Festuca arizonica



INTRODUCTORY


R.E. Rosiere, Tarleton State University


AUTHORSHIP AND CITATION:
Gucker, Corey L. 2006. Festuca arizonica. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
FESARI

SYNONYMS:
Festuca ovina L. var. arizonica (Vasey) Hackel ex Beal [123]

NRCS PLANT CODE [115]:
FEAR2

COMMON NAMES:
Arizona fescue
mountain bunchgrass
pinegrass

TAXONOMY:
The scientific name of Arizona fescue is Festuca arizonica Vasey (Poaceae) [28,55,64,66,67,121,122].

LIFE FORM:
Graminoid

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
None

DISTRIBUTION AND OCCURRENCE

SPECIES: Festuca arizonica
GENERAL DISTRIBUTION:
Arizona fescue is common in Arizona, New Mexico, and southern Colorado [68,78,121,122], and occurs in smaller populations in Nevada, Utah, and Texas. In Nevada Arizona fescue is restricted to the deserts of Clark County [67]. Grass Manual on the Web provides a map of Arizona fescue's distribution.

ECOSYSTEMS [43]:
FRES21 Ponderosa pine
FRES23 Fir-spruce
FRES28 Western hardwoods
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES37 Mountain meadows

STATES/PROVINCES: (key to state/province abbreviations)
UNITED STATES
AZ CO NM NV TX UT

BLM PHYSIOGRAPHIC REGIONS [14]:
7 Lower Basin and Range
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont

KUCHLER [73] PLANT ASSOCIATIONS:
K018 Pine-Douglas-fir forest
K019 Arizona pine forest
K020 Spruce-fir-Douglas-fir forest
K021 Southwestern spruce-fir forest
K022 Great Basin pine forest
K023 Juniper-pinyon woodland
K066 Wheatgrass-needlegrass

SAF COVER TYPES [37]:
209 Bristlecone pine
210 Interior Douglas-fir
211 White fir
216 Blue spruce
217 Aspen
219 Limber pine
220 Rocky Mountain juniper
237 Interior ponderosa pine
238 Western juniper
239 Pinyon-juniper

SRM (RANGELAND) COVER TYPES [106]:
411 Aspen woodland
412 Juniper-pinyon woodland
413 Gambel oak
504 Juniper-pinyon pine woodland
704 Blue grama-western wheatgrass

HABITAT TYPES AND PLANT COMMUNITIES:
While sometimes associated with blue grama (Bouteloua gracilis) and mountain muhly (Muhlenbergia montana), Arizona fescue often occurs in almost pure stands under open coniferous canopies [113].

Arizona fescue is a dominant in the following vegetation classifications:

Habitat, community type States and references
alpine grasslands AZ [57]
Arizona fescue-Thurber fescue (Festuca thurberi) CO [71]
Arizona fescue-mountain muhly (Muhlenbergia montana) CO [71] NM [33]
blue spruce (Picea pungens)/Arizona fescue AZ [39,75,86,110] CO [30,31,71,72,75] NM [30,39,75,110]
blue spruce/sparse shrub/Arizona fescue NM [80]
Colorado pinyon (Pinus edulis)/Arizona fescue AZ [75,110] CO [75] NM [110]
interior ponderosa pine (Pinus ponderosa var. scopulorum)/Arizona fescue CO [71,72]
mountain muhly-Arizona fescue CO [71]
montane grasslands AZ, NM, TX [99]
ponderosa pine (Pinus ponderosa)/Arizona fescue AZ [13,39,50,75,86,110] CO [30,31,75] NM [2,30,39,75,110]
ponderosa pine/screwleaf muhly (Muhlenbergia virescens)-Arizona fescue AZ [50] NM [2]
ponderosa pine/screwleaf muhly-Arizona fescue-blue grama (Bouteloua gracilis) AZ [50]
ponderosa pine/Gambel oak (Quercus gambelii)/mixed shrub/Arizona fescue NM [80]
quaking aspen (Populus tremuloides)/Arizona fescue CO [71,72]
Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca)/Arizona fescue AZ [3,39,75,110] CO [30,31,75] NM [2,30,39,75,110]
Rocky Mountain Douglas-fir-Gambel oak/Arizona fescue NM [80]
Rocky Mountain bristlecone pine (Pinus aristata)/Arizona fescue AZ [110] CO [31,71,72,75,95] NM [31,31,75,110]
Rocky Mountain bristlecone pine/Arizona fescue: wax current (Ribes cereum) phase CO [95]
Thurber fescue meadows NM [81]
white fir (Abies concolor)/Arizona fescue AZ [39,75,83] CO [13,30,31,75] NM [30,39,75,83]
white fir-Rocky Mountain Douglas-fir-ponderosa pine/Arizona fescue NM [80]

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Festuca arizonica

 

 

GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [28,51,55,67,68,78,121,122]).

Aboveground description: Arizona fescue is a cool-season, long-lived, perennial bunchgrass. Stems are densely clustered and measure 6 to 39 inches (15-100 cm) tall. The majority of Arizona fescue growth occurs during the rainy season, and plants live for 10 to 20 years [4,40,44,53,58,65,67,113,123]. The numerous tufted leaves are slender and stiff with involute margins. Leaf blade width is typically less than 3 mm, and length measures 6 to 16 inches (20-41 cm). Papery leaf sheaths are 1 to 4.7 inches (3-12 cm) long, persistent, and flatten with age [4,28,44,51,58,65,67,113,117,121,122]. Flower stalks and panicles stand above the leaves at 1 to 3 feet (0.3-0.9 m) tall. Flowers are arranged in a panicle that is 2 to 8 inches (6-20 cm) long and somewhat compressed. Spikelets are borne on alternate ascending branches. Spikelets are 0.2 to 0.6 inch (6-16 mm) long with 4 to 8 florets. Lemmas have minute awns (<2 mm long) or are awnless [4,28,51,65,78,113,117]. Seeds are small and light [53].

Belowground description: A deep, dense, fibrous root system allows Arizona fescue to tolerate dry conditions, bind soil, and withstand some trampling [44,65,113,117,119]. Roots are many branched with persistent root hairs. Lateral roots reach their maximum spread at a depth of about 12 inches (30 cm), and branching is greatest at approximately 6 inches (15 cm) below the soil surface [103].

Arizona fescue roots growing in 3 different soil types in central Colorado's Manitou Experimental Forest showed differences in maximum penetration depths, number of individual roots, and maximum lateral spread. Roots were densest, deepest, and had the greatest spread in ponderosa pine-dominated forests with Chubbs stony loam soils. These soils were calcareous, loose, and fertile. In Edole gravelly loam and Skeletal sandstone loam soils, maximum spread and penetration were slightly less, but considerably fewer individual roots were produced. Edole soils predominated in mixed ponderosa pine, Douglas-fir, quaking aspen forests. These soils had low fertility and were easily eroded. Skeletal sandstone soils were common in Douglas-fir-dominated forests. Skeletal sandstone soils were poorly developed and had low nutrient levels. Excavated plant and root system sizes are summarized below [15].

Plant

Root

Attribute measured height
(feet)
diameter
(inches)
number maximum penetration
(feet)
maximum lateral spread
(feet)
Chubbs stony loam 2.7 6 780 3.1 1.7
Edole stony loam 2.3 4 290 2.8 1.5
Skeletal sandstone loam 2.6 2.5 308 2.6 1.2

In a study designed to evaluate root competition between ponderosa pine seedlings and grasses, root growth of Arizona fescue seedlings was monitored and observed through glass planter boxes. The average growth rate of the 5 fastest growing roots was 3.7 inches (9.4 cm)/week. Several root growth flushes occurred throughout the spring and summer [74].

Mycorrhizal associations of 6 Arizona fescue plants taken from 2 sites in Colorado were diverse and abundant. The fine root mycorrhizal infection was rated a 4.7, where 5 was a rating for total root length infection. Individual plants had an average of 3.5 mycorrhizal fungal species associates [84].

RAUNKIAER [96] LIFE FORM:
Geophyte

REGENERATION PROCESSES:
Arizona fescue reproduces by seed. Seeds are considered to have "good viability" [117]. Following top-kill, Arizona fescue likely initiates new growth from underground growing points. Arizona fescue is common in 1st postfire year communities [102,118].

Pollination: Arizona fescue is wind pollinated [47,116].

Breeding system: Flowers produced by grasses of the Poaceae family are predominantly perfect, and outcrossing is common due to pollination by wind [55].

Seed production: Arizona fescue seed production is affected by land use, disturbances, and site conditions. One researcher reports that livestock like to feed on ripened seeds [111]. In the Manitou Experimental Forest in central Colorado, grazing impacted Arizona fescue flower production, but direct consumption of flowers or seeds was not reported. Comparisons of lightly, moderately, and heavily grazed areas revealed decreased Arizona fescue flower stalk production on moderately and heavily grazed areas. Areas were grazed for 16 to 18 years prior to the study and light, moderate, and heavy levels corresponded to 10% to 20%, 30% to 40%, and over 50% removal of herbage, respectively. The average number of flower stalks produced per plant was 10.5 on lightly grazed plots, 8.4 on moderately grazed plots, and 1.7 on heavily grazed plots [107].

Flower stalks had less biomass and height when Arizona fescue plants were grown under dense shade. Mature plants taken from the edge of a ponderosa pine forest in the Coconino National Forest of Arizona were greenhouse grown under dense shade where the red/far infrared ratio was 0.42, and photo flux density was 14%. Without shading Arizona fescue produced few flower stalks with thick culms. Under dense shade twice the number of flower stalks were produced, but flower stalks weighed 4 times less and had 33% of the height of those produced in full sun [87].

Seed production was nonexistent in the 1st postfire year following a late October prescription fire in a ponderosa pine forest in the Fort Valley Experimental Forest near Flagstaff, Arizona. However, in the 2nd postfire year, seed production by Arizona fescue was greater on low-severity burned than unburned sites [124]. See the Fire effects section for a more complete summary of this study.

Seed dispersal: Seeds are light and likely wind dispersed [53]. Arizona fescue seeds with awns may be transported by animals.

Seed banking: The literature, to date, provides no descriptions of Arizona fescue seed longevity. Arizona fescue did not emerge from soil collected in mid-September from old-growth and pole-sized ponderosa pine-Gambel oak forests in northern Arizona, although it grew in the study area. The lack of Arizona fescue emergence was suggested by researchers as a reflection of decreased Arizona fescue abundance in the area. Its absence may also have been a result of collection timing or missed germination requirements [108]. Collection timing may have been the more important factor, as another study reports that Arizona fescue had not dispersed seed by late October in ponderosa pine forests in north-central Arizona's Fort Valley Experimental Forest [124].

Arizona fescue, however, did emerge from soil cores taken from approximately 1-year-old burned and unburned ponderosa pine-Arizona fescue sites in the Coconino National Forest and ponderosa pine-Gambel oak-Arizona fescue forests in Northern Arizona University's Centennial Forest. Soil cores were kept intact and allowed to germinate outdoors without supplemental water. Ten Arizona fescue plants germinated from soil cores taken from the Coconino National Forest, but survival was 20%. Twelve Arizona fescue plants germinated from soil cores taken from the Centennial Forest, and survival was 17%. Data for burned and unburned sites were averaged, so whether or not seeds germinated from burned, unburned, or both burned and unburned soils is unknown [125].

Germination: In controlled studies, researchers found that Arizona fescue seed germinated over a wide variety of osmotic potentials, and total germination did not decrease much until reaching osmotic potentials of -1.5 MPa. Without water stress, germination exceeded 70%, and peak germination occurred on days 3 and 6. Germination was delayed as osmotic potential became more negative. Delays may be controlled by seed inhibitors, or a certain amount of water may need to be absorbed before germination is initiated [88].

Seedling establishment/growth: Arizona fescue seedlings grow at a slow to moderate rate as compared to perennial ryegrass (Lolium perenne) seedlings, which grow rapidly [53].

Asexual regeneration: Arizona fescue does not produce rhizomes [28], but plants can sprout from buried structures following top-killing events.

SITE CHARACTERISTICS:
Openings in dry ponderosa pine, Douglas-fir, quaking aspen, and mixed conifer forests are Arizona fescue's most typical habitats throughout its range [28,51,78,121,122,123].

Climate: In Arizona fescue habitats, the climate is semiarid continental. Arizona fescue mountain grasslands of Arizona, Colorado, and New Mexico occur where the maximum and minimum July temperatures average 81 F (27 C) and 50 F (10 C), respectively and the maximum and minimum January temperatures average 40 F (6 C) and 12 F (-11 C), respectively. Frost is common 212 days of the year, and mean annual precipitation is 20 inches (510 mm) [18]. Average weather conditions for Arizona fescue habitats were gathered from 14 weather stations throughout its range from 1961 to 1970. Average temperatures for the coldest and hottest months were 30 F (-3 C) and 64 F (18 C), respectively. Annual precipitation averaged 20 inches (510 mm) [120]. In the Manitou Experimental Forest of central Colorado, frost is possible in all months except July and August. Daytime temperatures rarely exceed 90 F (30 C), and winter temperatures can reach below -40 F (-40 C) [29].

Arizona fescue has a low temperature tolerance of -40 F (-40 C) and is found on sites receiving over 10 inches (300 mm) of precipitation per year [53]. Some suggest that the best growth occurs in areas that receive at least 14 inches (360 mm) of precipitation in a year [93]. Vegetation and climate data from the Pole Canyon drainage near Grants, New Mexico, suggest winter precipitation may dictate Arizona fescue's distribution. Arizona fescue occurred on higher elevation sites where 50% of the precipitation came in the winter but was absent from sites where only 40% of the annual precipitation came in the winter [92]. In ponderosa pine forests near Flagstaff, Arizona, Arizona fescue habitats receive an average of 22 inches (570 mm) of precipitation per year, but drought conditions are typical in May and June [82]. In central Colorado's Manitou Experimental Forest, precipitation averaged 15.8 inches (401 mm) over a 35-year period, and 75% of the precipitation fell from April through August. July was typically the wettest month, receiving 3.5 inches (89 mm) [29].

Elevation: Arizona fescue is considered most typical from 6,100 to 10,000 feet (1,900-3,000 m) throughout its range [113]. Elevational tolerances are summarized by state and/or region below.

State/region Elevation
Arizona 2,500 to 10,000 feet [58,68]
Colorado (southern mountains) 6,500-10,500 feet [51]
New Mexico 6,000 to 11,500 feet [4,44,78]
Nevada 2,000 to 3,500 feet [67]
Intermountain West 7,000-10,500 feet [28]

Soils: Clay loam soils are most typical of Arizona fescue habitats. Arizona fescue is common on sites with dry, shallow, clay loam soils but tolerates gravelly, sandy, or rocky soils as well [113]. The level of salt and acid tolerance is low [93]. While clay loam to sandy loam soils that are moderately well to well drained are preferred, Arizona fescue persists on shallow soils, tolerates slightly acid or slightly alkaline conditions, and has low fertility requirements. Inundation by 12 inches (30 cm) or more of water is tolerated for 14 to 21 days [53].

SUCCESSIONAL STATUS:
Arizona fescue is present in predominantly late seral or climax communities. The majority of vegetation types listed in the Habitat Types and Plant Communities are considered late seral or climax types. Arizona fescue tolerates some grazing and mechanical disturbances but often decreases in abundance or importance with increased disturbance intensity and/or duration. In northern Arizona, the ponderosa pine/Arizona fescue habitat type in the Arizona fescue phase is a climax type, but the ponderosa pine/screwleaf muhly-Arizona fescue-blue grama community type is a seral community maintained by grazing and/or logging disturbances [50].

The following diagram outlines the general secondary successional pathway of Arizona fescue in ponderosa pine forests of Arizona. Early seral communities are shown at the bottom. Community composition changes over time, in the absence of disturbances, are progressively higher in the diagram. The community at the top is stable and late seral. Disturbance severity and postdisturbance conditions will dictate which community, lower in the diagram, is the recovering community. Low severity disturbances and favorable postdisturbance conditions may not retrogress and instead pre- and postdisturbance communities would be the same [17].

 

Secondary successional stages may not be as discrete as the above diagram suggests. Overlapping of the stages and species is likely. The double sided arrows indicate that succession and retrogression are both possible. In the case of a severe disturbance, many or all of the intermediate stages could be skipped with denuded soil the result. Complete recovery of a bunchgrass community from the denuded soil stage could take more than 100 years under "reduced" stocking rates. Successional advancement of sites in northern Arizona from the denuded soil stage to the half shrub stage took 30 years under "reduced" livestock stocking rates [17].

A similar successional pathway is described on abandoned fields in the Pike's Peak region of Colorado. Sites were visited 3 months to 62 years following abandonment. The 1st stage was dominated by annual forbs and lasted 1 to 2 years. Species dominance was dictated by past land use and/or crop type. A perennial forb-dominated stage lasted 7 to 10 years. While labeled a perennial forb-dominated stage, annuals, perennial grasses, shrubs, and some ponderosa pine and Douglas-fir seedlings were also typical. A mixed grass-forb stage followed the perennial forb stage and lasted 10 to 25 years. Typically the same forbs as in the previous community were mixed with Stipa grasses (Stipa spp.) and wheatgrasses (Agropyron spp.) A subclimax grass stage dominated by Stipa and grama grasses (Bouteloua spp.) appeared 15 to 25 years after abandonment. It is in the subclimax grass stage when Arizona fescue 1st appears. Progression to a climax ponderosa pine-Douglas-fir-Arizona fescue forest follows this subclimax phase. As indicated above, disturbances may increase the duration of a community type or reverse succession. Consistent grazing on abandoned fields led to a community dominated by fringed sagebrush (Artemisia frigida), trailing fleabane (Erigeron flagellaris), tumblegrass (Schedonnardus paniculatus), and/or porcupine grass (Hesperostipa spartea) to the exclusion of all other species [61].

Shade relationships: Arizona fescue has moderate shade tolerance [117,119] and typically decreases in abundance as forests become dense [40].

Biomass of Arizona fescue plants was 63% less on densely shaded than unshaded sites in the Coconino National Forest. Information on the effect shade had on Arizona fescue flowering is presented in the Seed production section [87].

Grazing: Arizona fescue is intolerant of heavy grazing. Moderate grazing levels are tolerated, but substantial Arizona fescue losses are expected with heavy use [44]. Early spring grazing and year after year summer grazing should be avoided in Arizona fescue grasslands [58,117]. Arizona fescue's grazing sensitivity, however, makes it a good indicator of improper grazing management [44]. Decreased Arizona fescue in ponderosa pine/Arizona fescue habitat types of Arizona, Colorado, and New Mexico where livestock utilization is heavy are described by many [31,39,50].

In ponderosa pine/grassland communities of Arizona, the relative abundance of Arizona fescue was greater on ungrazed than grazed plots soon after grazing protection, but on sites with longer term protection the relative abundance of Arizona fescue was variable. Short-term protected sites were ungrazed for 1 year, and long-term protected sites were not grazed for 8 to 9 years. Grazed sites were utilized by native animals all year but grazed by cattle only in the summer until 70% of the standing biomass was removed. Researchers did not replicate this study or provide statistical analyses of the results making evaluation of the importance of grazing and site differences difficult. The relative abundance of Arizona fescue on short-term and long-term grazed and ungrazed sites is provided below [94].

  Long-term protection Short-term protection
Site 1 2 3 1 2
Grazed relative abundance (%) 1.36 3.10 2.8 50.2 30.2
Ungrazed relative abundance (%) 3.46 2.49 2.38 56.3 38.9

Heavy grazing of ponderosa pine/bunchgrass communities of Colorado's Manitou Experimental Forest decreased Arizona fescue's root size, number of branches, depth of penetration, and lateral spread. Sites were grazed by cattle at heavy and moderate levels for 17 years prior to the study, and ungrazed sites were protected for 20 years prior to study. Moderately grazed sites had 30% to 40% utilization, and heavily grazed sites had 50% or more utilization from June through October. The average maximum root penetration of Arizona fescue plants on ungrazed sites was 43 inches, on moderately grazed sites was 51 inches, and on heavily grazed sites was 32 inches. Maximum lateral root spread was 12 inches, 11.3 inches, and 8 inches on ungrazed, moderately grazed, and heavily grazed sites, respectively [103].

Arizona fescue production, density, plant height, and percent composition based on herbage yield were all lowest on heavily grazed sites in ponderosa pine-bunchgrass vegetation in central Colorado. Production and percent composition were greatest on moderately grazed sites, while density and plant height were greatest on ungrazed sites. Heavy grazing was 50% or more utilization of palatable graminoids, moderate grazing was characterized by 30% to 40% graminoid utilization, and light grazing levels achieved 10% to 20% graminoid utilization. Cattle grazing levels were achieved between 1942 and 1944. Grazed and ungrazed plots were evaluated in 1949 and 1950. Below is the summary of results [62]:

  Heavy Moderate Light Ungrazed
Year evaluated 1949 1950 1949 1950 1949 1950 1949 1950
Percent total composition 2.3 1.2 29.2 29.8 19.9 11.3 12.8 17.0
Mean number of plants/plot 1.2 2.9 8.7 8.9 5.0 3.1 12.4 13.0
Average leaf height 6.0 3.2 9.6 8.2 10.0 9.4 10.0 10.1
Production (air dry lbs/acre) 22 9 343 247 222 74 254 165

On heavily grazed sites in Colorado's Manitou Experimental Forest, Arizona fescue abundance, leaf height, flower stalk production, root depth, and root spread decreased on heavily grazed sites. Light, moderate, and heavy grazing corresponded to 10-20%, 30-40%, and over 50% removal of herbage, respectively, and occurred for 16-18 years prior to the study of grazing effects. Arizona fescue was reduced "considerably by prolonged close grazing." Coverage of Arizona fescue in grazing-protected exclosures was 3 times that of lightly and moderately grazed sites but was 11 to 15 times that of heavily grazed sites. Heavy and moderate grazing reduced Arizona fescue leaf height and flower stalk production. The average number of flower stalks produced per plant was 10.5 on lightly grazed plots, 8.4 on moderately grazed plots, and 1.7 on heavily grazed plots. When protected, however, plants began to recover; the number of flower stalks per plant increased with increasing time free from grazing. Root depth and spread were lowest on heavily grazed plots [107].

SEASONAL DEVELOPMENT:
Arizona fescue flowers in the summer. Flowers are produced from June to August in Nevada, New Mexico, and Arizona [67,68,78]. Seeds mature in September and October [117].

In north-central Arizona, Arizona fescue development was monitored on 2 sites for 3 years. Vegetative growth occurred from mid-April to late July, and flowers were produced from late July to early September. Seeds developed in early September to mid-November [19]. In ponderosa pine forests in Arizona's Fort Valley Experimental Forest, plants were not growing in late October, but seed had not yet dispersed. In this area seed dispersal may continue into the winter months [124].


FIRE ECOLOGY

SPECIES: Festuca arizonica
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Arizona fescue survives most fires. In a review, researchers indicate that Arizona fescue recovery is typically quick with summer monsoon moisture that follows dry-season surface fires in ponderosa pine forests of Arizona and New Mexico [105]. Arizona fescue production and abundance may even be greater on burned than unburned sites following surface or low-severity fires [49,52,102]. Severe fires, however, can reduce Arizona fescue abundance [118]. Sites burned severely will likely take longer to recover prefire community levels of Arizona fescue.

Information on the survival of Arizona fescue seed in burned soils was lacking. However, fall fires in Arizona fescue habitats eliminate at least the current year's seed by consuming seed heads [102].

Fire regimes: Fires occur frequently in blue spruce/Arizona fescue, Rocky Mountain bristlecone pine/Arizona fescue, white fir/Arizona fescue, and ponderosa pine/Arizona fescue habitat types. In these mostly open forests, crown fires are rare, and surface fires predominate [30,31]. Both lightning and human-caused fires are frequent in southwestern ponderosa pine forests. Droughts are typical in May and June, and cured grasses readily carry surface fires [82]. In southwestern pinyon-juniper (Pinus-Juniperus spp.) woodlands, lightning is most common in June and July [45].

Frequent fires in Arizona fescue habitats are considered important to the maintenance of forest openings and Arizona fescue persistence [86]. The exclusion of fire in southwestern ponderosa pine forests has led to large accumulations of litter (pine needles) and large woody debris that "impair the re-establishment" of Arizona fescue [102].

Fire return intervals: Arizona fescue habitats burned frequently in presettlement times. Arizona fescue grasslands like the Hart Prairie near Flagstaff, Arizona, burned at a "high frequency" prior to the early 1900s [40]. Before the 1870s, "light" surface fires burned every 2 to 5 years in southwestern ponderosa pine forests [26]. In a review, researchers report that low-severity surface fires burned dry ponderosa pine-Gambel oak forests of Arizona and New Mexico at 2- to 12-year intervals and wetter forests at a frequency of up to every 15 years, prior to the late 1800s. Grasses accumulated after several fire-free years and were typically dormant in the dry period (May-June) providing sufficient fine fuels to carry surface fires that rarely damaged established plants [105].

The mean fire return interval in a ponderosa pine/Arizona fescue habitat type in the Limestone Flats region of Arizona's Long Valley Experimental Forest was an estimated 2 years for the 1722 to 1900 time period. A fire chronology for the area was created from fire-scarred trees, one of which scarred 42 times in its 178-year lifespan. The mean fire return interval for that tree was 4 years [32].

Changes in fire regimes: Land use changes that accompanied settlement of the Southwest altered the fire regimes in Arizona fescue habitats. In a series of reviews, researchers indicate that livestock grazing, which was heaviest in the 1870s, fire exclusion, which began in the early 1900s, and timber logging practices in old-growth ponderosa pine forests increased tree density, canopy closure, vertical diversity, surface fuel loads and aerial fuel continuity, and reduced herbaceous and shrub cover. In these altered forests, the fire regime has changed from frequent "low-intensity" surface fires in presettlement time to "high-intensity" crown fires in postsettlement time [23,24,25].

Based on fire scars and age structure data, researchers estimated that the mean fire return interval for the ponderosa pine-Gambel oak forest at Camp Navajo, Arizona, was 3.7 years from 1637 to 1883. The minimum fire return interval was 2 years, while the maximum was 8 years. From scars that allowed the determination of fire season, 40% were spring fires, and 60% were summer fires. After 1883 just a single fire scar was located. Researchers suggested that the reintroduction of frequent low-severity fires would prove difficult in fire-excluded forest structures. Thinning practices may improve the likelihood of low-severity surface fires, but presettlement old-growth trees may still die. Stressful growing conditions in stands of dense small trees are suggested by others as a possible cause for the loss of presettlement trees to fire in thinned forests [42].

Prior to the mid-1800s in pinyon-juniper woodlands, productive sites had a fire return interval of 10 to 50 years. Crown fires may have occurred every 200 to 300 years when humidity levels were low, wind speeds were high, and canopy closure was sufficient. The fire frequency on harsher, less-productive sites could have exceeded 100 years. Extensive fires typically occurred when dry years followed exceptionally wet years that increased herbaceous and fine fuel coverage. Changes from presettlement fire regimes are often attributed to overgrazing. Overgrazing and year-long grazing that began in the mid- to late 1800s in pinyon-juniper woodlands reduced herbaceous cover, especially of cool-season grasses like Arizona fescue. Decreased herbaceous cover contributed to decreased infiltration, increased soil runoff, accelerated erosion, and decreased fire frequency. Woodlands changed from savannahs to dense pinyon-juniper forests with soils inhospitable to the reintroduction or re-establishment of herbaceous species, making restoration of presettlement fire regimes difficult. Since the overgrazing and year-long grazing in pinyon-juniper vegetation, fire size is typically small. Large fires occur only during extreme weather conditions. Very high temperatures, low precipitation levels, and high wind speeds are required to fuel large pinyon-juniper fires [45,46].

The following table provides fire return intervals for plant communities and ecosystems where Arizona fescue is important. For further information, see the FEIS review of the dominant species listed below.

Community or ecosystem Dominant species Fire return interval range (years)
western juniper Juniperus occidentalis 20-70
Rocky Mountain juniper Juniperus scopulorum <35
pinyon-juniper Pinus-Juniperus spp. <35 [90]
Rocky Mountain bristlecone pine P. aristata 9-55 [34,35]
Colorado pinyon Pinus edulis 10-400+ [41,46,69,90]
interior ponderosa pine* Pinus ponderosa var. scopulorum 2-30 [8,12,76]
Arizona pine Pinus ponderosa var. arizonica 2-15 [12,21,104]
quaking aspen (west of the Great Plains) Populus tremuloides 7-120 [8,48,79]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [8,9,10]
oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [90]
*fire return interval varies widely; trends in variation are noted in the species review

POSTFIRE REGENERATION STRATEGY [109]:
Caudex/herbaceous root crown, growing points in soil
Secondary colonizer (on-site or off-site seed sources)

FIRE EFFECTS

SPECIES: Festuca arizonica
IMMEDIATE FIRE EFFECT ON PLANT:
Arizona fescue is top-killed by fire.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No additional information is available on this topic.

PLANT RESPONSE TO FIRE:
Arizona fescue survives most fires. In a review, researchers indicate that Arizona fescue recovery is typically quick with summer monsoons that follow dry-season surface fires in Arizona and New Mexico ponderosa pine forests [105]. Arizona fescue production and abundance may even be greater on burned than control sites following low-severity fires [49,52,102]. Severe fires, however, can reduce Arizona fescue [118]. Sites burned severely will likely take longer to recover prefire community levels of Arizona fescue.

Information on the survival of Arizona fescue seed in burned soils was lacking. However, fall fires in Arizona fescue habitats eliminate at least the current year's seed by consumption of seed heads [102].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
The majority of studies reporting postfire recovery of Arizona fescue are prescription fires that burned in the fall. Natural fires in Arizona fescue habitats, however, are most common in the spring and summer seasons (see Fire ecology). The available literature does not allow for a comparison of the effects of fire season on Arizona fescue recovery. Fire severity, however, did vary in prescription fires, and increased fire severity typically meant decreased Arizona fescue abundance and/or increased recovery time to prefire or unburned levels.

Ponderosa pine forests: Arizona fescue increases or decreases following fire are likely affected most by the combined effect of forest structure and fire severity. Sackett and others [102] observed increases in Arizona fescue production in the 1st postfire year following prescription fires in ponderosa pine forests in Arizona's Long Valley Experimental Forest. Severity of these fires was not reported.

Arizona fescue and other grasses produced more biomass on burned than unburned sites in the 1st postfire year following a night November prescription fire in a ponderosa pine/Arizona fescue habitat type in Arizona's Fort Valley Experimental Forest. Arizona fescue and miscellaneous grasses made up 61% of the standing crop on burned sites, but on unburned sites Arizona fescue and miscellaneous grasses made up 28% of the standing biomass. The failure to distinguish grass species makes assessing the magnitude of Arizona fescue's individual increases impossible. The backing and strip headfires burned when litter layers had 8% to 19% moisture content. Air temperatures were 40 to 59 F (3-15C), and relative humidity was 21% to 48% at the time of burning. Fire spread at a rate of 1.2 to 1.8 m/min and produced flame lengths that rarely exceeded 20 inches (40 cm). Glowing combustion of the deep duff lasted 2 to 3 days, and some large wood debris smoldered as long as 4 weeks [52].

The frequency of Arizona fescue was greatest on high-intensity restoration plots, those that were thinned the most prior to burning in the ponderosa pine-dominated forests in Arizona's Fort Valley Experimental Forest. Fire season was not reported, and restoration intensity was based on level of tree removal rather than fire severity. No trees older than 120 years were cut. Mean pretreatment tree densities were 1,044 trees/ha, 1,492 trees/ha, and 956 trees/ha on low-intensity, medium-intensity, and high-intensity restoration sites, respectively. Average posttreatment tree densities were 243 trees/ha, 170 trees/ha, and 140 trees/ha on low-intensity, medium-intensity, and high-intensity restoration sites, respectively. Vegetation measurements were made in the 4th posttreatment year. The average frequency of Arizona fescue on control plots and low-intensity restoration plots was 812% (s). The mean posttreatment frequency of Arizona fescue was greatest, 1317%, on high-intensity restoration plots and lowest, 54%, on medium-intensity restoration sites. Note that variability was high; the standard deviation was often as large or larger than the averages for the plots [1].

Coverage of Arizona fescue was lower in communities sampled in the 1st postfire year than in prefire ponderosa pine forests in the Fort Valley Experimental Forest. Prefire and postfire differences in Arizona fescue were greatest in burned sapling and canopy sawtimber communities. Combination strip and headfires burned in October when understory vegetation was not actively growing, but seed had not dispersed. Temperatures were 57 to 64 F (14-18 C), and relative humidity averaged 21% at the time of burning. Fuel loads, fuel consumption, and heat yields for the ponderosa pine communities are summarized below [118].

Community Prefire tree density (stems/ha) Fuel load
(Mg/ha)
Total heat yield
(kJ/m)
Fuel consumption
(%)
Other notes
Open sawtimber ---- 17.1 1,600 25
Canopy sawtimber 120 145.9 ---- 95 thick litter accumulations, fires smoldered for days
Pole 1,730 46.2 42,082 55
Sapling 10,070 30.5 15,866 33 intensity of backing and headfires were 17 kW/m and 294 kW/m, respectively

The large decrease in Arizona fescue coverage in canopy sawtimber stands may be related to the high fuel loads, smoldering, and high consumption percentages. Decreases in the sapling community occurred in both burned and control plots but decreases were much greater on burned plots. It is possible that Arizona fescue plants growing under the high tree density (sapling community) were less resilient than those in the other stands [118]. A summary of Arizona fescue coverage on burned and unburned plots in the different stand types is provided in the graph below.

Arizona fescue plants in the pole and open sawtimber stands, described above, did not produce seed on burned sites in the 1st postfire year. However, 67% of the plants produced seed on burned sawtimber sites in the 2nd postfire year, which exceeded the percentage of plants producing seed in unburned sawtimber stands. Seed was produced in the pole stands in the 2nd postfire year but the percentage of seed producing plants was still much less than that of unburned sites. Fewer seed producing plants in burned pole stands than open sawtimber stands may be related to the postfire growing environment or total heat yield of the fire, which was much greater in pole stands. The percentage of plants producing seed on burned and unburned sites is provided below [124].

Pole

Open sawtimber

Status burned (n=12) unburned (n=8) burned (n=24) unburned
1st postfire year 0 88 0 67 (n=18)
2nd postfire year 17 50 67 39 (n=23)

Arizona fescue production was significantly (p=0.05) lower on burned than control sites visited 2 and 5 years following fire in young and old-growth ponderosa pine forests in Arizona's Coconino National Forest burned in fall prescription fires (see below). Young forests were dominated by trees with 4 to 10 inch (10-30 cm) dbh and a basal area of 40 to 50 m/ha. Open old-growth forests were dominated by larger trees (>10 inch (30 cm) dbh), and basal area was greater, 70 m/ha. One site burned in backfires set in November, 2 years prior to study. Thinning occurred 4 to 5 years before the fire, and sites were grazed lightly in the 1st postfire year. Sites visited in the 5th postfire year burned in strip headfires set in November. No postfire grazing occurred. Seven-year-old burned sites experienced strip headfires in October, and postfire grazing was "minimal" [5,7].

Control and burned production were significantly (p=0.05) different in young stands in postfire year 2 and in both young and old growth stands in post fire year 5.
For young stands in postfire year 7, there were no data available.

Quaking aspen woodlands: The production and coverage of Arizona fescue were typically greater in postfire than prefire quaking aspen-bunchgrass communities northwest of Flagstaff, Arizona. Density of Arizona fescue on burned and unburned sites was more variable. Prescription fires burned in October and were considered low severity. For the 4 sites, the average age of aspen trees ranged from 47 to 54 years, and average diameter ranged from 6.4 to 8.5 inches (16.2-21.6 cm). The majority of woody fuels were greater than 2 inch (5 cm) dbh, and herbaceous fuel loads on plots 1, 2, 3, and 4 were 91.4 kg/ha, 370 kg/ha, 783 kg/ha, and 339 kg/ha, respectively. Average fuel moisture contents for the sites ranged from 36% to 45%, and litter depth and moisture ranged from 0.43 to 1.3 inches (1.1-3.3 cm) and 13% to 31%, respectively. Fires burned when wind speeds were 3 to 6 miles/hour (5-10 km/hr) and temperatures were 50 to 59 F (10-15 C). While production and coverage of Arizona fescue were typically greater after fall fires than in prefire woodlands, increases over the same 2-year-period were consistently greater on unburned plots. Arizona fescue production and coverage were lower following fire in plot 3 where fuel loads were greatest and litter moisture was low. Density, however, increased after fire in plot 3. The production, coverage, and density of Arizona fescue on burned and unburned plots are summarized below [49]:

 

Plot 1

Plot 2

Plot 3

Plot 4

Burn status

burned unburned

burned

unburned burned unburned

burned

unburned

Postfire year pre 1 pre 1 pre 1 pre 1 pre 1 pre 1 pre 1 pre 1
production (kg/ha) 20.9 31.3 29.3 46.0 21.7 27.8 24.2 41.1 253.3 171.6 104.2 120.8 9.2 11.2 23.5 39.6
cover (%) 1.7 3.3 2.5 4.6 2.4 3.1 2.5 4.4 28.1 18.5 11.4 13.2 1.0 1.2 2.6 4.3
density (plants/m) 12.3 6.0 16.7 13.3 3.7 3.7 7.0 8.0 27.3 29.0 14.3 16.3 2.0 2.0 2.3 5.7

FIRE MANAGEMENT CONSIDERATIONS:
Studies of Arizona fescue recovery after spring and summer fires, which are the most common natural fire seasons, are lacking. While the above information allows for some predictions of Arizona fescue's recovery following fall fires and a variety of burning conditions, additional fire studies would increase the understanding of fire effects on Arizona fescue.

Additionally, the changes from presettlement forest structure in ponderosa pine forests has facilitated a change from low-severity surface fires to crown fires (see Fire ecology). While most understory species may be best adapted to the presettlement frequent surface fire regimes, nonnative species are becoming common on severely burned sites. Nonnative species including lambsquarters, Russian-thistle, and cheatgrass had the greatest coverage on high-severity burned sites following large wildfires in closed-canopy ponderosa pine/Mountain muhly, ponderosa pine/Arizona fescue, and ponderosa pine/blue grama forest associations on the Mogollon and Kaibab plateaus in central and northern Arizona [27]. Recovery stages and/or recovery rates of these severely burned sites may be altered, and management of these areas may require adaptation.


MANAGEMENT CONSIDERATIONS

SPECIES: Festuca arizonica
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Arizona fescue provides forage for livestock, elk, deer, and mountain goats and important habitat for birds, mammals, and native grazers in the southwest. As forage, Arizona fescue is rated "good" when green, and production is abundant in Arizona's high elevations [57,67,117]. Deer, elk, and bighorn sheep utilize Douglas-fir/Arizona fescue habitats for winter cover and forage in northern New Mexico and southern Colorado [31].

Livestock: In the Southwest, Arizona fescue and particularly the ponderosa pine/Arizona fescue habitat type are important to the livestock grazing industry [38]. Arizona fescue is thought to be more readily consumed by horses and cattle than by domestic sheep [65]. Some even suggest that domestic sheep avoid Arizona fescue [113]; however, others claim that Arizona fescue grazing by domestic sheep can be extensive [68].

Cattle: Cows readily consume Arizona fescue, which is considered most palatable in the summer [18,20]. Arizona fescue plants observed for 3 years in north-central Arizona began vegetative growth in mid-April and continued into late July. Reproduction occurred in late July and continued through mid-November. Development timing was suggested as a reason for cattle's summer preference and Arizona fescue's sensitivity to over grazing in the summer season [19].

On ponderosa pine/bunchgrass rangelands in central Colorado, Arizona fescue palatability ranked high among the available grasses. Utilization of Arizona fescue was 13% to 28% on the lightly grazed sites that had 10% to 20% of graminoids removed [63]. In ponderosa pine/bunchgrass communities of Colorado's Manitou Experimental Forest, western wheatgrass (Pascopyrum smithii), mountain muhly, and Arizona fescue made up 33% of spring, summer, and fall cattle diets [29]. In northern Arizona ponderosa pine forests, Arizona fescue's corrected utilization was 33%. Utilization was corrected by comparisons with associated species [20]. More information on Arizona fescue and Grazing is available.

Wildlife: A number of mammals and birds utilize Arizona fescue habitats for feeding and cover.

Elk: Rocky Mountain bristlecone pine/Arizona fescue and white fir/Arizona fescue habitats provide cover and important summer range to elk in northern New Mexico and southern Colorado [31,39,72].

Deer: Utilization of Arizona fescue by deer is typically low. Arizona fescue is considered "moderately" important to mule deer populations in New Mexico [16]. However, on Colorado's Manitou Experimental forest, mule deer did not utilize Arizona fescue in a ponderosa pine/bunchgrass community. The area was grazed by cattle also; whether or not this affected mule deer selection is unknown [29]. Arizona fescue made up 0.73% of total mule deer feeding time in the 2nd half of June in Arizona's Kaibab National Forest. Feeding on Arizona fescue was not observed in the 1st half of June, in July, or August. Observations were made in ponderosa pine, white fir, Douglas-fir, quaking aspen, and blue spruce forest types where Arizona fescue is often a dominant understory species, but Arizona fescue abundance was not reported [59].

Mountain goats: Observations and fecal analyses of mountain goats in the Collegiate Mountain Range in south-central Colorado revealed a heavy use of Arizona fescue in the low elevation (9,000 to 10,500 feet  (2,700-3,200 m)) range. Arizona fescue made up an estimated 23.4% of winter mountain goat diets [54].

Other mammals: A variety of small mammals including squirrels, mice, voles, and rabbits utilize openings in ponderosa pine and ponderosa pine-Douglas-fir habitats in the Manitou Experimental Forest in Colorado [85]. Carnivores in the Coconino National Forest, Arizona, utilized ponderosa pine habitats where Arizona fescue was common for food sources that included small mammals, ungulates, arthropods, birds, and reptiles [112].

Birds: A variety of bird species utilize openings in ponderosa pine and ponderosa pine-Douglas-fir habitats in Colorado's Manitou Experimental Forest. Birds expected to be found in these habitats 25% to 75% of the time included olive-sided flycatchers, mountain bluebirds, western meadowlarks, vesper sparrows, lark sparrows, and chipping sparrows [85]. Grasses in white fir/Arizona fescue habitats are thought to provide important insects for wild turkey broods in the Apache and Gila National Forests [39].

Palatability/nutritional value: Arizona fescue palatability varies with season, plant maturity, and type of grazer. Arizona fescue is considered moderately palatable [57], and on ponderosa pine/bunchgrass rangelands in central Colorado, it is considered one of the most palatable grasses available [63]. Arizona fescue's palatability is greatest during the growing season that typically coincides with the rainy season and decreases by mid- to late summer as the plant matures and leaves become tougher [56,113]. Arizona fescue is more palatable to horses and cattle than to domestic sheep [44].

Forage quality of Arizona fescue is rated fair to good [53], but water content is relatively low [113]. Herbage yield estimates range from 60 to 80 kg/ha under dense forest canopies and 1,100 to 1,300 kg/ha in openings that are moderately grazed [18].

In an ungrazed opening in ponderosa pine forests northwest of Flagstaff, Arizona, the standing crop of Arizona fescue produced 199 mg/cm of carbon, 7.8 mg/cm of nitrogen, 0.8mg/cm of sulfur, and 1.6 mg/cm of phosphorus [70]. The crude protein, phosphorus, and ash contents as well as digestibility were different for Arizona fescue plants growing in open meadows and under a canopy in ponderosa pine forests. The following results were provided in a review by Clary [17]:

  Crude protein Phosphorus Ash Digestibility
percent
Open 10.6 0.30 10.2 57.4
Canopy 7.5 0.24 11.6 51.6

In ponderosa pine forests north of Flagstaff, Arizona, researchers compared the nutritional value of Arizona fescue on unburned and 3-, 7-, and 20-year-old burned sites. Variation was low. The results are presented below [77]:

Protein Phosphorus Calcium

percentages

Unburned 6.1 0.66 0.12
3-year old burned area 7.4 0.73 0.14
7-year-old burned area 6.6 0.82 0.11
20-year-old burned area 7.4 0.82 0.09

The in-vitro digestibility and crude protein were 37% and 4.3%, respectively from 6 Arizona fescue plants collected from January through April in the Jemez Mountains of New Mexico [100]. In-vitro digestibility of Arizona fescue in ponderosa pine forests of northern Arizona was greatest in the upper plant portions sampled in the early part of July. Digestibility was evaluated on June 5th, July 1st, and August 22nd. Digestibility did not change much with increased ponderosa pine basal area [91].

Cover value: Arizona fescue likely provides cover for a number of small mammals and birds that utilize forest openings.

VALUE FOR REHABILITATION OF DISTURBED SITES:
An Arizona fescue cultivar, 'Redondo' from ponderosa pine forests of New Mexico, is adapted for revegetation and stabilizing disturbed soils [119]. Arizona fescue's dense root system makes it useful for soil stabilization and for use on dry sites [36,44]. 'Redondo' is also recommended in native landscaping. Fall seeding is considered best [93].

Arizona fescue was rated good to excellent in stand establishment and plant "vigor" in row plots in ponderosa pine sites in the Manitou Experimental Forest, Colorado. Seed was planted from 1945 to 1950 and evaluated in 1953. However, on other degraded range sites or abandoned agricultural sites with good seedbed preparation, Arizona fescue stand establishment and "vigor" rated fair to very poor [56]. On Kaiser Steel York Canyon Mine in New Mexico, Arizona fescue stands were rated fair to nearly poor, and "vigor" was good to above average 3 years after planting. Characteristics used to evaluate "vigor" and stands were not described [89].

OTHER USES:
No information is available on this topic.

OTHER MANAGEMENT CONSIDERATIONS:
Grazing: Arizona fescue's tolerance of moderate grazing but sensitivity to heavy grazing makes it a valuable indicator of improper grazing management [44,65]. A loss of Arizona fescue typically signals an unsatisfactory range condition [11]. A more extensive treatment of Arizona fescue and grazing is available in the earlier Grazing section.

Biomass estimation: An equation used to estimate Arizona fescue biomass that is based on plant basal area was developed in ponderosa pine stands in Arizona's Coconino National Forest. Developers caution that overstory condition, site condition, and past land use may be important factors to include to ensure precision [6].

Competition/allelopathy: Arizona fescue may inhibit associated plant species growth. When bottlebrush squirreltail (Elymus elymoides), blue grama, and ponderosa pine seeds germinated in water with Arizona fescue stem and leaf extracts, radicle extension was approximately 10%, 55%, and 40%, respectively, of the radicle extension in pure water [60].

Arizona fescue live foliage significantly (p<0.01) reduced average radicle elongation rates, radicle length, percent germination, and germination speed of ponderosa pine and yellow sweetclover (Melilotus officinalis) seeds. Arizona fescue plant material was dried and ground into a powder, mixed with water producing an extract that was used to keep seeds moist in petri dishes. When Arizona fescue roots or old litter were used to make the extracts, there were no inhibitory effects and, in fact, there were some stimulatory effects [97,98].

Larson and Schubert [74] found no evidence that Arizona fescue roots produced growth inhibitors that suppressed ponderosa pine root elongation; however, ponderosa pine seedlings grew best on sites without grasses [74].


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