More info for the terms: association, basal area, cover, density, ecotype, fire regime, hardwood, mesic, series, shrub, shrubs, tree, xeric
Site characteristics: Giant chinquapin occurs in a wide range of sites from warm, dry, exposed locations [7,47,78,79,82,116] to low-elevation mesic forests [95,116,139]. Shrubby forms are more common in relatively harsh environments [124,138,139], including exposed [82], dry, and high-elevation sites ([7,95,116,138], McMinn 1951 cited in [58]). Giant chinquapin trees are typically associated with low-elevation [116] mesic [95,116,139] forests, often on north-facing slopes [95,139], but they also occur on dry sites [116] and may thrive on moderately dry sites (See Moisture availability).
Although many reports associate giant chinquapin with “xeric” sites within its distribution, this term and others referring to moisture regime are often used in a relative sense, making it difficult to compare reports. For instance, 2 sources [51,73] described the western hemlock/giant chinquapin community as a comparatively xeric old-growth community of the western slope of the Oregon Cascade Range [51,73], while Means [117] described this same community as mesic when compared to dry Douglas-fir- and tanoak-dominated communities of the same region. Giant chinquapin was associated with comparatively moist parts of the ponderosa pine zone in central Oregon [42], and it was an indicator species for "moist" vegetation in the South Umpqua Basin of southwestern Oregon, an area that receives comparatively little rainfall (see Precipitation). Species that indicated dry sites in this study area included hollyleaved barberry (Mahonia aquifolium), California fescue (Festuca californica), and ponderosa pine [119].
The distribution of giant chinquapin occurs within an area of generally mild climate [20,113,116,124]. McKee [116] suggests that some shrubby individuals are an ecotype adapted to heavy snowpacks, cool temperatures, and short growing seasons common in the Oregon Cascade Ranges and eastern Oregon.
Elevation
Topography
Soil
Moisture availability
Precipitation
Temperature
Elevation: Giant chinquapin grows from near sea level [82] in the Coast Ranges of Oregon and California [116] to over 5,000 feet (1,500 m) in the Siskiyou Mountains [193]. It occurred on a site ranging from 660 to 1,150 feet (200-350 m) on the eastern slope of the Coast Ranges in Oregon [132]. In the Siskiyou Mountains of California and Oregon, giant chinquapin was most abundant from 2,500 to 3,500 feet (670-1,070 m) and was common from 1,500 to 4,500 feet (460-1,370 m). It was rare from 4,500 to 5,500 feet (1,370-1,680) and was not observed at higher elevations [193]. In central Oregon, giant chinquapin has been noted up to 5,000 feet (1,520 m) in mixed-conifer/snowbrush ceanothus/long-stolon sedge community (Ceanothus velutinus-Carex inops subsp. inops) [108] and ponderosa pine (Pinus ponderosa) communities [125,183]. Giant chinquapin occurred on a site in the Sierra Nevada at 4,300 feet (1,310 m) [93].
Shrubby giant chinquapins occur at higher elevations than giant chinquapin trees ([95,137,138], McMinn 1951 cited in [58]). In the Willamette, Mt Hood, and Siuslaw National Forests of Oregon, giant chinquapin occurs as a tree at low to midelevations and only occurs as a shrub at high elevations [173]. Giant chinquapin is commonly reported below about 4,500 feet in the Cascade Range ([6,164], Weisberg 1995 cited in [19]), while shrubby giant chinquapin occurs along the crest of the Cascade Range in Oregon up to 6,000 feet (1,830 m) [116]. The importance of giant chinquapin trees in 3 Douglas-fir-hardwood forests of the Klamath Mountains of California declined substantially above 3,900 feet (1,200 m), although tree forms occurred up to 5,250 feet (1,600 m) [95]. McKee [116] suggests that there are 3 giant chinquapin ecotypes, 1 of which is a shrubby form occurring at high elevations in the Oregon Cascade Range and eastern Oregon. Scrub golden chinquapin occurs at high elevations in the southern portion of giant chinquapin's range [7].
Topography: Giant chinquapin may be more common on ridges [47,95,151] and slopes [9,96,145,174,180], including those that are steep [47,84,174], than near streams [145] or in valley bottoms [151]. On 2 west-central Oregon watersheds, giant chinquapin was positively (P=0.008) associated with hillside topography [145], and it was inversely associated with percent slope on the Willamette National Forest [174]. In the western Cascade Range in Oregon, giant chinquapin was the dominant species on a site with a 40° slope [96]. Basal area of giant chinquapin in 63 zero-order stream basins averaged 0.2 m²/ha in valleys, 0.7 m²/ha on slopes, and 0.9 m²/ha on ridges [151]. Giant chinquapin occurrence in valley bottoms may be restricted to the interior and southern boundaries of its distribution [84]. For example, giant chinquapin trees had "significant cover" in ravines and valley bottoms in Douglas-fir-hardwood forests in the Klamath Mountains [95].
Although giant chinquapin occurs on all aspects, its growth form [95,139] and occurrence [95,192] suggest that north slopes may be more favorable, at least in some areas. In the Siskiyou Mountains, 47% of giant chinquapin stems were on north- and northeast-facing aspects, while only 5% occurred on south- to west-facing aspects [192]. In Douglas-fir-hardwood communities in the Klamath Mountains, the greatest cover of giant chinquapin trees consistently occurred on north- and northeast-facing aspects, and no substantial giant chinquapin stands occurred on slopes with aspects south of due east or due west [95]. According to Holland [84], giant chinquapins near the southern and interior margins of their distribution are restricted to north slopes. In contrast, on south-facing and southwest-facing slopes in the western Cascade Range in Oregon, giant chinquapin occurred as an overstory dominant [96] and as a midstory dominant under western hemlock (Tsuga heterophylla) [47,73]. In southwestern Oregon, a giant chinquapin-tanoak-sugar pine (Lithocarpus densiflorus-Pinus lambertiana) community usually occurred on south or southwestern aspects [9].
Soil: Giant chinquapin occurs in variable soil types [116] but is commonly associated with rocky [9,10,47,51,76,76,180] and/or unproductive soils [27,116,124,152]. In forests of southwestern Oregon, it often indicates rocky sites [9]. The shrub form commonly occurs on rocky sites [84,86,116]. Within Douglas-fir communities in southwestern Oregon, giant chinquapin was associated with the least productive sites [8].
Soil pH on sites with giant chinquapin is often acidic, with values ranging from around 4.1 [91,190] to 6.2 [5].
Giant chinquapin occurs on sites with various parent materials. Giant chinquapin shrubs occurred in 2 of 3 forest communities occurring on lava flows in Oregon [51]. Giant chinquapin, including scrub golden chinquapin [35,193], is associated with ultramafic [9,134] and serpentine [193] substrates.
It has been suggested that giant chinquapin may be more likely to develop into large trees on sites with deep soils, since these sites generally experience more moderate moisture regimes [116,124].
Moisture availability: Giant chinquapin occurs on sites that experience a wide range of soil moisture regimes, from xeric chaparral communities [116] to mesic redwood (Sequoia sempervirens) forests of the California coast [147]. On the most xeric sites within its range, giant chinquapin occurs mainly as a shrub ([7,95,116,138], McMinn 1951 cited in [58]). Scrub golden chinquapin occurred on dry exposures in central California [7], northwestern California, and southwestern Oregon [116]. The Douglas-fir-giant chinquapin/dwarf Oregon-grape (Pseudotsuga menziesii-Chrysolepis chrysophylla/Mahonia nervosa) association occurs in cool, moist areas of southwestern Oregon [9].
Giant chinquapin is often associated with moderately xeric sites. At lower elevations (2,000-3,000 feet (610-915 m)) on diorite in the Siskiyou Mountains of Oregon and California, it had a bimodal distribution across a moisture gradient based on topographic characteristics, with a peak on submesic sites and a larger peak on xeric sites [193]. Giant chinquapin has been considered an indicator of dry sites in Douglas-fir-western hemlock forests of the Pacific Northwest [50], on the Siuslaw [78] and Willamette [79] National Forests, and for the tanoak series of the Siskiyou Region [11]. Based on plant moisture stress in 2 western hemlock/giant chinquapin communities in the western Cascade Range of Oregon, giant chinquapin had high importance values on dry sites. It was not limited by moisture stress on these sites [202]. Giant chinquapin comprised a substantial component of the biomass of old-growth Douglas-fir stands in the H. J. Andrews Experimental Forest in relatively xeric locations [61]. This experimental forest is located on the west slope of the Cascade Range in central Oregon. A Douglas-fir-giant chinquapin community experienced greater water stress in the summer than 3 other major plant communities on a watershed in H. J. Andrews Experimental Forest [61]. In northwestern California, Douglas-fir-giant chinquapin forests occur on drier slopes than Douglas-fir forests [146]. In comparatively moist environments, giant chinquapin may be limited to openings, while it is increasingly competitive on drier sites [116].
Giant chinquapin may grow larger on comparatively xeric sites [30,61,95,137]. It occurred in the overstory of a dry mixed-conifer site with Douglas-fir and Pacific madrone (Arbutus menziesii), while it occurred in the midstory of a more mesic transition site and a wet site in the western hemlock zone [30]. Giant chinquapin reached its greatest development in the lower, drier portions of the Douglas-fir-grand fir association of the Nash Crater Lava Flows in Linn County, Oregon [137], and it occurred as trees on the driest sites of a west-central Oregon Cascade Range study area [187]. “Driest” must be considered in a relative sense, however, considering Roof’s [139] suggestion that development of large giant chinquapin trees requires "ample" winter rainfall and summer fog, and Keeler-Wolf’s [95] statement that giant chinquapin obtains subdominance in Douglas-fir-hardwood forests that receive ≥60 inches (1,520 mm) of precipitation annually.
In Douglas-fir-hardwood forests of the Klamath Region, giant chinquapin sexual reproduction (see Seedling establishment and plant growth) and density were generally greater on mesic than dry sites. The oldest giant chinquapin trees, estimated as 400 to 500 years old, occurred on the driest site, with annual precipitation from 60 to 70 (1,780 mm) inches. Since heart rot was more prevalent on somewhat moister sites, it was suggested that increased heart rot may have shortened giant chinquapin life spans on mesic sites [95].
Precipitation: Average annual precipitation on sites with giant chinquapin ranges from less than 20 inches (510 mm) in southern California [116] and portions of southern Oregon [74] to more than 160 inches (4,000 mm) in coastal Douglas-fir-western hemlock forests of California [84]. Much winter precipitation in the higher elevations of the Cascade Range [116,124] and central Oregon [44,108] falls as snow, while snow is uncommon along the California coast [84,147]. Giant chinquapin's conical shape and deflexed branches led Keeler-Wolf [95] to conclude that it is more tolerant of snow than tanoak or Pacific madrone and is adapted for mesic, upper-elevations of the Douglas-fir-hardwood zone.
Table 1. Average annual precipitation in regions of the western United States with giant chinquapin Region Average annual precipitation Central Oregon 25-30 inches (635-890 mm) [108,140] Umpqua Valley & Rogue River Basin 20-30 inches (510-760 mm) [74] Western Cascade Range
foothills: 44 inches (1,120 mm) [19]
40-60 inches (1,020-1,520 mm) [74]
91 inches (2,302 mm) [67]
Southern Cascade Range 30 and? 68 inches (760-1,730 mm) California and Oregon Coast Ranges 34-83 inches (865-2,110 mm) [113]
70-100 inches (1,780-2,540 mm) western slope in southern Oregon [74]
48 inches (1,222 mm) east slope in Oregon [132] Klamath Mountains 30 and? 68 inches (760-1,730 mm) [113]
22.3-64.4 inches (576-1,636 mm) [152] Northern California coast 20-118 inches (500-3,000 mm) (Miles and Goudey 1997 cited in [162])
≥98 inches (2,500 mm) east of Cape Mendocino [147] Sierra Nevada 30-68 inches (760-1,730 mm) [113]
67 inches (1,700 mm) [93] Central California coast western slopes: ≥39 inches (1,000 mm) [147]
Throughout most of its range, giant chinquapin experiences moist winters and dry summers [5,44,67,116,124,152,162,164]. This seasonal pattern occurs along the central California coast [147], and in northwestern California [20], southwestern Oregon [74], and central Oregon [44,67,164]. The summers are typically drier in the southern portions of the giant chinquapin's range [116]. In coastal areas, fog may provide additional moisture in the summer months [113,162].
Temperature: Temperatures experienced by giant chinquapin are generally mild [20,74,113,116]. Reported temperatures on sites with or near giant chinquapin range from winter lows of 19 °F (-7 °C) in northwestern California [20] and central Oregon [44] to summer highs of 98 °F (37 °C) on west slopes of the central California coast. On a burned site in central California, July temperatures may have exceeded 110 °F (46 °C) [5]. Number of frost-free days in the interior mountains where giant chinquapin occurs range from 116 to 240, while the number of frost-free days in the Coast Ranges of California and southwestern Oregon ranges from 204 to 338 (McDonald 1981 unpublished report and Stein 1981 unpublished report cited in [113]).
Table 2. Average temperatures (°F) within the giant chinquapin's distribution in winter and summer. When provided, average minima and maxima for each season are displayed, separated by a slash (/). Location Winter Summer Central Oregon 19/42 43/84 [44,67] Klamath Mountains (daily max/mins) 23-36/ 44-54 48-63/89-96 [152]
Klamath Mountains
33-41 62-75 [113] Coast Ranges of California and Oregon 41-50 57-71 [113,132]. Central California not reported/52 not reported/87 [162]
Along the northern distribution of giant chinquapin, there is an east-west gradient with eastern locations getting more snow [8] and having more variable temperatures [8,162] than western locations. This is the case in the Cascade Range [164], the Siskiyou Mountains [8], the Klamath Mountains [152], and the north coastal bioregion of California. In this region, a coastal site had only a 11.5 °F (6.4 °C) difference between winter and summer average maximum temperatures, while a more inland location near Napa Valley had a 34.7 °F (19.3 °C) difference between winter and summer average maximum temperatures [162].
Giant chinquapin is often associated with warm sites [9,77,202], although it can occur on cool sites, where the tree form is more common than shrub form [9,95,139]. It is an indicator of warm sites on the Mt Hood, Willamette [77], and Siuslaw National Forests [78]. The western hemlock-giant chinquapin/salal-Pacific rhododendron (Gaultheria shallon-Rhododendron macrophyllum) community has a warmer climate than western hemlock associations in the Cascade Mountains with less giant chinquapin [9]. Based on soil and air temperatures in western hemlock/giant chinquapin communities in the western Cascade Range of Oregon, giant chinquapin was categorized has having a center of importance on "medium hot" sites [202]. Scrub golden chinquapin occurs on warm exposures in the southern portion of the species' range [7].
Plant communities: Giant chinquapin occurs primarily in the understory of conifer and mixed-conifer-hardwood communities [9,51,73,75,80,86,146,181,194]. Shrub forms, including scrub golden chinquapin, occur in brushfields [74]. See the Fire Regime Table for a list of plant communities in which giant chinquapin may occur and information on the FIRE REGIMES associated with those communities.
Forests and woodlands: Giant chinquapin is most common in the midstory under conifers, although it occasionally occurs in the overstory [9,30]. It occurs in the midstory of Douglas-fir-hardwood [146], mixed-conifer [75,181], mixed-evergreen [80,194], western hemlock [9,51,73], white fir (Abies concolor), and Shasta red fir (Abies magnifica var. shastensis) communities [51,86]. A description of giant chinquapin occurrence in forest and woodland communities is provided in Table 3. Overstory cover in these communities ranges from open [98] to fairly dense [82,84]. In western hemlock/giant chinquapin communities, overstory cover was commonly <50% in the western Cascade Range in Oregon [51,73].
Giant chinquapin rarely occurs in pure stands [97,116]. It was the dominant species on 1 of 102 Forest Inventory and Analysis plots in dry hardwood communities of western Oregon [115]. In a survey of California hardwoods, only 1,000 acres (405 ha) of giant chinquapin-dominated stands were reported inside National Forests, and none were reported outside National Forests [21]. Giant chinquapin stands are isolated [7] and rarely exceed 25 acres (10 ha) [116]. In southwestern Oregon, giant chinquapin occurred in the overstory in stands of tanoak, tanoak and Douglas-fir, tanoak and white fir [9], and Douglas-fir and Pacific madrone [30].
In some forest and woodland communities, giant chinquapin has only been reported as a shrub. These include Jeffrey pine (Pinus jeffreyi) [90,184], mountain hemlock (Tsuga mertensiana) [77], and lodgepole pine (P. contorta)-Douglas-fir [99]. Scrub golden chinquapin occurs in knobcone pine (P. attenuata) communities in California [35] and Jeffrey pine communities in the Klamath Mountains [90].
Table 3. Plant communities in which giant chinquapin is common, including citations distinguishing growth form and/or variety Communities Growth form Conifer-dominated communities Redwood general [2,7,21,84,122,147]
tree [40,62,141,179,190]
scrub golden chinquapin [190]
Mixed-conifer general [21,93,97,106,131,164]
tree [49,50,51,62]
shrub [41,49,50,51,184]
scrub golden chinquapin [112] Ponderosa pine general [125,140,142]
shrub [200]
scrub golden chinquapin [122] Douglas-fir general [7,9,13,21,29,50,51,97,122,172,186,196]
tree [13,50,117]
shrub (large) [143] Western hemlock general [9,78,117]
tree [13,50,51,59,79,117]
shrub [47,79,143] White fir general [8]
tree [50]
shrub [184] Shasta red fir general [8]
tree [10]
shrub [50,51,184] Pacific silver fir (Abies amabilis) shrub [79] Bishop pine (P. muricata) general [91,130,190,191]
scrub golden chinquapin [122] Port-Orford-cedar (Chamaecyparis lawsoniana) general [8,157,193]
Mixed-conifer-hardwood communities Mixed-evergreen general [32,49,51,64,84,100,172,193]
tree [9,40,50,62]
scrub golden chinquapin [190] Douglas-fir-tanoak general [50,162]
Hardwood communities Tanoak general [11,21,84,152]
tree [9,50] Mixed-sclerophyll hardwood general [76]
Brushfields: Giant chinquapin shrubs of both varieties occupy brushfields [25,56,74], including chaparral [7,37]. Giant chinquapin shrubs have been noted in early-successional chaparral [160] and northern maritime chaparral [178]. Scrub golden chinquapin is a component of Oregon brushfields [74] including chaparral communities ([84,122,189], Gratkowski 1961a cited in [51]), such as conifer-forest chaparral ecotones [116], northern maritime chaparral [84], and "climax chaparral" [40]. Species commonly occurring in early-successional brushfield [25,74], early-successional chaparral [160], or successional chaparral [37] include greenleaf manzanita (Arctostaphylos patula) [37,74], hairy manzanita (A. columbiana) [74,160], snowbrush ceanothus [25,37,74], whitethorn ceanothus (C. cordulatus), and wedgeleaf ceanothus (C. cuneatus) [74,160]. Cascara buckthorn (Frangula purshiana), blackberries (Rubus spp.) [25,74], serviceberries (Amelanchier spp.), currants (Ribes spp.), and huckleberries (Vaccinium spp.) [74] may occur in early-successional brushfields.