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

GENERAL BOTANICAL CHARACTERISTICS:

Idaho fescue is a vigorous, native, long-lived, perennial, cool-season, bunchgrass [124,261]. Plants are strongly caespitose. Leaves are fine, dense, and mostly basal, with sheaths remaining firm and entire [70,132]. Culms are densely tufted in large bunches, with tuft 6 to 10 inches (15-25 cm) high, usually more than 1/2 the length of culms. Culms are erect, from 1 to 3.3 feet (0.3-1 m) tall [124,131,132,133,261]. Spikelets are 5- to 6-flowered, with large, awned seeds [70,124]. Plants have a strong root system [124] that can extend 16 inches (40 cm) deep in a 4-inch (10 cm) diameter plant [306]. In well-drained soils, root biomass is greatest at 0.8- to 1.6-inch (2-4 cm) depths [296]. Goodwin and Doescher [111] found that in both disturbed and undisturbed sites, 40% of root biomass was contained in the upper 0.8 inch (2 cm) of soil, and 60% was in the upper 4 inches (10 cm) of soil. Idaho fescue roots are infected with vesicular-arbuscular mycorrhizae, which may give it a competitive advantage over non-mycorrhizal plants and/or allow it to thrive on nutrient-poor soils or extreme environmental conditions [112,134,176,198].

RAUNKIAER [226] LIFE FORM:

Hemicryptophyte

REGENERATION PROCESSES:

Idaho fescue reproduces from seeds and tillers [261]. Seed production varies: it may produce a fair amount of seed of high viability [282] and it may have poor seed production and weak seedling vigor [119]. Ensign and others [101] observed considerable variation in reproductive success in Idaho fescue among and within ecotypes. Doescher and others [89] found Idaho fescue seeds selected from big sagebrush (Artemisia tridentata) habitat types germinated better and faster over wider temperature and water stress regimes than did seeds gathered from ponderosa pine habitat types. They speculate that this may reflect the variability of the environments in which the plants evolved. Chambers and others [55] note that Idaho fescue establishment from seed in alpine areas is episodic and dependent on proper environmental conditions for both seeds and seedlings in consecutive years.  

Seeds are produced in all but the driest years [111], but the percentage of viable seeds varies greatly from year to year [54]. Low seed viability may coincide with low seed fill, which can indicate poor overall development [56]. Although Johnston and others [148] found no relationship between plant basal area and the number of seeds produced in Idaho fescue on Alberta prairie topsoil, they did find that plants not summer-grazed by cattle produced larger seed crops than grazed plants. 

Chambers [54] observed a 13, 32, and 53% decrease in seed viability over 1, 2, and 3 years, respectively. Goodwin and others [110] found Idaho fescue seed requires after-ripening. The after-ripening period assures that at least 35% of the seed crop remains dormant for 6 months following dispersal - a strategy that promotes germination after winter precipitation has usually recharged soil moisture. Goodwin and others [111] found percent germination of Idaho fescue seed is related to soil water potential, with fewer seeds germinating at higher water stress levels. Smyth [254] presents evidence of seedbanking in Idaho fescue in British Columbia. Seed dispersal is limited to the immediate vicinity of the plant.

Tillering in Idaho fescue arises from a relatively small budding zone within a compact root crown area [62]. In cases of disturbance in which the root crowns of Idaho fescue survive, tillering may result in a rapid increase in size of Idaho fescue plants in non-competitive environments [145,209].

SITE CHARACTERISTICS:

Idaho fescue grows on many landforms, elevations, aspects, and soil types. It occurs at elevations from 990 feet (300 m) in Oregon to nearly 13,200 feet (4000 m) in Colorado [261]. It thrives in areas of 15 inches (380 mm) mean annual precipitation or greater [295], but is also found in areas with lower precipitation (7.3 inches (186 mm) at 1 site in Oregon). Idaho fescue has broad ecological amplitude and a wide range of productivity within and between habitat types in which it is a dominant species [205]. Because of its ubiquity, site characteristics are difficult to generalize. For example, Stubbendieck and others [261] report that Idaho fescue is most abundant on well-drained loams with a neutral to slightly alkaline pH, while other authors [73,130,140,223] report that it favors a slightly acid pH. In the northern Rocky Mountain region it is considered a species of the dry end of the moisture gradient, and in the southern Rockies it is a species of the moist end [75]. Since Idaho fescue occurs in a variety of ecosystems (grassland, sagebrush, forest, and alpine), it is probably most useful to look at site characteristics within each of these ecosystems.   

In the grasslands of the Intermountain region, Idaho fescue occurs in valleys, canyons, benches, slopes, and rolling hills bordering sagebrush/grasslands, juniper woodlands, or the lower treeline [36,77,117,187,219]. It is most commonly found in mesic grasslands, but is also a component of the more xeric grasslands dominated by bluebunch wheatgrass, where it usually occupies the cooler, moister microsites on north and east aspects [88,117,159,271]. It can be found on south-facing slopes at higher elevations [120]. It is found on a variety of parent materials and soil depths, but is most productive on well-drained, loamy to sandy soils [120,205]. In a western Montana grassland on morainal mounds in the upper Blackfoot Valley, Idaho fescue tolerated the widest extremes of environmental conditions present, though it did show a gradual decrease on south and southwest exposures of the mounds [31]. In the biscuit scablands (areas of rolling topography on basic flow lavas with "biscuits" of soil between islands of very shallow soil over lava) in eastern Oregon, Idaho fescue grows in the cool moist microsites of the biscuits [120,315].

In semi-arid sagebrush (Artemisia spp.) grasslands, Idaho fescue is found with bluebunch wheatgrass but is restricted to the cooler, moister sites [5,28,46,71,92,93,120,313,316], and tends to be found on deeper, well-drained, loamy to sandy textured soils [25,26,71,122,237]. Idaho fescue occurs as a dominant or co-dominant species on cool, moist microsites protected from wind, where there is more snow retention and less moisture loss than on less protected sites [73,294]. In a study of soil properties in big and low sagebrush (Artemisia arbuscula) communities in southern Idaho, Fosberg and Hironaka [105] concluded that moisture availability was more important than parent material in determining the distribution of bluebunch wheatgrass and Idaho fescue. When compared with 5 common grasses in the Great Basin (bluebunch wheatgrass, Thurber needlegrass, needle-and-thread grass (Hesperostipa comata), galleta (Pleuraphis jamesii), and Indian ricegrass (Achnatherum hymenoides), Idaho fescue and bluebunch wheatgrass were associated with soils in wetter and colder climates and with a slightly more acidic pH, higher water-holding capacity, higher clay contents, and lower bulk density than soils of other grasses. Idaho fescue had the narrowest environmental tolerances [223]. Johnson [144] says that moisture availability (which is enhanced by deeper soils and cooler microsites) determines the ability of Idaho fescue to persist at lower elevations.

Everett [103] examined the possibility of allelopathic effects of singleleaf pinyon and Utah juniper litter on seedling emergence of Idaho fescue, and found that the presence of litter can be a negative factor if seed is buried. Where Idaho fescue occurs in forest habitats with limber pine, ponderosa pine, and Douglas-fir, it is usually on the cool, dry aspects that border sagebrush-grass communities [120,186,221,256].

In the northern Rocky Mountains, Idaho fescue also occurs in mountain parks at upper elevations where tree growth is inhibited [77,79,170,193,216,225,235]. Daubenmire [75,80] speculates that the occurrence of these small parks in northern Idaho and eastern Washington represents areas of soil drought that may have resulted from the transfer of snow from the windward to the leeward slopes. Jensen [143] cites Idaho fescue as 1 of the major grasses at 4,950-9,900 feet (1500-3000 m) on Caribou National Forest, southeastern Idaho. On these sites, moisture becomes limiting soon after snowpack melts, producing drought conditions that dominate through most summer months on predominantly cold, cryic soils. Weaver and Collins [297] found Idaho fescue decreased in abundance with increasing snowpack in Montana. Several authors [21,63,85,120,141,220,225,245] have described alpine and subalpine communities with Idaho fescue as an important, sometimes dominant, component in several western states. Idaho fescue is the dominant understory species on many of the most arid whitebark pine sites [13,256].    

Mollisols are most commonly associated with grassland ecosystems; however, Nimlos and Tomer [211] found Mollisols under dry end Douglas-fir forests in southwest Montana, usually on sites where Idaho fescue is among the understory grass component. These sites may have been grasslands that were invaded by conifers. Similarly, the absence of Idaho fescue on unproductive Mollisols may indicate a disclimax where Idaho fescue has been eliminated by disturbance.

Idaho fescue occurs in the following elevational ranges:

SUCCESSIONAL STATUS:

As a climax species, Idaho fescue is a common component of many "pristine," "undisturbed," or "relict" areas [53,58,106,115,117,121,140,268,272]. It is a major component of late-seral ecosystems, but may also colonize suitable disturbed sites [56]. Idaho fescue communities may rely on periodic disturbance such as soil and slope movement to rejuvenate and maintain vigor of the plant community [144]. 

In cases where the level of disturbance is such that cover of Idaho fescue decreases (e.g., heavy grazing pressure or severe fire), Idaho fescue succeeds to various native and non-native increaser species. Some examples are bluegrasses (Poa spp.) [171,279,294], sagebrush (Artemisia spp.) [205,310], rubber rabbitbrush (Chrysothamnus nauseosus) and broom snakeweed (Gutierrezia sarothrae) [310], needlegrasses (Achnatherum and Hesperostipa spp.), lupine (Lupinus spp.) [53,146,205], phlox (Phlox spp.)[53,145,205,278], spotted knapweed [205,279,280], yellow starthistle (Centaurea solstitialis) [232], timothy (Phleum pratense) [279], and cheatgrass [171,205,224].

SEASONAL DEVELOPMENT:

In general, Idaho fescue starts growth in early spring, seeds mature by midsummer [101,261], and dispersal is prompt [110]. Weaver and Collins [297] report that the time required for seed maturation varies with different degrees of water stress - from 63 days without water stress to 37 days with early water stress. Seed germination requires 8 to 10 days [103]. From observations made in common snowberry/Idaho fescue community and greenhouse studies, Daubenmire [75] speculated that the ability of Idaho fescue to survive drought is related to its ability to germinate in autumn and grow intermittently in winter during periods of favorable weather and so be sufficiently advanced in development by the time drought intensifies in early summer that it can aestivate.

Mueggler [206] compared dates of phenological events for prominent grasses at 7,100 feet (2130 m) on southwestern and northeastern exposures in western Montana over 10 years. The start of growth was uncertain because green leaves were frequently present at the time of snowmelt, probably because they overwintered from fall regrowth. The following dates were recorded for phenology of Idaho fescue on southwestern exposures [206]:

On northeastern exposures, growth starts, 1st bloom emerges, and blooming is over in the same range of dates. Means are 3 to 4 days later than on southwestern exposures; dissemination started 6 days later, and plants dried 16 days later, on average. The appearance of flowerstalks and flowering were both correlated with May and June temperatures in that the warmer the temperatures, the earlier the appearance of flowerstalks [28]. The date of range readiness, as indicated by the appearance of Idaho fescue flowerstalks, differed as much as 5 weeks over 10 years, although in 2 out of 3 years the dates were within 2 weeks of the mean [206]. Other researchers report phenological dates for Idaho fescue in eastern Montana and Yellowstone National Park [240] and Oregon [128,251].

Related categories for SPECIES: Festuca idahoensis | Idaho Fescue