Subalpine Forests

*Flagged trees-trees sculpted by predominant winds

Aspen stands (Populus tremuloides)

*6,500-11,000 ft *sunny areas with deep, loamy fertile soil *reproduces by sprouting, rarely by seeds *stable and successional stands *clonal species

FIRE in ASPEN *stable stands pre 1880's every 10 years (prefers mid slopes, south facing) *stable stands influenced by adjacent ponderosa pine stand fire return intervals *successional stands pre 1880's more than every 100 years (higher elevation; similar to spruce/fir) *all even-aged stands= severe fire

*even-aged forest *7000-9,800 ft (not found in NM) *serotinous cones *aggressive pioneer species Lodgepole Pine (Pinus contorta)

Figure 1: Adult Dendroctonus (left) versus Ips (right). Note gradually curved wing of Dendroctonus. Actual size of Dendroctonus from 1/8 to 1/3 inch, Ips 1/3 to 1/4 inch

The reason why bark beetle outbreaks are so extensive and severe in Colorado today is because of four interacting ecological factors: (i) long-term drought that stresses trees; (ii) warm summers and (iii) warm winters, which enhance beetle growth and survival; and (iv) abundant food sources (trees) for beetles.

Mountain pine beetle epidemics have occurred in lodgepole pine forests for thousands of years. Epidemics lasting 5 to 20 years occur at irregular intervals, affecting large areas and often killing more than 80% of the trees of more than 10 centimeters diameter. Berkeley Daily Gazette – June 6, 1930 average minimum January temperature for Anaconda and Butte No long-term warming trend is evident in the January minimum temperatures.

Engelmann spruce/subalpine fir forest type *recognized by narrow crowns and dark green colors *cool, dark, humid *highest most continuous forest (9000-treeline)

Major disturbances: fire, windthrow, beetle infestation, avalanches

FIRE in Subalpine/Engelmann Spruce *infrequent, small fires due to late snowpack and summer rains *severe, stand destroying fires in rare dry years * years before 1880's *longest intervals at high elevation and moist drainages and valley bottoms

Subalpine fir (Abies lasiocarpa) *8,000 ft to timberline *shade tolerant *smaller than spruce *lower elevations than spruce

*high number of seedlings/high mortality rate *300 yrs or younger *slow growing (15" tree~ 175 yrs old) *least fire resistant conifer in West

Engelmann spruce (Picea englemanni) *above 8,500 ft *10 million acres in Rocky Mtns. *prefers deep, rich soil *not tolerant of full shade or full sun as seedlings *strong shade tolerance as adult tree

*best seed production between years; good seed crops every 2-3 years *trees easily live to 300+ years; yrs old are common

Fireweed (Chamerion danielsii)