The Pinus Cembroides is commonly known as the Border Pinyon, Mexican Pinyon as well as Papershell Pinyon.
The currently accepted scientific name of Mexican pinyon is Pinus cembroides Zucc. It is a member of the pine family (Pinaceae) . Two varieties in addition to the typical variety are recognized: papershell pinyon (P. c. var. remota Little) and Mexican pinyon (P. c. var. bicolor Little) . There is taxonomic disagreement about P. cembroides in the strict sense. Bailey and Hawksworth and others have split P. cembroides infrataxa and raised them to specific status . Two subspecies (P. c. ssp. lagunae D. K. Bailey and P. c. ssp. orizabensis D. K. Bailey) beside the typical subspecies of P. cembroides were recognized; however, recently each was raised to specific status . The two varieties, P. c. var. remota and P. c. var. bicolor, were synonomized to P. remota (Little) Bailey & Hawksworth and P. discolor Bailey & Hawksworth (border pinyon), respectively . All names are currently used in the literature. Bailey and Hawksworth relegated P. c. var. bicolor to synonomy with P. discolor based on differences in flowering times, bark color, needle color and number, and two monoterpene compounds . Variation in flowering time and needle number throughout the revised range of P. cembroides is inclusive of P. discolor characters . Therefore, this writeup considers P. cembroides in the broad sense. For readers who support the realignment, studies concerning United States populations of P. cembroides may be interpreted as P. discolor . Hybrids occur between Mexican pinyon and true pinyon (P. edulis) where their ranges overlap .Mexican pinyon is distributed in the mountains of western Texas, southwestern New Mexico, and southeastern Arizona . A large part of its range occurs in Mexico, extending from the United States border southward along the Sierra Madre Occidental and Sierra Madre Oriental into northern Puebla . Mexican pinyon also occurs in Baja California Sur . Papershell pinyon occurs on the Balcones escarpment of central and western Texas and extends into northern Mexico .Mexican pinyon occurs as individual scattered trees in interior chaparral and as occasional to frequent trees in the Madrean evergreen and encinal woodlands . Mexican pinyon becomes dominant in the pygmy conifer (Pinus spp.)-oak (Quercus spp.) scrub , pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands , and pine (Pinus spp.)-oak woodlands . Mexican pinyon is an important species in Douglas-fir (Pseudotsuga menziesii), Chihuahua pine (Pinus leiophylla var. chihuahuana), and ponderosa pine (P. ponderosa) series . Mexican pinyon is one of the dominant trees in pinyon series . It is minor in geographical range compared to true pinyon and is included in the true pinyon series, since Mexican pinyon replaces true pinyon across limited areas in Arizona and New Mexico Mexican pinyon occurs as a minor species in some of the relict Arizona cypress (Cupressus arizonica) forests that are in upland positions . Some of the publications that list Mexican pinyon as a dominant or indicator species are: (1) Preliminary classification for the coniferous forest and woodland series of Arizona and New Mexico (2) A series vegetation classification for Region 3 (3) Plant communities of Texas (Series level): February 1992 . Woody species associated with Mexican pinyon but not previously mentioned in Distribution and Occurrence include Arizona madrone (Arbutus arizonica), Texas madrone (Arbutus texana), western white honeysuckle (Lonicera albiflora), and Madrean mockorange (Philadelphus madrensis) .Some of the information provided here is attributed to:Pavek, Diane S. 1994. Pinus cembroides. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). , available at the USDA Fire Effects Information System (FEIS) website