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

GENERAL BOTANICAL CHARACTERISTICS:

Rocky Mountain maple has opposite, ascending to erect branches, rounded twigs, and a narrow crown [123,150,325]. The bark of Rocky mountain maple is smooth until maturity, when fissures develop [150,156,159,310,325]. Rocky mountain maple has a wide, spreading root system with a combination of deep and lateral woody roots [123,310,325].

Rocky Mountain maple may be monoecious [74,123,150,172,203,256,310] or dioecious [74,123,141,172,203,310,325,328]. Flowers are borne in loose terminal cymes arising from lateral buds [74] and grow in drooping clusters [123]. The paired seeds are winged samaras [74,123,141,150,325,328]. Seeds are 0.16 to 0.2 inch (4-5 mm) long [256] and samaras are 0.08 to 0.12 inch (20-30 mm) long [203].

RAUNKIAER [262] LIFE FORM:

REGENERATION PROCESSES:

Vegetative regeneration:
Following stem damage or top-kill, Rocky Mountain maple readily resprouts from the root crown [33,62,72,123,176,186,193,295]. Resprouts may not set seed for 3 years after disturbance [72].

Development:
Rocky Mountain maple experiences a rapid increase in height following disturbance, which tapers off around 20 years post-disturbance. Growth modeling estimates that Rocky Mountain maple may reach 4.2 feet (1.3 m) 2 years after disturbance and 10 feet (3 m) by 10 years after disturbance [178], and may overtop even rapidly growing tree seedlings [215]. Maximum heights are reached approximately 30 to 40 years after disturbance [233], on sites with 40 to 50% of full sunlight [144]. Even in closed canopies, Rocky Mountain maple grows above the dominant shrub layer [56].

SITE CHARACTERISTICS:

Location:
Rocky Mountain maple occurs on wetlands, streambanks, canyons, and upland mountain slopes [2,71,72,74,158,172,239,263,265,307,325]. Though it occurs on both moist and dry sites [4,21,30,31,61,74,123,151,190,203,310,312], Rocky Mountain maple is more closely tied to drainages in arid zones of its distribution [79,97,177,310,311,324,325], but occurs on drier exposures northward and at higher elevations [325]. On upland sites, Rocky Mountain maple grows on lower, mid, and upper slopes [82,177,228,236,271], alluvial terraces [123,259], summits, ridgetops [4,177], snow chutes [122,123,204], and talus slopes [166,174,204,208]. Rocky Mountain maple is found on gentle, moderate, and steep slopes [82,177,188,189,205,228,233,290,336], with slopes ranging from 15 to 67% [3,99].

Elevation:
In southern California, Rocky Mountain maple is found from 5,980 to 10,000 feet (1,823-3,048 m) [222,316]. In Arizona and New Mexico, it is found between 5,000 and 12,000 feet (1,524-3,658 m) [7,47,79,82,153,203,221,228,261,307,324] on all aspects [4,81,177,192,228,311,324]. The lower elevation sites are often along streams or drainages [47,48,81,99,177,221,228]. In Colorado and Utah, Rocky Mountain maple grows at 5,000 to 12,700 feet (1,524-3,871 m) [40,93,130,159,174,175,205,242,290,310,336], with northern aspects being optimal for growth and establishment [310].

In northern California, northwestern Nevada, and Oregon, Rocky Mountain maple is common between 2,800 and 9,000 feet (853-2,743 m) [64,175,244]. In Idaho, Montana, and Washington, Rocky Mountain maple occurs between 1,500 and 8,900 feet (457-2,712 m) [36,56,70,75,91,112,196,257,269,293,295,335] on all aspects [61,100,196,234,249]. On sites in Idaho, percent cover of Rocky Mountain maple increased with elevation, but frequency did not [339]. Though it occurs on all aspects, studies in northern Idaho found that Rocky Mountain maple had significantly greater (F=0.05) percent cover on southern aspects than on northern aspects [233]. In British Columbia, Rocky Mountain maple occurs from 1,148 to 4,760 feet (350-1,450 m) [188,189].

Soils:
Rocky Mountain maple occurs on silty, loamy, sandy, gravelly, and rocky soils [45,100,127,177,205,228,290,325,336], with a moderately acidic to slightly basic pH [290,310,325]. It grows on sandstone, limestone, basalt, gneiss, rhyolite, calcareous, and granitic parent materials [45,64,100,112,127,205,290,316]. Rocky Mountain maple grows on shallow [123,233] as well as relatively deep [100,150,228,233,236,310], well developed soils [3,4,156]. Rocky Mountain maple has high requirements of calcium, magnesium, nitrogen, potassium, and phosphorus [123,167,233]. In British Columbia, it is reported to be an indicator of nitrogen-rich soils [164].

Drought and Shade Tolerance:
Rocky Mountain maple occupies well-watered [164] and well-drained sites [45,100,123,177,228,310,325], though it will tolerate imperfectly drained soils, periodic flooding, and moderately high water tables [90,166,167,325]. Rocky Mountain maple occupies sites with a range of moisture levels, competing by adjusting total leaf area through stomatal control and shifting the water potential of its leaves [123]. Rocky Mountain maple has a weak to moderate drought tolerance [310,325] and is winter hardy [123,167,169,325]. It is also moderately shade tolerant [123,226,310,325], but experiences more vigorous growth and fruiting in full sun [325].

SUCCESSIONAL STATUS:

Rocky Mountain maple is a major component or dominant in seral shrub-dominant vegetation, which develops rapidly following disturbance in the northern Rockies [36,55,57,58,70,105,113,114,125,133,184,245,299,329,338]. Seral shrubfields result from recurring disturbance including fire and downslope movement of snow, ice, water, and rocks [55,184]. These shrubfields may actually inhibit tree seedling establishment through direct competition and indirectly by providing habitat for browsing animals that damage seedlings [125]. The Rocky Mountain maple/mallow ninebark complex frequently becomes dominant on sites in the northern Rockies [65]. Similar seral shrubfields occur in the southern Rockies. Rocky Mountain maple may actually provide shade to Douglas-fir seedlings aiding in establishment and survival [63].

Rocky Mountain maple may have higher percent cover or occur with greater frequency on more open sites [145,173]. However, Antos [15] found that Rocky Mountain maple shows little response to successional development, maintaining >5% cover in both young and old stands. Rocky Mountain maple is described as shade intolerant to shade tolerant [128,164]; the ability to persist in heavy shade makes it an important species in closed canopy stands [234].

SEASONAL DEVELOPMENT:

Related categories for SPECIES: Acer glabrum | Rocky Mountain Maple