Madrean Lower Montane Pine-Oak Forest and Woodland

Madrean Lower Montane Pine-Oak Forest and Woodland
The view SE from the Methodist Camp Road, with Muhlenbergia bunchgrass and a Schott’s yucca in the foreground near Pinery Canyon, 6100 feet, September 13, 2010. Along this relatively mesic canyon bottom, Apache and Ponderosa pine are up to 20 meters tall and combine for 15-40% cover, depending on aspect. Chihuahuan pine is rare, while Douglas fir is locally common in mesic locales. Silverleaf and Arizona oak combined are the dominant trees, 6 to 7 meters tall, with 24-60% cover. Manzanita is locally common on dry slopes.


The Madrean Lower Montane Pine-Oak Forest and Woodland ecosystem ranges from 5600 to 8400 feet and extends over 25 miles of the study area, from Rough Mountain at the northern end of the Chiricahuas, to Erickson Peak, between Rucker and Price Canyon at the southern end of the range. There is no Lower Montane Pine-oak ecosystem in the Dos Cabezas or Dragoon Mountains. The bedrock geology ranges from volcanic and sub-volcanic rocks from the middle Miocene to Oligocene that characterize much of the Chiricahuas, to sedimentary rocks with local volcanic units (Cretaceous to late Jurassic) found in the upper Cave Creek basin, to smaller inclusions of very old metamorphics (early Proterozoic; 1650 to 1800 Mya) and younger granites (early Miocene to Oligocene; 18 to 38 Mya) at the northern end of the Chiricahuas.

The pine-oak ecosystem clearly favors mesic slopes and canyon bottoms over xeric slopes (64% vs. 36%). The vegetation is a mosaic of P. leiophylla (Chihuahuan Pine) and P. engelmannii (Apache Pine) along with Juniperus deppeana, Pinus discolor, Quercus hypoleucoides, Q, emoryi and Q. arizonica. Douglas fir (Psuedotsuga menziesii), Pinus ponderosa, and P. arizonica can be locally common but are generally not co-dominant. The ecosystem includes drier slopes that lack the pines and Douglas fir, but the conifers return with the next fold in the landscape.

The ecological system is similar to the higher elevation Madrean Upper Montane Conifer-Oak Forest and Woodland, but with these key differences: (1) the Upper Montane Conifer-oak is more than 50% Douglas fir and big pines, while the Lower Montane Pine-oak is more than 50% oak; (2) the Lower Montane pine-oak holds Apache and Chihuahuan pine; and (3) the Lower Montane pine-oak can hold dense manzanita, silk tassel, and silverleaf oak, a kind of chaparral that favors colluvial slopes built of landslide debris.

This matches closely with The National Vegetation Classification System (NVCS) description, which adds:

"Subcanopy and shrub layers may include typical encinal and chaparral species such as Agave spp., Arbutus arizonica, Arctostaphylos pringlei, Arctostaphylos pungens, Garrya wrightii, Nolina spp., Quercus hypoleucoides, Quercus rugosa, and Quercus turbinella. Some stands have moderate cover of perennial graminoids such as Muhlenbergia emersleyi, Muhlenbergia longiligula, Muhlenbergia virescens, and Schizachyrium cirratum. Fires are frequent with perhaps more crown fires than ponderosa pine woodlands, which tend to have more frequent ground fires on gentle slopes."

The view east, on a slope above Pinery Canyon at 5600 feet, near Riggs Spring, 13 September, 2010. Chihuahuan pines (7 to 10 meters) are the dominant vegetation, with 15-25% cover.  The most common associates are pinyon pine (Pinus discolor) (6 meters, 10-14% cover), manzanita (1.5m, 10-14%), silverleaf oak (2.5 m, 10-14%), Arizona oak (4 m, 10-14%), alligator juniper (6 m, 5-9%), and beargrass (Nolina microcarpa) (1 m, 5-9%).  Bullgrass is the most common bunchgrass at this site (1 m, 5-9%).
The view west, towards Centella Point, from the Snowshed Trail in the Cave Creek watershed, 7200 feet, 13 June 2010. A typical open assemblage of Ponderosa pine and Douglas fir above silverleaf oak, Gambels oak, and Arizona oak. Bullgrass and alligator juniper are common associates. The dry slope in the background, right, is mostly oak and juniper; at less than 100 acres, is mapped as part of this ecosystem’s mosaic of oak and pine.
The view north, up a small side canyon off Pinery Canyon near Riggs Spring, 5700 feet, 13 September 2010. The Chihuahuan pines (Pinus leiophylla) are typically 15 meters tall, and give 15-25% cover. An abundance of 0.5 - 2.0 m trees shows considerable recruitment. Co-dominant species include Arizona oak (5 meters, 15-25% cover) and manzanita (2 m, 15-25%). Common species include alligator juniper (5 meters, 10-14% cover), Emory oak (2 m, 1-4%), Mimosa sp. (1.5 m, 1-4%), beargrass (1 m, 1-4%) and pinyon pine (3 m, 1-4%).

Other Vegetation Classifications

The Madrean Lower Montane Pine-Oak Forest and Woodland 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 The Madrean Lower Montane Pine-Oak Forest and 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 Lower Montane Pine-Oak Forest and Woodland*
Madrean Pinyon-Juniper Woodland
Mogollon Chaparral
Madrean Encinal
Rocky Mt. Montane Riparian

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)
Chihuahua pine/Arizona white oak (PILE/QUAR) (*dominant at lower elevations of ecosystem)
Apache pine/Arizona white oak (PIEN/QUAR) (* dominant at mid-elevations of ecosystem)
Ponderosa pine/silverleaf oak (PIPO/QUHY) (*dominant at higher elevations of ecosystem)
Apache pine/silverleaf oak (PIEN/QUHY)
Apache pine/screwleaf muhly (PIEN/MUVI)
Chihuahua pine/silverleaf oak (PILE/QUHY)
Chihuahua pine/pinyon rice grass (PILE/PIFI)
Chihuahua pine/pointleaf manzanita (PILE/ARPU)

USFS Potential Natural Vegetation Type (PNVT)
Madrean Pine-Oak Woodland*
Ponderosa Pine-Evergreen Oak
Interior Chaparral

Brown, Lowe, and Pase Biome
Madrean Montane Conifer Forest*
Madrean Evergreen Woodland
Interior Chaparral

Southwest Regional GAP Ecological System
NOTE: the ReGAP data set calls this ecosystem the Madrean Pine-Oak Forest and Woodland, omitting “Lower Montane” from the ‘official’ title.
Madrean Lower Montane Pine-Oak Forest and Woodland*
Madrean Pinyon-Juniper Woodland
Mogollon Chaparral
Madrean Encinal