Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest and Woodland

Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest and Woodland
View SSE above Turkey Park, just off road between Onion Saddle and Rustler Park, 2400 meters (7900 feet). A handsome pine catches the eye on this ENE facing slope, carpeted with grasses, especially Bromus sp., on September 13, 2010. Such pines can be either Pinus ponderosa (3-needle) or P. arizonica (typically 4 or 5 needle), and share dominance with Douglas fir. The pines are around 22 m tall, the firs about 20 m, and each provide about 24-40% cover. Gambel oak, white fir and Southwestern white pine each add another 1-4% cover.


This mixed-conifer ecosystem is found in the Chiricahua high country, from 7500 to 9000 feet, just below the aspen/spruce forest, and atop volcanic and sub-volcanic (almost but not quite extrusive) rocks, middle Miocene to Oligocene (15 to 38 Mya). The bedrock is rarely evident; more obvious is the roughly 50/50 split between dry and moist slopes, with the drier slopes hosting a mix of big pine (Pinus ponderosa, P. arizonica, P. strobiformis), while the Douglas fir (Pseudotsuga menziesii) and white fir (Abies concolor) prevail on moister slopes. All of these conifers are found downslope in the Madrean pine-oak ecosystems, where they live in the company of Madrean oaks like silverleaf, white, and netleaf oak. However, in this mixed-conifer ecosystem the only common oak is Gambel oak. Aspen and New Mexico locust can also be locally abundant, but usually not over areas larger than 40 acres. Likewise, steep scree slopes can hold silverleaf and netleaf oak, but such areas are uncommon in this ecosystem. Pockets of understory spruce are rare, and at the upper limits of this ecosystem. Meadows of 1 to 4 acres, such as Long Park, Barfoot Park, and Rustler Park, are common at saddles and basins.
The National Vegetation Classification System (NVCS) says it nicely:
Pseudotsuga menziesii and Abies concolor are most frequent, but Pinus ponderosa may be present to codominant...Abies concolor-dominated forests occupy cooler sites, such as upper slopes at higher elevations, canyon sideslopes, ridgetops, and north- and east-facing slopes which burn somewhat infrequently... This system was undoubtedly characterized by a mixed-severity fire regime in its "natural condition," characterized by a high degree of variability in lethality and return interval.
9200 feet, SE facing slope, June 15, 2010, Centella Point. The foreground shows a scree slope with Gambel oak closest to the camera, while the middle-ground holds young aspen. Beyond is a stand of big pines, likely Ponderosa and/or Arizona. Far downslope, at the head of a canyon, it is possible to make out the transition to the pointy Douglas firs of the Madrean Pine-oak ecosystem.
The view SW, near Bootlegger Saddle, between Long Park and Rustler Park, 8900 feet (2700 m), June 15, 2010. Ponderosa/Arizona pine are the dominant overstory, with 41-60% cover, typically 72 ft (22 m) tall. Douglas fir give another 15-25% cover. Gambel oak and chokecherry are scattered throughout the understory, but provide little cover.
View south from edge of Flys Park, 9000 feet (2750 m) showing aspen regeneration. This is at the upper edge of this ecosystem, and the lower edge of the aspen-spruce zone, and was formerly dominated by a mix of Douglas fir, ponderosa, and Southwestern white pine.
The view north in Long Park, 8900 feet (2700 m), June 15, 2010. Meadow with Iris missouriensis and Festuca arizonica, rimmed with Ponderosa, Douglas fir, and Southwestern white pine.

Other Vegetation Classifications

The Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer 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 Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer 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 Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest and Woodland, as mapped in this effort.

Landfire Existing Vegetation Type (EVT)
Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest and Woodland*
Madrean Lower Montane Pine-Oak Forest and Woodland
Southern Rocky Mountain Montane-Subalpine Grassland (burned areas, Snowshed Peak)
Rocky Mountain Gambel Oak-Mixed Montane Shrubland (burned areas, Snowshed Peak)

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

USFS Plant Habitat Type (Potential Association)
Douglas fir/screwleaf muhly (PSME/MUVI)*(mesic)
Ponderosa pine/screwleaf muhly (PIPO/MUVI) *(xeric)
Douglas fir/Gambel oak (PSME/QUGA)
Ponderosa pine/Gambel oak (PIPO/QUGA)
White fir/Gambel oak (ABCO/QUGA)
White fir/Rocky Mt. Maple (ABCO/ACGL)
White fir/Oregon grape (ABCO/BERE)

USFS Potential Natural Vegetation Type (PNVT)
Mixed conifer – Frequent fire *
Ponderosa Pine Forest

Brown, Lowe, and Pase Biome
Madrean Montane Conifer Forest*

Southwest Regional ReGAP Ecological System
Madrean Upper Montane Conifer-Oak Forest and Woodland*
Rocky Mountain Aspen Forest and Woodland