Photographs and drawings are presented by Averyanov et al. (2005).
Calocedrus rupestris
Bách xanh [Vietnamese].
This is one of the most recently discovered conifers, first described in 2004. As such it is the second new species in the Cupressaceae to be discovered in this century within the karst mountains of Vietnam (the first being Xanthocyparis vietnamensis, discovered in 2001). Its initial description (Averyanov et al. 2004) is in a very hard-to-get publication, but all required taxonomic information and much more are presented by Averyanov et al. (2005), freely available on the Web.
Type from Na Bo in Bac Kan province: 21.9455°N, 106.0858°E, 650-700 m elevation, 2004.06.03. L. Averyanov, N.T. Hiep, P.V. The, N.T. Vinh HAL 5441. Holotype HN, isotypes LE, MO.
Evergreen, monoecious trees up to 25 m tall and 100 cm DBH with a broadly rounded crown. Bark 8-12 mm thick, gray-brown to brown, fissured, fibrous and exfoliating in longitudinal strips, with numerous large resin ducts. Branchlets arranged in planar sprays, spreading and ascending, flattened, prominently jointed. Leaves decussate, in whorls of 4, scale-like, broadly obtuse to obtuse at apex, base decurrent. Leaves are dimorphic along the branchlet: the facial pair flattened, (1-)2-6(-7) × (1.5-)2-2.5 mm, the lateral pair boat-shaped, (1.5-)2-6(-7) × (0.3-)0.5.-0.75(-1) mm; without glands, uniform green or with very indistinct abaxial stomatal bands. Pollen cones terminal, solitary, cylindrical, (4.5-)5-6 × 1.5-2(-2.2) mm, with (8-)9-11 pairs of scales (the lowest 2-4 pairs sterile), each with 2-6 pendulous pollen sacs; microsporophylls 0.8-1(-1.2) × 1-1.2 mm, obtuse-rounded to broadly obtuse, with finely erose margin, obtuse to broadly obtuse at apex, light green turning to light brown; microsporangia broadly ovate to subspherical, 0.3-0.4 mm broad. Seed cone-bearing branchlets (stalks) terete or 4-angled, 0.5-1(1.5) mm long, with 6-8(-12) imbricate scales, obtuse to broadly obtuse at apex. Seed cones green-brown, terminal, solitary or paired at apex of lateral branchlets, ovate, (4-)5-6(-7) × (2.5-)3-4 mm, dehiscent when mature in first year, with 4 decussate, flat scales (very rarely with 1 additional basal pair of rudimentary scales); seed cone scales flattened, woody or somewhat leathery, broadly ovate, 4-6 × 2.5-4 mm; basal 2 scales fertile, dehiscent when ripe, normally 2-seeded (rarely 1), at apex incurved, rounded, sometimes with an indistinct, slightly flattened or concave plate with rough surface, rarely with a very small central umbo; apical pair sterile, connate. Seeds ovate to subovoid, acute, slightly flattened, with 2 large subapical, unequal wings 4-5 mm long. Resin abundant, bright yellow-orange, with pine-like fragrance; timber light yellow, odorless. Pollination occurs in December-January, with seeds maturing probably in September-October (Averyanov et al. 2005).
Averyanov et al. (2005) propose the following characters to discriminate C. rupestris from C. macrolepis:
| Character | C. macrolepis | C. rupestris |
| Apex of canopy leaves | acute | obtuse to broadly obtuse |
| Seed cone position | distinctly stalked, stalk usually recurved, cone commonly pendulous or sub-pendulous | subsessile (cone erect or sub-erect) |
| Seed cone form, dimensions | broadly cylindrical to elongate, 7-8(-12) x 3.5-4(-5) mm | broadly ovate, 4-6(-7) x 2.5-4 mm |
| Seed cone stalk and scales | 3-5 mm long, with 16-20 imbricate scales, each acute at apex | 0.5-1(-1.5) mm long. with 6-8(-12) imbricate scales, each obtuse to broadly obtuse at apex |
| Number of scales in seed cone | 6 | 4 (very rarely 6) |
| Apex of fertile scale in seed cone | distinctly recurved, apiculate, with short distinct mucro | incurved, rounded, sometimes with indistinct slightly flattened plate with rough surface, rarely with very small central umbo |
| Number af seeds (ovules) on fertile scale | 1 or 2 | 2 (rarely 1) |
China: Guangxi and Guizhou (Nong et al. 2011, Hoch 2017); Vietnam: the provinces of Bac Kan, Cao Bang, Ha Giang, Hoa Binh, Nghe An, Quang Binh, and Son La (Averyanov et al. 2005). Precise location data for the Chinese collections are not available, but see Hoch (2017) for a map; they are generally in the mountains near the Guangxi/Guizhou border. The range map shown here has location collections reported by Averyanov et al. (2005). The close proximity of some of these collections to the Laotian border indicates that the species may occur in Laos as well.
Specimen collection locales reported by Averyanov et al. (2005).
Within the species' latitudinal and elevational range it experiences a monsoon tropical climate, with a July-October wet season and annual rainfall of (1200-)2000(-3000) mm. Temperature is seasonally variable with winter lows cold enough to experience occasional frosts, and summer highs around 35°C.
C. rupestris occurs exclusively on rocky limestone (karst) terrain, a habitat that has a very high level of endemism and that includes a variety of other relict conifers including Amentotaxus argotaenia, A. hatuyenensis, A. yunnanensis, Cephalotaxus mannii, Dacrycarpus imbricatus, Dacrydium elatum, Chamaecyparis hodginsii, Keteleeria davidiana, Nageia fleuryi, Pinus kwangtungensis, Podocarpus neriifolius, P. pilgeri, Pseudotsuga sinensis, Taxus chinensis, Tsuga chinensis, and Xanthocyparis vietnamensis, not to mention Cycas dolichophylla and C. chevalieri. It is "an indicator of intact pristine primary climax aboriginal zonal relictual woods typical for ancient highly eroded remnant rocky limestone ridges in northern part of eastern Indochina" (Averyanov et al. 2005). I'm not sure what that means but it sounds provocative, particularly since it is paired with the claim that "in the past Calocedrus rupestris was undoubtedly widely distributed in northern Vietnam." Besides occurring commonly as a component of mixed conifer forest or mixed conifer-evergreen broadleaf forest, C. rupestris sometimes also occurs in pure stands with canopy heights typically 15-25 m. The forest also has dense subcanopy tree, shrub, and herb strata, each of which also has high primary species diversity. Lithophytic and epiphytic ferns and orchids are particularly numerous and diverse, with a high degree of endemism. Due to this extremely high botanical diversity of rare and endemic species, the remaining forests of C. rupestris are of globally significant conservation concern. Vietnamese endemic orchids are rapidly vanishing in their native habitat due to commercial collecting, while logging continues to threaten this species as well as other rare conifers found in its habitat.
The largest trees reported thus far are up to 120 cm DBH and 25 m tall, and some living trees are estimated to be 600 to 800 years old (Averyanov et al. 2005).
Averyanov et al. (2005) state that the species is subject to logging, which poses a serious threat to its survival. They also note that its habitat is extremely vulnerable to climate change, particularly to conditions of reduced humidity and precipitation.
Wikipedia (citing original material in Vietnamese) states that Phong Nha-Ke Bang National Park, Vietnam, has one of the largest intact karst forests hosting this species, with trees 500-600 years old. News reports published on Vietnamese websites in 2004 and 2005 indicate that Leonid Averyanov and his co-authors have hailed this park as supporting the finest known stands of this species. The area corresponds to the southernmost locale shown on the range map above.
The epithet "rupestris" means "rock-dwelling," as appropriate name for this tree of the karst (Averyanov et al. 2005).
Averyanov, L., Nguyen Tient Hiep, Pham Van The, and Phan Ke Loc. 2004. Calocedrus rupestris sp. nov. (Cupressaceae), new relict coniferous species from limestone areas of northern Vietnam. P. 40-44 in Basic Research in Life Sciences with Emphasis on Upland Agriculture and Forestry. Proceedings of the National Conference on Life Sciences, Thai Nguyen University, September 23, 2004. Hanoi: Science and Technics Publishing House [in Vietnamese].
Averyanov, L., Nguyen Tien Hiep, Phan Ke Loc, and Pham Van The. 2005. Distribution, ecology, and habitats of Calocedrus rupestris (Cupressaceae) in Vietnam. Turczaninowia 8(4):19-35.
Hoch, J. 2017. Extended range area of Calocedrus rupestris in China. Bull. of the Cupressus Conservation Project 6(3):51-61.
Nong Dong-Xin, Wu Wang-Hui, Jiang Ri-Hong, Huang Yu-Song, and Xu Wei-Bin. 2011. Notes on Calocedrus (Cupressaceae) in Guangxi, China. Guihaia 31(2):155-159.
The species account at Threatened Conifers of the World.
Last Modified 2023-12-17
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