|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.
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.
|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