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|Figure 1. Image © 2007 George W. Hartwell.|
|This review summarizes the scientific literature as of 2015 on fire effects to and ecology of sticky whiteleaf manzanita. Details and
documentation of source materials follow this summary. Common names are used in this Species Review. See the Appendix for a list of scientific names and links to other FEIS Species Reviews.
Sticky whiteleaf manzanita occurs in California and southwestern Oregon. It grows on dry sites in all soil textures and tolerates mafic soils. It occurs in chaparral, oak woodland, and low-elevation mixed-conifer communities. In chaparral, it grows in pure stands and in mixed chaparral with chamise, ceanothus species, and other manzanita species. The canopies of mature chaparral communities may be completely closed.
Sticky whiteleaf manzanita is a sclerophyllous species. It may live more than 100 years in chaparral. Its growing season is early, with flowers opening in late winter on low-elevation sites. It reproduces naturally only from seed. Seeds are stored in the soil seed bank, where they may remain dormant for decades. They require scarification and overwinter stratification to overcome dormancy, and fire is the usual mechanism that scarifies seed. Sticky whiteleaf manzanita grows best in mineral soil on open sites. It is an early-seral species in woodlands and forests. It is replaced successionally by shade-tolerant species as canopies close.
Fire of even low severity kills sticky whiteleaf manzanita, but it also helps overcome dormancy of soil-stored seed. Sticky whiteleaf manzanita seedlings establish in large numbers on sites where the species was present before fire. Live plants and sticky whiteleaf manzanita litter are highly flammable. The plant communities in which sticky whiteleaf manzanita occurs have a broad range of fire regimes, from moderate-interval, stand-replacement fires in chaparral to mostly frequent, low-severity surface fires in mixed-conifer communities.Sticky whiteleaf manzanita browse is unpalatable and low in nutrients, but its fruits are an important wildlife food. It may interfere with growth of conifer seedlings after fire or logging.
Arctostaphylos viscida subsp. mariposa (Dudley) Wells, Mariposa manzanita
Arctostaphylos viscida subsp. pulchella (Howell) Wells, sticky whiteleaf manzanita
Arctostaphylos viscida subsp. viscida, sticky whiteleaf manzanita
Hybrids: The subspecies occasionally occur in mixed populations , so intraspecific hybridization may occur. Putative sticky whiteleaf manzanita × hoary manzanita  and sticky whiteleaf manzanita × greenleaf manzanita [11,30,86] hybrids have been identified. Sticky whiteleaf manzanita × greenleaf manzanita hybrid swarms occur at around 4,600 feet (1,400 m) in the Sierra Nevada. One such swarm has been identified at Inspiration Point in Yosemite National Park .
|Figure 2. At Inspiration Point, Yosemite, sticky whiteleaf manzanita tends to occupy south slopes, greenleaf manzanita tends to occupy north slopes, and putative hybrids occupy slope bottoms . Image by Scott Oller.|
In this review, "Mariposa manzanita" refers to Arctostaphylos viscida subsp. mariposa; the other 2 subspecies are referred to by their scientific names. "Sticky whiteleaf manzanita" refers to the species as a whole. See the Appendix for list of common and scientific names used in this review and for links to other FEIS Species Reviews.SYNONYMS:
For Arctostaphylos viscida subsp. pulchella (Howell) Wells:
Arctostaphylos pulchella Howell
Arctostaphylos serpentinicola J.B. Roof (documented in )
|Figure 3. Sticky whiteleaf manzanita distribution. Map courtesy of USDA, NRCS. 2015. The PLANTS Database. National Plant Data Team, Greensboro, NC. (2015, June 19) .|
Sticky whiteleaf manzanita is native to California and southwestern Oregon. It occurs in the North Coast Ranges and the foothills of the Klamath-Siskiyou Mountains and the Sierra Nevada. It is distributed from Kern County, California, north to Josephine County, Oregon [29,83,85]. It is most common in the northern Sierra Nevada .
United States: CA, OR
SITE CHARACTERISTICS AND PLANT COMMUNITIES:
Site characteristics: Sticky whiteleaf manzanita grows on dry, sunny slopes at low to midelevations [20,85].
The climate in which sticky whiteleaf manzanita grows is mediterranean, with mild, wet winters and hot, dry summers [48,51]. Sticky whiteleaf manzanita is one of the most drought-resistant manzanita species, withstanding very low xylem water potentials . It possesses both morphological and physiological characteristics to reduce heat stress and water loss from transpiration . In southwestern Oregon, sticky whiteleaf manzanita presence was positively associated with warm, dry growing seasons at low elevations .
Sticky whiteleaf manzanita grows in soils of all textures (for example, [18,101,125]) but is most common on clay and clay loam [18,21,125]. It tolerates mafic and ultramafic soils [51,122]. For example, it codominates with chamise on both gabbro and nongabbro soils in El Dorado County, California . Arctostaphylos viscida subsp. pulchella is considered an indicator of serpentine soils in northern California , although it is not confined to such soils [40,51]. In the Klamath-Siskiyou Mountains of northern California and southwestern Oregon, Arctostaphylos viscida subsp. pulchella is common in leather oak woodlands on serpentine soils [40,50] and in Jeffrey pine woodlands on ultramafic soils derived from serpentine, gabbro, diorite, and granodiorite parent materials [35,89,122].
Sticky whiteleaf manzanita occurs at elevations of about 100 to 7,200 feet (30-2,200 m) .
Plant communities: Sticky whiteleaf manzanita grows in chaparral, oak woodlands, and mixed-conifer forests [10,51].
In chaparral, sticky whiteleaf manzanita grows in pure stands, with other manzanita species, in mixed ceanothus-manzanita stands, and in chamise stands [51,63,94,118,125]. Between 860 to 4,300 feet (860-1,280 m) on the Kaweah East Fork Watershed, sticky whiteleaf manzanita codominates with chamise and wedgeleaf ceanothus . In Madera County, Mariposa manzanita grows in mature mixed chaparral with wedgeleaf ceanothus and chaparral whitethorn . Whether pure or mixed, chaparral with sticky whiteleaf manzanita is often dense and impenetrable [54,83]. Canopy cover can be >85% .
Montane chaparral with sticky whiteleaf manzanita may succeed to Pacific ponderosa pine (hereafter, ponderosa pine), Jeffrey pine, or mixed-conifer forests  but is often successionally stable on dry slopes. Montane chaparral occurs at higher elevations, and generally on cooler sites, than other chaparral. In the North Coast Ranges and Klamath-Siskiyou Mountains, Mariposa manzanita occurs in montane chaparral at elevations from 2,000 to 5,000 feet (610-1,500 m) .
Nonnative annual grasses and forbs may establish in early postfire chaparral communities. On 5 burned chaparral sites in the southern Sierra Nevada, species richness was highest in postfire year 3. This was mostly due to an increase in nonnative annuals, especially silver hairgrass, foxtail chess, soft chess, and rattail sixweeks grass . These annuals may persist into late succession (beyond postfire year 90) .
Sticky whiteleaf manzanita often occurs in the understories of oak woodlands situated between or forming a mosaic with chaparral and mixed-conifer forests. At low elevations (3,000-4,000 feet (910-1,200 m)), it grows in interior live oak-blue oak-gray pine woodlands, usually in association with deer brush. Canyon live oak may dominate the overstory on mesic sites [4,96,108]. Mariposa manzanita often codominates with wedgeleaf ceanothus and chaparral whitethorn in blue oak-interior live oak woodlands. These communities typically have a large component of nonnative annual grasses in the ground layer [19,89,108]. In El Dorado County, sticky whiteleaf manzanita occurs in a mixed oak-pine forest of interior live oak, canyon live oak, California black oak, gray pine, and ponderosa pine. California buckeye and toyon are understory codominants . In Madera County, Mariposa manzanita dominates in blue oak-interior live oak/chaparral woodlands; valley oak and gray pine codominate the overstory. Wedgeleaf ceanothus, birchleaf mountain-mahogany, and California coffeeberry codominate in the understory. Ground cover is composed of nonnative annuals .
In California black oak woodlands, which are usually found in upper foothills, sticky whiteleaf manzanita typically codominates with greenleaf manzanita, deer brush, and/or mountain misery [5,51,93,110]. California black oak woodlands are generally seral communities that succeed to conifers without frequent fire . In upper northern California and southwestern Oregon, sticky whiteleaf manzanita grows in Oregon white oak-California black oak and Oregon white oak woodlands. Brewer's oak and sticky whiteleaf manzanita form a transitional chaparral community below California black oak woodlands in the Iron Mountain Research Natural Area on the Lassen National Forest .
Conifers, especially gray pine and ponderosa pine, are often important components of oak woodlands with sticky whiteleaf manzanita. On the Donald and Sylvia McLaughlin Natural Reserve in north-central California, sticky whiteleaf manzanita grows in leather oak-MacNab cypress-gray pine woodlands and chaparral, with chamise as an associate in the understory. These communities occur on shallow, rocky serpentine soils. They usually contain a diverse mixture of native forbs, and nonnative annuals are rare . In Whiskeytown National Recreation Area in the Klamath Mountains, sticky whiteleaf manzanita dominates the understory of a California black oak-knobcone pine community. Toyon and Pacific poison-oak are also common in the understory; canyon live oak is occasional in the overstory .Sticky whiteleaf manzanita is common in mixed-conifer forests in early to midsuccession. These forests are typically composed of ponderosa pine, coast Douglas-fir (hereafter, Douglas-fir), sugar pine, white fir, incense-cedar, and/or California black oak [73,89]. Giant sequoia may also be present . Deer brush often codominates the understory with sticky whiteleaf manzanita . On sites in early postfire succession, sticky whiteleaf manzanita and ceanothus species often codominate with sprouts of top-killed California black oak, tanoak, canyon live oak, and/or other sprouting hardwoods. Density of sticky whiteleaf manzanita and other shrubs decreases as the canopy closes and shade-tolerant trees such as white fir and incense-cedar increase in the understory . Sticky whiteleaf manzanita persists and is common in the shrub layers of midseral Pacific ponderosa pine-California black oak communities, growing up to 10 feet (0.3 m) tall beneath the canopy . On the Stanislaus National Forest, sticky whiteleaf manzanita dominates the understory of a mixed-conifer forest of white fir, Douglas-fir, sugar pine, and California black oak . On the Sierra National Forest, Mariposa manzanita codominates the understory of a mixed-conifer forest with Sierra gooseberry, deer brush, and mountain misery. Overstory dominants include white fir, ponderosa pine, Jeffrey pine, and sugar pine . In a survey on the Rogue River National Forest, Jeffrey pine-incense-cedar/sticky whiteleaf manzanita associations occurred on warm, dry soils derived from serpentine or diorite. Cover of sticky whiteleaf manzanita averaged 35% .
Sticky whiteleaf manzanita is an erect evergreen shrub. It ranges from 3 to 13 feet (1-4 m) tall and has spreading branches [2,83]. Plants are usually single-stemmed . Branches of mature plants often show ribbonlike, vertical strips of dead tissue, and dead branches usually remain attached [1,9]. Branch die-back and leaf shed occur during extended drought [9,94]. Branch die-back may also occur in plants in deep shade . This species lacks an enlarged root crown or burl .
The leaves, pedicels, and fruits of sticky whiteleaf manzanita are often glandular-viscid (sticky) , but this trait is variable, depending on subspecies and location . It is a sclerophyllous species [9,20,72]. The leaves are leathery, alternate, and held vertically, which reduces heat load and transpiration [11,72]. Studies on 4 sites across northern California found individuals on serpentine soils had thicker leaves than individuals on nonserpentine soils, and resorption of nitrogen was more efficient in individuals on serpentine soils . The fruit is a drupe. It has a thick endocarp surrounding the seeds . There are 5 to 6 seeds/drupe. The seeds are nutlets [2,103,115]. The nutlets are often bound together tightly , and their seed coats are hard [13,29,103].
|Figure 4. Ripening sticky whiteleaf manzanita fruits. Image by Richard W. Spjut.|
The laterally spreading, shallow roots usually penetrate less than 8 inches (20 cm) below ground [20,94]. In southwestern Oregon, a root profile of a pure sticky whiteleaf manzanita stand showed that most roots were fine, and they were concentrated at soil depths of <1.6 feet (0.5 m). The deepest fine roots extended no farther than 10 feet (3 m) below ground. Large roots extended to 8.2 feet (2.5 m) .
Stand structure: Mature chaparral is usually dense, with density declining in senescent stands. Sticky whiteleaf manzanita is typically less frequent and taller in forests than in chaparral. At Mineral King, Sequoia National Park, a 102-year-old chamise-sticky whiteleaf manzanita community had this structure :
|Table 1. Abundance of sticky whiteleaf manzanita and chamise in a 102-year-old community at Mineral King |
|Species||Basal cover (m²/ha)||Canopy cover (%)||Plants/ha|
|Sticky whiteleaf manzanita||51.8||9.0||1,220|
In a ponderosa pine-California black oak forest near Jackson, California, sticky whiteleaf manzanita formed a dense shrub layer about 10 feet (3 m) tall. Individual plants were 2 to 4 feet (0.6-1 m) apart. Sticky whiteleaf manzanita's litter layer was not well decayed. The litter layer ranged from 0.5 to 2 inches (1.3-5.1 cm) thick, with the "greater depths prevailing" .
Age: Sticky whiteleaf manzanita plants may live 90 years  or more [28,60,61]. On 12 chaparral sites across California, Keeley [60,61] found that all stands dominated by sticky whiteleaf manzanita and other obligate seeders were even-aged, dating back to the last fire. Stand ages ranged from 56 to 120 years [60,61], and no seedling recruitment was present in old stands . However, another study found that an uneven-aged structure developed in old stands. In the Klamath Mountains of southwestern Oregon, sticky whiteleaf manzanita-deer brush stands <30 years old were even-aged. Stands older than that were uneven-aged (n=31 stands and 242 plants total). The oldest sticky whiteleaf manzanita individual was >146 years old, and 44 sticky whiteleaf manzanitas were ≥100 years old. These old sticky whiteleaf manzanitas ranged from 4 to 20 inches (10-50 cm) in diameter. In uneven-aged stands, some sticky whiteleaf manzanitas were older than the last known fire, and some were considerably younger. The authors proposed that uneven-aged structure of old stands resulted from the last fire missing some plants, omissions in the fire record, and/or limited seedling establishment without fire  (see Germination).Raunkiaer  life form:
Pollination and breeding system: Flowers are perfect . Insects, particularly bees and flies, are the primary pollinators (review by ). Although sticky whiteleaf manzanita apparently hybridizes, its early flowering period helps keep hybridization to a minimum .
Seed production: Sticky whiteleaf manzanita first produces seed when it is 3  to 10  years old. Flower and seed production may fluctuate widely from year to year . The flowers have an extended period of development, and severe summer drought results in flowerbud abortion and leaf drop. Baker and others  surmised that since sticky whiteleaf manzanita is long-lived, failure to flower and set seed in some years is only a temporary set-back that does not seriously impact sticky whiteleaf manzanita reproduction in the long term.
Seed dispersal: The seeds are heavy, and most fall beneath or near the parent plant. Some seed dispersal occurs via frugivorous animals [13,48,72] such as American black bears and coyotes .
Seed banking: Sticky whiteleaf manzanita has a soil seed bank [13,48,72], which can be plentiful. Anderson  reported that sticky whiteleaf manzanita and deer brush were the 2 most common species found in the soil seed bank of a mixed-conifer forest on the Challenge Experimental Forest. Most viable seeds occurred in the top layer of soil, although many were stored in duff  (Table 2). A study in Marin County reported an average of 28,177 sticky whiteleaf manzanita seeds/m² of soil (SE 4,743). Seeds were not tested for viability [65,92].
|Table 2. Mean density of sticky whiteleaf manzanita seeds in the soil seed bank on the Challenge Experimental Forest (SE) |
|Soil layer||Viable seeds/m²|
|0-2 cm||57.6 (19.7)|
|2-4 cm||21.3 (11.8)|
Sticky whiteleaf manzanita's seed banks are apparently long-lived, remaining dormant in the soil for decades [13,48,72]. Nevertheless, manzanita (Arctostaphylos spp.) seed banks are replenished frequently when reproductive adults are present. Most manzanita seeds available for recruitment probably come from recently produced cohorts . On the watershed of the Kaweah East Fork River, sticky whiteleaf manzanita established after a prescribed fire in a chamise-sticky whiteleaf manzanita-wedgeleaf ceanothus community. Prior to the prescribed fire, the chaparral community had not burned for 125 years , suggesting a long period of seed banking. After the 2002 McNally wildfire, which burned 37,000 acres (15,000 ha) of mixed chaparral on the Sequoia National Forest, prefire stand ages were determined by sticky whiteleaf manzanita ring counts. Thirty-three stands were "ancient" (>90 years old), and 34 were "mature" (50-60 years old). In postfire year 1, average ratio of sticky whiteleaf manzanita seedlings:parents (shrub skeletons) was 6:19.3 in ancient stands and 12:23.0 in mature stands. This suggests that seed viability had declined in the ancient stands, but enough viable seed remained in the seed bank to support postfire regeneration. The authors concluded that "chaparral more than a century old is resilient to such long fire-free periods" . In conifer forests, sticky whiteleaf manzanita may still exist in the seed bank even after shade-tolerant conifers have replaced all sticky whiteleaf manzanita plants in the understory .
Minnich and Howard  stated that is takes at least 10 years for sticky whiteleaf manzanita to replenish its seed bank after fire.
Germination: Sticky whiteleaf manzanita seeds are dormant; they require scarification followed by overwinter stratification to overcome dormancy and germinate. Scarification may occur by heat, mechanically, or chemically [13,31,103]. Fire is the usual method of scarification in the field (see Plant response to fire), but heavy equipment can also scarify seeds [44,87]. Acid treatment breaks dormancy in the laboratory [13,79], and traveling through the digestive tract of frugivorous animals may scarify some seeds. However, seeds collected in coyote scat showed poor germination in the laboratory (1%-8%), and Kauffman and Martin  did not consider animal digestion a "significant factor in breaking dormancy" of sticky whiteleaf manzanita in the field.
Mechanisms of dormancy are not completely understood for manzanita species. Some studies suggest that soil-stored, scarified manzanita seed germinates after exposure to charate, while fresh, scarified seed does not (review by ).
Low germination rates (<30%) for sticky whiteleaf manzanita seeds are reported in laboratory studies [6,57]. However, precise requirements for sticky whiteleaf manzanita germination are not well known [28,57], and germination rates are likely higher in early postfire environments. Still, sticky whiteleaf manzanita and other manzanita species may have fewer viable seeds in the seed bank than associated shrub species. On 24 mixed-conifer sites in northern California, seeds of sticky whiteleaf manzanita and other manzanitas showed less viability, based on lack of intact endosperm, than seeds of associated ceanothus species (12.5% vs. 97.5% viability, respectively) . Seeds collected from sticky whiteleaf manzanita plants in northern California showed between-year differences in seed size and viability, with small seeds (produced in 1983) averaging 6.5% germination and large seeds (produced in 1984) averaging 10.6% germination in the laboratory .
Results from Durin and Muir's  study in southwestern Oregon (see Age) suggest that some sticky whiteleaf manzanita recruitment occurs without fire or mechanical disturbance . From collections in southern and central California chaparral, Keeley  found that some obligate seeders produce a small portion of nonrefractory seeds that do not require fire or other means of scarification for germination, although sticky whiteleaf manzanita was not one of the species studied. Durin and Muir  suggested that sticky whiteleaf manzanita produces some nonrefractory seed. In their study, sticky whiteleaf manzanita individuals that recruited during fire-free intervals showed suppressed growth but persisted for at least 46 years .
Seedling establishment and plant growth: Mineral soil is a favored seed bed for sticky whiteleaf manzanita . Seedling establishment typically occurs on burns, but it also occurs on sites that have been bulldozed or logged with heavy equipment, which can scarify seeds [58,103]. On mechanically disturbed sites, establishment is generally greatest where equipment has heavily impacted the soil .
Sticky whiteleaf manzanita grows rapidly on open sites. On 5 mixed-chaparral communities in the southern Sierra Nevada, cover of sticky whiteleaf manzanita and other shrubs increased 5-fold from postfire years 1 to 3 . In southwestern Oregon, a 12-year-old stand of pure sticky whiteleaf manzanita had an average height of 3.6 feet (1.1 m), basal area of 29.8 m²/ha, and density of 4,600 plants/ha . Minore and others  provide equations to predict sticky whiteleaf manzanita increases in stem length, crown area, and crown volume over time, based on research in southwestern Oregon.
Sticky whiteleaf manzanita may show compensatory growth after extreme dieback from drought. On the Sequoia National Forest, 1st- and 2nd-year twig growth was significantly greater on individuals with ≥90% branch dieback compared to those with less dieback (P<0.001). Individuals were measured at the end of an extended drought (1975-1977). All were 60 years old and growing on an open, south-facing slope characterized as "one of the driest locations in the vicinity". Only 3 of 90 individuals died during the drought .
See Plant response to fire for further information on growth rates of sticky whiteleaf manzanita.
Vegetative regeneration: Sticky whiteleaf manzanita does not sprout from the root crown [62,103].SUCCESSIONAL STATUS:
Manzanita and other chaparral communities are temporally and spatially stable. They are often described as "climax" or "fire climax" communities [48,51]. Sticky whiteleaf manzanita is generally dominant in postfire chaparral succession if it was dominant before fire. On 12 chaparral sites across California, Keeley  found that postfire recruitment was composed of seedlings and saplings of species present before fire (mostly chamise, manzanita species, and ceanothus species). Trees were rare except in old chaparral, in which woodland species such as interior live oak and toyon were establishing. However, Keeley  observed that "even in stands a century old, successional replacement of chaparral was not imminent".
Sticky whiteleaf manzanita occurs in early to midsuccession in coniferous forests [53,73] and oak woodlands . It frequently dominates early postfire and postlogging communities, with cover of sticky whiteleaf manzanita and other chaparral shrubs decreasing as the canopy closes with succession [46,69]. Sticky whiteleaf manzanita is classified as a disturbance indictor in mixed-conifer forests of northern California, only occurring in communities that are associated with frequent fire or other frequent disturbances .
Sticky whiteleaf manzanita may become abundant after logging [53,75], particularly on sites that are logged and then burned [73,75]. In a giant sequoia-sugar pine-ponderosa pine forest in Tulare County, sticky whiteleaf manzanita was abundant following logging in the 1940s. Studies in the mid-1960s found incense-cedar and white fir dominated the site, with white fir replacing sticky whiteleaf manzanita successionally in the understory .Terpenes and other toxins present in in the litter of sticky whiteleaf manzanita and other chaparral shrubs may allelopathically inhibit germination of some herbaceous species. Fire sets back succession not only by removing vegetation, but also by removing the allelopathic litter that prevents germination of herbaceous species. The "postfire flower show" characteristic of early-seral burns is likely due, in part, to removal of germination-inhibiting litter of sticky whiteleaf manzanita and other sclerophyllous species .
The seeds of sticky whiteleaf manzanita are fire resistant. Fire scarifies them, breaking dormancy (see Germination), but usually doesn't kill them. The hard seed coat of sticky whiteleaf manzanita seed is relatively impervious to fire damage, and seeds stored below the soil surface are insulated from fire. Some seedling establishment may occur after even intense, high-severity pile burns [103,109,120]. Sticky whiteleaf manzanita seedlings often grow in "fire rings" around perimeters of pile burns , suggesting that seeds in the center of the pile—where fire is most severe—were killed.
Fire-caused mortality is most likely for seeds stored in duff. However, sticky whiteleaf manzanita seeds are stored at various soil depths  (see Seed banking), and enough viable seed is stored at sufficient depths to support the next generation of sticky whiteleaf manzanita. This review found no instances where sticky whiteleaf manzanita did not establish after fire on sites where it was present before fire.Postfire regeneration strategy :
Sticky whiteleaf manzanita has many chemical properties and morphological features that make it flammable. See Fuels for details.
Plant response to fire: Sticky whiteleaf manzanita establishes from soil-stored seed after fire. Most seed germinates during the first postfire growing season, after winter stratification [29,48,51,95]. With prescribed spring burning, establishment of sticky whiteleaf manzanita may not occur until postfire year 2, and it may not be as great as establishment after fall burning .
Postfire mineral soil is a favorable seedbed for sticky whiteleaf manzanita . On the Biscuit Burn Complex in southwestern Oregon, sticky whiteleaf manzanita was positively associated with mineral soil on well-drained sites with low prefire cover of deciduous species (R²=0.64) .
|Figure 4. Sticky whiteleaf manzanita seedling. Photo taken by Becky Howard on the Stanislaus National Forest, 15 months after the 2014 Rim Wildfire.|
Since its establishment and growth are favored by mineral soil and open sites (see Regeneration Processes), sticky whiteleaf manzanita establishes in large numbers and grows quickly in postfire communities where it was present before fire. Stands are often dense 3 or 4 years after wildfire . Sticky whiteleaf manzanita generally remains dense in chaparral but over time, it declines in forests (see Successional Status). After clearcutting and windrow pile burning in a mixed-conifer forest on the Challenge Experimental Forest, sticky whiteleaf manzanita increased in abundance over 5 posttreatment years  (Table 3). Nine years following a chaparral fire in Yuba County, the combined density of sticky whiteleaf manzanita and codominant deer brush was 6,523 plants/acre (16,118/ha) .
|Table 3. Abundance and growth of sticky whiteleaf manzanita after clearcutting and windrow pile burning on the Challenge Experimental Forest |
(posttreatment year 1)
|41||1,680 (100)||70 (0)||0.3 (0.1)|
(posttreatment year 5)
|65||4,467 (146)||4,183 (153)||2.4 (0.2)|
Sticky whiteleaf manzanita produces seed in 10 postfire years or less (see Seed production).
Sticky whiteleaf manzanita may occur after fire in forest and woodland communities where it was only present in the seed bank before fire. In Madera County, Mariposa manzanita was not present on a 0.2-acre (0.08 ha) plot in an interior live oak/Pacific poison-oak woodland. After removing some of the overstory interior live oaks by crushing, prescribed burning was conducted in August 1987. In November 1988, 41 Mariposa manzanita seedlings occurred on the plot .
Fire studies about sticky whiteleaf manzanita in FEIS: The Research Project Summary Plant response to prescribed burning with varying season, weather, and fuel moisture in mixed-conifer forests of California provides information on using fall and spring prescribed fires in 3 mixed-conifer forests in northern California and describes the postfire responses of sticky whiteleaf manzanita and other species common in those forests. Best seedling establishment of sticky whiteleaf manzanita occurred after fall prescribed fires on the 3 sites (Blodgett Forest Research Station, the Challenge Experimental Forest, and the Quincy Ranger District of the Plumas National Forest). On the Quincy site, sticky whiteleaf manzanita seedling density was 15 times greater after fall fires than after spring fires. The researchers suggested that fall fires provided optimum timing for sticky whiteleaf manzanita establishment because fall fires allowed for the overwinter stratification period required after fire scarification .Other studies:
Sticky whiteleaf manzanita has several morphological as well as chemical features that make it highly flammable. During drought, plants undergo branch die-back. The live branches of mature sticky whiteleaf manzanitas are usually striped with dead tissue, and entire dead branches are often intertwined with the live, striped branches . The proportion of dead:live wood increases as plants age. Old, large shrubs usually have more dead than live wood  (see Figures 2 and 5). On live branches, the surface-to-volume ratio of leaves and twigs allows for maximum air circulation, resulting in high fire intensity and complete burning of the plant . Philpot  reported the heat value of sticky whiteleaf manzanita leaves and twigs at 8,942 BTU/pound (20,799 kJ/kg).
|Figure 5. Intertwined dead branches and peeling bark of a sticky whiteleaf manzanita stand. Image by Jean Pawek.|
Moisture content of chaparral species is generally highest in winter and spring and least in late summer and early fall [24,25]. High precipitation in winter and spring is essential for maintaining high live fuel moistures . For example, near Shasta Lake on the Shasta-Trinity National Forest, late winter (March) live fuel moisture of sticky whiteleaf manzanita plants ranged from 75% to 100%  after a wet February. However, sticky whiteleaf manzanita may not have high winter moisture content at high elevations or on all sites . In Tuolumne County, live fuel moisture of shrubs collected from south-facing slopes in 1962 was highest in mid-June at 3,200 feet (980 m, ~165% moisture content) and in mid-July at 5,200 feet (1,600 m, ~135% moisture content). Moisture content dropped rapidly in August and remained around 95% throughout winter, until the next growing season .
Moisture content of sticky whiteleaf manzanita leaves declines considerably during drought. On the Sequoia National Forest, mean foliage moisture content of sticky whiteleaf manzanita in the 2nd summer of an extended drought (1975-1977) was 47.5%. The summer after the drought, it was 77.7%. Annual precipitation during the drought averaged about 12 inches (300 mm), less than half of normal (26 inches (654 mm)) .
Sticky whiteleaf manzanita grows quickly and can produce considerable biomass. Fuel loads in chaparral may be 50 tons/ acre (112 tonnes/ha), releasing 12,000 BTUs/second/foot (44,000 kJ/second/m) in winds of 6 miles (10 km)/hour, and releasing much greater levels of energy in high winds . On a ponderosa pine plantation in Applegate Valley, southwestern Oregon, accumulated biomass of sticky whiteleaf manzanita after 14 years of growth averaged 19 tons/acre (43 tonnes/ha) .
Models: Several models are available for estimating sticky whiteleaf manzanita fuel loads. Hanson and Newton  provide equations for predicting sticky whiteleaf manzanita growth in height and basal diameter, and for predicting sticky whiteleaf manzanita biomass/individual and biomass/ha. The equations are based on data collected in Applegate Valley. Hughes and others  provide equations for predicting sticky whiteleaf manzanita biomass and leaf area index based on data from southwestern Oregon and northern California.
Fuel models for Yosemite National Park estimated that at low elevations, fuel loads are greatest in mixed conifer forests; these forests have been the plant communities most affected by fire exclusion in the Park. Sticky whiteleaf manzanita is an important component of the vegetation in mixed-conifer forests and chaparral in the Park .
Masticated fuels: Mastication, either with or without follow-up prescribed fire, is a common fuel treatment in plant communities with sticky whiteleaf manzanita. Limited studies [16,21] show changes in fire severity and fuel structure after mastication. Prescribed fire reduced masticated fuels, but the fall prescribed fires sometimes caused undesired damage or mortality to overstory trees. To date (2015), studies documenting the rate of decay in masticated fuels containing sticky whiteleaf manzanita and other sclerophyllous species were not available.
Mastication followed by prescribed fire successfully reduced fuel loads in southwestern Oregon (Table 4), but fall burning top-killed or killed overstory oaks. Two Oregon white oak-Pacific madrone-ponderosa pine woodlands were treated (at China Gulch and Hukill Hollow). Both sites had chaparral understories dominated by deer brush and sticky whiteleaf manzanita. Three or 4 years after mastication, the sites were burned under prescription in spring or fall. Spring fires resulted in low-severity, patchy burns. Fall fires were of moderate to high severity, with flame residence times of 4 minutes around the bases of Oregon white oaks. Spring burns did not consume all fuels or burn all plots, while fall burns either consumed or charred all fuels and burned all plots .
|Table 4. Fuel loads on masticated units before and after prescribed fires in southwestern Oregon |
In Whiskeytown National Recreation Area, fall (November) mastication of the understory of a California black oak-knobcone pine/sticky whiteleaf manzanita community drastically changed the structure and composition of the fuel bed but did not reduce fuel loads. Standing live material was converted to dead and small-sized surface fuels, with an approximate 200% average increase in 1-hour and 1,000-hour fuels and a >300% increase in 10-hour and 100-hour fuels. Shrub canopy cover was reduced from 64% to 2% by mastication. Spring (April-May) prescribed burning was conducted on masticated and unmasticated plots. Fire severity was greater on masticated than unmasticated plots, with greater mortality of knobcone pine and greater top-kill of California black oak and canyon live oak. The authors concluded that mastication followed soon after by prescribed fire had undesirable rates of mortality and top-kill to the overstory. In the short term, mastication apparently increased fire severity, although in the long term, it may result in lowered fire severity as masticated fuels decay and compact . See the Fire Study by Bradley and others  for further details.
Mastication followed by burning resulted in good establishment of Mariposa manzanita and other chaparral species on a mule deer winter range in Madera County, with better establishment after fall fire than late winter fire. Mixed chaparral (wedgeleaf ceanothus-chaparral whitethorn-Mariposa manzanita) was masticated and burned under prescription to increase browse. Mariposa manzanita had some recruitment (<250 seedlings/acre) the year of the late winter (1st week in March) prescribed fire. More seedlings established the following spring, with Mariposa manzanita density averaging about 1,000 seedlings/acre. However, Mariposa manzanita recruitment was twice as abundant the spring after the fall prescribed fire, averaging about 2,000 seedlings/acre. On both spring and fall burns, Mariposa manzanita seedling density was considerably less than that of wedgeleaf ceanothus or chaparral whitethorn. Those shrubs also established in highest numbers after the fall fire. Continued dominance by wedgeleaf ceanothus and chaparral whitethorn was the desired outcome, since mule deer find those species more palatable than sticky whiteleaf manzanita .
Prescribed burning of masticated fuels may kill some soil-stored seed of many species in the plant community. An 18-year-old ponderosa pine plantation, planted but not grubbed after a wildfire, had a dense understory dominated by sticky whiteleaf manzanita and common manzanita. Shrub height ranged from 5 to 13 feet (1.5-4 m), with ≥100% cover. Understory biomass was estimated at 33.4 tons/acre (75 tonnes/ha). On sites where manzanita cover was continuous, mastication of the understory produced a mulch layer averaging <1 inch (2.5 cm) thick. On sites where California black oak and other hardwoods were also present in the understory, mastication produced a mulch layer averaging 2 inches (5 cm) thick. One-fourth of treated areas had mulch deeper than 3 inches. Surface fire simulations in masticated manzanita fuels suggested that burning in dense, masticated fuels deeper than 3.0 inches (7.5 cm) would heat soil to above the lethal soil temperature for many plant tissues (140 °F (60 °C)). To reduce the risk of heating soils above the lethal threshold for seeds, the authors recommended burning similar masticated sites when soil is near saturation .
Chaparral: Rundel  wrote that "fire is unquestionably the dominant environmental factor influencing chaparral vegetation". Chaparral has severe, stand-replacement fires at moderate intervals [28,64]. Mean fire-return intervals after European settlement range from 40 to 100 years , with a maximum of about 150 years . Sites generally burn at 25- to 60-year intervals, depending upon site productivity, topography, and local climate [64,81]. Some speculate that chaparral can burn at intervals as short as 10 years, although such short fire-return intervals would be unusual . Chaparral stands >90 years old may be susceptible to senescence and seed bank attrition [64,124].
There is little evidence or documentation of presettlement fire-return intervals in chaparral , but some suggest that current fire regimes of chaparral are similar to presettlement regimes . Minnich  claimed that fire regimes of California chaparral have not changed much from presettlement times despite attempts at fire exclusion. However, Keeley and others  hypothesized that presettlement fire-return intervals for chaparral probably ranged from 20 to 60 years, and that fire-free intervals longer than 90 years are outside the historical range of variability .
Historically, most chaparral fires probably occurred during late summer and fall . Minnich and others  suggested that fires were smaller before European settlement, with different-aged burns forming a mosaic on the landscape. However, by 1919, fires were burning 62,000 acres (25,000 ha), and the mosaic patterns were being replaced by large-acreage burns .
Lightning is more common at elevations above than within chaparral, so historical ignitions were usually from forest fires burning downslope. Some chaparral fires were probably ignited by lightning, and some were probably anthropogenic [81,93]. Information on how often American Indians burned chaparral is sparse [70,81,93]. Anderson  reported that to encourage good fruit crops, the Yukots, Pomo, and other Native People broadcast-sowed some of the manzanita seed they collected (see Other Uses) and burned the collection area periodically.
Chaparral fires may be patchy. Chaparral landscapes in southern California are most likely to have completely stand-replacement fires, while those in the northern Sierra Nevada may exhibit more patchiness. However, there are few studies on patterns of chaparral fires at landscape levels . On the Donald and Sylvia McLaughlin Natural Reserve in north-central California, a wildfire burned through a mosaic of chaparral communities on serpentine- and nonserpentine (sandstone)-derived soils. Serpentine sites supported a leather oak-MacNab cypress-gray pine community with sticky whiteleaf manzanita; nonserpentine sites supported a California scrub oak-wedgeleaf ceanothus-toyon community without sticky whiteleaf manzanita. Prefire canopy cover exceeded 90% in both communities. Fire severity was less and time since fire was greater on the serpentine than the nonserpentine site, and postfire shrub recruitment and biomass accumulation were slower. Time since fire averaged 73.7 years on the serpentine site and 18.6 years on the nonserpentine site .
Mixed-conifer and oak woodlands: Before European settlement, mixed-conifer forests had a regime of mostly frequent, patchy surface fires. Sticky whiteleaf manzanita may not have been as common in the understories of mixed-conifer forests as it is now, with fire exclusion, because frequent fires tend to check shrub growth  (see Successional Status). On the Sequoia National Forest, sticky whiteleaf manzanita tends to dominate the understory of mixed-conifer stands on dry slopes, while white fir tends to dominate on mesic slopes. Before 1870, fires in giant sequoia-white fir-sugar pine forests with sticky whiteleaf manzanita averaged every 9 years on dry, west-facing slopes and every 16 years on mesic, east-facing slopes . American Indians likely set some of these fires [66,93]. On the Sierra National Forest, a mixed-conifer forest in which understory Mariposa manzanita codominated with mountain misery and Sierra gooseberry had mean fire-return intervals ranging from 3.2 to 5.4 years from 1770 to 1871. The area is considered a "lightning hot spot", averaging 1 strike/1.36 years. The author suggested frequent lightning strikes accounted for the short fire-return interval .
In a mixed oak-pine community in El Dorado County (described in Plant Communities), mean fire-return intervals ranged from 2 to 18 years from1850 to 1952, averaging 7.8 years. The authors suggested that prior to the 1940s, most ignitions were likely from ranchers conducting range burning. Ponderosa pines were probably more common in the community before the area was logged in 1952 .
Using LANDSAT imagery to quantify fire regimes in Yosemite National Park, Thode and others  found fire severity in chaparral was consistently high, but fire severity in conifer and live oak (interior live oak or canyon live oak) patches within chaparral was usually moderate. Oak woodlands, in which sticky whiteleaf manzanita was less important, had fire severities in the low and moderate ranges. Fire severity ranged from low to moderate in ponderosa pine-shrub forests and was moderate in California black oak woodlands and forests. At low elevations, the live oak and ponderosa pine communities had the most acreage burned . Fire severity was based on the Relative Differenced Normalised Burn Ratio for pixels (42-219=low, 220-565=moderate, >565=high) [80,113].
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:
However, prescribed fires are not often conducted in chaparral. They become difficult to control when fire-free intervals exceed 20 years. If burned at shorter intervals, chaparral at low elevations tends to become dominated by chamise at the expense of codominants such as sticky whiteleaf manzanita. When burned at intervals of <3 years, chamise chaparral converts to annual grassland .At higher elevations, annual prescribed burning may convert chaparral to forest on sites suitable for conifers. Yearly fires prevent sticky whiteleaf manzanita seedlings from maturing and gradually reduce the seed bank, so sticky whiteleaf manzanita is eventually eradicated [43,56,88].
Palatability and nutritional value: The high content of terpenes, tannins, and lignins in leaves—combined with low nitrogen and water content—makes sticky whiteleaf manzanita browse unpalatable to herbivores [72,104]. Mule deer generally avoid it, although they consume first-year seedlings and may consume mature plants in winter if more palatable browse is unavailable [14,15,37,38]. Palatability of sticky whiteleaf manzanita is rated as low for all classes of livestock [106,115].
Sticky whiteleaf manzanita browse is low in nutrients . The protein content of manzanita leaves collected on sites across northern California ranged from 6% in December and January—when mule deer are most likely to consume leaves—to 8% in August and September. Mule deer need a minimum of 7% protein in their diet for normal maintenance . Sticky whiteleaf manzanita leaves collected near Berkeley had the lowest mean phosphorus content (0.06%) of 11 sclerophyllous species analyzed .
Cover value: Sticky whiteleaf manzanita often forms dense stands that provide good cover and nesting sites for birds and small mammals .VALUE FOR REHABILITATION OF DISTURBED SITES:
Techniques to artificially break sticky whiteleaf manzanita's seed dormancy are not completely developed. The Woody plant seed manual  provides information on propagating manzanitas from seed but states that propagation from cuttings is the easiest method of artificial regeneration for manzanitas. However, artificial regeneration may be unnecessary on burns. Where it was present before fire, natural regeneration of sticky whiteleaf manzanita will likely be sufficient afterwards (see Plant response to fire).OTHER USES:
Sticky whiteleaf manzanita may not interfere with conifer regeneration on all sites. In mixed-conifer forests near Grants Pass, Oregon, sticky whiteleaf manzanita is considered an indicator species for sites where natural conifer regeneration is "easy" after partial cutting . Based on studies on the Challenge Experimental Forest, Oliver  predicted that shrub control will have little impact on conifer growth in the long term, but shrub control may increase conifer yields if short-rotation harvesting is planned .
Annual grasses, and grasses seeded in for postfire rehabilitation, may interfere with establishment and growth of sticky whiteleaf manzanita and other chaparral species [74,121]. In northern California, grass cover over about 50% excluded establishment of Mariposa manzanita and associated ceanothus species .Sticky whiteleaf manzanita can be harvested for biofuel. See Hanson and Newton  for details.
|Common and scientific names of plants mentioned in this review. Follow the links to FEIS Species Reviews.|
|foxtail chess||Bromus madritensis|
|rattail sixweeks grass||Vulpia myuros|
|silver hairgrass||Aira caryophyllea|
|soft chess||Bromus hordeaceus|
|Brewer's oak||Quercus garryana var. breweri|
|deer brush||Ceanothus integerrimus|
|California buckeye||Aesculus californica|
|California coffeeberry||Rhamnus californica|
|California scrub oak||Quercus berberidifolia|
|chaparral whitethorn||Ceanothus leucodermis|
|coastal sage scrub oak||Quercus dumosa|
|common manzanita||Arctostaphylos manzanita|
|deer brush||Ceanothus integerrimus|
|hoary manzanita||Arctostaphylos canescens|
|greenleaf manzanita||Arctostaphylos patula|
|leather oak||Quercus durata|
|Mariposa manzanita||Arctostaphylos viscida subsp. mariposa
|mountain misery||Chamaebatia foliolosa|
|Pacific poison-oak||Toxicodendron diversilobum|
|Sierra gooseberry||Ribes roezlii|
|sticky whiteleaf manzanita||Arctostaphylos viscida (this review)|
|wedgeleaf ceanothus||Ceanothus cuneatus|
|birchleaf mountain-mahogany||Cercocarpus montanus var. glaber|
|blue oak||Quercus douglasii|
|California black oak||Quercus kelloggii|
|canyon live oak||Quercus chrysolepis|
|coast Douglas-fir||Pseudotsuga menziesii var. menziesii|
|giant sequoia||Sequoiadendron giganteum|
|gray pine||Pinus sabiniana|
|interior live oak||Quercus wislizeni|
|Jeffrey pine||Pinus jeffreyi|
|knobcone pine||Pinus attenuata|
|MacNab cypress||Hesperocyparis macnabiana|
|Oregon white oak||Quercus garryana|
|Pacific ponderosa pine||Pinus ponderosa var. ponderosa|
|sugar pine||Pinus lambertiana|
|valley oak||Quercus lobata|
|white fir||Abies concolor|
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