Pinus rzedowskii — Wikipédia

Pinus rzedowskii is a kind of conifer in the Pinacea family that is only found in Mexico, in the region of Sierra Madre del Sur. Its populations are reduced in number and geographic extension; The species is therefore considered in danger of extinction.

It is a pine up to 30 meters if the conditions are optimal. Its trunk is usually straight and its bark is thick and rough. It has fairly deep longitudinal cracks, split into large plates.
The branches are thin and smooth. The sterile leaves, called cataphylla, are small and disappear fairly quickly in the life of the tree.
The terminal buds are small and do not contain a resin ^{[ first ]} .

The needles are soft are 6 to 10 cm long and less than a mm wide. Their green tends to gray or yellow. They are fascinated by 4 or five, and wrapped in a sheath deciduous . They only carry stomates on the lower faces.
Under the microscope, we observe a thin hypodermis, 2 to 4 resin channels and a single vascular beam. The latter characteristic makes him a member of the sub-genre Strobur ^{[ first ]} .

The male cones are placed in a spiral around the branches which are being growing. The female cones are roughly ovoid, shortly pedunculated, are 10 to 15 cm long and contain a lot of resin. Their scales end with an apophysis often wider, faired and carrying a sometimes pointed dorsal umbo.
The seeds are about 8 mm long and 5 mm wide and have an articulated wing 20 to 30 mm long ^{[ first ]} .

It is found in a mountainous region, on limestone outcrops above old volcanic formations.
The altitude varies between 2100 and 2400 meters and rainfall is around 1500 mm per year. It is accompanied by small oaks, various kinds of bushes, agaves and high grass. It is not accompanied by other pines, despite the presence of large pine -sodes nearby ^{[ first ]} .

It is a fairly rare pine which was only discovered in 1966 and was only described in 1969.

It has original characteristics. We classify it in the sub-genre Strobur , because it has only one vascular beam per needle, and in the section Parrya , but it differs from other species of these taxa by multiple characters, including the morphology of seeds, cones and its bark ^{[ first ]} .
Rzedowskii pine is sometimes classified among gable pines (subsection CEMBROIDS ) but it is also often placed outside this clade with two other species, Luntus crarkan and of Maximartinezii , then forming the subsection Rzedowskianae . It differs from other gable pines by the length of the seed wing, longer at P.Rzedowskii than in other gable pines ^{[ 2 ]} .

However, the classification of pines is still discussed and the lack of data due to the scarcity of Rzedowskii pine prevents any certainty. However, it seems likely that the Rzedowskii pine is a relatively old species; The points in common with other pines however far from him would be explained by the retention of ancestral characters ^{[ 3 ]} .

It is only found in three locations in Mexico, in the Sierra Madre del Sur. These three locations are separated from each other by at least 40 kilometers and two of the populations are very small (less than fifty individuals), the third containing a few thousand individuals. Forest lights have in the past destroy many adult trees and disturbed the regeneration of Rzedowski pines ^{[ 2 ]} , and all new fire would jeopardize their populations ^{[ 4 ]} .
The pines remain small in two of the localities because of the bad rocky substrate but reach more respectable sizes in the last ^{[ first ]} .