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Scientific name: Athrotaxis x laxifolia W.J. Hooker 1843
Synonyms: Athrotaxis cupressoides x Athrotaxis selaginoides, Athrotaxis doniana Henkel & W.Hochst.
Common names: Summit cedar
Tree to 10-15 m tall, monopodial, erect, with trunk to 0.5 m in diameter. Bark on old trees furrowed, exfoliating in thin flakes and long, shredding strips, light brown. Branches thick, ascending or spreading, forming a conical, dense crown, in old trees irregular and open. Foliage branches numerous, mostly alternate, spreading, scaly, rough with free leaf apices, ultimate branchlets slender, of unequal length, mostly persistent. Leaves helically arranged in ranks of 5, 4-12 × 2-3 mm (larger on leading, older branchlets), decurrent, imbricate, the distal part spreading slightly, lanceolate, widest at the point of curvature, keeled, margins entire. Apex incurved, obtuse, usually lustrous light green, leaves amphistomatic, with few stomata proximally on the abaxial face and two bands of widely spaced stomata adaxially, sometimes epistomatic. Pollen cones terminal or subterminal, at base surrounded by shortened leaves, 3-5 mm long, up to 4 mm wide, yellowish, turning brown Microsporophylls helically arranged, ca. 15, narrowly triangular, curved, concave, upper margin denticulate, short pedicellate, pollen sacs 2, oblong. Seed cones terminal on branchlets with non-modified leaves, solitary, mature cones globose or subglobose, 15-26 × 14-20 mm, with 14-18 helically arranged bract-scale complexes which part widely at maturity. Bract-scale complex clavate-peltate, when fully grown thin woody, with slightly depressed apex and prominently extended, incurved, keeled bract apex, abaxial surface rough and wrinkled, reddish brown, adaxial surface striated, reddish brown without visible seed marks. Seeds 30-40 per cone, obovate-oblong, ca. 2 mm long, with 2 narrow wings of slightly unequal size and shape and 0.5-1 mm wide positioned more or less in one plane.
In Tasmania this taxon is considered to be a hybrid between two other species (Athrotaxis cupressoides x Athrotaxis selagionides). The evidence is inconclusive and if of hybrid origin, it is more likely to be a nothospecies than that each individual tree is an F1 only. In cultivation these trees breed true to type.
Central and southern Tasmania. Growing with its parents; 900-1,200 m.
Red List Category & Criteria: Endangered
In 2000, this (notho)species was assessed as Vulnerable under criterion D1 with the global population estimated to be less than 1,000 mature individuals. No decline was indicated in that assessment. The area of occupancy (AOO), estimated using herbarium collection data and a grid of 2 km, is 40 km² which could be an underestimate as there are more localities not sampled for institutional herbaria. However, with the few trees present in each locality the 2 km grid (IUCN recommended standard) is likely to be too generous. The AOO is by all estimates much less than 500 km², the population is severely fragmented and when this species declines with its congeners, as it is reasonable to assume, it meets the B criterion for listing as Endangered (EN).
It is rarely encountered and occurs only in association with one or other of the latter two species. Populations are usually very small and consist of only a few individuals each.
Grows in dwarfed montane forest and temperate rain forest, often associated with the other species of Athrotaxis. Because it occurs usually as solitary individuals, rarely in small groups, and generally with or near one or both of the other species Athrotaxis cupressoides and Athrotaxis selaginoides, it is at risk of extinction mainly because of its low number of individuals overall. Nearly all of these are now in reserves, where increasing fire frequency is the main threat, it would also be impacted by invasive pathogens like Phytophthora and browsing by introduced rabbits.
This species has been taken into cultivation more often than its apparent rarity in the wild suggests and can be seen in several arboreta.
Nearly all known individuals are now in protected areas, where management is directed towards conservation of this and other species.
Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.
