Great Basin Pinyon-Juniper Woodland

The view southeast towards Four Mile Peak, from Four Mile Creek near French Gap Spring, 4600 feet, 27 September 2011. A woodland of single-needle pinyon, averaging 25-28 feet tall (8 m), dominate with a cover of 25-40%, with a mix of juniper and Quercus turbinella giving another 25-40%. Mountain mahogany (Cercocarpus montana) is a common associate, but typically with only 1-4% cover.

The Great Basin Pinyon-Juniper Woodland ecosystem is restricted to the northern end of the study area, where it ranges from 3900 at Four Mile Ranch to 5500 feet near French Gap. The ecosystem as mapped in the Galiuros is distinguished by a pinyon pine that is a close-relative of the single-needle pinyon of the Great Basin. The subspecies found in the Great Basin is Pinus monophylla var. monophylla. The Arizona subspecies of the single-needle pinyon has several Latin names, including Pinus fallax = Pinus edulis var. fallax = Pinus monophylla var. fallax, with the latter being the name currently accepted by ITIS. Because of the many names, the Galiuro species will be referred to as simply 'single-needle pinyon.'

 

Single-needle pinyon replaces the border pinyon at elevations below 5000 feet in the northern reaches of Rattlesnake and Sycamore Canyons, and completely replaces border pinyon in the Four Mile Canyon watershed. At the same time, Quercus turbinella and single-seed juniper (either Juniperus coahuilensis (= J. arizonica), or J. monosperma) become common associates.  At some locations (e.g. Photo Point 742 below), the Q. turbinella is dense enough to resemble chaparral, but this was the exception, and in swaths typically less than 25 acres. More typical of this ecosystem is a structure that is more open than that of the Madrean Pinyon-Juniper, raising the question: what’s so different about the northern Galiuros? Two things: climate and substrate.

 

In Arizona, the single-needle pinyon lives in places where the winter rainfall is relatively enhanced by the Mogollon Rim, north of the Galiuro Mountains. Although the Galiuros are only 30 miles long, the pattern holds when comparing Klondyke and Cascabel, the closest weather stations for the northern and southern limits of the Coronado’s boundary in the Galiuros. From November to April, Klondyke receives 43% of its annual precipitation (6.52 inches of 15.05 inches, 25 year record), while Cascabel gets 38% (5.17 of 13.44 inches, 43 year record). (http://www.wrcc.dri.edu/). It’s just a little shift in seasonality, but it may also explain why the Mexican blue oak, common in the Redfield watershed in the south, vanishes from the northern Galiuros, replaced by scrub oak.

 

At the same time, the landforms and geology of the northern Galiuros are very different from the rest of the range. As seen in the figure below, this is strongly correlated with the Great Basin Pinyon-Juniper Ecosystem.

 

The view SSE towards Four Mile Peak, from a trail near Roy Tank, on 26 September 2011, at 4800 feet (1460 m). The right foreground slope, facing south, is dominated by whitethorn acacia, with 40-60% cover, with mesquite and Mimosa as common associates; this was mapped as mesquite scrub when covering over 25 acres (about 10 ha). Smaller patches were mapped as part of the Great Basin PJ, which is shown here on the darker north-facing slopes that hold single-needle pinyon, (typically over 25 feet tall), along with scrub oak (Q. turbinella), and single-seed juniper.

 

 

The view SE up a slope holding 40 foot tall single-needle pinyon with 15-25% cover. Equally common were silktassel (Garrya wrightii) and manzanita (Arctostaphylos pungens), averaging 6 feet tall. Scrub oak (Quercus turbinella) was a common associate (7 ft, 10-14%), along with buckbrush (Ceanothus fendleri, 3 ft, 1-4%) and wait-a-minute (Mimosa aculeaticarpa var. biuncifera, 4 ft, 1-4%). Grasses were notably rare, with less than 1% cover. 27 September 2011, 4550 feet, 1400 meters.

 

 

The view WNW to an east facing slope with scrub oak (Quercus turbinella) as a dominant, standing 2 meters tall (6-7 feet) with 25-40% cover. The most common associates are single-needle pinyon (7 m, 15-25%), beargrass (1.3 m, 10-14%), single-seed juniper (5 m, 5-9%), wait-a-minute bush (Mimosa, 1.4 m, 5-9%), and banana yucca (1-4%). Grass was surprisingly common (10-14%), but most of this was an annual, stinkgrass (Eragrostis cilianensis). September 26, 2011, at 4700 feet (1430 m).

 

 

 

The Great Basin Pinyon-Juniper Woodland ecosystem includes elements of several vegetation types mapped or described in other classification schemes. In each of the seven schemes referred to below, the * symbol marks the vegetation type most similar to the Great Basin Pinyon-Juniper Woodland.

 

And what is meant by ‘most similar’? For the USFS Plant “Habitat Type” (Potential Association) and the Brown, Lowe, and Pase “Biome”, the * symbol denotes the best fit based on the description of the Habitat Type or Biome. For the Landfire, ReGap, and USFS PNVT and mid-scale dominance classifications, which are presently mapped as 30 meter pixels, the * symbol denotes the classification that was most commonly attributed within the Great Basin Pinyon-Juniper Woodland, as mapped in this effort. The actual percentage attributed is given in parenthesis (%).

 

For example, the Great Basin Pinyon-Juniper Woodland polygons created by this study were used as a 'cookie-cutter' on the Landfire Existing Vegetation Type (EVT) layer (see methods). Within this study’s Great Basin Pinyon-Juniper Woodland, 62% of the EVT pixels were attributed as Madrean Pinyon-Juniper, and only 1% as Great Basin Pinyon-Juniper Woodland (full list below).

 

Landfire Existing Vegetation Type (EVT, version 1.0.5)

Madrean Pinyon-Juniper Woodland * (62%)

Mogollon Chaparral (includes Q. turbinella alliance) (17%)

Madrean Juniper Savanna (7%)

North American Warm Desert Riparian Systems (4%)

Colorado Plateau Pinyon-Juniper Woodland (4%)

Madrean Encinal (3%)

Great Basin Pinyon-Juniper Woodland (1%)

 

Landfire Biophysical Setting (BpS, version 1.0.0, which is older but judged by the author as locally more accurate)

Mogollon Chaparral * (43%)

Madrean Pinyon-Juniper Woodland (39%)

North American Warm Desert Riparian Systems – Stringers (7%)

Madrean Juniper Savanna (7%)

Madrean Encinal (4%)

Rocky Mountain Montane Riparian Systems (1%)

Great Basin Pinyon-Juniper Woodland (<1%)

 

Oak-Juniper-Pinyon Mix * (86%) (JUDE2, JUDE2_QUAR, JUDE2_QUEM, JUDE2_QUERC, JUMO, JUNIP_QUERC, PICEB, PIMO, QUAR, QUAR_QUEM, QUEM, QUEM_QUOB, QUERC, QUOB)

Upper Pine-Oak * (8%) (PINUS_QUERC)

Desert and Semi-desert Shrub Mix (6%)

Pinus fallax/Quercus turbinella PIFA/QUTU2 *

Pinus fallax/Arctostaphylos pungens PIFA/ARPU5

 

USFS Potential Natural Vegetation Type (PNVT) based on 24 Oct 2011 draft map

Madrean Encinal * (48%)

Semi-Desert Grassland (35%)

Madrean Pine-oak Woodland (16%)

Brown, Lowe, and Pase Biome

Great Basin Conifer Woodland

 

Southwest Regional GAP Ecological System

Mogollon Chaparral * (48%)

Madrean Pinyon–Juniper (24%)

Apacherian-Chihuahuan Mesquite Upland Scrub (17%)

Madrean Pine-Oak (8%)