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Pinus stobiformis
Cones of the strobiformis group
Click on photo to enlarge.
1) Pinus strobifomis - Jemez Mountains, New Mexico.
Length 18 cm.
2) Pinus stobiformis - Sandia Mountains, Central New Mexico.
Length 15 cm. This cone looks more "flexilis" like than many of the cones farther north in the Jemez Mts. It is however much longer than the typical flexilis cone.
3) Pinus strobiformis - Mt. Lemmon, Arizona.
Length 21 cm.
4) Pinus strobiformis - Espinazo Del Diablo, West side of the Sierra Madre Occidental, Durango.
Length 40 cm.
Pinus stobiformis Pinus stobiformis Pinus stobiformis Pinus stobiformis
Pinus stobiformis Pinus stobiformis Pinus stobiformis Pinus stobiformis
5) Pinus strobiformis var. potosiensis - 2800 m. - Cerro Potosi, Nuevo Leon.
Length 28 cm.
6) Pinus strobiformis var. potosiensis - 2900 m. - Cerro Potosi, Nuevo Leon.
Length 19 cm.
7) Pinus strobiformis var. potosiensis (?) - 3200 m. - Cerro Potosi, Nuevo Leon.
Length 11 cm.
8) Pinus veitchii - East side of Popocatepetl, Puebla.
Length 39cm.
The trees at the top of Cerro Potosi have cones very different from those at lower elevations on the same mountain. Perry identified these trees as Pinus flexilis. Farjon called them Pinus flexilis var. reflexa, the same as the trees in Arizona and New Mexico. The trees in Arizona have a "flexilis" appearance, with up-turned branches and short needles. The cones in Southern Arizona and New Mexico gradually change from flexilis in the north, starting around the Grand Canyon, to strobiformis in the south. The strobiformis cones in Mexico gradually lengthen as you go south along the Sierra Madre Occidental though Sonora, Chihuahua and Durango, the longest cones being in Durango. At the southern end of the Sierra Madre Occidental, in Jalisco, it becomes difficult to distinguish Pinus strobiformis from Pinus veitchii. The populations of Pinus strobiformis in the Sierra Madre Occidental, with the exception of the gradual lengthening of the cones from north to south, are fairly consistent in their features from Northern Sonora through Durango. There are continuous highlands through this section. From northern Sonora through Southern Arizona and New Mexico, the Mountains are broken into islands. The Pinus strobiformis are thus separated into isolated populations. It is in this area that the transition from Pinus flexilis to Pinus strobiformis occurs, each isolated stand looking more like strobiformis as you go south. The trees at the top of Cerro Potosi are far removed from this transitional area. The trees do not have the "flexilis" appearance like the trees in Arizona. The cones also appear different. I believe that they are of a different origin than the transitional trees in the Arizona-New Mexico area, or perhaps have been isolated for a very long time on the high Mountain islands of the Sierra Madre Oriental.

Photos : © Jeff Bisbee
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8 September 2006
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