Exploring Mexico’s Endemic Conifers

Part 2 of my series on Mexico…

For those of you who have read my blog in the past, you’ll know that it’s primarily focused on mammals. Well, in the background, I also have an interest in conifers and try to take a look at interesting pines, firs, and more in the Western hemisphere. So, alongside observing as many endemic and endangered mammals as I could find, I also hoped to see many conifer species in Mexico a month or so ago.

Thankfully, many of the areas I traveled in–especially the Central Volcanic Arc and Sierra Madre Oriental–are also great sites to observe rare conifers. But before we go into what I saw, I figure I’ll start with a little primer on Mexico’s geography and conifers.

What many people sometimes don’t realize is that Mexico is a pretty mountainous country. Much of the place is elevated and many of its mountain ranges rise about 10,000 ft. As a result, these regions provide exactly the kind of climate and soils conifers thrive in.

The three major areas of conifer diversity in Mexico are in the West, East, and Center.

In the West, the Sierra Madre Occidental runs from Sonora in the Northwest to Jalisco in the South. Interestingly, the range maintains a remarkably similar species composition from North to South, albeit in rather diluted form at its extremes (it loses much of its diversity in the Arizona Sky Islands, for example). The lower slopes of the Eastern side of the range are dominated by high desert and Pinyon-Juniper Woodland, mostly consisting of Mexican Pinyon and various Juniper species; in the west, the range is bounded by the Sea of Cortez and Tropical thorn forest. The middle elevations of the range are dominated by a diversity of hard pine species, some of which are shared with other parts of Mexico, such as Pinus leiophylla, Pinus engelmannii, and Pinus arizonica. At the range’s crest, more mesic areas provide the right conditions for Southwest White Pine and locally, Rocky Mountain Douglas-fir, Durango Fir, and Chihuahuan Spruce.

To the East, the Sierra Madre Oriental stretches from extreme southern Texas to Southern Veracruz. The range, among Mexico’s most diverse, covers a huge array of climates and ecosystems. In the North, the range is remarkably similar to the Sierra Madre Oriental; however, the biodiversity is even higher as its highest summits occur as isolated ranges as opposed to a more consistently elevated region. The Northern Sierra Pena Nevada, Sierra de Arteaga, and Cerro del Potosi areas are home to a handful of endemics, including Potosi Pinyon, Martinez’s Spruce, Pinus nelsonii, Pinus pinceana, and Pinus johannis, alongside many species shared with the Sierra Madre Occidental and more broadly, the Rockies. In the South, higher ranges such as the Sierra Gorda in Queretaro and El Cielo in Tamaulipas hold an interesting range of species, with pine forests (dominated by Pinus pseudostrobus and Pinus patula) at high elevations and stunningly diverse cloud forests in areas blanketed by Atlantic rainfall. These areas, among the world’s most diverse, are meeting grounds for North and South–conifers here include Mexican Yew and Podocarpus matudae.

The most endemic-rich region however is Mexico’s Transvolvanic Arc. Almost all conifers of the region are only found in this mountain range, which stretches across Mexico from Colima on the Pacific to Veracruz on the Atlantic. Besides rich mid-elevation Pine forests, the region is home to unique moist Sacred Fir forests in the upper montane zone, and open Pinus hartwegii stands at the highest elevations, with an understory covered in bunchgrass. Interestingly, despite the high rates of endemism in the range, it holds comparatively few endangered conifers. Not sure why that is, but it is an interesting question to ponder.

With the primer done, I’ll just briefly go through what I saw. My exploration of conifers began on the cool plateaus of Michoacan, one of Mexico’s classic conifer landscapes. Here, I observed a variety of species and forest types characteristic of Mexico’s Transvolcanic Arc, including single-species Pinus pringlei forests on Cerro de la Cruz, pine-oak forests and volcanic slopes, and locally, pine-fir forests on Cerro Patamban and grassy, open Michoacan Pine woodlands near Lake Patzcuaro. I continued onto Mexico City, seeing the open Pinus hartwegii woodlands at the high elevations of Volcan El Pelado and onto the remote Oriental Basin, to see the world’s Southernmost Pinyon-Juniper woodlands on the slopes of Pico de Orizaba. My exploration of the Volcanic Arc ended in Veracruz, where I saw Abies hickellii and Pinus patula on the misty slopes beyond Cofre de Perote.

From there, I cut north along the Sierra Madre Oriental. After seeing diverse Pinyon-Juniper Woodlands on the lower slopes of Cerro del Potosi, I climbed up into the mountains of the Sierra de Arteaga. Here, I saw numerous species including Southwestern White Pine, Arizona Pine, Mexican Douglas-fir, and Abies vejarii. While I couldn’t reach the alpine zone, home to the rare Potosi Pinyon, I was very happy to see two very rare species–Pinus pinceana and Pinus nelsonii, both rare, primitive, and evolutionarily distinct relics of the region.

In the process, I had a bit of a pleasant surprise too. I was expecting significant deforestation and potential extirpation of populations of rare species, but I saw relatively little of this. Most forests I saw seemed to be in decent shape, at least as far as the tree size and health are concerned. While some species (notably narrow Mexican endemics) are undeniably under threat, it seems local conservation measures for various species (e.g. endangered endemics including Pinus maximartinezii and Pinus pinceana) are helping these species hold their own.

But there’s still a lot more to see. I have yet to observe Pinus chiapensis and Guatemalan Fir in Oaxaca’s Sierra Juarez, Pinus rzedowskii in Michoacan’s Sierra de Coalcoman, the high-altitude conifer forests of the Sierra Madre Occidental (Creel, Chihuahua), or the impressively weird Pinus maximartinezii of Zacateca’s Sierra de Morones. For sure, there’s a lot more places, species, and habitats to see. I’ll be back!

Venkat

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