Larix lyallii and L. occidentalis (Larix sect. Multiseriales) are similar morphologically and have similar geographic ranges. Just how closely the two species are related has not been determined, but they probably originated from a common ancestor resembling L. potaninii Batalin (Parker 1993). They may hybridize where their ranges overlap (Parish et al. 1996).
First described by Scots naturalist David Lyall in 1858 (Parish et al. 1996).
Trees to 25 m tall with dbh to 120 cm; crown sparse, conic to irregular. Bark thin, smooth, yellowish grey when young; becoming furrowed and flaking into red- to purple-brown scales with age. Branches horizontal, occasionally pendulous, often gnarled and irregularly spaced, persistent on trunk when dead; twigs strongly white- to yellow-tomentose for 2-3 years. Buds tomentose, scale margins ciliate. Needles deciduous, in bunches of 30-40 on short shoots 20-35×0.6-0.8 mm, 0.4-0.6 mm thick, keeled abaxially, 2-angled adaxially, light green, turning golden yellow in autumn; resin canals 40-80 µm from margins, each surrounded by 6-10 epithelial cells. Ovulate cones elliptic, upright, red when young, turning purplish and then brown with age, 2.5-4(5)×1.1-1.9 cm, on curved stalks 3-7×2.5-4 mm; scales 45-55, rounded, margins erose, abaxial surface tomentose at maturity; bracts tipped by awn 4-5 mm, exceeding mature scales by ca. 6 mm. Pollen 78-93 µm diam. Seeds yellow to purple, body 3 mm, wing 6 mm (Parker 1993, Parish et al. 1996).
Photos at left illustrate some of the major identifying features. Photo 2 shows an actively growing shoot on a sapling at Hart's Pass, North Cascades. The long shoot, about 10 cm long, has emerged this year and is near full elongation at this time, about 75% of the way through the growing season. The short shoots at its base show whorls from two (lateral buds) or three (terminal bud) years of prior growth. Photo 3 is taken in the autumn, when the foliage has turned golden yellow and is ready to fall. It shows leaves emerging from short shoots. Photo 4 shows mature seed and pollen cones. Photos 5 and 6 show bark on, respectively, a fairly young tree and a much older tree that is bearing epicormic branches.
Canada: Alberta and British Columbia; USA: Washington, Idaho and Montana at 1800-2400 m (Parker 1993). See also Thompson et al. (1999). Hardy to Zone 3 (cold hardiness limit between -39.9°C and -34.4°C) (Bannister and Neuner 2001).
See photo 7 at left. It is locally common on exposed northern subalpine slopes to timberline, often with very rocky soils, as seen in photos 8, 9 and 10. It has very low shade tolerance and, due to its thin bark, low fire tolerance (Parish et al. 1996). Its deciduous habit confers resistance to winter desiccation, permitting this species to reach timberline elevations that may be far above other conifers, and to retain an erect growth form on those sites; photo 6 shows erect trees growing over Abies lasiocarpa var. bifolia krummholz. Nonetheless, as shown in photo 11, it can form a krummholz in very extreme settings; the trees shown are in a recently deglaciated area near Sentinel Pass, Alberta. Despite its tolerance of harsh mountain environments, the species can occur and compete effectively with evergreen conifers on fairly good sites within its range. Photo 10 shows the landscape-scale distribution of trees in Larch Lakes Basin, where the largest and tallest known alpine larches grow. Besides occurring on rocky talus and exposed bedrock, larch in this setting also occurs on colluvial hillslope soils and on deep alluvial soils around the lakes, in the company of Abies lasiocarpa, Picea engelmannii, and even a few Tsuga mertensiana. On the rocky ridges here, it also grows with Pinus albicaulis (pers. obs. 1986-2012).
Although the geographic ranges of Larix lyallii and L. occidentalis overlap considerably, elevational differences of 150 to 300 m usually separate them. Some morphologically intermediate specimens have been collected from Washington and Montana (Parker 1993).
Both the largest and the tallest trees ever measured are at Larch Lakes, Washington. I found the big tree in 1993 (photo at left), but didn't return to get accurate measurements until Bob Van Pelt and I visited the site in October, 2004 (photo at left). The big tree was 215.1 cm DBH, 31.3 m tall, with a crown diameter of 18.0 m. The tall tree was in a closed-canopy stand of very tall trees west of the upper lake, in the company of many comparably tall trees; it was 38.5 m tall and 101.0 cm DBH.
The current record seems to be sample BAL091 from a tree collected near Baker Lake, Montana in 1997 by Malcolm Hughes, Connie Woodhouse and Peter Brown. This sample starts in 987 and ends in 1997 for a total history of 1,011 years, verified by crossdating (NCDC 2008). Other old tree records include:
Many collections from the North Cascades of WA and the Canadian Rockies. E.g., Colenutt and Luckman (1991).
Due to its small size and remote occurrence, its principal values are scientific (see "Dendrochronology") and aesthetic. Few trees are lovelier, either in spring when the soft green of the needles contrasts with deep snowdrifts still covering the ground in this species' alpine habitat, or in autumn, when its golden foliage complements the red of huckleberries and the icy blue of the sky.
Many very fine stands are to be found in the eastern Cascade Mountains, including the Alpine Lakes, Glacier Peak and Pasayten Wildernesses, North Cascades National Park (WA), and Manning Provincial Park (BC). It is also widespread and exemplary in much of the Canadian Rockies, such as in Banff National Park.
Mountain goats, bighorn sheep and black and grizzly bears all feed in alpine larch stands. Blue grouse feed on the needles (Parish et al. 1996).
Colenutt, Margaret E. and Brian H. Luckman. 1991. Dendrochronological investigation of Larix lyallii at Larch Valley, Alberta. Canadian Journal of Forest Research 21: 1222-1233.
Luckman, B.H. 2006. Current research. http://geography.uwo.ca/facilities/dendro/tree-ring-research.pdf, accessed 2007.10.22.
National Climate Data Center [NCDC]. 2008.07.25. Tree-Ring Data Search Results, Baker Lake (USA; 45N,114W; Hughes,M.K.;Woodhouse,C.A.;Brown,P.M.). http://hurricane.ncdc.noaa.gov/pls/paleo/fm_createpages.treering, accessed 2008.07.25.
Parlatore, F. 1863. Coniferas novas nonnullas descripsit, Florence (pp. 1-4).
Arno and Habeck (1972). Highly recommended.
Bakowsky, O.A. 1989. Phenotypic variation in Larix lyallii and relationships in the larch genus. M.Sc.F. thesis. Lakehead University.
Farjon (1990) provides a detailed account, with illustrations.
Last Modified 2012-11-28