Pinus maximartinezii Rzed.

Pinaceae

Endemic to two locations in northern Mexico where the main threats are grazing by livestock and fire

Distribution

Mexico: S Zacatecas (Sierra de Morones near Juchipila). A second location, La Muralla in Durango, has recently been reported (Gonzalez-Elizondo et al., 2011). It was discovered in December 2010. The extent of occurrence is estimated to be about 376km² with an actual area of occupancy estimated to be about 35km².

The population in the Sierra de Morones has ca. 2000–2500 mature individuals scattered on ridges and E-facing slopes, covering approximately 400ha (Ledig et al., 1999). There is regeneration, but it is under threat from seed collecting, roaming cattle and fire. On genetic grounds, Ledig et al., (1999) concluded that the species had gone through “an extreme bottleneck perhaps four to five generations ago, which is less than 1000 years in this species." Fires of more recent times have destroyed parts of the population, so in IUCN terms of three generations, here estimated to be around 150 years, there has probably been a decline in number of mature individuals.

In another attempt at counting trees, the vastly larger figure of 60,548 individuals was reported (Lara Rodriguez, 1997). This count presumably included all trees and was conducted by sampling over a larger area within the AOO in Zacatecas. The AOO was estimated to be 3500ha.
The new subpopulation in Durango has in excess of 900 mature trees with an AOO of ca. 110ha (Gonzalez-Elizondo et al., 2011).

Habitat and Ecology

The rock of the mountain in Zacatecas where P. maximartinezii occurs is in part sandstone or limestone and also metamorphic, the soils are very rocky and shallow. In Durango it grows on rocky soils of igneous origin. Precipitation is probably ca. 700–800 mm annually, virtually restricted to four months in the summer. Pinus maximartinezii is virtually the only pine here, but a few scattered individuals of P. leiophylla var. chihuahuana have been seen. Its altitudinal range is 1750–2400 metres above sea-level. Abundant are various large leaved species of deciduous Quercus, e.g. Q. macrophylla, which are bare during the long dry season from September to May. Fires occur regularly in the region in all vegetation types; it is not known whether this species is adapted well to reseed itself after fire. Pollen dispersal is usually in May–June; the ovuliferous cones take 18–24 months to reach maturity, and perhaps longer for the seeds to ripen fully. Seeds mostly remain in the cones. Squirrels are capable of biting off the apohyses to reach the seeds and probably store them. They, and probably also birds, may play a crucial role in effective seed dispersal, but this has not been investigated to date.

Human Uses

Like other 'piñon' (pinyon pines) in Mexico, this species is of local importance for its nutritious, edible seeds (Lopez Mata, 2001), which are harvested by local people and marketed in the region. Due to its low stature and branching of the trunk, its timber is not used. In Mexico, it is sometimes planted as an ornamental tree; elsewhere it is only grown in a few botanic gardens (e.g. at the University of California in Berkeley) and research nurseries; its horticultural merits could be greater than that since it is not too difficult to grow from seed in the nursery. Young trees retain an attractive blue juvenile foliage for several years.

Conservation Status

Global status

Endangered B1ab(ii,iii)+2ab(ii,iii)

Global rationale

Based on current knowledge, both the extent of occurrence (376km²) and the area of occupancy (35km²) are within the thresholds for Endangered. Two disjunct locations are known although it is possible that other subpopulations exist in the intervening areas. A recent decline in at least the quality of habitat has been observed in the main subpopulation in Zacatecas due to grazing and erosion. Discrepancies between the published counts for the Sierra de Morones subpopulation (2000–2500 mature individuals over 400ha – Ledig 1999 and 60,548 'individuals' over 3500ha – Lara Rodriguez, 1997) reflect different sampling strategies. The total size of the population is likely to be more than 10,000 mature individuals. On the basis of this information Pinus maximartinezii is assessed as Endangered under the B criteria.

Global threats

The main threats are fire and over grazing and subsequent erosion which result in few seedlings that succeed in establishing themselves. Intensive harvesting of cones and seeds may also diminish its chances of reproduction although recent studies indicate that this can be sustainable provided that grazing, erosion and fire are controlled (Lopez Mata & Galván Escobedo, 2011). Seed collections have been made in recent years to ensure ex situ conservation programmes. The land on which these pines grow is privately owned by villagers, who have an interest in the seed harvests as well as cattle grazing.

Conservation Actions

The local landowners (the stands on Sierra Morones are on private land) and villagers have a stake in the long term survival of this species, as its seeds have a (local) market value. Efforts are being made first and foremost to prevent forest fires, by limiting access and prohibiting camping etc. Some restoration work has been initiated. Control of grazing is less certain, as these constitute conflicting interests. The situation in the new locality in Durango is as yet unknown.