Dalea purpurea, purple prairie clover
League, Kevin R. 2004. Dalea purpurea, purple prairie clover. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/dalpur
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| DALPUR | purple prairie clover | Dalea purpurea | Life Form: Plants/Forb Kingdom: Plantae Class: Dicot Order: Fabales Family: Fabaceae Genus: Dalea | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Purple prairie clover.
Taxonomy
The currently accepted scientific name of purple prairie clover is Dalea purpurea Vent. (Fabaceae). Recognized varieties are as follows [63,112]:
- D. purpurea var. arenicola (Wemple) Barneby
- D. purpurea var. purpurea
Synonyms
- Petalostemum purpureum (Vent.) Rydb. [6,42,53]
Other Common Names
violet prairie clover
General Distribution
Purple prairie clover is indigenous through a large portion of North America. It is distributed from eastern British Columbia eastward through Manitoba and south to western Alabama and west to Arizona. Frequent to infrequent populations exist in its extreme western extent in eastern Colorado, Wyoming, and Montana and in its extreme eastern extent in Ontario southward to New York and Tennessee [48,63,100,112]. There is considerable overlap of distributions between Dalea purpurea var. purpurea and D. p. var. arenicola, although D. p. var. arenicola's distribution is more restricted to the western Great Plains [49]. Plants database provides a distributional map of purple prairie clover.
States and Provinces
- United States: AL AZ AR CO IL IN IA KS KY LA MI MN MS MO MT NE NM NY ND OH OK SD TN TX WI WY
- Canada: AB BC MB ON SK
Site Characteristics
Purple prairie clover grows on a variety of sites throughout the Great Plains including dry plains, prairies, hillsides, open woodlands, shaded ravines, sandhills, and roadsides. It occurs on mesic and xeric sites in mixed-grass and tallgrass prairies of the northern and central Great Plains and the shortgrass prairie of the southern Great Plains [24,49,80]. It is most common on marginal sites where soil is exposed and grasses have not formed dense stands [82]. Mean annual precipitation for regions where purple prairie clover subsists ranges from 11 inches (280 mm) in southeast Alberta [32] to 32 inches (810 mm) in Kansas [105] and Oklahoma [13] to 53 inches (1,350 mm) in Mississippi [115].
Purple prairie clover growing in Deuel County, South Dakota.
Soils
Purple prairie clover can be found in most soil types throughout the Great Plains [31]. In the northern Great Plains purple prairie clover is found in sandy to silty loams [17,19]. Some specific soil characteristics have been identified with purple prairie clover in the Nebraska Sandhill prairie region. Here purple prairie clover occurs most frequently in sandy soils that contain medium to coarse grains. It is thought that the coarse sands intercept precipitation with minimal runoff, allowing most of the moisture to reach far below the surface. Due to its taproot morphology, purple prairie clover is able to access moisture from deep in the soil profile and thus is able to persist in areas where other shallow-rooted species cannot [7]. Soils in Minnesota where purple prairie clover is present were found to have pH values of 6.4 to 6.7 [16], with soil depths ranging from 6 to 24 inches (15-6.1 cm) [22].
Elevation
In eastern Colorado purple prairie clover occurs at elevations from 3,500 to 7,500 feet (1,067-2,286 m) [53].
Plant Communities
Purple prairie clover is an important component of Great Plains grassland communities. It is considered "common" in most grassland habitat types of the midwestern United States and southern Canada. Graminoids dominate these regions, comprising 80% to 90% to the total plant population. Purple prairie clover and other forbs generally make up 10% or less of total plant population in the Midwest [119]. Purple prairie clover is found in tallgrass, shortgrass, or mixed-grass prairies. Common associates in tallgrass prairies include little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardii), prairie Junegrass (Koeleria macrantha), prairie dropseed (Sporobolus heterolepis), lead plant (Amorpha canescens), and silky aster (Aster sericeus). Associates in mid-grass prairie include silver bluestem (Bothriochloa saccharoides), purple threeawn (Aristida purpurea), sideoats grama (Bouteloua curtipendula), and sand dropseed (Sporobolus cryptandrus). Grass associates in shortgrass prairie include blue grama (Bouteloua gracilis), hairy grama (B. hirsuta), and buffalo grass (Buchloe dactyloides). Forb associates include wavyleaf thistle (Cirsium undulatum), gayfeather (Liatris punctata), and scarlet globemallow (Sphaeralcea coccinea). Forbs may be interspersed with several shrubs including American hazelnut (Corylus americana), smooth sumac (Rhus glabra), creeping juniper (Juniperus horizontalis) and/or trees including green ash (Fraxinus pennsylvanica), eastern cottonwood (Populus deltoides), eastern redcedar (Juniperus virginiana), white oak (Quercus alba), bur oak (Q. macrocarpa), and shagbark hickory (Carya ovata). Woody associates are especially common near riparian areas and on grassland/forest ecotones in the northern and eastern fringes of purple prairie clover's distribution [7,8,17,18,19,32,62].
Purple prairie clover also occurs in Nebraska sandhill prairie [7], cedar glade, limestone glade, dolomite glade [8], dry-mesic savanna, dry-mesic prairie, wet-mesic alluvial floodplain [19], quaking aspen (Populus tremuloides)-prairie ecotone [18], and mesic bur oak (Quercus macrocarpa), black oak (Quercus velutina), white oak (Quercus alba), and northern pin oak (Quercus ellipsoidalis) savanna communities [17]. In Illinois, it occurs in dolomite-hill prairie and "barren" communities [2,19].
In northern Arizona's Grand Canyon National Park, purple prairie clover is considered an "exotic species," and is found in riparian areas of the canyon [95].
A purple prairie clover inflorescence.
Botanical Description
The following description provides general characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [6,43,48,49,100,108,112]).
Purple prairie clover is a perennial forb, 8 to 35 inches (20-90 cm) tall, with a woody stem. The numerous leaves are 0.4-1.6 inches (1-4 cm) long, with 3 to 7 leaflets. The inflorescence is a 0.4- to 2.6-inch (1-7 cm) spike located at the ends of the branches. Branches are numerous, usually 3 per stem, but sometimes as many as 10 to 12. The mature purple prairie clover has a coarse, nonfibrous root system with a strong woody taproot that is 5.5 to 6.5 feet (1.7-2.0 m) deep. The taproot gives rise to several minutely branched lateral roots. The fruit is a 1- to-2-seeded pod enclosed in bracts [6,48,62,100,112].
Raunkiaer Life Form
- Hemicryptophyte [86]
Seasonal Development
Purple prairie clover is a warm-season forb that generally germinates during spring [84]. In May to August (depending on climate and geographic location), purple prairie clover produces several to many inflorescences. Average flowering dates for purple prairie clover from 5 years of observation in North Dakota were [99]:
| Phenological event | Earliest first bloom | Latest first bloom | Median date of full flowering | Median date when 95% of flowering complete | Flowering period (days) |
| Date | 17 June | 13 July | 15 July | 15 August | 35 |
Flowering dates for purple prairie clover are influenced more by temperature than precipitation. Warmer temperatures seem to promote earlier flowering, while warm temperatures and ample moisture in summer increase the duration of blooming [26]. Purple prairie clover seed matures in most locations from August to September [9]. In Minnesota seed development from anthesis to seed maturity took 15 weeks [16].
Regeneration Processes
Purple prairie clover reproduces by seed [16].
Pollination and Breeding System
Purple prairie clover is cross pollinated [16]. Mating system is primarily xenogamous, but self-pollination also occurs. In a Wisconsin prairie study, 45% of hand-pollinated, outcrossed flowers produced large, viable seeds, and 19% of selfed flowers produced seeds. Native bees and honeybees were pollinators [27].
Pollination is insect-mediated [16,27].
Seed Production
Seed production is highest with favorable soil moisture and nutrient conditions. A survey of native plant horticulturists in Minnesota indicated that purple prairie clover frequently produces low seed yields [15]. Another Minnesota study compared the phenological development of purple prairie clover in cultivated fields to noncultivated managed prairie. Cultivated fields produced 3 times as much seed as noncultivated prairie. Seed and inflorescence production on cultivated and noncultivated native prairie were [16]:
| Item | Cultivated Fields | Noncultivated Prairie |
|---|---|---|
| Number of inflorescences initiated/plant | 35.0 | 29.1 |
| Weight/inflorescence (g) | 0.36 | 0.25 |
| Seed weight/inflorescence | 0.043 | 0.015 |
| Number of seeds/inflorescence | 33.5 | 11.5 |
| Seed weight/plant (g) | 0.49 | 0.22 |
| Number of seeds/plant | 379.8 | 173.4 |
Cultivated fields were devoid of any other competing plants, fertilized, and only contained evenly spaced transplanted purple prairie clover plants from native prairie lands. The noncultivated, native prairie had a variety of other forb and grass species. The noncultivated prairie was under a regimen of prescribed fire every 2 to 3 years. Season of burning was not described [16]. Stevens [96] found that a single purple prairie clover plant may produce 368 seeds per plant (many of which may not mature), with seeds weighing 1.5 g/1,000 seeds.
Seed Dispersal
Neither fruits nor seeds have specialized means of dispersal; thus, most seed falls near the parent plant [110]. A seed dispersal study using purple prairie clover and other seed in cattle feed showed that following ingestion, cattle were inefficient vectors for dispersing viable purple prairie clover seed [37].
Seed Banking
Purple prairie clover has soil-stored seed [110], but further studies are needed on the relative importance of seed banking to purple prairie clover regeneration. A study on native Kansas prairie found low numbers of buried viable purple prairie clover seed [1].
Germination
Purple prairie clover germinates at soil temperatures ranging from 59 to 86 °F (15-30 °C) [9] while temperatures as low as 41 °F (5 °C) have broken dormancy [14]. A survey of native plant horticulture in Minnesota indicated low rates of germination of purple prairie clover [16]. Germination of purple prairie clover is enhanced by scarification, disturbing the litter and duff layers to expose soil, and stratification [14,100].
Seedling Establishment and Growth
Bjugstand and Whitman [14] used several varieties of forbs for reclamation of strip-mined land and found that purple prairie clover showed "excellent" germination and subsequent "vigorous" growth in the greenhouse. Purple prairie clover transplanted to reclamation areas continued to show excellent vigor and growth [14].
Vegetative Regeneration
The ability of purple prairie clover to regenerate vegetatively is unclear. Meier and Weaver [72] state that purple prairie clover does not reproduce asexually. However, Towne and Knapp [104] suggest that purple prairie clover sprouts from the root crown following top-kill by fire. Further research is needed on the ability of purple prairie clover to regenerate asexually.
Successional Status
Generally purple prairie clover is considered a mid- to late successional species [102]. Purple prairie clover can also fill a pioneer role, as seen in roadsides and disturbed locations [91]. The following is a general description of the successional pathways on prairie lands. Many details of succession in these associations remain unknown.
On the mixed-grass prairies of the southern Great Plains, purple prairie clover is part of a group of forbs found in late successional seres. A common pattern of succession in disturbed prairie regions begins with the dominance of native prairie annuals, nonnative annual weeds, and ragweeds (Ambrosia spp.), which may persist for 1 to 3 years. Soon following, a collection of nonnative and native grasses and perennial forbs, including purple prairie clover, create a mosaic of species that may take 15 to 40 years to develop, depending on environmental conditions and "competitive" factors. Common species that coexist with purple prairie clover in the tallgrass prairie during the later stages of succession include lead plant and prairie dropseed [91].
In its eastern range in forest openings where fires and other natural disturbances are suppressed, purple prairie clover can be shaded out by encroaching woody species [55]. Purple prairie clover is thought to be an indicator of prairie in its later successional sere and may be an indicator of pristine prairie ecosystems [91].
Immediate Fire Effects
Purple prairie clover is top-killed by fire [104].
Postfire Regeneration Strategy
- Caudex/herbaceous root crown, growing points in soil
- Ground residual colonizer (on-site, initial community) [97]
Fire Adaptations
Purple prairie clover establishes from soil-stored seed after fire. While not specifically documented, it is implied that purple prairie clover root crowns may survive burning that consumes the aerial portions of the plant, allowing postfire sprouting from the root crowns [104]. The large woody taproot allows for photosynthate and nutrient storage that can support postfire root crown sprouting. Additionally, fire creates favorable conditions (disturbed soil, decreased levels of mulch, reduced interference from forbs) that are favorable for purple prairie clover seedling establishment and growth [12,13,39,64].
Plant Response to Fire
Plant Growth
Purple prairie clover may recover from fire by establishing from soil-stored seed and sprouting from the root crown. Purple prairie clover has responded favorably to prescribed fire in various studies [12,13,39,64]. Due to the hard seedcoat of legumes like purple prairie clover, these species' germination rates maybe enhanced by burning [70].
Towne and Knapp [104] noted that purple prairie clover that was top-killed by fire showed great capacity to sprout after fire. There is no specific information available on how quickly purple prairie clover recovers after burning. Further research is needed on this topic.
Productivity
Several studies have focused on how the frequency of burning relates to productivity of purple prairie clover. Generally, annual burning favors annual grasses and reduces the abundance of perennial forbs including purple prairie clover [66]. Studies conducted in Minnesota in 1984 [101] and Missouri in 1964 [66] suggest that, compared to annual burning, biennial burning increases frequency and basal areas of legume species [66] including purple prairie clover [101]. In Wisconsin prairie restoration projects where purple prairie clover has prospered, managers recommend a 5-year burning interval [21].
Burning can enhance flower productivity in several prairie forbs including purple prairie clover. Purple prairie clover produced a greater abundance of inflorescences after a single spring burn on a Minnesota prairie than prior to burning [80]. The effects of this burn are attributed to the removal of litter and standing dead stems by the fire. Removal of litter allows for increased light intensities near the soil and thus higher soil temperatures, which enhance plant productivity. Litter reduces the presence and productivity of many forbs including purple prairie clover [39]. For more on the effects of litter on purple prairie clover, see Management Considerations.
The Great Plains region where purple prairie clover commonly occurs is typical of prairie and savanna ecosystems that require fire to maintain historical ranges of species composition and species richness [30]. Most of the available information has been based on short-term research [58]. Long-term effects (beyond the scope of current research; >20 years) of various fire regimes are not well known.
Season of Burning
Interactions between season of burn and purple prairie clover phenology are not well known [60]. While spring burning generally decreases the immediate abundance of forb species that are actively growing [2], legume species including purple prairie clover in Kansas have shown increased growth and vigor 3 years following spring burns, nearly doubling stem biomass on upland sites and quadrupling stem biomass on lowland sites [104].
While most studies find that forb production is compromised after late spring burning, Bidwell and others [12,13] found that late spring backburning increased the productivity of purple prairie clover and other forb species (see Fire Management Considerations). Testing seasonal differences in annual prescribed annual burning on a Kansas prairie for 8 years, Towne and Kemp [103] found that legume species including purple prairie clover increased in cover in response to burning at any season. Greatest increases occurred 6 years after fire treatments, on autumn and winter prescribed burn plots. Others have found that most forbs including purple prairie clover decrease in abundance after being top-killed by late spring burning, while purple prairie clover increases after autumn and early spring burning [46,87].
The effects of mid-summer burning are not available in current literature (2005). For the purposes of restoration ecology, dormant-season fires probably do not resemble historical disturbance regimes found before European settlement. It is suspected that varied burn seasons, and intervals brought by natural ignitions from lightning prior to the European settlement era, produced greater levels of biodiversity and species assemblages than any single management method for native prairie lands [60]. Unfortunately, information on purple prairie clover frequency and abundance prior to European settlement is not available.
Annual burning of prairie lands reduces available soil nitrogen and increases competition among plants limited by nitrogen availability [78]. Legumes including purple prairie clover have the ability to fix atmospheric nitrogen, and may have an advantage over other forbs and some grasses in nitrogen-stressed environments [69].
Fire Regimes
Historically fire has been an important natural component of grassland communities where purple prairie clover occurs [35]. Frequent, stand-replacement surface fires in plains grasslands and prairies affect species composition and vegetation dynamics [79]. Across the Great Plains, lightning-caused and human-caused fires may have occurred as frequently as every 1 to 10 years for thousands of years prior to European settlement [67,117]. The implications of the cessation of historical fire regimes in the last century on purple prairie clover are unknown. Purple prairie clover has responded favorably to burning in several prescribed fire studies [12,13,39,64] using various annual intervals and seasons (see Plant Response to Fire).
In some habitats fire is necessary to maintain purple prairie clover. For example, along woodland-grassland ecotones in purple prairie clover's eastern range, the cessation of fire has caused encroachment of woody species that shade out purple prairie clover and reduce its abundance [45].
The following list provides fire return intervals for plant communities and ecosystems where purple prairie clover is important. It may not be inclusive. For additional fire regime information, search FEIS for this species by entering the species name on the Advanced Search page and selecting “Fire Regime” as the publication type.
| Community or Ecosystem | Dominant Species | Fire Return Interval Range (years) |
|---|---|---|
| sugar maple-basswood | Acer saccharum-Tilia americana | >1,000 [109] |
| bluestem prairie | Andropogon gerardii var. gerardii-Schizachyrium scoparium | <10 [67,79] |
| Nebraska sandhills prairie | A. gerardii var. paucipilus-S. scoparium | <10 |
| bluestem-Sacahuista prairie | A. littoralis-Spartina spartinae | <10 [79] |
| silver sagebrush steppe | Artemisia cana | 5-45 [56,85,117] |
| sagebrush steppe | A. tridentata/Pseudoroegneria spicata | 20-70 [79] |
| basin big sagebrush | A. tridentata var. tridentata | 12-43 [89] |
| mountain big sagebrush | A. tridentata var. vaseyana | 15-40 [5,23,75] |
| Wyoming big sagebrush | A. tridentata var. wyomingensis | 10-70 (40**) [107,118] |
| plains grasslands | Bouteloua spp. | <35 [79,117] |
| blue grama-needle-and-thread grass-western wheatgrass | B. gracilis-Hesperostipa comata-Pascopyrum smithii | <35 [79,88,117] |
| blue grama-buffalo grass | B. gracilis-Buchloe dactyloides | <35 [79,117] |
| blue grama-tobosa prairie | Bouteloua gracilis-Pleuraphis mutica | <35 to <100 [79] |
| cheatgrass | Bromus tectorum | <10 [81,114] |
| sugarberry-America elm-green ash | Celtis laevigata-Ulmus americana-Fraxinus pennsylvanica | <35 to 200 [109] |
| northern cordgrass prairie | Distichlis spicata-Spartina spp. | 1-3 [79] |
| black ash | Fraxinus nigra | <35 to 200 [109] |
| Ashe juniper | Juniperus ashei | <35 [79] |
| cedar glades | J. virginiana | 3-22 [52,79] |
| yellow-poplar | Liriodendron tulipifera | <35 [109] |
| wheatgrass plains grasslands | Pascopyrum smithii | <5-47+ [79,85,117] |
| pine-cypress forest | Pinus-Cupressus spp. | <35 to 200 [4] |
| sycamore-sweetgum-American elm | Platanus occidentalis-Liquidambar styraciflua-Ulmus americana | <35 to 200 [109] |
| eastern cottonwood | Populus deltoides | <35 to 200 [79] |
| aspen-birch | P. tremuloides-Betula papyrifera | 35-200 [38,109] |
| quaking aspen (west of the Great Plains) | P. tremuloides | 7-120 [4,50,73] |
| mesquite | Prosopis glandulosa | <35 to <100 [71,79] |
| Texas savanna | P. glandulosa var. glandulosa | <10 [79] |
| black cherry-sugar maple | Prunus serotina-Acer saccharum | >1,000 [109] |
| mountain grasslands | Pseudoroegneria spicata | 3-40 (10**) [3,4] |
| bur oak | Quercus macrocarpa | <10 [109] |
| oak savanna | Q. macrocarpa/Andropogon gerardii-S. scoparium | 2-14 [79,109] |
| shinnery | Q. mohriana | <35 [79] |
| Fayette prairie | S. scoparium-Buchloe dactyloides | <10 [109] |
| little bluestem-grama prairie | S. scoparium-Bouteloua spp. | <35 [79] |
| elm-ash-cottonwood | Ulmus-Fraxinus-Populus spp. | <35 to 200 [38,109] |
| **mean | ||
Fire Management Considerations
Fire severity affects purple prairie clover survivorship and postfire productivity. Bidwell and others [12,13] noted the effects of using a backing fire versus a headfire. In postfire year 1, abundance of forbs (including purple prairie clover) was 26% greater on backfired plots compared to headfired plots. This may be due to a reduction in interference from tallgrasses, such as prairie Junegrass and little bluestem, which are negatively affected by late spring burning. Also, backfires often create a mosaic of burned and unburned patches that may provide favorable microsites where purple prairie clover can escape lethal fire temperatures [13].
Federal Status
None
Other Status
Purple prairie clover is globally ranked as G5: demonstrably secure [74]. State rankings are as follows [106]:
| Location | Rank |
|---|---|
| Kentucky | Special concern |
| Michigan | Probably extirpated |
| Ohio | Presumed extirpated |
| Tennessee | Endangered |
Importance to Wildlife and Livestock
Purple prairie clover produces excellent forage for livestock and wildlife. When abundant on pasture lands it may be an important component in hay [62,100]. Purple prairie clover is recommended for use in restoration seed mixtures. It produces forage with high yields, extended grazing periods, and increased nutritional values [84,90]. Pronghorn graze purple prairie clover on summer ranges of Montana [113]. A 2-year study in Minnesota found that white-tailed deer did not browse purple prairie clover [40], although this does not imply that deer and other ungulates never graze this species.
Palatability and Nutritional Value
In North Dakota, crude protein levels of purple prairie clover ranged from 12% in June to 8% in August [84]. Due to its high palatability and high concentrations of nutritional protein, purple prairie clover is generally considered one of the most important legumes in native grasslands on the Great Plains, although some rare instances of bloat have been reported in livestock [62,100]. Crude and digestible protein content of purple prairie clover are as follows [76]:
| Crude Protein | 14.10% |
| Digestible Protein | |
| cattle | 9.90% |
| domestic goats | 9.70% |
| domestic rabbits | 9.60% |
| domestic sheep | 10.10% |
| horses | 9.50% |
Cover Value
No information is available on this topic.
Value for Rehabilitation of Disturbed Sites
Purple prairie clover is commonly found in seed mixtures recommended for revegetation, reclamation [34,93], and native prairie restoration projects [65]. Gustafson and others [51] found that by using several local seed sources of purple prairie clover for restoration projects, local gene pools were maintained and regional genetic diversity was enhanced, promoting persistence and vigor in restored purple prairie clover populations. Purple prairie clover is frequently used in seed mixes for erosion control due to its ability to establish on disturbed sites and its capability to condition soil with nitrogen [92]. Legumes such as purple prairie clover fix atmospheric nitrogen in the soil. They may have an advantage over forbs and some grasses in degraded prairie or pasture sites [24,62].
Propagation
Purple prairie clover germination is enhanced in scarified soils [100]. Purple prairie clover in its natural habitat is often found in disturbed locations such as black-tailed prairie dog towns [98] and on dug mounds created by American badgers [83]. Stratification [100] and inoculation with rhizobium [65] have increased germination success of purple prairie clover in the laboratory. Purple prairie clover has been successfully used in several roadside vegetation projects throughout the Great Plains [28,33]. In a strip-mine reclamation project, purple prairie clover demonstrated excellent success as a colonizer, exhibiting high rates of germination and subsequent vigorous seedling growth in the greenhouse and afterwards during transplanting [14].
Purple prairie clover is highly dependent upon mycorrhizal fungi. A mycorrhizal inoculation study found prairie species uptake and transport of soil nutrients such as phosphorus and zinc was enhanced by mycorrhizae, but the study did not show any substantial effects on purple prairie clover seedling emergence [54]. Conversely, a study that used a benomyl (a fungicide specifically for the removal of mycorrhizae in soils) considerably lowered survivorship of purple prairie clover [116].
Purple prairie clover is susceptible to interference from exotic species during establishment due to its relatively slow rate of seedling growth compared to that of nonnative invasive species. In North Dakota some populations of purple prairie clover have been completely eliminated by infestations of leafy spurge (Euphorbia esula) [25]. Reducing weed interference using herbicide applications (imazethapyr + imazapic) has been successful in improving establishment of purple prairie clover in Nebraska [10].
Other Uses
Native Americans boiled purple prairie clover leaves for food. The Ponca tribe chewed the roots for their pleasant flavor and made tea from leaves. The Pawnee used the stems to make brooms. Native American used boiled leaves to make a poultice for dressing on wounds [47]. Laboratory studies have found antibacterial and fungicidal compounds in purple prairie clover [61].
Other Management Considerations
Low- to moderate grazing pressure may enhance purple prairie clover production by removing vegetative cover [18], but overgrazing can decrease coverage and frequency of purple prairie clover [49]. In Illinois, populations of purple prairie clover have recovered in areas where they had been removed under high grazing pressure [19]. In Iowa, purple prairie clover was 1 species in a large group of native forbs that decreased or disappeared under unspecified grazing pressure [111].
In prairies near forest lands, encroachment of forest species into grasslands changes vegetation structure and composition. In eastern Nebraska, eastern redcedar encroachment into prairies has been linked to the decline of many prairie species, including purple prairie clover, due to shading [45].
The accumulation of litter on prairies affects purple prairie clover populations. In Kansas, purple prairie clover decreased during a 50-year study on tallgrass prairie that has seen a shift from summer haying to spring biannual burning. The author speculates that these decreases resulted from the cessation of mid-summer mowing. In this study mowing was thought to be responsible for the removal of biomass during the summer months, altering microhabitat conditions that had supported purple prairie clover. The increase of mulch thickness may explain decreases in purple prairie clover and other native forbs [36]. In a study of the effects of cessation of mowing and introduction of prescribed fire, forbs including purple prairie clover increased in abundance due to the reduction of mulch [29]. For more on the effects of litter on purple prairie clover, see Immediate Fire Effects.
Experimental research on effects of small rodent herbivory on native forb populations found that herbivory by meadow voles reduced purple prairie clover density [59,77]. Whether or not these findings in laboratory communities were applicable to prairie communities was unclear.
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems
- FRES10 White-red-jack pine
- FRES14 Oak-pine
- FRES15 Oak-hickory
- FRES17 Elm-ash-cottonwood
- FRES19 Aspen-birch
- FRES21 Ponderosa pine
- FRES29 Sagebrush
- FRES31 Shinnery
- FRES32 Texas savanna
- FRES33 Southwestern shrubsteppe
- FRES36 Mountain grasslands
- FRES38 Plains grasslands
- FRES39 Prairie [44]
BLM Physiographic Regions
- 8 Northern Rocky Mountains
- 9 Middle Rocky Mountains
- 10 Wyoming Basin
- 11 Southern Rocky Mountains
- 13 Rocky Mountain Piedmont
- 14 Great Plains
- 15 Black Hills Uplift
- 16 Upper Missouri Basin and Broken Lands [11]
Kuchler Plant Associations
- K016 Eastern ponderosa forest
- K017 Black Hills pine forest
- K018 Pine-Douglas-fir forest
- K019 Arizona pine forest
- K023 Juniper-pinyon woodland
- K053 Grama-galleta steppe
- K056 Wheatgrass-needlegrass shrubsteppe
- K058 Grama-tobosa shrubsteppe
- K059 Trans-Pecos shrub savanna
- K060 Mesquite savanna
- K061 Mesquite-acacia savanna
- K062 Mesquite-live oak savanna
- K063 Foothills prairie
- K064 Grama-needlegrass-wheatgrass
- K065 Grama-buffalo grass
- K066 Wheatgrass-needlegrass
- K067 Wheatgrass-bluestem-needlegrass
- K068 Wheatgrass-grama-buffalo grass
- K069 Bluestem-grama prairie
- K070 Sandsage-bluestem prairie
- K071 Shinnery
- K073 Northern cordgrass prairie
- K074 Bluestem prairie
- K075 Nebraska Sandhills prairie
- K076 Blackland prairie
- K081 Oak savanna
- K082 Mosaic of K074 and K100
- K083 Cedar glades
- K084 Cross Timbers
- K085 Mesquite-buffalo grass
- K086 Juniper-oak savanna
- K087 Mesquite-oak savanna
- K088 Fayette prairie
- K089 Black Belt
- K095 Great Lakes pine forest
- K098 Northern floodplain forest
- K099 Maple-basswood forest
- K100 Oak-hickory forest
- K101 Elm-ash forest
- K102 Beech-maple forest
- K111 Oak-hickory-pine [68]
SAF Cover Types
- 14 Northern pin oak
- 15 Red pine
- 16 Aspen
- 20 White pine-northern red oak-red maple
- 25 Sugar maple-beech-yellow birch
- 26 Sugar maple-basswood
- 27 Sugar maple
- 28 Black cherry-maple
- 39 Black ash-American elm-red maple
- 40 Post oak-blackjack oak
- 42 Bur oak
- 46 Eastern redcedar
- 51 White pine-chestnut oak
- 52 White oak-black oak-northern red oak
- 53 White oak
- 55 Northern red oak
- 57 Yellow-poplar
- 58 Yellow-poplar-eastern hemlock
- 59 Yellow-poplar-white oak-northern red oak
- 61 River birch-sycamore
- 62 Silver maple-American elm
- 63 Cottonwood
- 64 Sassafras-persimmon
- 65 Pin oak-sweetgum
- 66 Ashe juniper-redberry (Pinchot) juniper
- 67 Mohrs (shin) oak
- 68 Mesquite
- 73 Southern redcedar
- 87 Sweetgum-yellow-poplar
- 88 Willow oak-water oak-diamondleaf (laurel) oak
- 89 Live oak
- 91 Swamp chestnut oak-cherrybark oak
- 92 Sweetgum-willow oak
- 93 Sugarberry-American elm-green ash
- 94 Sycamore-sweetgum-American elm
- 108 Red maple
- 109 Hawthorn
- 110 Black oak
- 235 Cottonwood-willow
- 236 Bur oak
- 237 Interior ponderosa pine
- 241 Western live oak
- 242 Mesquite [41]
SRM Rangeland Cover Types
- 301 Bluebunch wheatgrass-blue grama
- 303 Bluebunch wheatgrass-western wheatgrass
- 304 Idaho fescue-bluebunch wheatgrass
- 305 Idaho fescue-Richardson needlegrass
- 309 Idaho fescue-western wheatgrass
- 310 Needle-and-thread-blue grama
- 311 Rough fescue-bluebunch wheatgrass
- 322 Curlleaf mountain-mahogany-bluebunch wheatgrass
- 323 Shrubby cinquefoil-rough fescue
- 502 Grama-galleta
- 505 Grama-tobosa shrub
- 601 Bluestem prairie
- 602 Bluestem-prairie sandreed
- 603 Prairie sandreed-needlegrass
- 604 Bluestem-grama prairie
- 605 Sandsage prairie
- 606 Wheatgrass-bluestem-needlegrass
- 607 Wheatgrass-needlegrass
- 608 Wheatgrass-grama-needlegrass
- 609 Wheatgrass-grama
- 610 Wheatgrass
- 611 Blue grama-buffalo grass
- 612 Sagebrush-grass
- 613 Fescue grassland
- 614 Crested wheatgrass
- 615 Wheatgrass-saltgrass-grama
- 701 Alkali sacaton-tobosagrass
- 702 Black grama-alkali sacaton
- 703 Black grama-sideoats grama
- 704 Blue grama-western wheatgrass
- 705 Blue grama-galleta
- 706 Blue grama-sideoats grama
- 707 Blue grama-sideoats grama-black grama
- 708 Bluestem-dropseed
- 709 Bluestem-grama
- 710 Bluestem prairie
- 711 Bluestem-sacahuista prairie
- 712 Galleta-alkali sacaton
- 713 Grama-muhly-threeawn
- 714 Grama-bluestem
- 715 Grama-buffalo grass
- 716 Grama-feathergrass
- 717 Little bluestem-Indiangrass-Texas wintergrass
- 718 Mesquite-grama
- 719 Mesquite-liveoak-seacoast bluestem
- 720 Sand bluestem-little bluestem (dunes)
- 721 Sand bluestem-little bluestem (plains)
- 722 Sand sagebrush-mixed prairie
- 724 Sideoats grama-New Mexico feathergrass-winterfat
- 725 Vine mesquite-alkali sacaton
- 727 Mesquite-buffalo grass
- 728 Mesquite-granjeno-acacia
- 729 Mesquite
- 730 Sand shinnery oak
- 731 Cross timbers-Oklahoma
- 732 Cross timbers-Texas (little bluestem-post oak)
- 733 Juniper-oak
- 734 Mesquite-oak
- 735 Sideoats grama-sumac-juniper
- 801 Savanna
- 802 Missouri prairie
- 803 Missouri glades
- 804 Tall fescue
- 805 Riparian
- 809 Mixed hardwood and pine [94]
1. Abrams, Marc D. 1988. Effects of burning regime on buried seed banks and canopy coverage in a Kansas tallgrass prairie. The Southwestern Naturalist. 33(1): 65-70. [4415]
2. Anderson, Kling L.; Smith, Ed F.; Owensby, Clenton E. 1970. Burning bluestem range. Journal of Range Management. 23: 81-92. [323]
3. Arno, Stephen F. 1980. Forest fire history in the Northern Rockies. Journal of Forestry. 78(8): 460-465. [11990]
4. Arno, Stephen F. 2000. Fire in western forest ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 97-120. [36984]
5. Arno, Stephen F.; Gruell, George E. 1983. Fire history at the forest-grassland ecotone in southwestern Montana. Journal of Range Management. 36(3): 332-336. [342]
6. Bare, Janet E. 1979. Wildflowers and weeds of Kansas. Lawrence, KS: The Regents Press of Kansas. 509 p. [3801]
7. Barnes, P. W.; Harrison, A. T.; Heinisch, S. P. 1984. Vegetation patterns in relation to topography and edaphic variation in Nebraska Sandhills prairie. Prairie Naturalist. 16(4): 145-157. [396]
8. Baskin, Jerry M.; Baskin, Carol C. 2000. Vegetation of limestone and dolomite glades in the Ozarks and midwest regions of the United States. Annals of the Missouri Botanical Gardens. 87(2): 286-294. [38098]
9. Belcher, Earl. 1985. Handbook on seeds of browse -- shrubs and forbs. Technical Publication R8-TP8. Atlanta, GA: U.S. Department of Agriculture, Forest Service, Southern Region. 246 p. In cooperation with: Association of Official Seed Analysts. [43463]
10. Beran, Daniel D.; Masters, Robert A.; Gaussoin, Roch E. 1999. Grassland legume establishment with imazethapyr and imazapic. Agronomy Journal. 91(4): 592-596. [49172]
11. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434]
12. Bidwell, Terrence G.; Engle, David M. 1992. Relationship of fire behavior to tallgrass prairie herbage production. Journal of Range Management. 45(6): 579-584. [19785]
13. Bidwell, Terrence G.; Engle, David M.; Claypool, P. Larry. 1990. Effects of spring headfires and backfires on tallgrass prairie. Journal of Range Management. 43(3): 209-212. [11141]
14. Bjugstad, Ardell J.; Whitman, Warren C. 1982. Perennial forbs for wildlife habitat restoration on mined lands in the northern Great Plains. In: Proceedings, 62nd annual conference of the Western Association of Fish and Wildlife Agencies; 1982 July 19-22; Las Vegas, Nevada: 257-271. [2932]
15. Bohnen, Julia L. 1994. Seed production and germination of native prairie plants. St. Paul, MN: University of Minnesota. 109 p. Thesis. [51407]
16. Bohnen, Julia L.; Hancheck, Anne M. 1994. Flowering and seed yield in three species of prairie plants. HortTechnology. 4(3): 255-259. [48909]
17. Bowles, Marlin L.; McBride, Jenny L. 1998. Vegetation composition, structure, and chronological change in a decadent midwestern North American savanna remnant. Natural Areas Journal. 18(1): 14-27. [27556]
18. Brand, M. D.; Goetz, H. 1978. Secondary succession of a mixed grass community in southwestern North Dakota. Annual Proceedings of the North Dakota Academy of Science. 32(2): 67-78. [7512]
19. Bronny, Christopher. 1989. One-two punch: grazing history and the recovery potential of oak savannas. Restoration and Management Notes. 7(2): 73-76. [11412]
20. Bronny, Christopher. 1991. Dolomite hill prairie restoration underway at Byron Forest Preserve District (Illinois). Restoration and Management Notes. 9(2): 106-107. [17576]
21. Brye, K. R.; Kucharik, C. J. 2003. Carbon and nitrogen sequestratation in two prairie topochronosequences on contrasting soils in southern Wisconsin. American Midland Naturalist. 149: 90-103. [43827]
22. Buell, Murray F.; Facey, Vera. 1960. Forest-prairie transition west of Itasca Park, Minnesota. Bulletin of the Torrey Botanical Club. 87(1): 46-58. [14171]
23. Burkhardt, Wayne J.; Tisdale, E. W. 1976. Causes of juniper invasion in southwestern Idaho. Ecology. 57: 472-484. [565]
24. Burton, Joseph C. 1972. Nodulation and symbiotic nitrogen fixation by prairie legumes. In: Zimmerman, James H., ed. Proceedings, 2nd Midwest prairie conference; 1970 September 18-20; Madison, WI. Madison, WI: University of Wisconsin Arboretum: 116-121. [2909]
25. Butler, Jack L.; Cogan, Daniel R. 2004. Leafy spurge effects on patterns of plant species richness. Journal of Range Management. 57(3): 305-311. [49818]
26. Callow, J. Michael; Kantrud, Harold A.; Higgins, Kenneth F. 1992. First flowering dates and flowering periods of prairie plants at Woodworth, North Dakota. Prairie Naturalist. 24(2): 57-64. [20450]
27. Cane, James H. 2006. An evaluation of pollination mechanisms for purple prairie-clover, Dalea purpurea (Fabaceae: Amorpheae). The American Midland Naturalist. 156(1): 193-197. [64067]
28. Christiansen, Paul A. 1995. Establishment of prairie species by overseeding into burned roadside vegetation. In: Hartnett, David C., ed. Prairie biodiversity: Proceedings, 14th North American prairie conference; 1994 July 12-16; Manhattan, KS. Manhattan, KS: Kansas State University: 167-169. [28249]
29. Collins, Scott L.; Knapp, Alan K.; Briggs, John M.; [and others]. 1998. Modulation of diversity by grazing and mowing in native tallgrass prairie. Science. 280: 745-747. [30535]
30. Collins, Scott L.; Wallace, Linda L., eds. 1990. Fire in North American tallgrass prairies. Norman, OK: University of Oklahoma Press. 175 p. [14201]
31. Corbett, Erica A.; Anderson, Roger C. 2001. Patterns of prairie plant species in Illinois landscape. In: Bernstein, Neil P.; Ostrander, Laura J., eds. Seeds for the future; roots of the past: Proceedings of the 17th North American prairie conference; 2000 July 16-20; Mason City, IA. Mason City, IA: North Iowa Community College: 177-181. [46511]
32. Coupland, R. T. 1992. Overview of the grasslands of North America. In: Coupland, R. T., ed. Natural grasslands: Introduction and western hemisphere. Ecosystems of the World 8A. Amsterdam, Netherlands: Elsevier Science Publishers B. V.: 147-149. [23824]
33. Cull, Margaret Irene. 1978. Establishing prairie vegetation along highways in the Peoria area. In: Glenn-Lewin, David C.; Landers, Roger Q., Jr., eds. Proceedings, 5th Midwest prairie conference; 1976 August 22-24; Ames, IA. Ames, IA: Iowa State University: 172-177. [3378]
34. Darling, Andrea P.; Young, Steve A. 1984. The effects of native hay mulch on soil stabilization and introduction of native species on strip mined lands in southeastern Montana. In: Proceedings, 3rd biennial symposium on surface coal mine reclamation on the Great Plains; 1984 March 19-21; [Location unknown]. [Place of publication unknown]: [Publisher unknown]: 296-306. On file with: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. [22605]
35. Daubenmire, R. 1968. Ecology of fire in grasslands. In: Cragg, J. B., ed. Advances in ecological research. Vol. 5. New York: Academic Press: 209-266. [739]
36. Dornbush, Mathew E. 2004. Plant community change following fifty-years of management at Kalsow Prairie Preserve, Iowa, U.S.A. The American Midland Naturalist. 151(2): 241-250. [48494]
37. Douchette, K. M.; Wittenberg, K. M.; McCaughey, W. P. 2001. Seed recovery and germination of reseeded species fed cattle. Journal of Range Management. 54(5): 575-581. [39414]
38. Duchesne, Luc C.; Hawkes, Brad C. 2000. Fire in northern ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 35-51. [36982]
39. Ehrenreich, John H.; Aikman, John M. 1963. An ecological study of the effect of certain management practices on native prairie in Iowa. Ecological Monographs. 33(2): 113-130. [9]
40. Englund, Judy Voigt; Meyer, William J. 1986. The impact of deer on 24 species of prairie forbs. In: Clambey, Gary K.; Pemble, Richard H., eds. The prairie: past, present and future: Proceedings of the 9th North American Prairie Conference; 1984 July 29 - August 1; Moorhead, MN. Fargo, ND: Tri-College University Center for Environmental Studies: 210-212. [3575]
41. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]
42. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]. Portland, OR: Dioscorides Press. 1632 p. (Dudley, Theodore R., gen. ed.; Biosystematics, Floristic & Phylogeny Series; vol. 2). [14935]
43. Flora of North America Association. 2006. Flora of North America: The flora, [Online]. Flora of North America Association (Producer). Available: http://www.fna.org/FNA. [36990]
44. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]
45. Gehring, Janet L.; Bragg, Thomas B. 1992. Changes in prairie vegetation under eastern red cedar (Juniperus virginiana L.) in an eastern Nebraska bluestem prairie. The American Midland Naturalist. 128(2): 209-217. [19788]
46. Gibson, David J. 1989. Hulbert's study of factors effecting botanical composition of tallgrass prairie. In: Bragg, Thomas B.; Stubbendieck, James, eds. Prairie pioneers: ecology, history and culture: Proceedings, 11th North American prairie conference; 1988 August 7-11; Lincoln, NE. Lincoln, NE: University of Nebraska: 115-133. [14029]
47. Gilmore, Melvin Randolph. 1919. Uses of plants by the Indians of the Missouri River region. In: 33rd annual report of the Bureau of American Ethnology. Washington, DC: Bureau of American Ethnology: 44-154. [6928]
48. Gleason, Henry A.; Cronquist, Arthur. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. 2nd ed. New York: New York Botanical Garden. 910 p. [20329]
49. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
50. Gruell, G. E.; Loope, L. L. 1974. Relationships among aspen, fire, and ungulate browsing in Jackson Hole, Wyoming. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 33 p. In cooperation with: U.S. Department of the Interior, National Park Service, Rocky Mountain Region. [3862]
51. Gustafson, Danny J.; Gibson, David J.; Nickrent, Daniel L. 2002. Genetic diversity and competitive abilities of Dalea purpurea (Fabaceae) from remnant and restored grasslands. International Journal of Plant Sciences. 163(6): 979-990. [48911]
52. Guyette, Richard; McGinnes, E. A., Jr. 1982. Fire history of an Ozark glade in Missouri. Transactions, Missouri Academy of Science. 16: 85-93. [5170]
53. Harrington, H. D. 1964. Manual of the plants of Colorado. 2d ed. Chicago: The Swallow Press, Inc. 666 p. [6851]
54. Hartnett, D. C.; Samenus, R. J.; Fischer, L. E.; Hetrick, B. A. D. 1994. Plant demographic responses to mycorrhizal symbiosis in tallgrass prairie. Oecologia. 99(1-2): 21-26. [30423]
55. Heikens, Alice L.; Robertson, Philip A. 1995. Classification of barrens and other natural xeric forest openings in southern Illinois. Bulletin of the Torrey Botanical Club. 122(3): 203-214. [39656]
56. Heyerdahl, Emily K.; Berry, Dawn; Agee, James K. 1994. Fire history database of the western United States. Final report. Interagency agreement: U.S. Environmental Protection Agency DW12934530; U.S. Department of Agriculture, Forest Service PNW-93-0300; University of Washington 61-2239. Seattle, WA: U.S. Department of Agriculture, Pacific Northwest Research Station; University of Washington, College of Forest Resources. 28 p. [+ appendices]. Unpublished report on file with: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. [27979]
57. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]
58. Higgins, Kenneth F.; Kruse, Arnold D.; Piehl, James L. 1989. Effects of fire in the Northern Great Plains. Ext. Circ. EC-761. Brookings, SD: South Dakota State University, Cooperative Extension Service, South Dakota Cooperative Fish and Wildlife Research Unit. 47 p. [14749]
59. Howe, H. F.; Brown, J. S.; Zorn-Arnold, B. 2002. A rodent plague on prairie diversity. Ecology Letters. 5(1): 30-36. [48912]
60. Howe, Henry F. 1994. Response of early- and late-flowering plants to fire season in experimental prairies. Ecological Applications. 4(1): 121-133. [27810]
61. Hufford, Charles D.; Jia, Yimin; Croom, Edward M., Jr.; Muhammed, Ilias; Okunade, Adewole L.; Clark, Alice M. 1993. Antimicrobial compounds from Petalostemum purpureum. Journal of Natural Products. 56(11): 1878-1889. [50811]
62. Johnson, James R.; Nichols, James T. 1970. Plants of South Dakota grasslands: A photographic study. Bull. 566. Brookings, SD: South Dakota State University, Agricultural Experiment Station. 163 p. [18483]
63. Kartesz, John T.; Meacham, Christopher A. 1999. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Available: North Carolina Botanical Garden. In cooperation with: The Nature Conservancy, Natural Resources Conservation Service, and U.S. Fish and Wildlife Service [2001, January 16]. [36715]
64. Kirsch, Leo M.; Kruse, Arnold D. 1973. Prairie fires and wildlife. In: Proceedings, annual Tall Timbers fire ecology conference; 1972 June 8-9; Lubbock, TX. Number 12. Tallahassee, FL: Tall Timbers Research Station: 289-303. [8472]
65. Kirt, Russell R. 2001. A sixteen year assessment of vegetational changes in prairie seed broadcast and seedling transplant sites. In: Bernstein, Neil P.; Ostrander, Laura J., eds. Seeds for the future; roots of the past: Proceedings of the 17th North American prairie conference; 2000 July 16-20; Mason City, IA. Mason City, IA: North Iowa Community College: 98-106. [46517]
66. Kucera, C. L.; Koelling, Melvin. 1964. The influence of fire on composition of central Missouri prairie. The American Midland Naturalist. 72(1): 143-147. [1383]
67. Kucera, Clair L. 1981. Grasslands and fire. In: Mooney, H. A.; Bonnicksen, T. M.; Christensen, N. L.; Lotan, J. E.; Reiners, W. A., tech. coords. Fire regimes and ecosystem properties: Proceedings of the conference; 1978 December 11-15; Honolulu, HI. Gen. Tech. Rep. WO-26. Washington, DC: U.S. Department of Agriculture, Forest Service: 90-111. [4389]
68. Kuchler, A. W. 1964. United States [Potential natural vegetation of the conterminous United States]. Special Publication No. 36. New York: American Geographical Society. 1:3,168,000; colored. [3455]
69. Lauenroth, W. K.; Dodd, J. L. 1979. Response of native grassland legumes to water and nitrogen treatments. Journal of Range Management. 32(4): 292-294. [50740]
70. Martin, Robert E.; Cushwa, Charles T. 1966. Effects of heat and moisture on leguminous seed. In: Proceedings, 5th annual Tall Timbers fire ecology conference; 1966 March 24-25; Tallahassee, FL. Tallahassee, FL: Tall Timbers Research Station: 159-175. [18925]
71. McPherson, Guy R. 1995. The role of fire in the desert grasslands. In: McClaran, Mitchel P.; Van Devender, Thomas R., eds. The desert grassland. Tucson, AZ: The University of Arizona Press: 130-151. [26576]
72. Meier, Gretchen; Weaver, T. 1997. Desirables and weeds for roadside management--a northern Rocky Mountain catalogue. Report No. RHWA/MT-97/8115. Final report: July 1994-December 1997. Helena, MT: State of Montana Department of Transportation, Research, Development, and Technology Transfer Program. 145 p. [29135]
73. Meinecke, E. P. 1929. Quaking aspen: A study in applied forest pathology. Tech. Bull. No. 155. Washington, DC: U.S. Department of Agriculture. 34 p. [26669]
74. Michigan Department of Natural Resources, Michigan Natural Features Inventory. 1999. Michigan's special plants, [Online]. Michigan State University Extension (Producer). Available: http://web4.msue.msu.edu/mnfi/data/specialplants.cfm [2005, February 8]. [37225]
75. Miller, Richard F.; Rose, Jeffery A. 1995. Historic expansion of Juniperus occidentalis (western juniper) in southeastern Oregon. The Great Basin Naturalist. 55(1): 37-45. [25666]
76. National Academy of Sciences. 1971. Atlas of nutritional data on United States and Canadian feeds. Washington, DC: National Academy of Sciences. 772 p. [1731]
77. Nickel, Anne M.; Danielson, Brent J.; Moloney, Kirk A. 2003. Wooded habitat edges as refugia from microtine herbivory in tallgrass prairies. Oikos. 100(3): 525-533. [48913]
78. Ojima, Dennis S.; Schimel, D. S.; Parton, W. J.; Owensby, C. E. 1994. Long- and short-term effects of fire on nitrogen cycling in tallgrass prairie. Biogeochemistry. 24: 67-84. [23999]
79. Paysen, Timothy E.; Ansley, R. James; Brown, James K.; Gottfried, Gerald J.; Haase, Sally M.; Harrington, Michael G.; Narog, Marcia G.; Sackett, Stephen S.; Wilson, Ruth C. 2000. Fire in western shrubland, woodland, and grassland ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-volume 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 121-159. [36978]
80. Pemble, R. H.; Van Amburg, G. L.; Mattson, Lyle. 1981. Intraspecific variation in flowering activity following a spring burn on a northwestern Minnesota prairie. In: Stuckey, Ronald L.; Reese, Karen J., eds. The prairie peninsula--in the "shadow" of Transeau: Proceedings, 6th North American prairie conference; 1978 August 12-17; Columbus, OH. Ohio Biological Survey: Biological Notes No. 15. Columbus, OH: Ohio State University, College of Biological Sciences: 235-240. [3435]
81. Peters, Erin F.; Bunting, Stephen C. 1994. Fire conditions pre- and postoccurrence of annual grasses on the Snake River Plain. In: Monsen, Stephen B.; Kitchen, Stanley G., comps. Proceedings--ecology and management of annual rangelands; 1992 May 18-22; Boise, ID. Gen. Tech. Rep. INT-GTR-313. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 31-36. [24249]
82. Piper, Jon K.; Gernes, Mark C. 1989. Vegetation dynamics of three tallgrass prairie sites. In: Bragg, Thomas B.; Stubbendieck, James, eds. Prairie pioneers: ecology, history and culture: Proceedings, 11th North American prairie conference; 1988 August 7-11; Lincoln, NE. Lincoln, NE: University of Nebraska: 9-14. [14011]
83. Platt, William J. 1975. The colonization and formation of equilibrium plant species associations on badger disturbances in a tall-grass prairie. Ecological Monographs. 45: 285-305. [6903]
84. Posler, G. L.; Lenssen, A. W.; Fine, G. L. 1993. Forage yield, quality, compatibility, and persistence of warm-season grass-legume mixtures. Agronomy Journal. 85(3): 560-563. [48902]
85. Quinnild, Clayton L.; Cosby, Hugh E. 1958. Relicts of climax vegetation on two mesas in western North Dakota. Ecology. 39(1): 29-32. [1925]
86. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. [2843]
87. Rosburg, Thomas R. 2001. Effects of late spring fires on the survival, growth, and reproduction of prairie forbs. In: Bernstein, Neil P.; Ostrander, Laura J., eds. Seeds for the future; roots of the past: Proceedings of the 17th North American prairie conference; 2000 July 16-20; Mason City, IA. Mason City, IA: North Iowa Community College: 48-58. [46493]
88. Rowe, J. S. 1969. Lightning fires in Saskatchewan grassland. The Canadian Field-Naturalist. 83: 317-324. [6266]
89. Sapsis, David B. 1990. Ecological effects of spring and fall prescribed burning on basin big sagebrush/Idaho fescue--bluebunch wheatgrass communities. Corvallis, OR: Oregon State University. 105 p. Thesis. [16579]
90. Schellenberg, M. P.; Banerjee, M. R. 2001. The potential of legume-shrub mixtures for optimum forage production in southwestern Saskatchewan: a greenhouse study. Canadian Journal of Plant Science. 82(2): 357-363. [48906]
91. Schramm, Peter. 1992. Prairie restoration: a twenty-five year perspective on establishment and management. In: Smith, Daryl D.; Jacobs, Carol A., eds. Recapturing a vanishing heritage: Proceedings, 12th North American prairie conference; 1990 August 5-9; Cedar Falls, IA. Cedar Falls, IA: University of Northern Iowa: 169-177. [24737]
92. Sharp Brothers Seed Co. 1989. Grasses and forbs for erosion control. Fact Sheet. Amarillo, TX: Sharp Brothers Seed Co. 2 p. [18015]
93. Sharp Brothers Seed Company. 1989. Catalog of wildflowers and forbs. Amarillo, TX: Sharp Brothers Seed Company. 20 p. [18001]
94. Shiflet, Thomas N., ed. 1994. Rangeland cover types of the United States. Denver, CO: Society for Range Management. 152 p. [23362]
95. Stevens, Lawrence E.; Ayers, Tina. 2002. The biodiversity and distribution of exotic vascular plants and animals in the Grand Canyon region. In: Tellman, Barbara, ed. Invasive exotic species in the Sonoran region. Arizona-Sonora Desert Museum Studies in Natural History. Tucson, AZ: The University of Arizona Press; The Arizona-Sonora Desert Museum: 241-265. [48667]
96. Stevens, O. A. 1957. Weights of seeds and numbers per plant. Weeds. 5: 46-55. [44071]
97. Stickney, Peter F. 1989. FEIS postfire regeneration workshop--April 12: Seral origin of species comprising secondary plant succession in Northern Rocky Mountain forests. 10 p. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT. [20090]
98. Stockrahm, Donna M. Bruns; Olson, Theresa Ebbenga; Harper, Elizabeth K. 1993. Plant species in black-tailed prairie dog towns in Billings County, North Dakota. Prairie Naturalist. 25(2): 173-183. [23167]
99. Stubbendieck, James; Nichols, James T.; Butterfield, Charles H. 1989. Nebraska range and pasture forbs and shrubs (including succulent plants). Extension Circular 89-118. Lincoln, NE: University of Nebraska, Nebraska Cooperative Extension. 153 p. [10168]
100. Stubbendiek, James; Conard, Elverne C. 1989. Common legumes of the Great Plains: an illustrated guide. Lincoln, NE: University of Nebraska Press. 330 p. [11049]
101. Svedarsky, W. D.; Buckley, P. E.; Feiro, T. A. 1986. The effect of 13 years of annual burning on an aspen-prairie ecotone in northwestern Minnesota. In: Clambey, Gary K.; Pemble, Richard H., eds. The prairie: past, present and future: Proceedings of the 9th North American Prairie Conference; 1984 July 29 - August 1; Moorhead, MN. Fargo, ND: Tri-College University Center for Environmental Studies: 118-122. [3540]
102. Tilman, David. 1986. Nitrogen-limited growth in plants from different successional stages. Ecology. 67(2): 555-563. [2809]
103. Towne, E. Gene; Kemp, Ken E. 2003. Vegetation dynamics from annually burning tallgrass prairie. Journal of Range Management. 56(2): 185-192. [47258]
104. Towne, E. Gene; Knapp, Alan K. 1996. Biomass and density responses in tallgrass prairie legumes to annual fire and topographic position. American Journal of Botany. 83(2): 175-179. [26608]
105. Towne, Gene; Owensby, Clenton. 1984. Long-term effects of annual burning at different dates in ungrazed Kansas tallgrass prairie. Journal of Range Management. 37(5): 392-397. [2357]
106. U.S. Department of Agriculture, Natural Resources Conservation Service. 2006. PLANTS database (2006), [Online]. Available: https://plants.usda.gov /. [34262]
107. Vincent, Dwain W. 1992. The sagebrush/grasslands of the upper Rio Puerco area, New Mexico. Rangelands. 14(5): 268-271. [19698]
108. Voss, Edward G. 1985. Michigan flora. Part II. Dicots (Saururaceae--Cornaceae). Bull. 59. Bloomfield Hills, MI: Cranbrook Institute of Science; Ann Arbor, MI: University of Michigan Herbarium. 724 p. [11472]
109. Wade, Dale D.; Brock, Brent L.; Brose, Patrick H.; Grace, James B.; Hoch, Greg A.; Patterson, William A., III. 2000. Fire in eastern ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 53-96. [36983]
110. Wasser, Clinton H. 1982. Ecology and culture of selected species useful in revegetating disturbed lands in the West. FWS/OBS-82/56. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service, Office of Biological Services, Western Energy and Land Use Team. 347 p. Available from NTIS, Springfield, VA 22161; PB-83-167023. [2458]
111. Weaver, J. E.; Hansen, W. W. 1941. Native midwestern pastures: their origin, composition and degeneration. University of Nebraska Conservation Bulletin 22. [Lincoln, NE]: [University of Nebraska]. 93 p. [20777]
112. Weber, William A.; Wittmann, Ronald C. 1996. Colorado flora: eastern slope. 2d ed. Niwot, CO: University Press of Colorado. 524 p. [27572]
113. Wentland, Harold James. 1968. Summer range habits of the pronghorn antelope in central Montana with special reference to proposed sagebrush control study plots. Bozeman, MT: Montana State University. 65 p. Thesis. [43984]
114. Whisenant, Steven G. 1990. Postfire population dynamics of Bromus japonicus. The American Midland Naturalist. 123: 301-308. [11150]
115. Wieland, Ronald G.; Gordon, Ken L.; Wiseman, J. B.; Elsen, Dean S. 1991. Agencies inventory and restore prairie openings in Bienville National Forest (Mississippi). Restoration & Management Notes. 9(2): 105-106. [17577]
116. Wilson, Gail W. T.; Hartnett, David C. 1997. Effects of mycorrhizae on plant growth and dynamics in experimental tallgrass prairie microcosms. American Journal of Botany. 84(4): 478-482. [27918]
117. Wright, Henry A.; Bailey, Arthur W. 1982. Fire ecology: United States and southern Canada. New York: John Wiley & Sons. 501 p. [2620]
118. Young, James A.; Evans, Raymond A. 1981. Demography and fire history of a western juniper stand. Journal of Range Management. 34(6): 501-505. [2659]
119. Zajicek, J.M.; Hetrick, B.A. Daniels; Owensby, C.E. 1986. The influence of soil depth on mycorrhizal colonization of forbs in the tallgrass prairie. Mycologia. 78(2): 316-320. [4167]