Forest in Yunnan; iNaturalist observation 103096460 [刘光裕 Liu Guangyu, 2021.11.01].
Foliage and nearly-mature cone on a tree in habitat, Yunnan; iNaturalist observation 128290281 [桃子, 2022.07.28].
Shoot with mature pollen cones on a tree in habitat, Yunnan; iNaturalist observation 40690737 [benanna, 2020.03.23].
Pinus yunnanensis
云南松 Yúnnán sōng (lit. Yunnan pine), Yunnan pine.
Synonymy (homotypic):
There are two varieties, P. yunnanensis Franch. var. yunnanensis (syn. P. yunnanensis var. tenuifolia W.C.Cheng & Y.W.Law 1975, P. insularis var. tenuifolia (W.C.Cheng & Y.W.Law) Silba 1990, P. yunnanensis subsp. tenuifolia (W.C.Cheng & Y.W.Law) Silba 2009) and P. yunnanensis Franch. var. pygmaea (Hsueh f.) Hsueh f. 1978 (syn. P. densata var. pygmaea Hsueh f. 1975, P. tabuliformis var. pygmaea (Hsueh f.) Silba 1990, P. yunnanensis subsp. pygmaea (Hsueh f.) Silba 2009). Var. tenuifolia is here reduced to a synonym; it differs only in having drooping needles, and as such may warrant designation as a forma.
Molecular analyses using both nuclear and plastid markers have consistently placed this species sister to P. kesiya (or P. densata, thought to have originated as a P. kesiya × yunnanensis hybrid) in a clade with other E Asian members of subsection Pinus including P. hwangshanensis, P. tabuliformis, and P. thunbergii (Wang et al. 1999, Geada López et al. 2002, Gernandt et al. 2005). Both P. kesiya and P. tabuliformis currently have adjunct distributions, suggesting these taxa may have diverged only recently and through a vicariant process. In this context it is relevant that genetic diversity within P. yunnanensis has a strong geographic component, with populations in different portions of its range optimally adapted to distinct environmental factors, dominantly temperature, water relations, and seasonality (Wang et al. 2013); similar findings have come from a common garden experiment within the species' native range (Sun et al. 2020a).
A broad zone of introgression occurs where P. yunnanensis and P. kesiya distributions overlap in southern Yunnan. The introgression is asymmetrical, with P. kesiya as the pollen donor. The observed population structure suggests a post‐glaciation range expansion in P. yunnanensis, with P. kesiya range expanding during glacial and contracting during interglacial episodes (Gao et al. 2023).
Trees to 30 m tall and 100 cm dbh, usually with a single (sometimes forked) trunk and spreading or downcurving branches forming a domed or flat-topped crown. Bark first rough with pulvini, becoming scaly, longitudinally fissured, irregularly platy with age; gray-brown weathering to gray. Twigs stout, glabrous, reddish-brown, weathering brown. Buds ovoid-oblong, acute, to 25 mm long (lateral buds smaller), red-brown, scales appressed, not resinous. Leaves in fascicles of (2-)3, living 2-3 years, 7-20(-30) cm long, straight, 1-1.2 mm thick, pliant but rarely drooping, margins finely serrulate, light green, fine lines of stomata on all surfaces, basal sheath 10-15 mm long, persistent. Pollen cones short-cylindrical, ca. 20 mm long, yellow at maturity. Seed cones in whorls of 2-5, nearly sessile, opening at maturity but usually persisting several years, nearly symmetrical, when closed ovoid-conical, 5-10 × 3.5-4.5 cm, 5-7 cm wide when opened, green, maturing brown. Seed scales woody, stiff, obovate, basal scales spreading widely, apophyses raised, transversely keeled, umbo nearly flat or slightly raised, bearing a very small prickle. Seeds ovoid, 4-5 mm long, brown, with a 12-15 × 5 mm light brown wing (Farjon 2010). Pollen is dispersed in April/May, and cones ripen in October of the second year. Young trees begin to bear cones after about 10 years, and it is usually 3 years between mast crops (Baidu Baike 2024).
The type variety is distingished by stature (trees to 30 m tall), leaves 10-20(-30) cm long, rarely drooping, seed cones opening at maturity and falling a few years afterwards. Var. pygmaea is distinguished by a shrubby growth form found in high mountains, commonly with multiple stems; leaves 7-13 cm long; and seed cones variably serotinous, persistent (Farjon 2010).
China: E Guangxi, E Guizhou, S Sichuan, Yunnan. Occurs at (600-) 1500-2500 (-3320) m elevation, sometimes in valleys and gorges but forming extensive stands on high mountain slopes, usually on dry sites. In places it reaches the alpine timberline and grows as a shrub. It is well adapted to dry and infertile soils, and high elevation provenances tolerate severe frost. (Farjon 2010, Deng et al. 2013). Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001, presumably referring to var. yunnanensis). Climate change models for the latter 21st century predict relatively little distribution change but a moderate habitat suitability loss for P. yunnanensis (Gao et al. 2023).
The most widely-distributed native tree in Yunnan, Pinus yunnanensis is a fire-adapted pine that is readily killed by fire and regenerates prolifically to form extensive pure stands. Such a life history is common in subgenus Pinus, particularly in sections Pinus and Contortae. In the absence of fire, P. yunnanensis is commonly seral to evergreen broadleaf forest dominated by trees such as Castanopsis orthacantha and Lithocarpus dealbatus; typically the Pinus forest predominates for about 60 years, with the Pinus component dying out from about 95 to 165 years after disturbance (Tang et al. 2013). P. yunnanensis also occurs as a component of a wide variety of mixed-composition forests including with broadleaf evergreens, with broadleaf deciduous trees, and at the highest elevations with P. armandii. Common angiosperm codominants include Lithocarpus variolosus, Quercus griffithii, Castanopsis orthacantha, Schima argentea, Quercus griffithii, and Quercus rehderiana (Tang et al. 2020). In recent times P. yunnanensis has extended its range as competing broadleaf forests are logged (Richardson and Rundel 1998). Besides fire and logging, the other common disturbance leading to stand origination is landslides (Tang et al. 2020).
Important pests and pathogens affecting P. yunnanensis include the bark beetles and pine shoot beetles Tomicus yunnanensis and T. minor, which can cause massive death of pine trees (Liu et al. 2019). These beetles are a common vector for introduction of the blue-stain fungus Leptographium yunnanense, with greatest vulnerability to infection observed as a result of warm, wet summer weather (Salle et al. 2008). Other pests of major concern include the Japanese pine sawyer beetle Monochamus alternatus and the pine shoot moth Dioryctria rubella. Remote sensing has shown widespread mortality in P. yunnanensis forests during the period 2009-2020 due to the depredations of these insects (Liu et al. 2022). Other reported pests include several defoliators in the genus Dendrolimus, pit-cutting beetles in the genus Blastophagus, and tip borers in the genus Dioryctria (Baidu Baike 2024).
The conservation status of P. yunnanensis is assessed as "Least Concern" due to its large range and absence of ongoing population declines.
The oldest known living specimen, 163 years, was documented by Tang et al. (2020), who also recorded a tree 116 cm dbh and 33 m tall; this was based on a study in old-growth forests of the Tianchi National Nature Reserve in the Xuepan Mountains, Yunlong County, northwestern Yunnan. This age was derived using dendrochronological methods. The same authors refer to a study by Li et al. (2007) in Yongren, central Yunnan, that reported trees to 257 years old, "but they did not provide data on ring width and did not explain how they collected age data."
Pinus yunnanensis is currently an important tree in China, utilized to an extent equaled by few other species. The naturally-regenerated stands cover 55-60 thousand km2, along with about 3000 km2 of plantations. Besides production of pole and saw timber, the tree is used for fuel, pulp, plywood, and a wide range of engineered wood products; the resin is tapped, the bark is used to produce tannins, and the foliage is used both as fodder for animals and to extract essential oils. The species is also used for wind breaks, erosion control, and as an ornamental tree. Locally, it has become invasive (Farjon 2010). A novel timber defect is "twisted trunk", a condition that greatly reduces the species' utility for timber. The phenomenon is still not well understood but seems to be due to environmental factors including soil nutrients and composition of the belowground microbial community (Li et al. 2023). The species is still used in traditional Chinese medicine; the resins can be used to promote muscle growth, relieve pain, remove dampness and kill insects. The "knots" [trans.?] treat rheumatism and serve as an analgesic. The plant can also be used to treat painful swelling, malignant sores, warts, and ringworm, eczema, joint pain, and difficulty in flexion and extension (Baidu Baike 2024).
In contrast, traditional uses of P. yunnanensis do not seem to have been widely reported. The Dulong people of Yunnan prefer it for making log beehives (Cheng et al. 2020) and they used the "turpentine" to treat trauma (Cheng et al. 2022). The Buyi people seem to have used the resins for treatment of rheumatism and various traumas (Xiong et al. 2020), and the Yi people use the pollen to prepare an edible cake (Sun et al. 2020b).
In science, the species has been used in a variety of dendrochronological studies considering both climate (Yang et al. 2018, Shen et al. 2020) and ecological relationships (Tang 2013, 2020).
No data as of 2023.11.03.
The epithet refers to the species' occurrence in Yunnan.
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A very extensive photo gallery at the China Natural Herbarium, accessed 2024.01.22.
Last Modified 2024-01-22
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