Madrean Pinyon-Juniper-Oak Woodland

Madrean Pinyon-Juniper-Oak Woodland
The view SE into the hills above East Whitetail Canyon of the Chiricahua Mountains, 5200 feet, 11 June 2010. Junipers are the dominant tree, 5 meters tall, with 15-25% cover, with associated pinyon (P. discolor; 3 meter tall, 1-4% cover) and Arizona oak (3 meters, 10-14%). Other common species include beargrass (Nolina microcarpa), foreground left; wait-a-minute (Mimosa biuncifera), and Agave palmeri, each with 1-4% cover. Mesquite and manzanita were uncommon, and were respectively limited to either deep soils or skeletal soils. Bunchgrasses (grama, cane bluestem, and muhly) average 0.3 m tall and gave 10-14% cover.


The Madrean Pinyon-Oak-Juniper Woodland is by far the largest ecosystem in the study area, in part because of its broad range in elevation - from 4600 feet in Buckeye Canyon in the Dos Cabezas Mountains up to 8800 feet on the south slope of Johnson Peak in the Chiricahuas, above Rucker Canyon. Not surprisingly, the ecosystem also takes in a diversity of landforms and substrates.

About 25% of the ecosystem is on slopes less than 18% (10 degrees); 72% is on steep slopes of 18-70% (10-35 degrees); 3% is on very steep slopes exceeding 70%. Parent materials include the massive extrusive rocks that characterize much of the Chiricahuas, ancient metamorphics including schist and marble, young granites in the Dos Cabezas and Dragoons, and sedimentary rocks ranging from the Pliocene to the Paleozoic.

Yet another reason for the immensity of this ecosystem is its broad definition, which includes all lands where juniper or pinyon or oak are the dominant trees, except where they are part of a mosaic with large conifers, in which case they were mapped as part of the lower pine-oak ecosystem. Furthermore, the presence of localized sedimentary rocks interbedded with more extensive volanics was associated with patches of mountain mahogany as the dominant woody plant, with hardly an oak, pinyon, or juniper in sight. Where these patches were on small scale (under 200 acres), they were mapped as part of the pinyon-juniper-oak ecosystem. Where the sedimentary strata were extensive, they were separately mapped in an ecosystem typified by rosette grasslands, pinyon pine, and mountain mahogany.

Below are several examples of the diversity within the Madrean Pinyon-Oak-Juniper Woodland.

The view east from the Snowshed Trail, 6200 feet, Cave Creek watershed, 13 June 2010. In contrast to the extrusive rocks in the background, the foreground parent material is a limy sandstone that it is associated with a shift to a more open vegetation of mountain mahogany, pinyon, Agave, beargrass, and sotol (Dasylirion wheeleri). Abundant grasses, mostly grama, give 26-40% cover.


The view NW in Tex Canyon, Chiricahuas, of alluvial terraces about two miles north of the Krentz Ranch, 5340 feet, 12 June 2010. The deep soils support not only the dominant juniper (10 meters tall, 15-25% cover) and associated Emory and Arizona oak (8 meters, 10-14% cover, combined), but also dropseed grass and Apache plume (right foreground). Pinyon pine add another 1-4% cover, and scattered walnut, sycamore and hackberry trace the dry channel.


The view east of a north-facing slope near the Snowshed Trail, Cave Creek watershed, 6380 feet, 13 June 2010. Pinyon pine, 11 meter tall, are the clear dominant, with 15-25% cover amid much downed wood. Common associates include Yucca schottii, mountain mahogany (Cercocarpus montanus), silktassel (Garrya wrightii), and netleaf oak. Grasses are notably absent.


The view NW towards Dos Cabezas, from a north-facing slope near the summit of Cooper Peak, 7700 feet, 11 Sept 2010. This woodland is dominated by Gambels oak, which sometimes forms open stands of 7 meter tall trees, and sometimes forms small copses of 3-4 meter tall trees. This woodland is restricted to north-facing slopes, and extends from 7900 feet down to 6500 feet, with mountain mahogany and alligator juniper as common associates. Late-summer grasses were largely side-oats grama, with patches of bull muhly and squirrel tail, Elymus elymoides.


The view SW near Pine Canyon, Chiricahua Mts., 5300 feet, 13 September, 2010. The dominant trees on this rocky slope are 2 meter tall Quercus toumeyi, with 15-15% cover. Common associates include manzanita (1 meter, 5-9% cover), alligator juniper (4 m, 5-9%), pinyon pine (2 m, 1-4%), beargrass (1 m, 1-4%) and sotol (1 m, 1-4%).  Silktassel is present but uncommon. Grasses give scant cover (<5%), and include wolftail, crinkle awn (Trachypogon secundus), and pinyon rice grass (Piptocheatium fimbriatum).


The view east in Happy Camp Canyon, Dos Cabezas Mts., 5100 feet, 11 September, 2010. A typical mix of Emory and Arizona oak, combining for 15-25% cover. Grasses, mostly sideoats and Lehman’s love grass, are abundant, with 26-40% cover. Alligator juniper adds another 5-9% cover.


The view SSE of a steep slope above Happy Camp Canyon, 6100 feet, Dos Cabezas Mts., 11 September, 2010. Silktassel is the dominant woody plant, 4 meters tall and with 26-40% cover. Common associates include mountain mahogany (4 meters, 15-25%) and Arizona oak (4 m, 15-25%. Grasses are uncommon.


The view south, near the Council Rocks, Dragoon Mts., 4900 feet, 31 August 2010. The big trees are Emory oak (10 meters tall, 15-25% cover). Mesquite and wait-a-minute are uncommon.  Grasses, mostly Lehman’s love grass and hairy grama, averaged 0.75 meters tall at summer’s end, and gave 41-60% cover. Forbs such as Evolvulus arizonicus and the tall yellow composite Hymeothrix wizlizenii were common amid the grasses.


Other Vegetation Classifications

The National Vegetation Classification System (NVCS) does not list an ecosystem that describes the Madrean Pinyon-Oak-Juniper Woodland ecosystem mapped in this study. This is because the ecosystem is meant to include two NVCS ecosystems: the higher elevation Madrean Pinyon-Juniper Woodland; and the generally lower Madrean Encinal. The latter has lower tree and shrub cover, and more grass.

As mapped in this study, the observed ecosystem includes elements of several vegetation types mapped or described in other classification schemes. In each of the six schemes referred to below, the * symbol marks the vegetation type most similar to the Madrean Pinyon-Oak-Juniper Woodland.

And what is meant by ‘most similar’? For the USFS Plant "Habitat Type" (Potential Association), the USFS "Potential Natural Vegetation Type" (PNVT), and the Brown, Lowe, and Pase "Biome", the * symbol denotes the best fit based on the description of the Habitat Type, PNVT, or Biome. For the Landfire, ReGap, and USFS mid-scale classifications, which are presently mapped at a 30 meter resolution and were used in creating the map, the * symbol denotes the classification that was most commonly attributed within The Madrean Lower Montane Pine-Oak Forest and Woodland, as mapped in this effort. 

Landfire Existing Vegetation Type (EVT)
Madrean Encinal*
Madrean Pinyon-Juniper Woodland
Mogollon Chaparral
Rocky Mt. Montane Riparian
Madrean Lower Montane Pine-Oak Forest and Woodland
Apacherian-Chihuahuan Semi-Desert Grassland and Steppe
Apacherian-Chihuahuan Mesquite Upland Scrub

USFS Mid-scale Dominance Type
Upper Pine-Oak (PINUS_QUERC)
Ponderosa Pine (PIPO)
Upper Evergreen Forest Tree Mix (PIPO_PSME, PSME, TETX)

USFS Plant Habitat Type (Potential Association)
Arizona white oak/bullgrass (QUAR/MUEM) *
Arizona white oak/pinyon ricegrass (QUAR/PIFI)
Arizona cypress/silverleaf oak (CUAR/QUHY)
Emory oak/pointleaf manzanita (QUEM/ARPU)
Emory oak/sideoats grama (QUEM/BOCU) * on alluvial fans at the foot of mountains
Emory oak/common sotol (QUEM/DAWH2)
Silverleaf oak/longtongue muhly (QUHY/MULO)
Border pinyon/bullgrass (PIDI/MUEM)
Border pinyon/pinyon ricegrass (PIDI/PIFI)
Border pinyon/silverleaf oak (PIDI/QUHY) * on very rocky slopes
Border pinyon/Toumey oak (PIDI/QUTO2)

USFS Potential Natural Vegetation Type (PNVT)
Madrean Encinal Woodland *
Interior Chaparral

Brown, Lowe, and Pase Biome
Madrean Evergreen Woodland *

Southwest Regional GAP Ecological System
Madrean Encinal *
Madrean Pinyon-Juniper Woodland
Mogollon Chaparral
Madrean Lower Montane Pine-Oak Forest and Woodland
Rocky Mt. Montane Riparian