sprouting from the caudex [79,117]. Some plants may sprout from rhizomes [115,116].
Pollination: Small burnet is pollinated by bees [97].
Breeding system: Small burnet populations in North America are mostly derived from European stock selected for rapid seedling establishment and growth, high seed production, cold tolerance, and high forage value for wildlife and livestock [58,81,89,146]. Because of founder effects and subsequent breedings in the United States to enhance only these traits, overall genetic diversity of North American populations is probably low compared to native European populations.
Small burnet is monoecious [109]. Rarely, it is also apomictic [87,109].
Flower and seed production: Small burnet first flowers and sets seed at 2 years of age [124].
Small burnet produces seed prolifically on mesic sites [120]. In dryland pastures on the San Juan Basin Research Center, Colorado, small burnet was the highest seed producer among 11 species tested. Across 3 years, mean small burnet seed production ranged from 623 to 1,307 seeds/3 m² [39]. Small burnet generally does not reproduce in the most xeric areas of the Great Basin [128].
Herbivorous animals can reduce small burnet's ability to reproduce from seed [152]. Ungulates, lagomorphs, granivorous rodents, and grasshoppers sometimes consume small burnet seeds so heavily that there is little net seed production [127,152]. Small burnet usually produces seed on such sites when rodent and lagomorph populations are low and/or when livestock grazing is controlled. Dense grass stands also impair small burnet's ability to set seed and persist in wildlands [127].
Seed dispersal: Small burnet seed remains in the hypanthium when dispersed. Hypanthia are dispersed by animals, and possibly by wind and water. In the Great Basin, small burnet has established from unretreived seed in rodent caches [127]. The wings on most small burnet hypanthia may facilitate wind and/or water dispersal; speculation on the function of the wings was not found in the literature. In a study of flooded meadow communities in France, small burnet was present in soil seed banks on riverbanks subjected to periodic, short-term floods [147]. Small burnet is reported mostly from shorelines in Michigan [149]. These studies raise the possibility that water disperses small burnet hypanthia.
Seed banking: Small burnet has a persistent soil seed bank [67,99,141,147,147]. Studies in northwestern Europe found viable small burnet seed persisted for at least 30 years in the soil. Mean small burnet seed density was 24 seeds/m²; mean burial depth was 4 inches (10 cm) (review by [136]). In greenhouse studies in Italy, small burnet germinants showed 63% frequency in soil samples collected from grassland. In soil samples collected on former grassland sites converted to cedar (Cedrus deodora, C. atlantica) plantations 26 years before the study, small burnet germinants had 20% and 40% frequency in soils collected from plantations with respectively "sparse" and "dense" cedar plantings [72].
Small burnet seed stored in a warehouse for 25 years showed no appreciable drop in germinability, raising the possibility of a long-lived seedbank on some sites. Mean seed viability after 2 years was 88%; viability was still 88% after 15 years and 83% after 25 years of storage [125,126]. Humid conditions reduce the viability of soil-stored small burnet seed [29].
Germination and emergence: Germination rate of commercial small burnet seed is "excellent" [58]. Germination rates of 90% to 95% have consistently been obtained in Great Basin wildlands [58,82,120]. Small burnet seed from a commercial mixture showed 90% germination in field trials near Silver Lake, Oregon. Study plots were in a western juniper (Juniperus occidentalis) community (review by [69]).
Seeds require an afterripening period before germinating [58,106]. In the laboratory, 80% of small burnet seed germinated within 21 days of sowing, and 91% of the seed had germinated 35 days after sowing [59]. Warehouse-stored seed showed improved germination rates each year through 3 years of dry storage [125]. Information on small burnet seed viability and emergence rates for naturally-reproducing North American populations were not available as of 2008. Naturally reproducing small burnet populations in Spain showed 50% emergence in the field (Salmeron 1966, cited in [29]).
The paired seeds in small burnet's hypanthium emerge within 1 to 4 days of one another, with the earliest emergent usually dominating [29]. In the greenhouse, commercial small burnet seed from Oregon showed 54% emergence. Plants germinating from large seeds had higher mean stem and root lengths, more massive roots, and larger leaf areas than plants from small seeds (P<0.05) [25]. Highest seedling emergence occurs when small burnet hypanthia are lightly covered with soil no more than 0.25 inch (6 cm) deep [127]. Soil texture may affect emergence rate. In field studies in New Zealand, small burnet seed from Oregon showed 62.2% emergence in sand and 26.5% emergence in silty loam [27].
Seedling establishment/growth: North American populations of small burnet grow well on arid rangelands [127]. Because of deliberate selection and breeding, North American populations often have greater seedling survivorship and "vigor" and are more productive than small burnet populations in the Old World [25,81,117]. Small burnet establishes easily from commercial seed, usually providing "good ground cover" within 1 or 2 years of seeding [127]. Small burnet seedlings grow taproots "rapidly" [157], providing access to moist, lower soils layers early in development. Its overall growth is rated as "rapid" and "good to excellent" in sagebrush, pinyon-juniper, and mountain brushland zones [83,120,156].
Small burnet stands may be self-sustaining in the Great Basin, provided they are protected from grazing enough to set seed every 3 or 4 years [127]. Small burnet in New Zealand reseeded naturally after domestic sheep and rabbits were excluded [30].
Vegetative regeneration: Small burnet sprouts from the caudex [79,117]. Some plants also sprout from rhizomes [109,115,116,119], but rhizomes are short [116,119], so clonal expansion of small burnet is limited [119].
Small burnet is commonly found on disturbed sites [49,101,110,132,149,156]. It often grows on roadsides in the eastern United States [42,132,149]. It is infrequent in eastern Colorado, occurring on disturbed mountain meadows [153]. An Australian study found small burnet biomass was greater on highly disturbed plots (hand or rotary tilled) compared to undisturbed plots (P<0.002). Nitrogen and phosphorus fertilization reduced small burnet cover compared to cover on unfertilized plots (P<0.001) [14].
Small burnet usually occurs in open areas but tolerates light shade [89,129], (review by [117]). It is reported, for example, on open sites in Michigan [149]. Small burnet established well in a partially shaded Oregon white oak (Quercus garryana) rangeland near Corvallis, Oregon. The site was thinned to an open canopy, underburned, and seeded to small burnet and other forage plants for domestic sheep [46].
Small burnet usually declines quickly on sites where it is seeded in. Plummer [156] rates small burnet's ability to spread on wildlands of the Intermountain West as "poor" from seed and nonexistent vegetatively. Small burnet was part of a seed mix used on skid trails the autumn following the May 1972 Rattle Fire on the Coconino National Forest, Arizona. In postfire year 2, it had not spread from the skid trails into the ponderosa pine (Pinus ponderosa) community [7,90]. Small burnet may spread into native communities under "ideal climatic and environmental conditions", however. As of 2008, it had been reported as invasive on only one site, in Wyoming [119].
Small burnet presence in early succession may facilitate establishment of later-successional native species [43], although field studies are needed to test this effect.
The scientific name of small burnet is Sanguisorba minor Scop. (Rosaceae) [18,42,49,57,60,101,112,149,153,155].
Subspecies in North America are:
Sanguisorba minor subsp. magnolii (Spach) Briq. [112,143]
Sanguisorba minor subsp. minor [85,112]
Sanguisorba minor Scop. subsp. muricata (Spach ex Bonnier & Layens) Nordborg
[49,57,60,112]
Small burnet is often used in seed mixes for postfire rehabilitation [49,120], postfire weed control, greenstripping [48,79,93,108], posttreatment rehabilitation after chaining for juniper control [15,16,22,89,111], erosion control [89,117], and other rehabilitation projects [108,155].
Small burnet is usually started from seed grown in commercial seed orchards [98,119,146]. Bareroot or container stock is sometimes used [98,121,122]. Small burnet's rate of seedling establishment depends in part upon its relative composition in the seed mix. At recommended seeding rates, its ability to establish on disturbed sites in the Intermountain West is well documented [21,22,69,88]. Small burnet showed densities of over 14,000 plants/acre, for example, 3 years after it was seeded onto a Colorado pinyon-Utah juniper site near Ephram, Utah. The site had been chained to reduce tree density, then seeded with a native-nonnative grass and forb mix. Small burnet and dryland alfalfa were the 2 most common forbs on the rehabilitation site, with small burnet comprising 62% of total density of seeded plants. Small burnet density was greater than that of any other seeded herb, although nonnative cheatgrass and bur buttercup (Ceratocephala testiculata) established in greater numbers than small burnet [21,22].
Small burnet sometimes fails to establish or establishes in only small numbers [134]. On some sites, litter and/or litter toxins may reduce establishment rates. A greenhouse study found Utah juniper litter reduced small burnet establishment 25% compared to controls [53]. In a related field study in Utah County, Utah, small burnet failed to establish after seedings under Utah juniper with litter, under Utah juniper with litter removed, or in tree interspaces. Other seeded species established successfully on the study site [52]. The authors did not speculate on possible reasons for small burnet's failure to establish in the field.
Site preparation and seeding techniques can greatly affect restoration results. For information on seeding techniques and rates, see these sources: [15,54,83,86,98,119].
