Madrean Oak/Conifer/Manzanita on Rocks

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Description:

The view southeast into Indian Bread Rocks, Dos Cabezas Mts., 4300 feet, 12 September 2010. Here, at the lowest elevation within this ecosystem, the dominant vegetation is an even mix of Emory oak and Arizona oak, typically 4 meters tall, with 10-25% cover (combined). Common associates, all with 1-4% cover, include the Sonoran desert species jojoba and wild cotton (Gossypium thurberi) along with sotol (Dasyilirion), silktassel, and Lehmans love grass.

Description

The Madrean Conifer-Juniper-Oak on Rocks ecosystem is characterized by bedrock making up 50% or more of the landscape. Much of this is steep: 24% of the ecosystem is on slopes exceeding 70% (35 degrees); 70% is on slopes between 18 and 70%, and only 6% is on slopes less than 18%. Parent materials are generally granite (Dos Cabezas and Dragoons) or rhyolite (Chiricahuas). Because the ecosystem is based primarily on the landform, its elevation range is broad, from 4300 feet at Indian Bread Rocks to 8500 feet at Portal Peak. At all elevations, however, a pattern persists: dense vegetation interrupted by rock that amplifies the precipitation runoff.

The view south from an imagined vantage above Silver Peak, near Portal. Cave Creek runs along the bottom of the image, while the South Fork runs down along the left. On the left is the south fork of Cave Creek. The ‘rock’ ecosystem is clearly to the left.

The broad elevation range is reflected in the diversity of vegetation, from primarily oaks at lower elevations, to Douglas fir and Ponderosa at the top. Overall, however, the dominant conifer is pinyon pine (Pinus discolor) and the dominant oak is silverleaf (Quercus hypoleucoides), typically 4 - 6 meters tall, and combining for 10-25% cover. Rubble chutes between outcrops are typically home to manzanita and silktassel, 1-2 meters tall, with 10-14% cover. Rhus choriophylla and alligator juniper are locally common, but not dominant. Bunchgrasses such as bullgrass, wolftail, and crinkleawn, were common but usually did not provide over 5% cover.

The view southwest in the West Stronghold, Dragoon Mts., 5600 feet, 31 August 2010. The dominant vegetation is pinyon pine and silverleaf oak, combining for 15-25% cover. Manzanita, Rhus, Arizona oak, and silktassel each add another 1-4% cover.

The view northwest from the mouth of Pine Canyon, Chiricahua Mts., 5400 feet, 13 September 2010. Shown is the terminus of a long low ridge, not impressive yet rocky enough to hold the typical vegetation of this ecosystem: pinyon pine (4 meters tall, 15-25% cover), Toumey oak (2 meters, 25-39%), manzanita (1.5 m, 1-4%), sotol (1 m, 1-4%), and beargrass (1 m, 1-4%). Bunchgrasses - Lycurus and Trachypogon- add another 1-4% cover.

Other Vegetation Classifications

The National Vegetation Classification System (NatureServe.org) does not list an ecosystem that describes the Madrean Oak-Conifer-Manzanita on Rocks ecological system. However, it’s clear that 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 Oak-Conifer-Manzanita on Rocks ecological system.

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 Madrean Oak-Conifer-Manzanita on Rocks, as mapped in this effort.

Landfire Existing Vegetation Type (EVT)
(Note: the Landfire EVT algorithm does not recognize rocks, and was unreliable in identifying vegetation in rocky areas)
Madrean Lower Montane Pine-Oak Forest and Woodland *
Madrean Encinal
Madrean Pinyon-Juniper Woodland
Mogollon Chaparral

USFS Mid-scale Dominance Type
OakJP * (JUDE2, JUDE2_QUAR, JUDE2_QUEM, JUDE2_QUERC, JUMO, JUNIP_QUERC, PICEB, PIMO, QUAR, QUAR_QUEM, QUEM, QUEM_QUOB, QUERC, QUOB)
Upper Pine-Oak (PINUS_QUERC)
Ponderosa Pine (PIPO)
Upper Evergreen Forest Tree Mix (PIPO_PSME, PSME, TETX)

USFS Plant Habitat Type (Potential Association)
Border pinyon/silverleaf oak (PIDI/QUHY) *
Border pinyon/Toumey oak (PIDI/QUTO2)
Border pinyon/bullgrass (PIDI/MUEM)
Arizona cypress/silverleaf oak (CUAR/QUHY)
Scarp Woodlands (2TD)

USFS Potential Natural Vegetation Type (PNVT)
(Note: no PNVT provided a good match)
Madrean Encinal Woodland *
Madrean Pine-Oak Woodland
Interior Chaparral

Brown, Lowe, and Pase Biome
Madrean Evergreen Woodland *

Southwest Regional GAP Ecological System
Madrean Encinal * (tied with Madrean PJ Woodland)
Madrean Pinyon-Juniper Woodland * (tied with Madrean Encinal)
North American Warm Desert Bedrock Cliff and Outcrop
Mogollon Chaparral
Madrean Lower Montane Pine-Oak Forest and Woodland