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

GENERAL BOTANICAL CHARACTERISTICS:

Thurber needlegrass is a native, perennial, cool-season bunchgrass [63,81]. This species is densely tufted with erect culms 12 to 24 inches (30-60 cm) tall, and involute blades 4 to 10 inches (10-25 cm) long and 0.04 to 0.08 inch (1-2 mm) wide. The culms are narrow, erect, and few flowered [44]. Inflorescence characteristics include 3- to 9-inch- (7-24 cm) long panicles and single-flowered spikelets with sharp calluses and awned lemmas [81]. The crown typically acquires a circular appearance, as the plant dies from the center outward [24]. Maximum reported rooting depth of Thurber needlegrass in Idaho is 24 inches (61 cm) [75].

RAUNKIAER LIFE FORM [64]:

Hemicryptophyte

REGENERATION PROCESSES:

Thurber needlegrass reproduces from seeds and tillers [81]. However, regeneration is usually by seed on sites where the grass has been killed by fire [41]. Reestablishment on burned sites may be relatively slow due to low germination and seedling vigor [41], and because seed production is usually "low" [81]. Heavy seed production after fire has been reported in central Oregon [60,90]. Because the seed is undesirable to livestock, a large portion matures, allowing for fairly good reproduction rates [84] even in grazed areas. In a controlled environment study, Thurber needlegrass had a maximum germination rate of 25% and an optimum germination temperature of 59-77 degrees Fahrenheit (15-25^oC) [53].

SITE CHARACTERISTICS:

Thurber needlegrass is commonly found in semiarid landscapes [1,52,56,57,58], and occurs on a variety of soil types [1,42,58], most of which are dry and coarse textured [81]. This species is often found on arid hillsides [48,97], and is most prevalent on north and east slopes where there is more moisture and less variation in temperature [38,48,91].

Specific examples of sites where Thurber needlegrass is prevalent follow:

SUCCESSIONAL STATUS:

Thurber needlegrass is a climax species in many sagebrush/grassland, pinyon-juniper, and western juniper plant associations [41]. Burning and other disturbances often favor annual species such as cheatgrass over perennial grasses such as Thurber needlegrass, so Thurber needlegrass is most common in mid-successional seres [48,73,90]. The increase of perennial species such as Thurber needlegrass may either be correlated to the attainment of the critical biomass necessary for seed production or to the increase in ground cover that provides a favorable microsite for seed germination and plant survival [48]. A study of secondary succession in north-central Nevada found Wyoming big sagebrush was a principal increaser species in the overstory while Thurber needlegrass was a principal understory decreaser in late succession [27].

SEASONAL DEVELOPMENT:

Thurber needlegrass begins annual growth in early spring [67,81], fruits from May to June [67,70], produces ripe seed mid to late July [67,81], and continues growth until October [70]. A study in southern Idaho found Thurber needlegrass grew rapidly in the spring, then become largely dormant in summer. After autumn rains, this grass regrew for a longer period of time than most associated grasses [79,84].

The following data indicate the seasonal development of Thurber needlegrass near Silver Lake, Oregon [40]:

Related categories for SPECIES: Achnatherum thurberianum | Thurber Needlegrass