• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Grand fir is a native tree. It characteristically has a wide crown, although there is considerable variation in crown width and continuity [14,57]. Heights of mature trees range from 140 to 200 feet (43-61 m) along the coast and from 131 to 164 feet (40-50 m) inland [71,104]. The bole of mature trees may reach 79 inches dbh (200 cm) on the Washington coast but usually ranges from 20 to 40 inches dbh (51-102 cm) [71]. Bark is thin on young trees (mean=0.9 cm for a 20-cm diameter tree) and moderately thick at maturity (m=1.7 cm for a 40-cm diameter tree) [14,144,169]. Finch [64] projected that the bark of a grand fir is 4.3% of the tree's dbh. (For comparison, western white pine and western larch are 1.8 and 7.4% of tree dbh, respectively).

Grand fir has a well-developed taproot [14,103,124,134]. On dry sites the taproot grows to moderate depths while on moist sites shallow lateral roots prevail, and the taproot may be absent [71]. Depth of horizontal roots is moderate compared to associated conifers [103,124,134].

Several morphological characteristics of grand fir lend to its relative flammability. Branching habit is low and dense; stands tend to be dense as well [169]. The foliage has a higher surface-to-volume ratio than that of associated conifers, and the needles are retained longer on the tree (m=7 years) [112]. On the Priest River Experimental Forest in northern Idaho, foliage comprised a greater proportion of total crown weight in grand fir than in 8 associated conifer species. Biomass allocation to smaller-diameter branchwood (< 2 inches (5 cm)) relative to larger-diameter branchwood was also greater in grand fir than most associated conifers [57].

Older grand fir support pervasive rotting fungi but frequently reach 250 years of age and occasionally exceed 300 years [14,71]. Camp [34] found that in the Cascade Range of Washington, grand fir in 21 late-successional stands ranged from 15 to 256 years of age, with a mean age of 83 years.

Grand fir is moderately drought tolerant [34].

RAUNKIAER [147] LIFE FORM:

Phanerophyte

REGENERATION PROCESSES:

Cones: Cone and seed production begins at 20 to 50 years of age, and cone productivity increases with age [54,174,183]. In a good year, an average grand fir tree produces over 40 cones [71]. A year of heavy cone production is typically followed by several years of light production [73,158,174,185,179]. Pollen and ovulate cones begin development during the summer and go through a period of winter dormancy before pollination, fertilization, and seed production the 2nd spring and summer [165]. Hard frosts may inhibit cone development [71].

Seeds: Trees in Oregon and Washington may produce over 200 seeds per cone [74]. The number of seeds produced annually on inland sites ranges from 12,800 per acre (31,600/ha) to 23,500 per acre (58,100/ha) [71]. The winged seeds are of medium weight compared to other conifers and are wind-dispersed a few hundred feet from the parent [14,183]. Over 4 years (1974-1977), grand fir seed rain in central Oregon ranged from 810 to 60,718 seeds per acre (2025-151,795/ha) per year; sound seed ranged from 4.5 to 33.3% [158]. Seeds stratify over winter and are not viable beyond the 1st spring [71,123,148,183]. Germination is extremely variable but is seldom over 50% [14,71,54]. Li and others [126] found that in collections from coastal British Columbia, light increased germination rates in unstratified seed (light/dark germination= 89/80%) but had no significant effect on germination rates of stratified seed (92/93%, p=0.05) [71].

Seedling establishment: Despite the perception of grand fir as a primarily late-successional species, it shows good establishment on recently disturbed sites [10,78], and mineral soil is the most favorable seedbed [78,158]. Grand fir also establishes in light to moderate understory shade and in small openings in mature forests [10]. Uneven-aged grand fir establishment may occur over an "extended period of years" [87].

Over 30% of grand fir seedlings die during the 1st year, and an additional 10% die their 2nd year. Biotic agents and drought usually cause early losses. Initial seedling root penetration is deep on sites exposed to full sunlight so that seedlings are relatively resistant to drought. However, on shaded sites root penetration is slow, and drought is the major cause of seedling mortality [71,45]. East of the Cascade crest, water deficits are seldom critical past the seedling stage [103,198].

Grand fir has shown good establishment after silvicultural treatments. After shelterwood cutting in grand fir-Shasta red fir in central Oregon, seedling establishment of both firs was best on mineral soil (created by bulldozing). Seedling density decreased as litter and slash depth increased [158]. In central Idaho, grand fir showed better seedling establishment than 5 associated conifers on logged sites, establishing on clearcuts or shelterwood cuts within an average of 7 years (range=0-30 yrs). It was less successful than most conifer associates on broadcast burned sites, but still showed 33% frequency on lightly scarified burns and 23% frequency on heavily scarified burns [78]. A western redcedar-western hemlock/pachistima habitat type on the Deception Creek Experimental Forest of northern Idaho was horse-logged (shelterwood cut or clearcut followed by broadcast burning). Four years after treatments, grand fir showed moderately good seedling establishment compared to 6 other conifer species; only western white pine and western hemlock established in greater densities. Density of grand fir averaged 1.4 seedlings/yd² (1.8/m²) on the shelterwood site and 0.1 seedling/yd² (0.2/m²) on the clearcut and broadcast burned site. Grand fir continued to establish during the 20-year study period. Twenty years after treatment, grand fir density was still moderate compared to other conifers, at 12.1 stems/yd² (15.1/m²) on the shelterwood and 2.5 stems/yd² (3.1/m²) on the clearcut [23].

Growth: Grand fir is the fastest growing of all North American firs. It may reach 140 feet (43 m) in 50 years on Coastal Range and interior northern California sites [156]. On the eastern slope of the Cascade Range, Washington, grand fir grew more rapidly in the absence of Douglas-fir but was not affected by presence or absence of lodgepole pine [39].

Vegetative reproduction: Grand fir reproduces solely from seed and does not sprout from the root crown [71,155]. It may produce epicormic branches on the lower bole if light and space become available. Epicormic sprouting may contribute considerable volume to a disturbed stand [14].

SITE CHARACTERISTICS:

Climate and moisture regime: Grand fir tends to dominate moderately moist habitats. In the northern Rocky Mountains, grand fir habitat types indicate areas where the climate is moderated by the Pacific maritime influence [43,145,171]. Generally, drier sites are occupied by Douglas-fir while western redcedar and western hemlock dominate wetter habitats [10,38,131]. Inland, grand fir is most abundant on sites averaging 25 inches (635 mm) or more annual precipitation that are either too dry for, or beyond the range of, western hemlock and western redcedar [14]. Habeck [84] found that in the Selway-Bitterroot Wilderness of northern Idaho and western Montana, grand fir forests were most extensive on mid-elevation (3,500-4,00 feet), mesic slopes. They fingered into wetter, western redcedar types and were scarce on drier types. Grand fir is a relatively minor stand component in wet, dense coastal forests [187]. In southern British Columbia, it is most common on moist soils and is infrequent on dry or wet soils [117]. Although it is the most drought-tolerant of the Pacific Northwest firs, moisture is limiting in grand fir's southernmost distribution. Grand fir occurs only on moist slopes in northeastern California [174]. West of the Cascade Range in Oregon and California, it occurs mainly on moist valley bottoms [14].

Grand fir is tolerant of fluctuating water tables and floods [117].

Soils: Soil parent materials in which grand fir grows include sandstone, pumice, weathered lava or granite, and gneiss [71,31]. Grand fir is not generally restricted by soil type but does best on streamside alluvium and deep, nutrient-rich valley bottoms [71,117,155,174]. If there is adequate moisture, grand fir in central and eastern Oregon grows on pumice and other shallow, exposed soils [71]. On the Mendocino Coast of California grand fir occurs on soils of pH 5 [107].

Elevation: Grand fir occurs at elevations up to 6,000 feet (1,830 m) in the Cascade Range and northern Rocky Mountains [14,71]. West of the Cascade Range, it is usually restricted to low-elevation valleys [14]. Elevations are listed below by region.

	Minimum feet (m)	Maximum feet (m)
western British Columbia	sea level	1000 (305) [14]
California	sea level	5000 (1525) [14,71,102,174]
Idaho	2000 (610)	6000 (1830) [122,19]
western Montana	4300 (1290)	4700 (1410) [11]
Oregon Cascades	----	6025 (1825) [14,71,174]
western Oregon	sea level	3000 (915) [14]
Washington Cascades	----	4000 (1220) [14,71,174]
western Washington	590 (180)	1000 (305) [14,174]

SUCCESSIONAL STATUS:

Grand fir occurs in the overstory of both seral and late-successional forests [9,71,91,47,52,83,87]. It is climax throughout the grand fir series and is a major seral species in some western redcedar, western hemlock, subalpine fir, and Pacific silver fir habitat types [91]. It exhibits moderate growth in the open, yet is shade-tolerant enough to establish and grow beneath an open forest canopy [9,60,130,145,183]. Grand fir is not as shade-tolerant as western redcedar, hemlocks, or other firs and does not establish beneath a closed canopy [71,156,148,155,187,183]. Succession to a grand fir overstory is usually slower on shrubfields than on sites where grand fir developed beneath a forest canopy [10,49,157]. In grand fir habitats on Clearwater River drainages in northern Idaho, succession to a woody overstory was retarded by bracken fern (Pteridium aquilinum) or western coneflower (Rudbeckia occidentalis) invasion, and by northern pocket gopher browsing young grand fir and other conifer regeneration [59].

Grand fir does not require disturbance to establish and persist on most sites [15,188]; however, where western hemlock or western redcedar is the climax dominant, fire or other periodic disturbance is needed to maintain grand fir [14]. Grand fir may colonize a site soon after fire or other stand-replacing disturbance. Grand fir advance regeneration and seedling coverage were highest among 5 conifers following a severe Douglas-fir tussock moth outbreak that killed most of the grand fir-Douglas-fir overstory on the Wenaha-Tucannon Wilderness, Oregon. Although ponderosa pine seedlings showed faster growth rates than grand fir seedlings, the authors predicted that in the absence of fire, grand fir would continue to dominate the site despite repeated tussock moth outbreaks [192].

In the Swan Valley of western Montana, a grand fir understory usually developed in late succession beneath Douglas-fir that replaced early-succession lodgepole pine and western larch. Grand fir seedling establishment on early seral sites occurred mainly where lodgepole pine and western larch seed sources were lacking, such as the center of large, stand-replacement burns [9]. Descriptions of seral communities that occur in grand fir habitat types in Montana's Swan Valley and in central Idaho are available [9,43,171,172].

Dale and others [47] developed a model of long-term succession (500+ years) in western Washington and Oregon. The model predicts that in the absence of disturbance, grand fir is an early mid-seral species that is eventually replaced by Pacific silver fir, western hemlock, and mountain hemlock (Tsuga mertensiana). The model also predicts successional pathways after disturbance events including fire, windstorm, insect outbreak, and clearcutting.

SEASONAL DEVELOPMENT:

Time of grand fir budding varies over several months depending on early spring temperatures. Generally, budding occurs from late March to mid-May at low elevations and in June at higher elevations [71,75]. Shoot elongation follows bud burst; cones generally open for pollination during shoot elongation [54,75]. Cones ripen from August to September of the same year and begin to disintegrate and dispense seed about a month later [71,75].

Grand fir phenology in several locations is given below [179]:

Location	Bud break	Pollination	Cones ripen	Seeds disperse
BC	mid-March	April	August	---- (no data)
northern ID	mid-June	----	August	early Sept.
western OR and WA	mid-April to mid-May	----	----	mid-Sept.
Linn Co., OR	mid-June	----	----	----
Mendocino Co., CA	early April	----	----	----

Phenological observations of grand fir made over an 8-year period in northern Idaho and western Montana are summarized below [157]:

	Earliest date	Average date	Latest date
Shoots start	April 19	May 18	June 25
Buds burst	April 5	May 25	June 11
Pollen starts	May 1	June 4	July 2
Pollen ends	May 20	June 20	July 14
Shoot growth ends	June 9	August 3	August 31
Winter buds formed	June 16	August 14	October 11
Cones full size	July 7	August 5	August 26
Cones open	August 30	September 9	October 11

Related categories for SPECIES: Abies grandis | Grand Fir