• 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:

Severe fire top-kills redstem ceanothus, but low-severity fires may leave portions of the crown undamaged [65,78,88]. Because portions of the root crown can survive, mortality of mature plants is usually low [65,68]. Seeds of redstem ceanothus can survive surface fires when buried in the soil, though severe, duff-reducing fires may kill some seed [77,83,103].

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:

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PLANT RESPONSE TO FIRE:

Redstem ceanothus usually increases rapidly after fire through seedling establishment and/or basal sprouting, and initial postfire canopy recovery or development is usually rapid [68,70,86,88]. Plants burned in the spring sprout readily and continue growing until onset of winter dormancy. Plants burned in the fall usually do not sprout until the following spring. Sprouting is more likely after fires of relatively low severity, where preburn plant vigor is high [70]. Owens [88] observed that vigorous basal sprouting is stimulated by total destruction of the crown. In that study annual twig growth was greater on plants with more than 50% canopy mortality than on those with less than 50% mortality.

Following prescribed broadcast shrubfield burns in western redcedar habitat in northern Idaho, researchers observed that plants burned in late March or early April resumed growth within 4 to 8 weeks, whereas those burned in October did not sprout until spring [63,68,86]. Because none of the treatment areas burned completely, sampling was restricted to plants completely top-killed by the fire. The table below shows the mean number of basal sprouts before the fire and at the end of the 1st growing season after spring and fall burning [68].

	Preburn	Postburn
Spring (n=23)	4.1	32.3
Fall (n=18)	2.9	25.6

Large reserves of dormant seed in the soil seed bank allow redstem ceanothus to reoccupy a site where mature plants are absent, and seeds are the primary mode of postfire regeneration [77]. Because fire stimulates the germination of seed, large even-aged stands often result [63,68,86]. In the Idaho study described in the previous paragraph, as many as 96% of all seedlings emerged during the 1st year, with emergence decreasing during the following 3 years [63,68,86]. Redstem ceanothus seedling emergence on those sites was noted up to 8 years after fire [86].

Germination and establishment is typically better after late summer or fall fires than after spring fires [5,16,85,86,111]. Soil moisture is usually lower in fall; so late-season burns tend to be hotter at the soil surface, causing greater heat scarification. Initial seedling emergence may be up to 4 times greater following fall burns than following spring burns [16]. In northern Idaho, fall burns resulted in the germination of 242,000 seeds per acre (599,010/ha) by the following spring [63]. Approximately 60,000 seedlings per acre (148,515/ha) emerged following spring burns in the same area [62,63,64]. Orme and Leege [86] observed seedling emergence of 186,000 per acre (460,396/ha) after fall burns, but only 47,000 per acre (113,861/ha) after spring burns. A hot summer crown fire in the Selway drainage of Idaho produced 400,000 seedlings per acre (990,099/ha) [111]. Seed bank densities declined from 0.92 per square foot (10/m²) in undisturbed stands to 0.5 per square foot (5/m²) on 2-year-old burns within western redcedar habitat types of northern Idaho [77]. For more information about heat-stimulation of germination, please refer to sections on Botanical and Ecological Characteristics and Fire Ecology in this report.

Seedling survival is also typically greater after fall burns. Researchers observed 29% seedling survival after fall burns, but only 15% survival after spring burns. Seedlings establishing after spring burns must often compete with vigorous stands of bracken (Pteridium aquilinum) or thimbleberry when overtopped by these fast-growing species. Seedlings that followed fall burns exceeded average heights of those produced by spring burns within 4 months. Seedling height on spring-burned plots in Idaho ranged from 1.6 to 2.3 inches (4.0-5.7 cm) by 16 months [86]. Fall seedlings grew from 1.0 to 1.7 inches (2.5-4.3 cm) in height by the 4th month and averaged 2.6 to 5.1 inches (6.6-13 cm) after 16 months of growth [62,64,86].

Postfire canopy recovery or development can be rapid and vigorous in both forests and brushfields. The duration and magnitude of redstem ceanothus dominance generally increases with the severity of fire [16,37,38,50,78]. In northern Idaho, canopy cover from redstem ceanothus seedlings reached nearly 12% within 2 years in a clearcut and burned western redcedar forest [77,78]. In that study, maximum cover was reached by postfire year 5 in severely burned sites then decreased through postfire year 15. Initial cover development was much slower on low-severity burns and continued to increase until postfire year 15 [78]. High-severity burns were characterized as including little remaining unconsumed surface organic matter or dead and fallen wood less than 3 inches (7.5 cm) in diameter [77,78].

Postfire recovery is also generally rapid in grand fir, Douglas-fir, and ponderosa pine communities. Heights of 3-year-old redstem ceanothus seedlings averaged 0.8 feet (0.2 m) and increased to 2.4 feet (0.7 m) by postfire year 12 in grand fir habitat types of central Idaho. Seedling numbers increased rapidly by the 2nd season following wildfire in ponderosa pine communities of Idaho, with heights comparable to those attained in unburned plots by the 4th year after fire [72].

In a northern Idaho shrubfield, maximum crown heights ranged from 23 to 60 inches (58-152 cm) within 2 years after fire where average preburn crown height of 70 inches (177 cm) had been reported. Crown diameter increased to 50 inches (128 cm) from a preburn average of 31 inches (79 cm) [65].

In the Blue Mountains of eastern Oregon, Johnson [50] measured redstem ceanothus response to fire in mixed stands of ponderosa pine and Douglas-fir. The shrub was not present in any of the stands before burning but reached 12% cover within 5 years after fire. Fires on those sites were described as severe, meaning tree and shrub canopies were consumed and tree boles deeply charred.

Fires that are "too frequent or intense" may eliminate ceanothus species by destroying seeds and plants [16,83].  

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:

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FIRE MANAGEMENT CONSIDERATIONS:

Redstem ceanothus declines as brushfields age, and may disappear from the understory if dense tree canopy develops [63,65,80]. Prescribed fire can be a useful tool for rejuvenating decadent stands, enhancing overall browse production, and increasing mineral availability for deer and elk [68,72]. Increases in deer and elk utilization of redstem ceanothus are commonly observed within several years after fire [111]. Burning at 10- to 15-year intervals has been suggested for maintaining vigor and browse value [65,72]. The authors do not discuss any limit to the number of burn cycles that can be repeated. Although forage availability may be reduced the first 2 years after fire, overall production subsequently increases dramatically over preburn levels [52]. Browse production can be increased 4-fold after burns in Douglas-fir/ninebark habitat types of western Montana, with much of the increase attributable to redstem and snowbrush ceanothus [32]. Seasonal timing of prescribed burns can influence the benefit to ungulates. During the 1st winter after treatment, spring burns provide browse in the form of vigorous sprouting and growth. Fall burns yield little if any immediate winter forage [68].

Orme and Leege [86] recommend fall burning "after frost has cured herbaceous fuels and before fall rains have saturated the ground and fuels." Temperatures should ideally be above 70 degrees Fahrenheit (21 ^oC), and humidity below 30%. However, burning can be carried out at lower temperatures and higher humidity if vegetation is first slashed to promote greater heat scarification at the ground surface. Spring burns can sometimes be effective on dry east or west aspects at high elevations [86].

Related categories for SPECIES: Ceanothus sanguineus | Redstem Ceanothus