An initial
reduction in wolfstail abundance is typical after fire. Very low wolfstail
abundance is possible in the early postfire months [20]. However, in the limited number of fire studies in wolfstail habitats, recovery to prefire or unburned abundance
was typical by the 2nd or 3rd postfire growing season [1,10,11,73]. Fire season
or severity differences possibly important to the postfire wolfstail response
were not evident from these few studies.
Cover of wolfstail on burned sites was lowest 2.5 years
after an early April, "low heat intensity" fire in a New Mexico blue grama grassland [20]. In the only study to
compare fire severities, wolfstail recovered best and quickest on
sites that burned with the lowest severity [73].
Given the desert and semidesert climate of wolfstail habitats, postfire moisture is
likely important to postfire growth and reproduction. Fire effects on wolfstail
are reported for desert grasslands, shrublands, and woodlands, but their
geographic range includes only Arizona, New
Mexico, and a small part of Texas, which represent only a portion of wolfstail's range.
Desert grassland
fires: Wolfstail
density had returned to prefire levels 2 years after a 12 June 1984 prescribed fire
on a southeastern Arizona semidesert grassland [10,11].
Time since fire
Time since fire (approximate)
Wolfstail was listed as one of many species that occurred on burned sites
after a mid-March wildfire in pinyon-oak-juniper woodlands and oak shrublands in
Big Bend National Park. The fire burned after a 7-month drought when
rainfall was about 3.9 inches (100 mm) less than average. Burned sites were
visited one month and 18 months after fire [41]. Whether or not
wolfstail was observed on one or both visits is unclear. Wolfstail abundance was
not reported.
This description provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [4,36,43,75]). For a description of common wolfstail and bristly wolfstail and a systematic key to distinguish the wolfstail species, see Reeder [4,58].
Wolfstail is a tufted perennial grass. Plants can be compressed, erect, or widely spreading at the base [4,19,25,71]. Stems are fine and grow 8 to 24 inches (20-60 cm) tall [17,30,75]. Wolfstail is short lived. On the Santa Rita Experimental Range in southern Arizona, the oldest wolfstail plants were 9 years old [18].
Wolfstail has fine, stiff, mostly basal leaves. Leaf blades are flat to folded and typically measure 1.6 to 5 inches (4-13 cm) long and 1 to 3 mm wide [4,23,43]. Leaves sometimes have sharp, bristle-like tips [71]. The spike-like panicle is bristly, cylindrical, and resembles a wolf's tail. Panicles are typically 1.2 to 5.1 inches (3-13 cm) long, 3 to 8 mm long, and densely flowered [19,43,71]. Spikelets are paired and single flowered [19,75]. Glumes and lemmas are awned. Awns can measure up to 7 mm long [19,36]. Often the lower of the paired spikelets is staminate or sterile and the upper is bisexual; however, any spikelet may be fertile, staminate, or sterile. Paired spikelets are shed together [4,58]. Seed grains are spindle-shaped [4]. Wolfstail seeds collected from an ungrazed area in southeastern Arizona averaged 0.21 mg [56]. Wolfstail produces coarse, fibrous roots [67]. Rhizomes are lacking [27,67]. Descriptions of rooting depth and spread were not found in the reviewed literature.
Fire adaptations: In the few fire studies in wolfstail habitats, the wolfstail postfire regeneration methods were not described. Wolfstail likely establishes from seed buried or transported on burned sites [47]. Vegetative regeneration seems possible but was not reported in the literature as of 2008.
FIRE REGIMES: Lightning, dry conditions, and fires are common in late spring or early summer in wolfstail habitats. In oak woodlands and savannas of the southwestern United States and northern Mexico, late spring and early summer lightning fires are common. In the Peloncillo Mountains of southern Arizona and New Mexico, fires are typical in June or early July before summer rains [24]. Before European settlement of the Great Plains, large fires probably occurred in drought years that followed 1 to 3 years of above-average precipitation, which resulted in an accumulation of fine fuel. When relative humidity was low and air temperatures and wind speeds were high, fires could easily spread many miles [69,76].
Fire frequency in wolfstail habitats was likely higher before European settlement of the Southwest. Based on the fire frequency in western and southeastern pine/grassland communities, personal experience, and the establishment and growth patterns of woody plants, researchers suggested that the presettlement fire frequency in level to rolling Great Plains grasslands was 5 to 10 years. In the Rolling Plains and Edwards Plateau of Texas, where topography is rough and dissected by breaks and rivers, fires probably burned less frequently at intervals of 15 to 30 years [69,76]. In a review of western pinyon-juniper communities, Wright and others [77] suggest that desert grassland fires every 10 to 30 years were likely before settlement. Fires at this frequency would have restricted the expansion of pinyon and juniper trees into grasslands.
The fire regime for wolfstail in the understory of pinyon-juniper communities is likely much more variable than that of grassland communities. Colorado pinyon-Utah juniper (J. osteosperma) woodlands in southern Colorado burned in stand-replacing fires at approximately 400-year or longer rotations. Low-severity surface fires were rare [22]. Fire frequency in Colorado pinyon-juniper communities is likely dictated by fuel loading and composition. When understory and overstory vegetation is sparse, fire spread is unlikely without extreme fire weather, and fire-free intervals are likely much longer than those in woodlands with a well-developed understory and/or high tree density. See Colorado pinyon for a more complete discussion on the FIRE REGIMES in Colorado pinyon-juniper habitats.
Heavy grazing and other early European land use activities likely decreased the fire frequency in southwestern wolfstail habitats. The cultivation of large land sections reduced fuel, and large herds of livestock, primarily cattle, reduced the abundance and continuity of fine fuels. In the Great Plains grasslands, cultivation has reduced fuel continuity and the potential for widespread fire [69,76]. In the southern Arizona counties of Pima, Santa Cruz, and Cochise, livestock numbered over 200,000 in the late 1800s and early 1900s. Livestock were likely concentrated on desert grasslands (Bahre 1991, cited in [45]). In oak woodlands and savannas in the southwestern United States and northern Mexico, decreased abundance of fine fuels through heavy livestock grazing reduced fire frequencies and increased woody species abundance [24]. Similar species composition changes are noted in a review of pinyon-juniper habitats. Researchers suggest that decreased fine fuel abundance through livestock grazing allowed pinyon and juniper trees to establish in grasslands that used to burn frequently enough to kill pinyon and juniper seedlings and other juveniles [77]. On the Fort Stanton Experimental Range, an April surface fire in a predominantly blue grama grassland killed all oneseed junipers that were less than 4 feet (1.2 m) tall. Colorado pinyons survived better, since tress less than 6 feet (1.8 m) tall were rare within the area before the fire [20].
A pattern of reduced fire frequency after European settlement is not evident in all southwestern wolfstail habitat types. Fire scars from Arizona cypress (Cupressus arizonica), Mexican pinyon (Pinus cembroides), and juniper in Big Bend National Park, Texas, indicated that fire frequencies did not differ before or after 1880. On average, woodland fires burned every 70 years. The range of fire-return intervals was 9 to 60 or more years for the 1780 to 1940 time period [48,49].
While decreased fire frequency with fuel reductions by heavy grazing is noted for many southwestern areas, the introduction, establishment, and recent spread of many annual and perennial nonnative grasses have increased the fire frequency in other areas. Nonnative grasses such as cheatgrass (Bromus tectorum), red brome (B. madritensis), Mediterranean grasses (Schismus spp.), and lovegrasses are possible in wolfstail habitats and have the potential to alter fuel loads and fire frequencies. Information on the effects of these and other nonnative species on FIRE REGIMES in the interior West is available in Chapter 8 of [59]. See Plant Response to Fire for a discussion of fire's potentially different effects on lovegrasses and wolfstail.
The following table provides fire regime information that may be relevant to wolfstail. Find further fire regime information for the plant communities in which these species may occur by entering the species' names in the FEIS home page under "Find FIRE REGIMES".
Fire regime information on vegetation communities in which wolfstail may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models [39]. These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from the name of each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model. Southwest Great Basin South-central US Southeast Southwest Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics Percent of fires Mean intervalWolfstail probably recovers quickly after most fires. However, the recovery of wolfstail following multiple fires is unknown. Additional information specific to fire season, fire severity, and repeated fire would improve the future management of wolfstail populations.
A 1993 review addresses potential hazards and provides guidelines for burning southern Great Plains grasslands. Head fires typically burn successfully, and control is straightforward when relative humidity is 25% to 40%, air temperatures are 70 to 75 °F (21-24 °C), and wind speeds exceed 8 miles (13 km)/hour. However, burning conditions may need adjusting for fuel volatility, topography, and desired fire severity [69].
In the Southwest, wolfstail occurs on open rocky slopes, hills, plains, and mesas [27,30,32,36,67,75].
Aspect: Wolfstail grows on a variety of exposures [67]. On the Gila National Forest, the Colorado pinyon-alligator juniper/gray oak/wolfstail habitat type is most common on southeastern and southwestern exposures, and the Colorado pinyon-alligator juniper/Apache plume/wolfstail-bottlebrush squirreltail habitat type is most common on northeastern exposures [29]. On New Mexico's Fort Stanton Experimental Ranch, wolfstail cover was greatest on the south side and lowest on the north side of oneseed junipers (J. monosperma) and Colorado pinyons [2].
Climate: The climate is semiarid to arid in wolfstail habitats. References consulted throughout this review showed that climates in wolfstail habitats varied somewhat by site and site condition class. Minimum and maximum temperatures and precipitation levels reported are specific to the location identified and based on a finite time period.
In southern Arizona, wolfstail occurs in Santa Cruz County where January minimum temperatures average 35 °F (1.7 °C), and June maximums average 90.3 °F (32.4 °C) [8]. In Sasabe, Arizona, annual precipitation ranged from 8 to 19.4 inches (200-490 mm) for a 13-year period. Droughts were common in May and June before the substantial summer rains [73]. Wolfstail habitats in central New Mexico's Sevilleta National Wildlife Refuge, average 9.6 inches (245 mm) of annual precipitation. Winter temperatures average 36 °F (2 °C), and summer temperatures average 88 °F (31 °C) [50].
In Marfa, Texas, August soil surface temperatures were highest on rolling grassland sites in "poor" rangeland condition. Soil surface temperatures reached 120 °F (49 °C) on the "poor" sites with sparse litter and vegetation cover. Sites in "good" condition had soil surface temperatures of 110 °F (43 °C), and rangeland sites in "excellent" condition had soil surface temperatures of 104 °F (40 °C)[40].
Elevation: Wolfstail is common at midelevation sites [25]. Wolfstail occurs from 1,900 to 11,000 feet (570-3,400 m) throughout the southwestern United States, which is a wider range than reported in the table below. Lycurus setosus occupies a broader range of elevations than L. phleoides [4].
State elevational range of wolfstail (feet) Arizona 4,000-7,000 [32,36] Colorado 4,400-8,000 [27] New Mexico 5,000-8,500 [23,43] Utah 4,990-6,990 [71]Soils: Wolfstail grows on a variety of soils but typically grows best on sandy gravelly loams [67]. Wolfstail occurred on both granite and limestone soils in the Mule Mountains of Arizona, but cover and frequency were about twice as great on granite as on limestone [72]. On the Appleton-Whittell Research Ranch, wolfstail was common on upland mesa sites with fine-textured, rich, reddish-yellow soils but did not occur on limestone outcrops [9]. In Santa Cruz County, Arizona, wolfstail occurred on soils that had low pH and were low in available nitrates and/or potassium [52].
Wolfstail provides habitat for deer and rabbits and food for birds and livestock.
Deer/elk: On the Gila National Forest, the Colorado pinyon-alligator juniper/Apache plume/wolfstail-bottlebrush squirreltail habitat type receives moderate deer and low elk use [29].
Small mammals: Nearly all (97.1%) night survey sightings of white-sided jackrabbits occurred in mixed-grassland habitats from May to August in the Animas and Playas valleys of New Mexico. Grama, ring muhly (Muhlenbergia torreyi), buffalo grass (Buchloe dactyloides), and wolfstail dominated the grasslands [5].
Birds: It is likely that many bird species feed on wolfstail seeds. However, as of this writing (2008), information was only available for sparrows and wild turkeys. In captive feeding studies on wild-caught chipping sparrows and white-crowned sparrows, 8 chipping sparrows consumed 150 wolfstail seeds, and 1 white-crowned sparrow consumed 17 seeds [56]. Of 24 wild turkeys killed in October or November on southeastern Arizona's San Carlos Indian Reservation, 2 crops contained wolfstail seed heads [51].
Livestock: Cattle and domestic sheep consume wolfstail, but consumption is typically greater by cattle. On the Fort Stanton Experimental Ranch, the dry weight percentage of wolfstail in cattle diets ranged from a high of 19.2% in August to a low of 2.3% in April. For domestic sheep, the high was 8.2% in July and the low was 0.7% in January. There were 34.5 acres/AU in the year-round grazed area, which transitioned from of grama-galleta (Pleuraphis jamesii) grassland to oneseed juniper-Colorado pinyon woodland [64]. In another study on the Fort Stanton Experimental Ranch, wolfstail comprised a major portion of cattle diets during growing and dormant seasons in Colorado pinyon-juniper woodlands [37].
Palatability/nutritional value: Wolfstail is described as important, good to very good forage with moderate to high livestock palatability in the Southwest [23,32,34,36]. Humphrey [31] reported that wolfstail is most palatable during and just after summer rains.
Wolfstail is rarely abundant or found in pure stands [9,32].
Although it may occur with high frequency, cover is rarely high [12]. Desert grasslands,
interior or Arizona chaparral communities, oak (Quercus spp.) savannas,
and pinyon-juniper (Pinus-Juniperus spp.) woodlands are common wolfstail habitat [15,21,32,34,42,54,67].
Blue grama (Bouteloua gracilis)
is commonly associated with wolfstail [33,66].
Wolfstail is dominant or important in the following vegetation
classifications:
Arizona interior chaparral vegetation in central Arizona,
Society for Range Management type 503 [61]
blue grama-wolfstail grasslands on the Sevilleta National Wildlife Refuge of central New Mexico [50]
Colorado pinyon-alligator juniper/gray oak (P. edulis-J. deppeana/Q. grisea)/wolfstail
habitat types on
the Gila National Forest
Colorado pinyon-alligator juniper/Apache plume (Fallugia paradoxa)/wolfstail-bottlebrush
squirreltail (Elymus elymoides) habitat types
on the Gila National Forest [29]
As of this writing (2008), wolfstail regeneration on burned sites was not described. It is unclear whether wolfstail sprouts vegetatively, establishes from on-site or off-site seed sources, or recovers through a combination of one or more methods. On the Appleton-Whittell Research Ranch, wolfstail emerged from a soil sample taken from a burned grama-dominated grassland site. The density of seed was not reported, and soil samples were collected 1 month to 1 year after fire. Wolfstail did not emerge from soil samples collected from burned lovegrass-dominated grassland [47]. Fire severity was not described.
A greenhouse study suggests that the loss of mycorrhizae from burned sites may decrease postfire wolfstail growth and increase postfire growth of neighboring lovegrasses. Researchers compared May-burned and unburned soils collected in southern Arizona. Mycorrhizal infection percentages were much lower on burned than unburned soils. Wolfstail seed in soils without mycorrhizae produced plants with lower shoot-to-root ratios and root biomass than those in soils with mycorrhizae. Within the 90-day study period, wolfstail plants in soils without mycorrhizae did not flower. The absence of mycorrhizae produced opposite effects on native and nonnative lovegrasses. Lovegrass growing without mycorrhizae produced greater shoot-to-root ratios and biomass and produced seed earlier than plants with mycorrhizae [53].
Increased presence of lovegrasses can affect wolfstail abundance. On the Appleton-Whittell Research Ranch, wolfstail cover was significantly greater (P<0.001) on semidesert grasslands dominated by native blue grama (5.9% wolfstail cover) than on those dominated by nonnative lovegrass (1.6% wolfstail cover) [7].
Wolfstail reproduces by seed [18]. Literature describing asexual regeneration was not found in the reviewed literature.
Information on the reproductive biology of wolfstail is lacking. Both staminate and perfect flowers are produced, and flowers are primarily wind pollinated. Genetic studies of L. setosus revealed high levels of genetic variation similar to outcrossing plants [55].
Awns on the lemmas and glumes suggest that seed dispersal by animals is possible. Seed germination requirements are unknown.
Seed production: The number of seeds typically produced by wolfstail was not reported. Gay and Dwyer [23] report that seed production can be reduced by heavy grazing and that heavy grazing may eliminate local wolfstail populations.
Seed banking: Field reports of wolfstail seed longevity in the soil are lacking. On the Appleton-Whittell Research Ranch in southeastern Arizona, wolfstail emerged from a soil sample taken from a burned grama grassland. The density of seed was not reported, and soil samples were collected 1 month to 1 year after fire. Wolfstail did not emerge from soil samples collected from burned, nonnative, lovegrass (Eragrostis spp.)-dominated grasslands or unburned grama grasslands [47].
Wolfstail seeds stored indoors for 20 years failed to germinate after "standard germination tests". Seeds were collected on or near Arizona's Sierra Ancha Experimental Forest and were not protected from humidity or temperature extremes. No germination tests were conducted on newly collected seed [65].
Seedling establishment/growth: On the Santa Rita Experimental Range, wolfstail produced more seedlings on grazed than ungrazed sites, but seedlings survived better on ungrazed than grazed sites. Wolfstail produced an average of 6.2 and 3.1 seedlings/m²/year on grazed and ungrazed sites, respectively. First year survival was 30.7% on grazed and 50% on ungrazed sites. Seedling mortality was greatest in the first 2 years [18].
Survival of wolfstail seedlings on grazed and ungrazed sites [18] Wolfstail age 1 2 3 4 5 6 7 8 Survival on grazed site (%) 15.7 4.2 3 0.6 0 0 0 0 Survival on ungrazed site (%) 46 27.3 22.7 13.6 9.1 9.1 9.1 0Vegetative regeneration: Because wolfstail is a bunchgrass, spread by tillers is likely. As of this writing (2008), however, vegetative regeneration was not documented.
From the few studies on succession in wolfstail habitats, it seems that wolfstail tolerates only minimal levels of shading and disturbance. Most studies of disturbance in wolfstail habitats involve grazing and/or shrub removal. Additional studies on succession in wolfstail habitats are needed.
Shade: In New Mexico, wolfstail grew best in interspaces or at the edge of oneseed juniper and Colorado pinyon canopies [2,62], but on Arizona's Appleton-Whittell Research Ranch, wolfstail often grew within shrub canopies, especially yerba de pasmo (Baccharis pteronioides) canopies [9]. Tree and shrub canopy closure was likely different in the 2 studies and may have affected wolfstail distribution. On the Fort Stanton Experimental Ranch, wolfstail had much greater basal cover in interspaces than under the canopy of oneseed juniper and Colorado pinyon. Researchers suggested severe shading, decreased soil moisture, high litter concentrations, and/or allelopathic effects beneath the canopy likely restricted wolfstail growth [2]. In New Mexico wolfstail basal cover increased with increasing distance from oneseed juniper trunks. Canopy closure was at least 89% and litter depths were up to 1.7 inches (4.3 cm) adjacent to the trunk. At the edge, canopy cover was reduced by more than half, and litter depth was negligible. Wolfstail basal cover was significantly (P<0.0242) lower at the trunk than at the canopy edge. No wolfstail plants grew adjacent to the trunk, and at the canopy edge basal cover was at least 2.2% [62].
Grazing: The majority of studies show that wolfstail cover is greatest on ungrazed sites. Wolfstail abundance typically decreases as grazing duration and intensity increase. Judd [34] reported that heavy livestock grazing can eliminate wolfstail. Canfield [18] found that wolfstail was predominant on sites with light or no grazing on Arizona's Santa Rita Experimental Range. In Texas, wolfstail was described as increasing temporarily but later decreasing with heavy grazing. In Marfa, Texas, range condition was considered "excellent" and "good" when 5% and 10% of the composition was wolfstail, respectively. Grasslands that lacked wolfstail were in "poor" condition [40].
In Santa Cruz County, Arizona, wolfstail cover was significantly (P<0.05) greater on ungrazed than grazed grama grasslands. Grazed and ungrazed sites were compared 13 years after the construction of livestock exclosures [8]. Wolfstail cover was also greater on protected than grazed sites on the Appleton-Whittell Research Ranch. On Bald Hill, wolfstail cover was 1.9% one year after livestock removal and 2.6% sixteen years after livestock removal. Along the fence line of the Ranch, wolfstail cover was 1.1% on the grazed side and 1.8% on the protected side. Cover of plains lovegrass (E. intermedia) was 10 times greater on the protected side than on the grazed side of the fence line. Plains lovegrass may have interfered with wolfstail on the protected side [13].
On 6 of 8 rolling grassland sites on the Sonoita Plain of northern Santa Cruz County, wolfstail cover was greater on ungrazed than grazed sites. On the remaining 2 sites, wolfstail cover was greater on grazed than ungrazed plots [6]. On blue grama grasslands in south-central New Mexico, wolfstail cover decreased with increased cattle grazing duration regardless of continuous or short-duration grazing patterns [74].
Basal cover of wolfstail 5 and 6 years after continuous and short-duration cattle grazing [74] Treatment Duration (years) Average basal cover (%) Continuous grazing 5 2.5 6 1.4 Short-duration grazing 5 1.2 6 1.0Fire: Based on the few available fire studies in wolfstail habitats, an initial reduction in wolfstail abundance is typical after fire. However, recovery to prefire or unburned levels is common by the 2nd or 3rd postfire growing season regardless of the fire season, fire severity, or community type. For additional information on this topic, see Fire Effects.
The scientific genus name for wolfstail is Lycurus spp. Kunth (Poaceae)
[4,35]. There are 2 wolfstail species recognized in North America:
Lycurus phleoides Kunth [4,35], common wolfstail
Lycurus setosus (Nutt.) CG Reeder [4,35,70], bristly wolfstail
Infrataxa:
Taxonomic recognition of wolfstail species is inconsistent.
Recognition of L. setosus is relatively new and not entirely accepted.
Welsh and others [71] suggest that the
variable and somewhat inconsistent morphological differences between the Lycurus
species do not warrant discrimination at the species level [71]. Florae from
California [28], Arizona [36], New Mexico [43], and Utah [71] do not list
L. setosus as part of their state flora, but the North American Flora [4] indicates
that L. setosus occurs in each of those states. Harrington [27] describes L. phleoides
in Colorado, but a later Colorado flora by Weber and Wittman [70]
suggests that L. setosus was misidentified as L. phleoides in the
earlier Colorado flora. Distribution maps presented in the Flora of North
America [4] indicate that both L. phleoides and L. setosus occur in Colorado.
Given this confusion, wolfstail species are not distinguished throughout the
majority of this review. The common name "wolfstail" is used when referring to
species identified in the literature as either L. phleoides or
L. setosus. The vast majority of literature cited in this review names L.
phleoides as the species studied; however, the true identity of species
identified as L. phleoides is suspect given the taxonomic treatment and
species distributions presented by Reeder in these sources: [4,58]. According to Reeder,
L. setosus is the more widely distributed of the wolfstail species [4,58], but
only 3 studies cited in this review [16,47,55] name L. setosus as the
plant investigated. In 1 of the 3 articles, Burgess [16]
cited work by Canfield [18] and changed the L. phleoides name used by
Canfield to L. setosus.
