• IMMEDIATE FIRE EFFECT ON PLANT
• DISCUSSION AND QUALIFICATION OF FIRE EFFECT
• PLANT RESPONSE TO FIRE
• DISCUSSION AND QUALIFICATION OF PLANT RESPONSE
• FIRE MANAGEMENT CONSIDERATIONS

IMMEDIATE FIRE EFFECT ON PLANT:

Wright and others [98] concluded that Thurber needlegrass is probably the least fire-resistant needlegrass, largely due to its densely tufted stems [90,106]. Aboveground vegetation is often consumed by fire [97], and burning has been found to decrease this needlegrass' vegetative and reproductive vigor [86]. The seasonal response to burning is important in determining the extent of damage by fire [100]; early-season burning is more damaging than late-season burning [10,35,86,87,90]. The smaller the basal diameter, the less the plants are damaged by fire [90,97,100,106]. The root crowns of this species often show sub-surface charring [79], but Thurber needlegrass often survives wildfire and continues growth when conditions are "favorable" [48].

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:

Thurber needlegrass vegetation and reproduction are decreased with burning [10,14,86,87]. On the Arid Lands Ecology Reserve in south-central Washington, 3 years of burn monitoring showed that the average length of the leaves, culms, and spikes of Thurber needlegrass were shortened each year the area was burned, and the basal area and phytomass production were reduced [86,87]. Basal area has also been reduced by fire in Oregon [10] and California [14]. Stanton [79] found flowerstalk production was much reduced the year following a burn; however, the number of inflorescences may increase after fire disturbance [97]. Tagged Thurber needlegrass showed 21% mortality in a BLM prescribed burn; of those surviving, 91% produced seedheads [16].

Fire-caused mortality of Thurber needlegrass varies by both plant size and season [100]. A study in Idaho found the plants suffered high mortality from June fires, were extremely susceptible to damage from burning in July, but were relatively resistant to fire in August [97]. An eastern Oregon study determined that mortality for this species was 50% in May, 70% in June, and 10% in November. The season of burn is important in determining the extent of damage to Thurber needlegrass, but bunch size determines the amount of fire damage to individual bunches [100]. Presumably, when fuel volume is small, less heat is released immediately above the perennating buds [19]; therefore, smaller bunches are less likely to be damaged by fire [97,100]. In a wildfire with higher surface temperatures than in a controlled study, large Thurber needlegrass plants showed greater mortality and basal area reduction than experimentally burned plants [14]; however, soil heated from 482 to 1382 degrees Fahrenheit (250-750 ^oC) increased the emergence of Thurber needlegrass seedlings [9].  

PLANT RESPONSE TO FIRE:

If not killed outright by fire, Thurber needlegrass generally recovers slowly [90]. Living tissue often survives only at the periphery of the crown [97]. Thurber needlegrass plants that survive fire may have reduced vigor for many years [12]. Although recovery time is variable, preburn herbage levels have been nearly reached after 3 years of regrowth on some sites [87]. Competitive perennial and annual grasses often inhibit the postburn re-establishment of Thurber needlegrass [14,32,102,105].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:

Evidence suggests that the short-term productivity of Thurber needlegrass is decreased following fire [87]. However, on limited sites where Thurber needlegrass was only "mildly damaged" by fire, herbage production exceeded that of unburned plots within 3 years of burning [87]; this result was uncommon as regrowth is usually slow [12,87].

Regeneration of Thurber needlegrass is often dependent on competition from other species. Cheatgrass is a highly successful competitor with seedlings of Thurber needlegrass [32]. Basal cover of bluebunch wheatgrass and Sandberg's bluegrass equaled or exceeded prefire levels at Lava Beds National Monument in California, at the expense of Thurber needlegrass and Idaho fescue [14].  

FIRE MANAGEMENT CONSIDERATIONS:

Wildfires in the big sagebrush/grasslands of the Great Basin can be extremely detrimental or beneficial, depending on management goals and rehabilitation efforts. Destruction of degraded big sagebrush communities by wildfires presents an opportunity for improvement in the range condition by seeding with perennial grasses and browse species. However, this opportunity can be quickly lost because the weed control effects of a wildfire are temporary. Failure to rehabilitate burned areas quickly may risk further environmental degradation [32]. The success of techniques for revegetation of degraded big sagebrush communities burned in wildfires often depends on the level of competition from cheatgrass [105]. Evidence also suggests that when Thurber needlegrass is burned and then grazed, recovery can be impaired [60].

Data suggest that prescribed fires contribute to a substantial decrease in mature bunches of Thurber needlegrass; however, due to Thurber needlegrass' stable frequency levels and postfire seedling establishment, negative long-term effects are negligible [13]. It is recommended that prescribed burning take place during the fall to minimize damage to dominant cool-season plants such as Thurber needlegrass [96].

Related categories for SPECIES: Achnatherum thurberianum | Thurber Needlegrass