|Common manzanita in foreground. Photo courtesy of © 1994 David Graber.|
Arctostaphylos manzanita subsp. elegans (Jepson) P. V. Wells, Konocti manzanita
Arctostaphylos manzanita subsp. glaucescens P.V. Wells, whiteleaf manzanita
Arctostaphylos manzanita subsp. laevigata (Eastwood) Munz, Contra Costa manzanita
Arctostaphylos manzanita subsp. manzanita, typical subspecies
Arctostaphylos manzanita subsp. rooffii (Gankin) P. V. Wells, Roof’s manzanita
Arctostaphylos manzanita subsp. wieslanderi P. V. Wells, [7,21,37], Wieslander’s manzanita
In this review, "common manzanita" refers to information that is general to the species. Subspecies are referred to by the common names listed above.
Hybrids: The typical subspecies (A. manzanita subsp. manzanita) hybridizes with Stanford's manzanita (A. stanfordiana) in the North Coast Ranges of California. . Common manzanita hybridizes with True’s manzanita (A. mewukka subsp. truei), producingA. × laxiflora Heller [33,71].SYNONYMS:
|Map courtesy of USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC. (2013, June 7).|
Common manzanita is endemic to California. It occurs in the North Coast Ranges and extends eastward and southward to the Cascade Range and Sierra Nevada foothills [1,21,36]. In the lower elevations of northern California, common manzanita is one of the most widespread species of its genus . The typical subspecies is the most widespread, occurring at low elevations in the North Coast Ranges, east through the Cascade Range, and throughout the Sierra Nevada foothills. The other subspecies have narrow distributions [21,37].
Climate: Common manzanita is often associated with blue oak (Quercus douglasii) woodlands and chaparral . These communities occupy sites with mediterranean climates, where winters are mild and wet and summers are hot and dry [9,43]. Blue oak woodlands have considerable climatic variability, with annual precipitation ranging from 10 to 60 inches (250-1,500 mm) and averaging 20 inches (520 mm) . In many of California's chaparral communities, annual precipitation ranges from 10 to 30 inches (250-750 mm) . Where common manzanita occurs in coastal mixed-forest associations, it is subject to heavy, frequent fogs [27,64].
Elevation: Common manzanita occurs from sea level to 4,900 feet (1,500 m) . In the inner North Coast Ranges, it occurs from 250 to 4,000 feet (250-1,200 m) . Most subspecies occur at low to middle elevations (approximately 1,650-3,300 feet (500-1,000 m)), but the typical subspecies occurs down to sea level, and Wieslander’s manzanita may occur up to 4,900 feet (1,500 m) in coniferous forests [7,21]. Whiteleaf manzanita has the most restricted elevational range, occurring only between 650 and 2,000 feet (200-600 m) .
Soil: Common manzanita occupies a variety of soils. It is most common on dry, rocky sites [1,25,62,73], although it also occurs on fairly productive sites . Woodland sites may have gentle terrain with deep soils, while chaparral sites often have steep slopes and shallow, rocky soils [53,61]. In the redwood-Douglas-fir (Sequoia sempervirens-Pseudotsuga menziesii var. menziesii) zone of the inland North Coast Ranges, common manzanita occurs on moderately developed soil derived from weathered sandstone parent material . Where common manzanita grows in ponderosa pine (Pinus ponderosa var. ponderosa) forest in Lake County, the soil is gravelly loam, slightly to moderately acidic, 3 to 4 feet (0.9-1.2 m) deep, moderately permeable, and well drained . In the higher elevations of the interior southern North Coast Ranges, Konocti manzanita usually grows in rocky, volcanic substrates [21,58]. Although common manzanita tolerates serpentine soils [4,28,70], it generally occurs on nonserpentine soils . It is more abundant on patchy rather than continuous serpentine soils .
Plant communities: Common manzanita occurs in chaparral, oak (Quercus spp.) woodlands, and coniferous forests of northern and central California. In many communities it occurs as an associated species; however; it is dominant in some chaparral of the North Coast Ranges [65,66]. It forms closed pygmy forests in the Napa Ranges , "impenetrable low forests" in the middle and inner Coast Ranges , and thickets of "solid forest-like growth" in the North Coast Ranges .
In the North Coast Ranges, common manzanita is associated with chamise (Adenostoma fasciculatum) chaparral [12,14,46], other chaparral communities [65,66], Oregon white oak (Q. garryana) woodlands [16,48], blue oak woodlands [1,32], and mixed broadleaf-evergreen forests . In the Sierra Nevada and Cascade Range foothills, common manzanita occurs in blue oak  and blue oak-gray pine (P. sabiniana) woodlands , ponderosa pine forests , and montane chaparral .See the Fire Regime Table for a list of plant communities in which common manzanita may occur and information on the fire regimes associated with those communities.
|Common manzanita flowers. Photo courtesy of Dr. Robert T. and Margaret Orr © California Academy of Sciences.|
Common manzanita is an erect, evergreen shrub that may also grow as a single-stemmed tree [7,19,21]. It typically grows from 6 to 12 feet (2-3.6 m) tall [36,51,66] but can reach 26 feet (8 m) tall [7,21]. It is generally widely branched from its base with long, crooked branches . The bark is thin and smooth when young and peels in paper-thin flakes as it ages [62,66]. Its thick leaves are wide- or oblong-ovate to obovate and 1 to 2 inches (2.5 to 5 cm) long and 0.4 to 1.4 inches (1- 3.5 cm) wide. The urn-shaped, white to pinkish flowers occur in drooping panicles. The fruit is a berry-like drupe that contains 3 to 4 seeds that are protected by a very dense, impervious layer of carpellary tissues [7,35,44]. Although common manzanita may have a taproot , it is typically shallowly rooted [34,35,41]. Five of the 6 subspecies lack a burl, but Roof’s manzanita has a prominent burl [7,21].Raunkiaer  life form:
Pollination and breeding system: Common manzanita produces perfect flowers [7,62], which are visited by nectar-collecting bees  that likely pollinate the flowers. Obligate seeders (i.e., most common manzanita subspecies) generally have more flowers and produce more nectar than sprouting manzanita taxa [22,49].
Seed production: Common manzanita produces "abundant" seed . Mature plants produce seed almost every year, with higher seed production in some years than others . Over 2 consecutive years at Hopland Research Station in Mendocino County, common manzanita produced 3.3 and 4.2 seeds/fruit and had 50.6% and 63.4% seed set . Common manzanita may produce seed at 4 to 5 years old .
Seed dispersal: Most common manzanita fruits fall beneath or near the parent plant [38,40]. Mammals including foxes, coyotes, and American black bears may disperse the seeds long distances [10,15].
Seed banking: Common manzanita stores its dormant seeds in the soil seed bank [10,35]. Seed longevity in the field was not reported in the literature reviewed (as of 2013), but the soil seed bank is likely long-lived. In the Napa Range, Jepson  reported that common manzanita seedlings appeared in large numbers 10 to 40 years after land cleared for cultivation or grazing was abandoned, suggesting that common manzanita seeds remain viable in the seed bank for at least 10 to 40 years.
Rates of seed predation may be high for manzanita species. Studies of 2 manzanita species (bigberry (A. glauca) and Eastwood (A. glandulosa) manzanita) in southern California chaparral found that there was no net gain in the size of their persistent seed banks, even with high seed inputs and the absence of fire for 10 years. Most of the seed loss appeared to be due to rodent predation rather than germination or loss of viability .
Germination: Common manzanita seeds are dormant and germinate readily after fire breaks seed dormancy [6,10,26,30].
In laboratory experiments, some seed heating treatments improved germination rates of common manzanita. In one study, common manzanita seeds were exposed to 10 temperatures of dry heat ranging from 100 to 300 °F (38-150 °C) for 5 minutes. Peak germination occurred at 240 to 260 °F (115-127 °C), with 11% germination. Unheated controls had 3% germination. Of the 11 shrub species tested, only 3 species, including common manzanita, "showed any life" when heated to the highest temperatures (280 and 300 °F (138-150 °C)) . Seeds collected from Boggs Mountain State Forest were treated with combinations of 6 levels of heat ranging from 77 to 212 °F (25-100 °C) with dry or moist heating, winter stratification (3 months at 41 °F (5 °C)), and leachate from burned litter, but germination was negligible for all treatments (1 seed out of 1,400) .
Seedling establishment and plant growth: Common manzanita seedling establishment is rare except following fire [10,35,41]. Common manzanita seedlings may be abundant during the first growing season after fire. However, survival is often low, and the initial pulse of seedlings may be greatly reduced during subsequent years [10,30]. Along the Napa Range and in Mendocino County, Jepson  reported that common manzanita seedlings occurred in large numbers in abandoned fields or vineyards, suggesting that common manzanita may establish without fire.
Biswell  examined seedling emergence following wildfire in the Tehama Range of the Sierra Nevada foothills and reported that manzanita (common manzanita and sticky whiteleaf manzanita (A. viscida)) seedling emergence was greatly enhanced the first growing season after fire (Table 1). In postfire year 1, there were more than 7 times as many manzanita seedlings in burned shrublands sites than unburned herbaceous sites and twice as many manzanita seedlings in burned herbaceous sites than unburned herbaceous sites. See Plant response to fire for information on seedling establishment after wildfires on Quail Ridge Reserve, Napa County, and the Rogue River-Siskiyou National Forest.
|Table 1. Number of manzanita* seedlings that emerged each year after wildfire on the Tehama Range, northern California |
|*Data for common manzanita and whiteleaf manzanita were pooled.|
Common manzanita is a slow-growing  and long-lived shrub [41,42] that produces seed a few years after establishment .
Vegetative regeneration: Five of the 6 subspecies of common manzanita cannot regenerate asexually, but Roof's manzanita has a burl that may sprout after top-kill [7,21,74].SUCCESSIONAL STATUS:
In chaparral of the North Coast Ranges, Konocti manzanita establishes in the first growing season after fire and may persist for decades where fire is absent. In one stand, growth rings indicated that the stand age and time-since-fire was 74 years. Konocti manzanita was the dominant species (24% relative dominance). Although woodland tree seedlings were present, there was no indication of imminent successional replacement of chaparral . Manzanitas such as common manzanita, which have arborescent growth and are long-lived, can be "vigorous" in old chaparral stands because they remain above other vegetation . Keeley  suggests that in long absences of fire, mesic closed chaparral communities become dominated by sprouting shrubs, while obligate seeders persist in arid open sites.
In oak woodlands, common manzanita occurs in open, grassy sites in the Bay Area and foothills of the Coast Ranges and Sierra Nevada [48,53]. It often dominates early-successional woodland and forest sites "after fire has destroyed the tree species" .In forest communities, common manzanita may occur in the understory of ponderosa pine stands in the Sierra Nevada , mixed broadleaf-coniferous forest in the North Coast Ranges , and ponderosa pine-Douglas-fir stands of northern California . It occurs in the early postfire successional stage in ponderosa pine, Sierran mixed-conifer, white fir (Abies concolor), and Jeffrey pine (P. jeffreyi) forests on the west side of the Sierra Nevada . In a redwood (Sequoia sempervirens) forest managed for timber production, common manzanita comprised a large proportion of the shrub cover in early-seral stands that were clearcut and burned, but it was absent from older thinned stands. The authors suggested that lack of burning, reduced soil disruption, and relatively dense forest canopies precluded common manzanita establishment in the older thinned stands .
Immediate fire effects on plant:
Fire kills most common manzanita subspecies even at low severity [1,19,34,35]. Roof's manzanita may only be top-killed [7,21]. The roots of common manzanita are generally poorly developed, shallow, and vulnerable to heat [34,35], and its bark is thin and peels with age [62,66], offering little protection from fire.
Postfire regeneration strategy :
For all subspecies:
Ground residual colonizer (on site, initial community)
For Roof's manzanita:
Tall shrub, with a sprouting root crown
For all other subspecies:
Shrub without adventitious buds and without a sprouting root crown
Fire adaptations and plant response to fire:
Roof's manzanita has a burl that enables it to sprout following fire [7,21].
Plant response to fire: Common manzanita establishes from soil-stored seed after fire [6,10,26,30]. Roof’s manzanita may also establish by sprouting from the burl after fire [7,21]. Density of common manzanita typically increases after fire because fire breaks dormancy of seeds stored in the soil seed bank [6,10,26,30].
In blue oak woodlands of Quail Ridge Reserve, common manzanita seedling density 1 year after wildfire was higher in burned plots than unburned plots, although differences were not significant. An "intense crown fire" caused 100% mortality and greatly reduced the basal area of common manzanita (P<0.05). Of 7 unburned plots, only 1 had common manzanita seedlings (13.33 seedlings/ha), whereas 4 of the 7 burned plots contained seedlings (ranging from 13.33-100 seedlings/ha). Blue oak and interior live oak (Q. wislizeni) sprouted after the fire. However, because mule deer preferred to browse oak sprouts, common manzanita might have an advantage in the postfire environment .
In the mixed-oak woodlands and shrublands of the Tehama Range, seedling emergence of common manzanita and sticky whiteleaf manzanita (species were pooled) was higher compared to an adjacent unburned site the first growing season after wildfire (Table 1). There were more than 7 times as many manzanita seedlings in burned shrub-dominated sites than unburned herbaceous-dominated sites and twice as many manzanita seedlings in burned herbaceous sites than unburned herbaceous sites in the first year after fire. While manzanita seedling emergence rate was high the first spring after fire, more than half of the seedlings died by the following autumn (25 of 54 plants survived), and only 1 plant survived through the following winter. The high mortality of shrubs in the study area was attributed primarily to competition for water from herbaceous vegetation and drought .
In a ponderosa pine-Douglas-fir stand on the Rogue River-Siskiyou National Forest, the number of common manzanita shrubs increased by 918 times, from 0.12 shrub/m² to 108 seedlings/m², after a "destructive" fire left "the area in an almost denuded condition" .
At the time of this writing (2013), no information documenting the postfire sprouting densities or growth rates of Roof's manzanita sprouts was available. However, Arevalo  reported the presence of basal sprouts of common manzanita (no subspecies given) after an "intense" crown fire in blue oak woodlands and chamise chaparral in Napa County.FUELS AND FIRE REGIMES:
Fire regimes: Common manzanita experiences a variety of fire regimes across its distribution in chaparral, woodlands, and forests. For example, chaparral communities with common manzanita historically experienced somewhat infrequent, stand-replacement crown fires with fire-return intervals ranging from 30 to 125 years (reviews and models by ). Historical fire-return intervals in chaparral communities with common manzanita likely averaged 50 years in interior chaparral (reviews and models by ) and 73 years in the Coast Ranges (reviews and models by ), Cascade Range, and Sierra Nevada (reviews and models by ). Woodland and forest communities with common manzanita in the understory historically experienced frequent, low-severity surface fires at intervals of 5 to 30 years [1,47].
See the Fire Regime Table for further information on fire regimes of vegetation communities in which common manzanita may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".FIRE MANAGEMENT CONSIDERATIONS:
Fuel reduction treatments including mechanical mastication are increasingly being used in sites where common manzanita occurs. Mastication converts shrubs and small trees into fractured woody particles, creating dense fuelbeds. Recent investigations assessed whether mastication may increase fire intensity, increase fuel drying rates, and cause extreme soil heating. Laboratory studies comparing intact common manzanita (1.2-7.9 inch (3-20 cm) sticks) and fractured common manzanita fuelbeds, assembled from samples collected from the Six Rivers National Forest, found mean flame heights were 36% higher in intact fuelbeds (33 inches (83 cm)) compared with fuelbeds composed of fractured particles (24 inches (61 cm), P<0.001). Fuelbeds composed of intact common manzanita burned with greater intensity than those of fractured particles. Both fuelbed types sustained flaming combustion with fireline intensities ranging from 60 to 140 kJs-1m-1, suggesting that masticated fuels can support flaming combustion despite their high bulk density .
Kreye and others  examined fuel moisture dynamics of intact and masticated common manzanita particles in the laboratory. They found that drying rates of intact and fractured particles did not differ at the fuelbed surface or within the fuelbed. However, both intact and fractured particles at the fuelbed surface dried more quickly than fuels at deeper levels, which dried about 3 times more slowly. The authors note that masticated fuelbeds have higher bulk densities and higher loadings of 1- and 10-hour fuels than intact fuelbeds and that masticated fuelbeds lose moisture slowly. Longer-than-expected fuelbed drying times may lead to difficulties predicting fire behavior and rating fire danger. They call for further research about fuel moisture dynamics with varying fuelbed bulk densities, fuel loads, and fuelbed depths .Busse and others  found that soil heating from fire can cause biological damage in dry soil with mastication mulch depths greater than 3 inches (7.5 cm). Soil heating was measured during prescribed fires on plots with 4 mulch depths (0, 1, 3, 5 inches (0, 2.5, 7.5, 12.5 cm)) and 2 soil moisture contents (4% and 25%). The study sites were in two northern California 18-year old ponderosa pine plantations with clay loam soil and dense understories dominated by masticated manzanita (including common manzanita) or tanoak (Lithocarpus densiflorus). In dry soil, temperatures exceeded the lethal threshold for plants (140 F° (60°C)) at nearly all mulch depths. They exceded the threshold for at least 7 hours throughout the 3.9-inch (10 cm) soil profile for the 2 deepest mulch depths. In moist soil, peak temperatures exceeded the lethal threshold to only 1 inch (2.5 cm) in the soil profile for all but the deepest mulch treatments. Duration above 140 F° (60°C) increased linearly with mulch depth, and it was 3 to 7 times greater in dry soil than moist soil. There was no evidence of postfire water repellency in dry or moist soil .
Common manzanita browse is rated as poor to useless for domestic goats and mule deer and useless for cattle, domestic sheep, and horses . It may be important forage for dusky-footed woodrats in coastal redwood habitats .
Palatability and nutritional value: Common manzanita browse has low palatability, but plants may be eaten to some extent [6,10,52,62]. In oak woodland winter range, the foliage may be eaten when young plants grow in an "open manner" and mule deer can access the leaves. Heavy winter browsing may kill or set back reproduction in young plants. After a wildfire on the Tehama Winter Range of the western Sierra Nevada foothills, young plants were browsed each winter by Columbian black-tailed deer. This prevented seed production of common manzanita for at least the 12-year duration of the study . Postfire browsing of common manzanita seedlings was also reported on a heavily-stocked mule deer range in Lake County .
The low palatability of common manzanita may give a competitive advantage in postfire or heavily browsed sites. After a wildfire in oak woodlands and chamise chaparral on the Quail Ridge Reserve, preferential browsing of blue oak and interior live oak sprouts by mule deer decreased the regeneration success of the oaks, potentially giving a competitive advantage to common manzanita in the postfire environment . In mule deer- and livestock-browsed mixed-oak and manzanita chaparral at the Hopland Field Station, Mendocino County, unpalatable shrub species grew taller than palatable shrub species. Manzanitas (common manzanita, Eastwood manzanita, and hoary manzanita (A. canescens) attained the greatest heights (5 feet (1.5 m), followed by scrub interior live oak (Q. wislizeni var. frutescens) (3 feet (0.9 m)), Pacific poison-oak (Toxicodendron diversilobum) (1 foot (0.3 m)) and chamise (1 feet (0.3 m)). Where browsing was excluded, scrub interior live oak was the tallest, followed by chamise and manzanita, and finally Pacific poison-oak (heights were 7, 5, and 3 feet (2.1, 1.5, and 1.9 m) respectively). Manzanita cover was greatest on browsed sites, while scrub interior live oak cover was greatest on unbrowsed sites .
Cover value: No information is available on this topic.VALUE FOR REHABILITATION OF DISTURBED SITES:
The following table provides fire regime information that may be relevant to common manzanita habitats. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
|Fire regime information on vegetation communities in which common manzanita may occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models , which were developed by local experts using available literature, local data, and/or expert opinion. This table summarizes fire regime characteristics for each plant community listed. The PDF file linked from each plant community name describes the model and synthesizes the knowledge available on vegetation composition, structure, and dynamics in that community. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Coastal sage scrub-coastal prairie||Replacement||8%||40||8||900|
|Surface or low||62%||5||1||6|
|California oak woodlands||Replacement||8%||120|
|Surface or low||91%||10|
|Surface or low||78%||13|
|California mixed evergreen||Replacement||10%||140||65||700|
|Surface or low||32%||45||7|
|Surface or low||98%||20|
|Surface or low||74%||30|
|Mixed conifer (north slopes)||Replacement||5%||250|
|Surface or low||88%||15||10||40|
|Mixed conifer (south slopes)||Replacement||4%||200|
|Surface or low||80%||10|
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [1,2].
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