Holodiscus dumosus

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INTRODUCTORY


Photo by Mary Ellen (Mel) Harte, Bugwood.org

AUTHORSHIP AND CITATION:
Fryer, Janet L. 2010. Holodiscus dumosus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
HOLDUM

NRCS PLANT CODE [83]:
HODU

COMMON NAMES:
rockspirea
bush oceanspray
bush rock spirea
glandular oceanspray

TAXONOMY:
The scientific name of rockspirea is Holodiscus dumosus (Nutt.) Heller (Rosacea) [15,19,38,40,54,55,61,89,90].

The Holodiscus taxonomy is confused because rockspirea, creambush oceanspray (H. discus), and small-leaved rockspirea (H. microphyllus) are taxonomically and morphologically similar [15,54,61]. Authorities separating these 3 closely related taxa do so based on different leaf morphologies [15,54] and distributions [54]. This review follows the taxonomy of Lis (in [33]), who is authoring the Flora of North America's [23] Holodiscus chapter. In Lis's treatment, rockspirea, creambush oceanspray, and small-leaved rockspirea are treated as separate and distinct species [33]. Some systematists lump either rockspirea and creambush oceanspray [39,67,89], creambush oceanspray and small-leaved rockspirea [38], or all 3 [88] into single species.

SYNONYMS:
Holodiscus discolor (Pursh.) Maxim. var. dumosus (Nutt.) Maxim. [67]

LIFE FORM:
Shrub

DISTRIBUTION AND OCCURRENCE

SPECIES: Holodiscus dumosus
GENERAL DISTRIBUTION:
Rockspirea is native to the interior West and northern Mexico. It occurs from central Idaho south to southern Arizona and the Big Bend region of Texas and east to the edge of the plains grasslands in east-central Wyoming, Colorado, and New Mexico [5,15,55]. Its distribution continues south into the upper third of Mexico [5,67,90]. Plants Database provides a distributional map of rockspirea.

HABITAT TYPES AND PLANT COMMUNITIES:
Rockspirea grows in cold- to warm-temperate coniferous, hardwood, and shrubland communities of the Central and Southern Rocky Mountains, the Great Basin, and the Southwest [9]. It is most common in coniferous communities, particularly Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca). A survey in Zion National Park found rockspirea was most frequent in Rocky Mountain Douglas-fir and rock-crevice communities (33% and 32% frequency, respectively). It was also frequent in hanging garden and riparian hardwood communities (20% and 16% frequency) but was infrequent in interior ponderosa pine (Pinus ponderosa var. scopulorum) and mountain brush communities (≤3% frequency in each) [30].

Coniferous communities: Rockspirea is often characteristic to dominant in the understories of Rocky Mountain Douglas-fir [1,4,53], southwestern ponderosa pine (includes interior ponderosa pine and Arizona pine (P. p. var. arizonica)) [58,62,64], and mixed-conifer [69] forests and woodlands. It often dominated the shrub layer of low-elevation Rocky Mountain Douglas-fir/Gambel oak [62] and interior ponderosa pine/Gambel oak (Quercus gambelii) [66] communities of the Southwest. Kuchler describes rockspirea as a characteristic to dominant shrub of southwestern ponderosa pine-Rocky Mountain Douglas-fir forests in the southern Rocky Mountains [45], Great Basin bristlecone pine-limber pine (P. aristata-P. flexilis) [44] forests and woodlands in high elevations of the Great Basin, and southwestern ponderosa pine forests in Arizona [43].

Great Basin: In western Nevada, rockspirea grows in Rocky Mountain Douglas-fir, Great Basin bristlecone pine [44], and red fir (Abies magnifica) [39] communities. Welsh and others [89] call it "nearly ubiquitous" in coniferous and other plant communities of Utah.

Colorado: Rockspirea occurs in Colorado pinyon-juniper/soapweed yucca/blue grama (P. edulis-Juniperus spp./Yucca glauca/Bouteloua gracilis)) woodlands of western Colorado [14] and in Engelmann spruce (Picea engelmannii)-Rocky Mountain Douglas-fir and Rocky Mountain bristlecone pine (Pinus aristata) forests of west-central Colorado [1]. It is occasional in blue spruce/sprucefir fleabane (Picea glauca/Erigeron eximius) habitat types of the San Juan Mountains [17].

Arizona: Rockspirea grows in Rocky Mountain Douglas-fir [4], pine (Pinus spp.) [40], spruce (Picea spp.) [40], and white fir (A. concolor) [62] forests and woodlands of Arizona. In the Santa Teresa Mountains, it is a component of sky-island Rocky Mountain Douglas-fir and interior ponderosa pine communities [10]. In the Rincon Mountain Wilderness, rockspirea occurs in mixed-conifer forests dominated by Rocky Mountain Douglas-fir and white fir on north- and northeast-facing slopes and by southwestern white pine (P. strobiformis) and interior ponderosa pine on northwest-facing slopes. Quaking aspen (Populus tremuloides) stands are often interspersed among these coniferous forests. Southern aspects, on which rockspirea may also grow, are typically dominated by southwestern white pine and oaks, including Arizona oak (Q. arizonica), Emory oak (Q. emoryi), and silverleaf oak (Q. hypoleucoides) [4]. On the Gunnison National Forest, rockspirea had 2% to 6% average cover in Rocky Mountain Douglas-fir habitat types [41]. It is characteristic in Engelmann spruce/Rocky Mountain maple (Acer glabrum) habitat types of the Chiricahua Mountains [62].

New Mexico: In the White Mountains, rockspirea is important in interior ponderosa pine-Gambel oak/New Mexico locust (Robinia neomexicana) communities [26,27]. In the Rio Grande Wild and Scenic River Recreation Area, big sagebrush, broom snakeweed (Gutierrezia sarothrae), and rockspirea codominate the understory of a canyon-bench interior ponderosa pine woodland [76]. Rockspirea is occasional in blue spruce/sprucefir fleabane habitat types of the Sangre de Cristo Mountains [17].

Mexico: In the Sierra Occidentale of Nuevo Leon, rockspirea occurs in subalpine border pinyon (P. culminicola) scrub [5].

Riparian hardwood and other hardwood communities: Among hardwood communities, rockspirea is reported most often in riparian communities but is also common in mesic montane and canyon-bottom communities. It occurs in riparian quaking aspen/willow (Salix spp.) communities of northeastern Nevada [12] and in quaking aspen woodlands of Rocky Mountain National Park, Colorado [11]. On the Coronado National Forest, Arizona, rockspirea grows in Arizona sycamore-velvet ash/mule fat (Platanus wrightii-Fraxinus velutina/Baccharis salicifolia) riparian communities [14]. In southwestern New Mexico, it grows along the Mimbres River in cottonwood/Goodding willow (Populus spp./Salix gooddingii) woodlands communities below about 7,450 feet (2,270 m). Fremont cottonwood (P. fremontii), narrowleaf cottonwood (P. angustifolia), and/or lanceleaf cottonwood (P. × acuminata) are overstory dominants [7]. Rockspirea is common in canyon bottomlands of Canyon de Chelly National Monument, Arizona. Overstory species in these canyon-bottomland communities include boxelder (Acer negundo) and shrub live oak (Quercus turbinella) [29].

Shrublands: Rockspirea grows in big sagebrush (Artemisia tridentata), woody draw, and mountain shrub communities. In western and central Nevada, it is characteristic of upper-elevation big sagebrush-grass communities that occur above the pinyon-juniper (Pinus-Juniperus spp.) zone. This big sagebrush zone may extend from 5,000 to over 9,800 feet (1,500-3,000 m) elevation [6]. In northeastern Nevada, rockspirea is an important component of big sagebrush communities in and just upland from riparian zones [57]. In Colorado it is generally rare east of the Front Range, but it is a characteristic component of mixed-shrub associations that occur in woody draws of the eastern foothills [85]. On plateaus east of Pike's Peak, rockspirea is a characteristic species of skunkbush sumac (Rhus trilobata)-Gambel oak foothill thickets within the plains grassland ecosystem [72]. In studies across Utah, rockspirea was a minor species in curlleaf mountain-mahogany (Cercocarpus ledifolius) communities [16]. In the Organ Mountains of New Mexico, it occurred in hairy mountain-mahogany/yucca-canyon sage (Cercocarpus breviflorus/Yucca spp.-Salvia ramosissima) communities, and it had low cover (2%) but high frequency (51%) in Gambel oak/snowberry (Symphoricarpos spp.) associations [18]. On the summit of Mt Livermore in western Texas, it is a component of a bald-hill formation of scrubby shrubs and sparse herbs. Just below the summit, rockspirea codominates on talus slopes with Gambel oak [34].

Vegetation classifications describing plant communities in which rockspirea is dominant are listed below.

Arizona New Mexico

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Holodiscus dumosus

Photo by Dave Powell, USDA Forest Service, Bugwood.org
GENERAL BOTANICAL CHARACTERISTICS:
Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [15,19,40,54,55,89,90]).

Form and woody parts: Rockspirea is a deciduous [15,87] shrub from 1.6 to 20 feet (0.5-6.2 m) tall [15,39,89]. It is generally shorter than creambush oceanspray [75]. Its form is spreading [32,54]; mature plants may reach 5 to 10 feet (1.5-3 m) across [79]. Main branches arise from the root crown [79]. Terminal branches may be weakly spinescent [15]. Bark is shreddy [55]. The roots are dense and spreading [75,79]. Its roots reach at least 12 inches (30 cm) below ground [83].

Leaves and reproductive organs: The leaves occur mainly on spur branches; they range from 0.4 to 0.9 inch (1-2.3 cm) long and 0.2 to 0.5 inch (0.4-1.2 cm) wide [15,87]. Rockspirea leaves and inflorescences are smaller than those of creambush oceanspray [75]. Its inflorescence is a panicle or a raceme [15,40,90] from 2 to 8 inches (5-20 cm) long [87]. The flowers are small [32,90], about 2 mm across [55,87]. The fruit is an achene [15,19,54,89] from 1.4 to 2.2 mm long [15], bearing 1 seed [15,67].

Life span and physiology: Life span of rockspirea is reported as "moderate" [79,83]. Rockspirea is drought tolerant [79,83].

Raunkiaer [68] life form:
Phanerophyte

SEASONAL DEVELOPMENT:
The floral buds of rockspirea swell in early spring, but flowering does not generally occur until summer. Fruits ripen in late summer and are dispersed through November (review by [74]).

Flowering times of rockspirea across its distribution
Area Period
Arizona, Tsegi Canyon June-July [35]
New Mexico June-September [55]
Nevada June-August [39]
Texas June-September [67]
Great Basin June-August [61]
Intermountain region late June-August [15]
Mexico July-September [90]

REGENERATION PROCESSES:
Rockspirea sprouts vegetatively [83] and establishes from seed [25,65]. Further information on rockspirea regeneration is needed.

Vegetative regeneration: Rockspirea sprouts [83] from the root crown [8]. Its sprouting ability is not well documented [75]. Since creambush oceanspray and rockspirea are closely related (see Taxonomy) and sprouting is the primary method of regeneration for creambush oceanspray [56,78], sprouting it is likely rockspirea's primary method of regeneration as well.

Pollination and breeding system: Rockspirea flowers are perfect [73,89]. They are pollinated by insects [73].

Seed production: Kearney and others [40] describe rockspirea's flower production as "ample" [40].

Seed dispersal: Wind disperses rockspirea seeds [8,75].

Seed banking: Rockspirea probably maintains a soil seed bank [75], although this was not documented as of 2010. Creambush oceanspray establishes from soil-stored seed [81] occasionally; rockspirea likely establishes from seed as well.

Germination: Seed viability may be low in rockspirea. One study found seed soundness averaged 7% for rockspirea (King 1947 cited in [75]). Seeds are dormant and probably require overwinter stratification in the field. Stratification for 18 weeks at 41 °F (5 °C) broke rockspirea seed dormancy in the greenhouse [75]. Shaw and others [73,75] speculate that heat from fire may break dormancy of rockspirea seed, although this has not been documented.

Seedling establishment and plant growth: On the Wasatch Plateau in central Utah, Plummer [65] found that rockspirea established from planted seed spread as the artificial regeneration matured and produced its own seed. Rockspirea seedlings generally grow slowly [74].

SITE CHARACTERISTICS:
Rockspirea prefers sites with features that ameliorate the arid conditions that prevail across its distribution.

Soils: Rockspirea is most common on medium-textured soils [79] but also grows in coarse soils. It prefers clays, clay loams [65], and loams [76] but is reported on sandy soils in Tsegi Canyon, northeastern Arizona [35]. On the Lincoln National Forest, rockspirea grows on alluvial deposits and on sideslopes with colluvial parent materials [2]. According to fact sheets, soils supporting rockspirea are neutral to alkaline [47,73], and rockspirea tolerates carbonate and low-fertility soils [83].

Parent materials: Rockspirea is common on soils of volcanic origin [47,60]. It grows in sandstone-derived soils in Zion National park, Utah [31]. Rockspirea frequently grows in rock and rock fragments [89]. It grows in rock crevices in Zion National Park [30]. In the Rio Grande Wild and Scenic River Recreation Area, it grows on rock outcrops and talus slopes [76]. On the Gila National Forest, corkbark fir/rockspirea and Rocky Mountain Douglas-fir/rockspirea habitat types occur in scree. White fir/rockspirea habitat types occur on scree in the San Mateo Mountains and on the Cibola National Forest [22].

Moisture: Rockspirea occupies regions that are generally drier than the habitats of creambush oceanspray [21]. However, it is most common on relatively mesic sites within desert and other arid ecosystems. Slopes supporting rockspirea are generally well drained (review by [79]).

Rockspirea's occurrence on relatively mesic sites is well documented. It was rare in an 1898 survey of the Red Desert of southern Wyoming, occurring only below permanent winter snowdrifts [63]. Rockspirea is dominant in interior ponderosa pine-Gambel oak communities above the San Augustin Plains of New Mexico, but it does not occur in lower-elevation Colorado pinyon-alligator juniper (Juniperus deppeana) associations. The author attributed this to higher soil moisture levels in the interior ponderosa pine association [66]. East of the Front Range of Colorado, rockspirea grows in woody draws that are more mesic than surrounding plains grasslands [85]. Engelmann spruce (Picea engelmannii)/Rocky Mountain maple habitat types of the Chiricahua Mountains, in which rockspirea is characteristic, occur on cold, moist to mesic slopes at high elevations [62]. The Rocky Mountain Douglas-fir/Rocky Mountain maple habitat type of south-central Arizona also occurs on cool, moist slopes [62].

Topography and aspect: Rockspirea is common in canyons and on rocky ledges, cliffs, plateaus, and escarpments [19,39,61,67,88,89]. In the Rio Grande Wild and Scenic River Recreation Area, it grows on very steep to vertical slopes [76]. Rockspirea frequently grows on cliffs in Arizona; it is especially common in the Grand Canyon [40]. It grows in canyon bottomlands of Canyon de Chelly National Monument, Arizona [29] and on canyon slopes in the Rio Grande Wild and Scenic River Recreation Area [76].

Rockspirea favors slopes that provide protection from extreme weather, with aspect often varying with elevation. In Colorado and New Mexico it occurs in blue spruce habitat types, which occur on slopes that are protected from extreme sun and wind [17]. In Zion National Park, rockspirea was more common in rock crevices receiving low amounts of direct sunlight than in crevices receiving moderate or high amounts of direct sunlight (x =2.3, 0.2, or 0.5 plants/m of crevice, respectively) [31]. It is most frequent on north-facing slopes at either low elevations or in its southernmost distribution. Aspect is generally southerly at high elevations [79]. In ponderosa pine-Douglas-fir/Gambel oak communities of the White Mountains, New Mexico, rockspirea occurs on north- and east-facing slopes [27]. On the Lincoln National Forest, the rockspirea phases of white fir/Rocky Mountain maple and Douglas-fir/Gambel oak habitat types are most common in cool drainages at low elevations and on ridges and knolls at high elevations. These phases occur mostly on north- and northwest-facing slopes but also on westerly slopes if the slopes are cool and wet [2]. Rockspirea is restricted to north-facing volcanic cliffs in the Sierra Juarez of Baja California Norte [90]. On Cerro la Parra, a volcanic mountain in the Sierra Juarez, rockspirea was rare and found only on north-facing slopes [60]. In hairy mountain-mahogany associations of the Organ Mountains, New Mexico, rockspirea occurs on west-facing slopes at intermediate elevations (6,700-7,600 feet (2,000-2,300 m)) and on south-facing slopes above 7,600 feet (2,300 m) [18]. On the Gila National Forest, a Rocky Mountain Douglas-fir/rockspirea habitat type occurs on southerly slopes at 9,600 feet (2,926 m) elevation, and a corkbark fir/rockspirea habitat type occurs on a south-facing, 54% slope at 9,900 feet (3,018 m) elevation. On the Gila National Forest, a corkbark fir/rockspirea habitat type occurs on a south-facing, 54% slope at 9,900 feet (3,018 m) elevation. In New Mexico, white fir/rockspirea habitat types of the San Mateo Mountains and the Cibola National Forest occur on south-facing, 50% to 60% slopes from 9,200 to 9,240 feet (2,804-2,816 m) elevation [22].

Elevation: Rockspirea is mostly restricted to middle and upper elevations in the Southwest but grows on relatively cool sites at low elevations (for example, [2,18]).

Elevational ranges of rockspirea across its distribution
Area Range (feet)
Arizona 5,500-10,000 [40]
Colorado 5,500-10,000 [32]
Nevada 3,000-9,000 [39]
New Mexico 6,500-10,000 [55]
White Mountains, New Mexico 7,500-8,700 [5,27]
Texas 5,000-10,500 [67,87]
Utah 4,200-11,600 [89]
Great Basin 4,500-11,000 [61]
Intermountain region 4,600-9,800 [15]
Nuevo Leon, Mexico 11,300-11,900 [5]

SUCCESSIONAL STATUS:
Rockspirea occurs in all stages of succession as long as the canopy is open (review by [79]) or only partially closed [47]. It grows on both seral shrubfields and in climax forest habitat types [73]. In successional stages of the rockspirea phase of white fir/Gambel oak habitat types on the Lincoln National Forest, rockspirea and other shrubs dominate for "a few years" after stand-replacement fire [59]. After a stand-replacement fire in ponderosa pine-Douglas-fir/Gambel oak forests in the White Mountains of New Mexico, rockspirea and other shrubs became important around postfire year 2. Conifers become important from postfire years 15 to 20, reclaiming the overstory in postfire year 50 or beyond [27]. See Plant response to fire for further information on this topic.

FIRE EFFECTS AND MANAGEMENT

SPECIES: Holodiscus dumosus

 

 

 

FIRE EFFECTS:

Rockspirea growing in a slowly regenerating mixed-conifer forest 25 years after the 1977 Mt Elden Wildfire. Viewed from the Sunset Trail on the Coconino NF, with Mt Elden in background. Photograph © Lee Dittmann; used with permission from www.nazflora.org.

Immediate fire effect on plant: Fire top-kills rockspirea [8].

Postfire regeneration strategy [77]:
Tall shrub, adventitious buds and/or a sprouting root crown
Small shrub, adventitious buds and/or a sprouting root crown
Ground residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Secondary colonizer (on- or off-site seed sources)

Fire adaptations and plant response to fire:
Fire adaptations: Rockspirea sprouts from the root crown [8] and establishes from seed [25] after fire. Seed source origins (seed bank, lightly burned patches, or seed transported from off site) were not documented as of 2010. Shaw and others [73,75] speculate that heat from fire can stimulate germination, but experimental evidence of this was lacking as of 2010.

Plant response to fire: In a review, Bradley and others [8] noted that postfire regeneration is poorly documented for rockspirea, but that rockspirea establishes after fire by sprouting from the root crown and likely from off-site, wind-dispersed seed as well. Further research is needed on the fire ecology of rockspirea. Postfire responses are better documented for creambush oceanspray, to which rockspirea is closely related. Many aspects of the fire ecology of creambush oceanspray that are reviewed in FEIS are likely applicable to rockspirea as well.

Succession may proceed slowly in conifer/rockspirea communities of the Southwest. Rockspirea established from seed following the 8,000-acre (3,000 ha) Saddle Mountain Fire on the Kaibab National Forest, Arizona. It showed 0.03% cover and 0.01% frequency in postfire year 45. Rockspirea established primarily in severely burned areas; the author suggested the seed was transported from parent plants on unburned or lightly burned areas [25].

In the White Mountains of New Mexico, rockspirea was present in Gambel oak-ponderosa pine and Gambel oak-Douglas-fir communities in postfire years 21 and 27, respectively. Its importance value was higher in Gambel oak-ponderosa pine than in Gambel oak-Douglas-fir communities. Both sites were on north aspects [27].

FUELS AND FIRE REGIMES: Fuels: As of 2010, little published information was available on rockspirea's contribution to fuel loads. Fuel loads in plant communities where rockspirea is important likely vary with site moisture regime, aspect, and elevation.

Alexander and others [2] found that the rockspirea phase of white fir/Gambel oak habitat types on the Lincoln National Forest generally had a well-developed litter layer. In west-central New Mexico, rockspirea abundance was low in an interior ponderosa pine-Gambel oak/rockspirea/mountain muhly community. Stand structure was open, with a poorly developed understory and ground layer. Other common understory species provided <2% total cover; herbaceous plants had ≤24% total cover [66].

Cover, density, and frequency of rockspirea in the understory of a ponderosa pine-Gambel oak/rockspirea/mountain muhly community in New Mexico [66]
Relative foliage cover (%) 1.3
Understory cover (%) 0.1
Foliage/100 feet²/acre² 21.8
Relative density (%) 0.9
Plants/acre 1.8
Frequency (%) 1.7
Relative frequency (%) 1.0
Seedling frequency (%) 0

Differences in shrub biomass between cattle-grazed and ungrazed plots were not significant in a riparian quaking aspen/willow (Salix spp.)/currant (Ribes spp.)-western snowberry community in northeastern Nevada. Rockspirea was an important component of the shrub layer. Biomass of grazed and ungrazed shrub understories is shown below. The authors also provide biomass measures for overstory, willow, and herbaceous components of the community [12].

Shrub biomass (g/m²) in a northeastern Nevada quaking aspen/willow riparian community [12]
 
Grazed
Ungrazed
Live Dead Total Live Dead Total
Foliage 18.6 negligible 18.6 13.8 negligible 13.8
Wood 24.8 11.7 36.5 23.4 3.1 26.5
Total 43.4 11.7 55.1 37.2 3.1 40.3

Fire regimes: The coniferous and hardwood communities in which rockspirea occurs historically experienced mostly frequent, low- to mixed-severity fires. Fire-return intervals tend to lengthen from dry, low-elevation sites to cool, high-elevation sites [80]—where rockspirea is most common (see Site Characteristics)—but this trend may be weak. In fire studies across Arizona and New Mexico, Swetnam and others [80] found a wide range of fire frequencies within and among coniferous forests. Generally, southwestern ponderosa pine communities experienced fire at 2- to 10-year intervals, while higher-elevation, mixed-conifer communities experienced fire at 5- to 15-year intervals [80]. Southwestern shrubland ecosystems usually experience fire at <100-year intervals. Mountain shrub ecosystems tend to have shorter average fire-return intervals (20-50 years) [49] than Arizona chaparral (50-100 years) [48].

In the Rincon Mountain Wilderness of Arizona, Baisan and Swetnam [4] found that mixed-conifer forests of Rocky Mountain Douglas-fir-white fir and southwestern white pine-interior ponderosa pine had a history mostly of large (>500 acres (200 ha)) surface fires that occurred from May to July. The mean fire-return interval from 1748 to 1886 was 9.9 years, with a range of 3 to 19 years. Since fire exclusion, fires have become more infrequent and severe [4,10].

DeVelice and others [17] report "heavy disturbance" by fire and grazing is widespread in blue spruce/sprucefir fleabane habitat types of the San Juan and Sangre de Cristo mountains.

Jones [37] reports that fires were historically uncommon in the rockspirea phase of white fir/Gambel oak habitat types on the Lincoln National Forest. Conditions in these forests are generally wetter than other mixed-conifer types, and fires are mostly of low or mixed severity [37].

See the Fire Regime Table and FEIS reviews of interior ponderosa pine, Arizona pine, Rocky Mountain Douglas-fir, Great Basin bristlecone pine, Rocky Mountain bristlecone pine, white fir, and corkbark fir for further information on fire regimes of vegetation communities in which rockspirea may occur.

FIRE MANAGEMENT CONSIDERATIONS:
Rockspirea and other sprouting shrubs may facilitate postfire establishment of conifers. On the Lincoln National Forest, New Mexico, survivorship of Douglas-fir seedlings was assessed 1 year after planting on a 22-year-old burn. Precipitation was below normal the year after planting, and soil moisture content was near the permanent wilting point by the end of June. Rockspirea, Rocky Mountain maple, and honeysuckle (Lonicera spp.) dominated north-facing slopes. On those slopes, Douglas-fir seedlings growing under or next to shrubs had higher survivorship than seedlings in the open, and Douglas-fir seedling survivorship increased with shrub density. This trend was also true for other aspects. Across aspects, Douglas-fir seedling survivorship was 79% with shrub shade and 35% in the open [13].

To date (2010), information of rockspirea's response to fire was too scarce to make recommendations on managing rockspirea with fire. Based on limited information, rockspirea is likely to survive and thrive after low- to moderate-severity fires that create or maintain an open stand structure.

MANAGEMENT CONSIDERATIONS

SPECIES: Holodiscus dumosus
FEDERAL LEGAL STATUS:
None

OTHER STATUS:
Information on state- and province-level protection status of plants in the United States and Canada is available at NatureServe.

IMPORTANCE TO WILDLIFE AND LIVESTOCK:
Rockspirea typically provides limited browse for wild ungulates. It is common on the summer ranges of big game species [21,73], although its habit of growing on steep slopes and cliffs (see Topography and aspect) makes it inaccessible on many sites [73]. Mule deer browse it (reviews by [46,75]); their use is generally moderate in fall and light in other seasons (review by [75]). A study on a winter rangeland in Sawatch Range of central Colorado found mountain goat use of rockspirea browse varied across 2 years. Frequency of use was 58% in 1978 and 5% in 1979, when snow pack was greater than in 1978 and rockspirea less available. However, mountain goat use in both years was high, given that rockspirea had 2% relative shrub density in 1978 and trace availability in 1979 [1]. In southern Colorado rockspirea provided trace amounts of forage to bighorn sheep in spring and 10% of the total diet in summer. It was not used in fall or winter [82]. Elk browsed rockspirea sprouts "severely" in postfire years 6 to 15 after the La Mesa Fire in Bandelier National Monument, New Mexico [3].

Smaller mammals also eat rockspirea. Lagomorphs browse it (reviews by [74,75]). Rockspirea clippings were found in bushy-tailed woodrat middens in Gunnsion County, Colorado [24]. Rockspirea has also been collected in ancient woodrat middens [36].

Plant communities where rockspirea is common to dominant provide habitat for a variety of wildlife species. In the Rio Grande Wild and Scenic River Recreation Area, interior ponderosa pine/big sagebrush-broom snakeweed-rockspirea woodlands provide breeding habitat for at least 26 passerine bird species. Total passerine population density on study grids in these woodlands was 168 breeding pairs/40 ha [76]. Big sagebrush communities in and near riparian zones near Wells, Nevada, provide habitat for small mammals. Rockspirea is an important component of this vegetation [57]. Conifer/rockspirea scree habitat types of Arizona and New Mexico also provide habitat for small mammals [22,53]. Mixed-conifer/mixed-shrub forests of the Sacramento Mountains, in which rockspirea is important to dominant, provide habitat for the Sacramento Mountain salamander [71], a federally listed Species of Concern [84].

Palatability and/or nutritional value: Although common and browsed frequently on some sites, rockspirea is not as palatable as many associated browse species ([21,73,74], review by [75]). Ungulates may make little use of rockspirea if more palatable shrubs are available [21,73].

Cover value: No information is available on this topic.

VALUE FOR REHABILITATION OF DISTURBED SITES:
Rockspirea has good potential for Burned Area Recovery and other restoration plantings (review by [75]), although to date (2010), its use in Burned Rea Recovery planting had not been documented. It is recommended for planting on dry sites, including those that are rocky and/or unstable (reviews by [73,74]), and has been used in highway, riparian, windbreak, wildlife, and erosion-control plantings (review by [74]).

Rockspirea is propagated from seeds [47,83,83,87], layering [87] or cuttings [47,83,87]. On the Wasatch Plateau of central Utah, Plummer [65] found rockspirea established and spread from planted seed. In relation to 19 other woody species, he rated its ability to establish as "medium" and its growth rate and ability to spread from seed as "good". Planting sites were ≥9,500 feet (2,900 m) in elevation [65].

As of 2010, restoration use of rockspirea was hindered by lack of commercially available seed [73,75,79,83]. Shaw and others [74] provide information on propagating rockspirea from cuttings or seed collected locally.

OTHER USES:
Rockspirea is planted as an ornamental [73,75].

Information on the traditional uses of rockspirea is scant. Native Americans of the Great Basin ate the seeds, and pioneers made nails from the wood [73,74]. The Navajo used a decoction of the leaves to treat influenza [86]. The Tewa ate the fruits [87].

OTHER MANAGEMENT CONSIDERATIONS:
Grazing: Rockspirea is not usually overbrowsed due to its relative unpalatability and habit of growing in often inaccessible places [73]. In riparian areas used as livestock rangelands, it may be ignored at the expense of grasses. Shrubs, including rockspirea, showed no significant differences in biomass between cattle-grazed and ungrazed plots in a quaking aspen/willow riparian community in northeastern Nevada. Grasses were abundant in the groundlayer vegetation, and cattle preferred the grasses to the shrubs [12].

Because they retain heat and snow melts off from them early, conifer/rockspirea scree habitat types of Arizona and New Mexico are important sites for groundwater recharge [22].

APPENDIX: FIRE REGIME TABLE

SPECIES: Holodiscus dumosus
The following table provides fire regime information that may be relevant to rockspirea habitats. Follow the links in the table to documents that provide more detailed information on these fire regimes.

Fire regime information on vegetation communities in which rockspirea may occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models [51], 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.
Southwest Great Basin Northern and Central Rockies
Southwest
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Southwest Grassland
Montane and subalpine grasslands with shrubs or trees Replacement 30% 70 10 100
Surface or low 70% 30    
Southwest Shrubland
Southwestern shrub steppe Replacement 72% 14 8 15
Mixed 13% 75 70 80
Surface or low 15% 69 60 100
Southwestern shrub steppe with trees Replacement 52% 17 10 25
Mixed 22% 40 25 50
Surface or low 25% 35 25 100
Low sagebrush shrubland Replacement 100% 125 60 150
Interior Arizona chaparral Replacement 100% 125 60 150
Mountain sagebrush (cool sage) Replacement 75% 100    
Mixed 25% 300    
Gambel oak Replacement 75% 50    
Mixed 25% 150    
Mountain-mahogany shrubland Replacement 73% 75    
Mixed 27% 200    
Southwest Woodland
Madrean oak-conifer woodland Replacement 16% 65 25  
Mixed 8% 140 5  
Surface or low 76% 14 1 20
Ponderosa pine/grassland (Southwest) Replacement 3% 300    
Surface or low 97% 10    
Bristlecone-limber pine (Southwest) Replacement 67% 500    
Surface or low 33% >1,000    
Southwest Forested
Riparian forest with conifers Replacement 100% 435 300 550
Riparian deciduous woodland Replacement 50% 110 15 200
Mixed 20% 275 25  
Surface or low 30% 180 10  
Ponderosa pine-Gambel oak (southern Rockies and Southwest) Replacement 8% 300    
Surface or low 92% 25 10 30
Ponderosa pine-Douglas-fir (southern Rockies) Replacement 15% 460    
Mixed 43% 160    
Surface or low 43% 160    
Southwest mixed conifer (warm, dry with aspen) Replacement 7% 300    
Mixed 13% 150 80 200
Surface or low 80% 25 2 70
Southwest mixed conifer (cool, moist with aspen) Replacement 29% 200 80 200
Mixed 35% 165 35  
Surface or low 36% 160 10  
Aspen with spruce-fir Replacement 38% 75 40 90
Mixed 38% 75 40  
Surface or low 23% 125 30 250
Stable aspen without conifers Replacement 81% 150 50 300
Surface or low 19% 650 600 >1,000
Lodgepole pine (Central Rocky Mountains, infrequent fire) Replacement 82% 300 250 500
Surface or low 18% >1,000 >1,000 >1,000
Spruce-fir Replacement 96% 210 150  
Mixed 4% >1,000 35 >1,000
Great Basin
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Great Basin Grassland
Mountain meadow (mesic to dry) Replacement 66% 31 15 45
Mixed 34% 59 30 90
Great Basin Shrubland
Basin big sagebrush Replacement 80% 50 10 100
Mixed 20% 200 50 300
Wyoming big sagebrush semidesert Replacement 86% 200 30 200
Mixed 9% >1,000 20 >1,000
Surface or low 5% >1,000 20 >1,000
Wyoming big sagebrush semidesert with trees Replacement 84% 137 30 200
Mixed 11% >1,000 20 >1,000
Surface or low 5% >1,000 20 >1,000
Wyoming sagebrush steppe Replacement 89% 92 30 120
Mixed 11% 714 120  
Interior Arizona chaparral Replacement 88% 46 25 100
Mixed 12% 350    
Mountain big sagebrush Replacement 100% 48 15 100
Mountain big sagebrush with conifers Replacement 100% 49 15 100
Mountain sagebrush (cool sage) Replacement 75% 100    
Mixed 25% 300    
Montane chaparral Replacement 37% 93    
Mixed 63% 54    
Gambel oak Replacement 75% 50    
Mixed 25% 150    
Mountain shrubland with trees Replacement 22% 105 100 200
Mixed 78% 29 25 100
Curlleaf mountain-mahogany Replacement 31% 250 100 500
Mixed 37% 212 50  
Surface or low 31% 250 50  
Great Basin Woodland
Ponderosa pine Replacement 5% 200    
Mixed 17% 60    
Surface or low 78% 13    
Great Basin Forested
Interior ponderosa pine Replacement 5% 161   800
Mixed 10% 80 50 80
Surface or low 86% 9 8 10
Ponderosa pine-Douglas-fir Replacement 10% 250   >1,000
Mixed 51% 50 50 130
Surface or low 39% 65 15  
Great Basin Douglas-fir (dry) Replacement 12% 90   600
Mixed 14% 76 45  
Surface or low 75% 14 10 50
Aspen with conifer (low to midelevation) Replacement 53% 61 20  
Mixed 24% 137 10  
Surface or low 23% 143 10  
Douglas-fir (warm mesic interior) Replacement 28% 170 80 400
Mixed 72% 65 50 250
Aspen with conifer (high elevation) Replacement 47% 76 40  
Mixed 18% 196 10  
Surface or low 35% 100 10  
Stable aspen-cottonwood, no conifers Replacement 31% 96 50 300
Surface or low 69% 44 20 60
Spruce-fir-pine (subalpine) Replacement 98% 217 75 300
Mixed 2% >1,000    
Aspen with spruce-fir Replacement 38% 75 40 90
Mixed 38% 75 40  
Surface or low 23% 125 30 250
Stable aspen without conifers Replacement 81% 150 50 300
Surface or low 19% 650 600 >1,000
Northern and Central Rockies
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northern and Central Rockies Shrubland
Riparian (Wyoming)
Mixed 100% 100 25 500
Wyoming big sagebrush Replacement 63% 145 80 240
Mixed 37% 250    
Basin big sagebrush Replacement 60% 100 10 150
Mixed 40% 150    
Mountain shrub, nonsagebrush Replacement 80% 100 20 150
Mixed 20% 400    
Mountain big sagebrush steppe and shrubland Replacement 100% 70 30 200
Northern and Central Rockies Forested
Ponderosa pine (Northern and Central Rockies) Replacement 4% 300 100 >1,000
Mixed 19% 60 50 200
Surface or low 77% 15 3 30
Ponderosa pine-Douglas-fir Replacement 10% 250   >1,000
Mixed 51% 50 50 130
Surface or low 39% 65 15  
Douglas-fir (xeric interior) Replacement 12% 165 100 300
Mixed 19% 100 30 100
Surface or low 69% 28 15 40
Douglas-fir (warm mesic interior) Replacement 28% 170 80 400
Mixed 72% 65 50 250
Douglas-fir (cold) Replacement 31% 145 75 250
Mixed 69% 65 35 150
Persistent lodgepole pine Replacement 89% 450 300 600
Mixed 11% >1,000    
Lower subalpine lodgepole pine Replacement 73% 170 50 200
Mixed 27% 450 40 500
Lower subalpine (Wyoming and Central Rockies) Replacement 100% 175 30 300
Upper subalpine spruce-fir (Central Rockies) Replacement 100% 300 100 600
*Fire Severities
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 [28,50].

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